diff options
Diffstat (limited to 'Documentation')
32 files changed, 1439 insertions, 1306 deletions
diff --git a/Documentation/admin-guide/blockdev/drbd/figures.rst b/Documentation/admin-guide/blockdev/drbd/figures.rst index bd9a4901fe46..9f73253ea353 100644 --- a/Documentation/admin-guide/blockdev/drbd/figures.rst +++ b/Documentation/admin-guide/blockdev/drbd/figures.rst @@ -25,6 +25,6 @@ Sub graphs of DRBD's state transitions :alt: disk-states-8.dot :align: center -.. kernel-figure:: node-states-8.dot - :alt: node-states-8.dot +.. kernel-figure:: peer-states-8.dot + :alt: peer-states-8.dot :align: center diff --git a/Documentation/admin-guide/blockdev/drbd/node-states-8.dot b/Documentation/admin-guide/blockdev/drbd/peer-states-8.dot index bfa54e1f8016..6dc3954954d6 100644 --- a/Documentation/admin-guide/blockdev/drbd/node-states-8.dot +++ b/Documentation/admin-guide/blockdev/drbd/peer-states-8.dot @@ -1,8 +1,3 @@ -digraph node_states { - Secondary -> Primary [ label = "ioctl_set_state()" ] - Primary -> Secondary [ label = "ioctl_set_state()" ] -} - digraph peer_states { Secondary -> Primary [ label = "recv state packet" ] Primary -> Secondary [ label = "recv state packet" ] diff --git a/Documentation/arm64/pointer-authentication.rst b/Documentation/arm64/pointer-authentication.rst index f127666ea3a8..e5dad2e40aa8 100644 --- a/Documentation/arm64/pointer-authentication.rst +++ b/Documentation/arm64/pointer-authentication.rst @@ -53,11 +53,10 @@ The number of bits that the PAC occupies in a pointer is 55 minus the virtual address size configured by the kernel. For example, with a virtual address size of 48, the PAC is 7 bits wide. -Recent versions of GCC can compile code with APIAKey-based return -address protection when passed the -msign-return-address option. This -uses instructions in the HINT space (unless -march=armv8.3-a or higher -is also passed), and such code can run on systems without the pointer -authentication extension. +When ARM64_PTR_AUTH_KERNEL is selected, the kernel will be compiled +with HINT space pointer authentication instructions protecting +function returns. Kernels built with this option will work on hardware +with or without pointer authentication support. In addition to exec(), keys can also be reinitialized to random values using the PR_PAC_RESET_KEYS prctl. A bitmask of PR_PAC_APIAKEY, diff --git a/Documentation/bpf/btf.rst b/Documentation/bpf/btf.rst index d0ec40d00c28..1ebf4c5c7ddc 100644 --- a/Documentation/bpf/btf.rst +++ b/Documentation/bpf/btf.rst @@ -3,7 +3,7 @@ BPF Type Format (BTF) ===================== 1. Introduction -*************** +=============== BTF (BPF Type Format) is the metadata format which encodes the debug info related to BPF program/map. The name BTF was used initially to describe data @@ -30,7 +30,7 @@ sections are discussed in details in :ref:`BTF_Type_String`. .. _BTF_Type_String: 2. BTF Type and String Encoding -******************************* +=============================== The file ``include/uapi/linux/btf.h`` provides high-level definition of how types/strings are encoded. @@ -57,13 +57,13 @@ little-endian target. The ``btf_header`` is designed to be extensible with generated. 2.1 String Encoding -=================== +------------------- The first string in the string section must be a null string. The rest of string table is a concatenation of other null-terminated strings. 2.2 Type Encoding -================= +----------------- The type id ``0`` is reserved for ``void`` type. The type section is parsed sequentially and type id is assigned to each recognized type starting from id @@ -504,7 +504,7 @@ valid index (starting from 0) pointing to a member or an argument. * ``type``: the type with ``btf_type_tag`` attribute 3. BTF Kernel API -***************** +================= The following bpf syscall command involves BTF: * BPF_BTF_LOAD: load a blob of BTF data into kernel @@ -547,14 +547,14 @@ The workflow typically looks like: 3.1 BPF_BTF_LOAD -================ +---------------- Load a blob of BTF data into kernel. A blob of data, described in :ref:`BTF_Type_String`, can be directly loaded into the kernel. A ``btf_fd`` is returned to a userspace. 3.2 BPF_MAP_CREATE -================== +------------------ A map can be created with ``btf_fd`` and specified key/value type id.:: @@ -581,7 +581,7 @@ automatically. .. _BPF_Prog_Load: 3.3 BPF_PROG_LOAD -================= +----------------- During prog_load, func_info and line_info can be passed to kernel with proper values for the following attributes: @@ -631,7 +631,7 @@ For line_info, the line number and column number are defined as below: #define BPF_LINE_INFO_LINE_COL(line_col) ((line_col) & 0x3ff) 3.4 BPF_{PROG,MAP}_GET_NEXT_ID -============================== +------------------------------ In kernel, every loaded program, map or btf has a unique id. The id won't change during the lifetime of a program, map, or btf. @@ -641,13 +641,13 @@ each command, to user space, for bpf program or maps, respectively, so an inspection tool can inspect all programs and maps. 3.5 BPF_{PROG,MAP}_GET_FD_BY_ID -=============================== +------------------------------- An introspection tool cannot use id to get details about program or maps. A file descriptor needs to be obtained first for reference-counting purpose. 3.6 BPF_OBJ_GET_INFO_BY_FD -========================== +-------------------------- Once a program/map fd is acquired, an introspection tool can get the detailed information from kernel about this fd, some of which are BTF-related. For @@ -656,7 +656,7 @@ example, ``bpf_map_info`` returns ``btf_id`` and key/value type ids. bpf byte codes, and jited_line_info. 3.7 BPF_BTF_GET_FD_BY_ID -======================== +------------------------ With ``btf_id`` obtained in ``bpf_map_info`` and ``bpf_prog_info``, bpf syscall command BPF_BTF_GET_FD_BY_ID can retrieve a btf fd. Then, with @@ -668,10 +668,10 @@ tool has full btf knowledge and is able to pretty print map key/values, dump func signatures and line info, along with byte/jit codes. 4. ELF File Format Interface -**************************** +============================ 4.1 .BTF section -================ +---------------- The .BTF section contains type and string data. The format of this section is same as the one describe in :ref:`BTF_Type_String`. @@ -679,7 +679,7 @@ same as the one describe in :ref:`BTF_Type_String`. .. _BTF_Ext_Section: 4.2 .BTF.ext section -==================== +-------------------- The .BTF.ext section encodes func_info and line_info which needs loader manipulation before loading into the kernel. @@ -743,7 +743,7 @@ bpf_insn``. For ELF API, the ``insn_off`` is the byte offset from the beginning of section (``btf_ext_info_sec->sec_name_off``). 4.2 .BTF_ids section -==================== +-------------------- The .BTF_ids section encodes BTF ID values that are used within the kernel. @@ -804,10 +804,10 @@ All the BTF ID lists and sets are compiled in the .BTF_ids section and resolved during the linking phase of kernel build by ``resolve_btfids`` tool. 5. Using BTF -************ +============ 5.1 bpftool map pretty print -============================ +---------------------------- With BTF, the map key/value can be printed based on fields rather than simply raw bytes. This is especially valuable for large structure or if your data @@ -849,7 +849,7 @@ bpftool is able to pretty print like below: ] 5.2 bpftool prog dump -===================== +--------------------- The following is an example showing how func_info and line_info can help prog dump with better kernel symbol names, function prototypes and line @@ -883,7 +883,7 @@ information.:: [...] 5.3 Verifier Log -================ +---------------- The following is an example of how line_info can help debugging verification failure.:: @@ -909,7 +909,7 @@ failure.:: R2 offset is outside of the packet 6. BTF Generation -***************** +================= You need latest pahole @@ -1016,6 +1016,6 @@ format.:: .long 8206 # Line 8 Col 14 7. Testing -********** +========== Kernel bpf selftest `test_btf.c` provides extensive set of BTF-related tests. diff --git a/Documentation/bpf/faq.rst b/Documentation/bpf/faq.rst new file mode 100644 index 000000000000..a622602ce9ad --- /dev/null +++ b/Documentation/bpf/faq.rst @@ -0,0 +1,11 @@ +================================ +Frequently asked questions (FAQ) +================================ + +Two sets of Questions and Answers (Q&A) are maintained. + +.. toctree:: + :maxdepth: 1 + + bpf_design_QA + bpf_devel_QA diff --git a/Documentation/bpf/helpers.rst b/Documentation/bpf/helpers.rst new file mode 100644 index 000000000000..c4ee0cc20dec --- /dev/null +++ b/Documentation/bpf/helpers.rst @@ -0,0 +1,7 @@ +Helper functions +================ + +* `bpf-helpers(7)`_ maintains a list of helpers available to eBPF programs. + +.. Links +.. _bpf-helpers(7): https://man7.org/linux/man-pages/man7/bpf-helpers.7.html
\ No newline at end of file diff --git a/Documentation/bpf/index.rst b/Documentation/bpf/index.rst index 610450f59e05..91ba5a62026b 100644 --- a/Documentation/bpf/index.rst +++ b/Documentation/bpf/index.rst @@ -5,104 +5,32 @@ BPF Documentation This directory contains documentation for the BPF (Berkeley Packet Filter) facility, with a focus on the extended BPF version (eBPF). -This kernel side documentation is still work in progress. The main -textual documentation is (for historical reasons) described in -:ref:`networking-filter`, which describe both classical and extended -BPF instruction-set. +This kernel side documentation is still work in progress. The Cilium project also maintains a `BPF and XDP Reference Guide`_ that goes into great technical depth about the BPF Architecture. -libbpf -====== - -Documentation/bpf/libbpf/index.rst is a userspace library for loading and interacting with bpf programs. - -BPF Type Format (BTF) -===================== - .. toctree:: :maxdepth: 1 + instruction-set + verifier + libbpf/index btf - - -Frequently asked questions (FAQ) -================================ - -Two sets of Questions and Answers (Q&A) are maintained. - -.. toctree:: - :maxdepth: 1 - - bpf_design_QA - bpf_devel_QA - -Syscall API -=========== - -The primary info for the bpf syscall is available in the `man-pages`_ -for `bpf(2)`_. For more information about the userspace API, see -Documentation/userspace-api/ebpf/index.rst. - -Helper functions -================ - -* `bpf-helpers(7)`_ maintains a list of helpers available to eBPF programs. - - -Program types -============= - -.. toctree:: - :maxdepth: 1 - - prog_cgroup_sockopt - prog_cgroup_sysctl - prog_flow_dissector - bpf_lsm - prog_sk_lookup - - -Map types -========= - -.. toctree:: - :maxdepth: 1 - - map_cgroup_storage - - -Testing and debugging BPF -========================= - -.. toctree:: - :maxdepth: 1 - - drgn - s390 - - -Licensing -========= - -.. toctree:: - :maxdepth: 1 - + faq + syscall_api + helpers + programs + maps bpf_licensing + test_debug + other +.. only:: subproject and html -Other -===== - -.. toctree:: - :maxdepth: 1 + Indices + ======= - ringbuf - llvm_reloc + * :ref:`genindex` .. Links: -.. _networking-filter: ../networking/filter.rst -.. _man-pages: https://www.kernel.org/doc/man-pages/ -.. _bpf(2): https://man7.org/linux/man-pages/man2/bpf.2.html -.. _bpf-helpers(7): https://man7.org/linux/man-pages/man7/bpf-helpers.7.html .. _BPF and XDP Reference Guide: https://docs.cilium.io/en/latest/bpf/ diff --git a/Documentation/bpf/instruction-set.rst b/Documentation/bpf/instruction-set.rst new file mode 100644 index 000000000000..fa7cba59031e --- /dev/null +++ b/Documentation/bpf/instruction-set.rst @@ -0,0 +1,467 @@ + +==================== +eBPF Instruction Set +==================== + +eBPF is designed to be JITed with one to one mapping, which can also open up +the possibility for GCC/LLVM compilers to generate optimized eBPF code through +an eBPF backend that performs almost as fast as natively compiled code. + +Some core changes of the eBPF format from classic BPF: + +- Number of registers increase from 2 to 10: + + The old format had two registers A and X, and a hidden frame pointer. The + new layout extends this to be 10 internal registers and a read-only frame + pointer. Since 64-bit CPUs are passing arguments to functions via registers + the number of args from eBPF program to in-kernel function is restricted + to 5 and one register is used to accept return value from an in-kernel + function. Natively, x86_64 passes first 6 arguments in registers, aarch64/ + sparcv9/mips64 have 7 - 8 registers for arguments; x86_64 has 6 callee saved + registers, and aarch64/sparcv9/mips64 have 11 or more callee saved registers. + + Therefore, eBPF calling convention is defined as: + + * R0 - return value from in-kernel function, and exit value for eBPF program + * R1 - R5 - arguments from eBPF program to in-kernel function + * R6 - R9 - callee saved registers that in-kernel function will preserve + * R10 - read-only frame pointer to access stack + + Thus, all eBPF registers map one to one to HW registers on x86_64, aarch64, + etc, and eBPF calling convention maps directly to ABIs used by the kernel on + 64-bit architectures. + + On 32-bit architectures JIT may map programs that use only 32-bit arithmetic + and may let more complex programs to be interpreted. + + R0 - R5 are scratch registers and eBPF program needs spill/fill them if + necessary across calls. Note that there is only one eBPF program (== one + eBPF main routine) and it cannot call other eBPF functions, it can only + call predefined in-kernel functions, though. + +- Register width increases from 32-bit to 64-bit: + + Still, the semantics of the original 32-bit ALU operations are preserved + via 32-bit subregisters. All eBPF registers are 64-bit with 32-bit lower + subregisters that zero-extend into 64-bit if they are being written to. + That behavior maps directly to x86_64 and arm64 subregister definition, but + makes other JITs more difficult. + + 32-bit architectures run 64-bit eBPF programs via interpreter. + Their JITs may convert BPF programs that only use 32-bit subregisters into + native instruction set and let the rest being interpreted. + + Operation is 64-bit, because on 64-bit architectures, pointers are also + 64-bit wide, and we want to pass 64-bit values in/out of kernel functions, + so 32-bit eBPF registers would otherwise require to define register-pair + ABI, thus, there won't be able to use a direct eBPF register to HW register + mapping and JIT would need to do combine/split/move operations for every + register in and out of the function, which is complex, bug prone and slow. + Another reason is the use of atomic 64-bit counters. + +- Conditional jt/jf targets replaced with jt/fall-through: + + While the original design has constructs such as ``if (cond) jump_true; + else jump_false;``, they are being replaced into alternative constructs like + ``if (cond) jump_true; /* else fall-through */``. + +- Introduces bpf_call insn and register passing convention for zero overhead + calls from/to other kernel functions: + + Before an in-kernel function call, the eBPF program needs to + place function arguments into R1 to R5 registers to satisfy calling + convention, then the interpreter will take them from registers and pass + to in-kernel function. If R1 - R5 registers are mapped to CPU registers + that are used for argument passing on given architecture, the JIT compiler + doesn't need to emit extra moves. Function arguments will be in the correct + registers and BPF_CALL instruction will be JITed as single 'call' HW + instruction. This calling convention was picked to cover common call + situations without performance penalty. + + After an in-kernel function call, R1 - R5 are reset to unreadable and R0 has + a return value of the function. Since R6 - R9 are callee saved, their state + is preserved across the call. + + For example, consider three C functions:: + + u64 f1() { return (*_f2)(1); } + u64 f2(u64 a) { return f3(a + 1, a); } + u64 f3(u64 a, u64 b) { return a - b; } + + GCC can compile f1, f3 into x86_64:: + + f1: + movl $1, %edi + movq _f2(%rip), %rax + jmp *%rax + f3: + movq %rdi, %rax + subq %rsi, %rax + ret + + Function f2 in eBPF may look like:: + + f2: + bpf_mov R2, R1 + bpf_add R1, 1 + bpf_call f3 + bpf_exit + + If f2 is JITed and the pointer stored to ``_f2``. The calls f1 -> f2 -> f3 and + returns will be seamless. Without JIT, __bpf_prog_run() interpreter needs to + be used to call into f2. + + For practical reasons all eBPF programs have only one argument 'ctx' which is + already placed into R1 (e.g. on __bpf_prog_run() startup) and the programs + can call kernel functions with up to 5 arguments. Calls with 6 or more arguments + are currently not supported, but these restrictions can be lifted if necessary + in the future. + + On 64-bit architectures all register map to HW registers one to one. For + example, x86_64 JIT compiler can map them as ... + + :: + + R0 - rax + R1 - rdi + R2 - rsi + R3 - rdx + R4 - rcx + R5 - r8 + R6 - rbx + R7 - r13 + R8 - r14 + R9 - r15 + R10 - rbp + + ... since x86_64 ABI mandates rdi, rsi, rdx, rcx, r8, r9 for argument passing + and rbx, r12 - r15 are callee saved. + + Then the following eBPF pseudo-program:: + + bpf_mov R6, R1 /* save ctx */ + bpf_mov R2, 2 + bpf_mov R3, 3 + bpf_mov R4, 4 + bpf_mov R5, 5 + bpf_call foo + bpf_mov R7, R0 /* save foo() return value */ + bpf_mov R1, R6 /* restore ctx for next call */ + bpf_mov R2, 6 + bpf_mov R3, 7 + bpf_mov R4, 8 + bpf_mov R5, 9 + bpf_call bar + bpf_add R0, R7 + bpf_exit + + After JIT to x86_64 may look like:: + + push %rbp + mov %rsp,%rbp + sub $0x228,%rsp + mov %rbx,-0x228(%rbp) + mov %r13,-0x220(%rbp) + mov %rdi,%rbx + mov $0x2,%esi + mov $0x3,%edx + mov $0x4,%ecx + mov $0x5,%r8d + callq foo + mov %rax,%r13 + mov %rbx,%rdi + mov $0x6,%esi + mov $0x7,%edx + mov $0x8,%ecx + mov $0x9,%r8d + callq bar + add %r13,%rax + mov -0x228(%rbp),%rbx + mov -0x220(%rbp),%r13 + leaveq + retq + + Which is in this example equivalent in C to:: + + u64 bpf_filter(u64 ctx) + { + return foo(ctx, 2, 3, 4, 5) + bar(ctx, 6, 7, 8, 9); + } + + In-kernel functions foo() and bar() with prototype: u64 (*)(u64 arg1, u64 + arg2, u64 arg3, u64 arg4, u64 arg5); will receive arguments in proper + registers and place their return value into ``%rax`` which is R0 in eBPF. + Prologue and epilogue are emitted by JIT and are implicit in the + interpreter. R0-R5 are scratch registers, so eBPF program needs to preserve + them across the calls as defined by calling convention. + + For example the following program is invalid:: + + bpf_mov R1, 1 + bpf_call foo + bpf_mov R0, R1 + bpf_exit + + After the call the registers R1-R5 contain junk values and cannot be read. + An in-kernel `eBPF verifier`_ is used to validate eBPF programs. + +Also in the new design, eBPF is limited to 4096 insns, which means that any +program will terminate quickly and will only call a fixed number of kernel +functions. Original BPF and eBPF are two operand instructions, +which helps to do one-to-one mapping between eBPF insn and x86 insn during JIT. + +The input context pointer for invoking the interpreter function is generic, +its content is defined by a specific use case. For seccomp register R1 points +to seccomp_data, for converted BPF filters R1 points to a skb. + +A program, that is translated internally consists of the following elements:: + + op:16, jt:8, jf:8, k:32 ==> op:8, dst_reg:4, src_reg:4, off:16, imm:32 + +So far 87 eBPF instructions were implemented. 8-bit 'op' opcode field +has room for new instructions. Some of them may use 16/24/32 byte encoding. New +instructions must be multiple of 8 bytes to preserve backward compatibility. + +eBPF is a general purpose RISC instruction set. Not every register and +every instruction are used during translation from original BPF to eBPF. +For example, socket filters are not using ``exclusive add`` instruction, but +tracing filters may do to maintain counters of events, for example. Register R9 +is not used by socket filters either, but more complex filters may be running +out of registers and would have to resort to spill/fill to stack. + +eBPF can be used as a generic assembler for last step performance +optimizations, socket filters and seccomp are using it as assembler. Tracing +filters may use it as assembler to generate code from kernel. In kernel usage +may not be bounded by security considerations, since generated eBPF code +may be optimizing internal code path and not being exposed to the user space. +Safety of eBPF can come from the `eBPF verifier`_. In such use cases as +described, it may be used as safe instruction set. + +Just like the original BPF, eBPF runs within a controlled environment, +is deterministic and the kernel can easily prove that. The safety of the program +can be determined in two steps: first step does depth-first-search to disallow +loops and other CFG validation; second step starts from the first insn and +descends all possible paths. It simulates execution of every insn and observes +the state change of registers and stack. + +eBPF opcode encoding +==================== + +eBPF is reusing most of the opcode encoding from classic to simplify conversion +of classic BPF to eBPF. For arithmetic and jump instructions the 8-bit 'code' +field is divided into three parts:: + + +----------------+--------+--------------------+ + | 4 bits | 1 bit | 3 bits | + | operation code | source | instruction class | + +----------------+--------+--------------------+ + (MSB) (LSB) + +Three LSB bits store instruction class which is one of: + + =================== =============== + Classic BPF classes eBPF classes + =================== =============== + BPF_LD 0x00 BPF_LD 0x00 + BPF_LDX 0x01 BPF_LDX 0x01 + BPF_ST 0x02 BPF_ST 0x02 + BPF_STX 0x03 BPF_STX 0x03 + BPF_ALU 0x04 BPF_ALU 0x04 + BPF_JMP 0x05 BPF_JMP 0x05 + BPF_RET 0x06 BPF_JMP32 0x06 + BPF_MISC 0x07 BPF_ALU64 0x07 + =================== =============== + +When BPF_CLASS(code) == BPF_ALU or BPF_JMP, 4th bit encodes source operand ... + + :: + + BPF_K 0x00 + BPF_X 0x08 + + * in classic BPF, this means:: + + BPF_SRC(code) == BPF_X - use register X as source operand + BPF_SRC(code) == BPF_K - use 32-bit immediate as source operand + + * in eBPF, this means:: + + BPF_SRC(code) == BPF_X - use 'src_reg' register as source operand + BPF_SRC(code) == BPF_K - use 32-bit immediate as source operand + +... and four MSB bits store operation code. + +If BPF_CLASS(code) == BPF_ALU or BPF_ALU64 [ in eBPF ], BPF_OP(code) is one of:: + + BPF_ADD 0x00 + BPF_SUB 0x10 + BPF_MUL 0x20 + BPF_DIV 0x30 + BPF_OR 0x40 + BPF_AND 0x50 + BPF_LSH 0x60 + BPF_RSH 0x70 + BPF_NEG 0x80 + BPF_MOD 0x90 + BPF_XOR 0xa0 + BPF_MOV 0xb0 /* eBPF only: mov reg to reg */ + BPF_ARSH 0xc0 /* eBPF only: sign extending shift right */ + BPF_END 0xd0 /* eBPF only: endianness conversion */ + +If BPF_CLASS(code) == BPF_JMP or BPF_JMP32 [ in eBPF ], BPF_OP(code) is one of:: + + BPF_JA 0x00 /* BPF_JMP only */ + BPF_JEQ 0x10 + BPF_JGT 0x20 + BPF_JGE 0x30 + BPF_JSET 0x40 + BPF_JNE 0x50 /* eBPF only: jump != */ + BPF_JSGT 0x60 /* eBPF only: signed '>' */ + BPF_JSGE 0x70 /* eBPF only: signed '>=' */ + BPF_CALL 0x80 /* eBPF BPF_JMP only: function call */ + BPF_EXIT 0x90 /* eBPF BPF_JMP only: function return */ + BPF_JLT 0xa0 /* eBPF only: unsigned '<' */ + BPF_JLE 0xb0 /* eBPF only: unsigned '<=' */ + BPF_JSLT 0xc0 /* eBPF only: signed '<' */ + BPF_JSLE 0xd0 /* eBPF only: signed '<=' */ + +So BPF_ADD | BPF_X | BPF_ALU means 32-bit addition in both classic BPF +and eBPF. There are only two registers in classic BPF, so it means A += X. +In eBPF it means dst_reg = (u32) dst_reg + (u32) src_reg; similarly, +BPF_XOR | BPF_K | BPF_ALU means A ^= imm32 in classic BPF and analogous +src_reg = (u32) src_reg ^ (u32) imm32 in eBPF. + +Classic BPF is using BPF_MISC class to represent A = X and X = A moves. +eBPF is using BPF_MOV | BPF_X | BPF_ALU code instead. Since there are no +BPF_MISC operations in eBPF, the class 7 is used as BPF_ALU64 to mean +exactly the same operations as BPF_ALU, but with 64-bit wide operands +instead. So BPF_ADD | BPF_X | BPF_ALU64 means 64-bit addition, i.e.: +dst_reg = dst_reg + src_reg + +Classic BPF wastes the whole BPF_RET class to represent a single ``ret`` +operation. Classic BPF_RET | BPF_K means copy imm32 into return register +and perform function exit. eBPF is modeled to match CPU, so BPF_JMP | BPF_EXIT +in eBPF means function exit only. The eBPF program needs to store return +value into register R0 before doing a BPF_EXIT. Class 6 in eBPF is used as +BPF_JMP32 to mean exactly the same operations as BPF_JMP, but with 32-bit wide +operands for the comparisons instead. + +For load and store instructions the 8-bit 'code' field is divided as:: + + +--------+--------+-------------------+ + | 3 bits | 2 bits | 3 bits | + | mode | size | instruction class | + +--------+--------+-------------------+ + (MSB) (LSB) + +Size modifier is one of ... + +:: + + BPF_W 0x00 /* word */ + BPF_H 0x08 /* half word */ + BPF_B 0x10 /* byte */ + BPF_DW 0x18 /* eBPF only, double word */ + +... which encodes size of load/store operation:: + + B - 1 byte + H - 2 byte + W - 4 byte + DW - 8 byte (eBPF only) + +Mode modifier is one of:: + + BPF_IMM 0x00 /* used for 32-bit mov in classic BPF and 64-bit in eBPF */ + BPF_ABS 0x20 + BPF_IND 0x40 + BPF_MEM 0x60 + BPF_LEN 0x80 /* classic BPF only, reserved in eBPF */ + BPF_MSH 0xa0 /* classic BPF only, reserved in eBPF */ + BPF_ATOMIC 0xc0 /* eBPF only, atomic operations */ + +eBPF has two non-generic instructions: (BPF_ABS | <size> | BPF_LD) and +(BPF_IND | <size> | BPF_LD) which are used to access packet data. + +They had to be carried over from classic to have strong performance of +socket filters running in eBPF interpreter. These instructions can only +be used when interpreter context is a pointer to ``struct sk_buff`` and +have seven implicit operands. Register R6 is an implicit input that must +contain pointer to sk_buff. Register R0 is an implicit output which contains +the data fetched from the packet. Registers R1-R5 are scratch registers +and must not be used to store the data across BPF_ABS | BPF_LD or +BPF_IND | BPF_LD instructions. + +These instructions have implicit program exit condition as well. When +eBPF program is trying to access the data beyond the packet boundary, +the interpreter will abort the execution of the program. JIT compilers +therefore must preserve this property. src_reg and imm32 fields are +explicit inputs to these instructions. + +For example:: + + BPF_IND | BPF_W | BPF_LD means: + + R0 = ntohl(*(u32 *) (((struct sk_buff *) R6)->data + src_reg + imm32)) + and R1 - R5 were scratched. + +Unlike classic BPF instruction set, eBPF has generic load/store operations:: + + BPF_MEM | <size> | BPF_STX: *(size *) (dst_reg + off) = src_reg + BPF_MEM | <size> | BPF_ST: *(size *) (dst_reg + off) = imm32 + BPF_MEM | <size> | BPF_LDX: dst_reg = *(size *) (src_reg + off) + +Where size is one of: BPF_B or BPF_H or BPF_W or BPF_DW. + +It also includes atomic operations, which use the immediate field for extra +encoding:: + + .imm = BPF_ADD, .code = BPF_ATOMIC | BPF_W | BPF_STX: lock xadd *(u32 *)(dst_reg + off16) += src_reg + .imm = BPF_ADD, .code = BPF_ATOMIC | BPF_DW | BPF_STX: lock xadd *(u64 *)(dst_reg + off16) += src_reg + +The basic atomic operations supported are:: + + BPF_ADD + BPF_AND + BPF_OR + BPF_XOR + +Each having equivalent semantics with the ``BPF_ADD`` example, that is: the +memory location addresed by ``dst_reg + off`` is atomically modified, with +``src_reg`` as the other operand. If the ``BPF_FETCH`` flag is set in the +immediate, then these operations also overwrite ``src_reg`` with the +value that was in memory before it was modified. + +The more special operations are:: + + BPF_XCHG + +This atomically exchanges ``src_reg`` with the value addressed by ``dst_reg + +off``. :: + + BPF_CMPXCHG + +This atomically compares the value addressed by ``dst_reg + off`` with +``R0``. If they match it is replaced with ``src_reg``. In either case, the +value that was there before is zero-extended and loaded back to ``R0``. + +Note that 1 and 2 byte atomic operations are not supported. + +Clang can generate atomic instructions by default when ``-mcpu=v3`` is +enabled. If a lower version for ``-mcpu`` is set, the only atomic instruction +Clang can generate is ``BPF_ADD`` *without* ``BPF_FETCH``. If you need to enable +the atomics features, while keeping a lower ``-mcpu`` version, you can use +``-Xclang -target-feature -Xclang +alu32``. + +You may encounter ``BPF_XADD`` - this is a legacy name for ``BPF_ATOMIC``, +referring to the exclusive-add operation encoded when the immediate field is +zero. + +eBPF has one 16-byte instruction: ``BPF_LD | BPF_DW | BPF_IMM`` which consists +of two consecutive ``struct bpf_insn`` 8-byte blocks and interpreted as single +instruction that loads 64-bit immediate value into a dst_reg. +Classic BPF has similar instruction: ``BPF_LD | BPF_W | BPF_IMM`` which loads +32-bit immediate value into a register. + +.. Links: +.. _eBPF verifier: verifiers.rst diff --git a/Documentation/bpf/libbpf/index.rst b/Documentation/bpf/libbpf/index.rst index 4f8adfc3ab83..4e8c656b539a 100644 --- a/Documentation/bpf/libbpf/index.rst +++ b/Documentation/bpf/libbpf/index.rst @@ -3,8 +3,6 @@ libbpf ====== -For API documentation see the `versioned API documentation site <https://libbpf.readthedocs.io/en/latest/api.html>`_. - .. toctree:: :maxdepth: 1 @@ -14,6 +12,8 @@ For API documentation see the `versioned API documentation site <https://libbpf. This is documentation for libbpf, a userspace library for loading and interacting with bpf programs. +For API documentation see the `versioned API documentation site <https://libbpf.readthedocs.io/en/latest/api.html>`_. + All general BPF questions, including kernel functionality, libbpf APIs and their application, should be sent to bpf@vger.kernel.org mailing list. You can `subscribe <http://vger.kernel.org/vger-lists.html#bpf>`_ to the diff --git a/Documentation/bpf/maps.rst b/Documentation/bpf/maps.rst new file mode 100644 index 000000000000..f41619e312ac --- /dev/null +++ b/Documentation/bpf/maps.rst @@ -0,0 +1,52 @@ + +========= +eBPF maps +========= + +'maps' is a generic storage of different types for sharing data between kernel +and userspace. + +The maps are accessed from user space via BPF syscall, which has commands: + +- create a map with given type and attributes + ``map_fd = bpf(BPF_MAP_CREATE, union bpf_attr *attr, u32 size)`` + using attr->map_type, attr->key_size, attr->value_size, attr->max_entries + returns process-local file descriptor or negative error + +- lookup key in a given map + ``err = bpf(BPF_MAP_LOOKUP_ELEM, union bpf_attr *attr, u32 size)`` + using attr->map_fd, attr->key, attr->value + returns zero and stores found elem into value or negative error + +- create or update key/value pair in a given map + ``err = bpf(BPF_MAP_UPDATE_ELEM, union bpf_attr *attr, u32 size)`` + using attr->map_fd, attr->key, attr->value + returns zero or negative error + +- find and delete element by key in a given map + ``err = bpf(BPF_MAP_DELETE_ELEM, union bpf_attr *attr, u32 size)`` + using attr->map_fd, attr->key + +- to delete map: close(fd) + Exiting process will delete maps automatically + +userspace programs use this syscall to create/access maps that eBPF programs +are concurrently updating. + +maps can have different types: hash, array, bloom filter, radix-tree, etc. + +The map is defined by: + + - type + - max number of elements + - key size in bytes + - value size in bytes + +Map Types +========= + +.. toctree:: + :maxdepth: 1 + :glob: + + map_*
\ No newline at end of file diff --git a/Documentation/bpf/other.rst b/Documentation/bpf/other.rst new file mode 100644 index 000000000000..3d61963403b4 --- /dev/null +++ b/Documentation/bpf/other.rst @@ -0,0 +1,9 @@ +===== +Other +===== + +.. toctree:: + :maxdepth: 1 + + ringbuf + llvm_reloc
\ No newline at end of file diff --git a/Documentation/bpf/bpf_lsm.rst b/Documentation/bpf/prog_lsm.rst index 0dc3fb0d9544..0dc3fb0d9544 100644 --- a/Documentation/bpf/bpf_lsm.rst +++ b/Documentation/bpf/prog_lsm.rst diff --git a/Documentation/bpf/programs.rst b/Documentation/bpf/programs.rst new file mode 100644 index 000000000000..620eb667ac7a --- /dev/null +++ b/Documentation/bpf/programs.rst @@ -0,0 +1,9 @@ +============= +Program Types +============= + +.. toctree:: + :maxdepth: 1 + :glob: + + prog_* diff --git a/Documentation/bpf/syscall_api.rst b/Documentation/bpf/syscall_api.rst new file mode 100644 index 000000000000..f0a1dff087ad --- /dev/null +++ b/Documentation/bpf/syscall_api.rst @@ -0,0 +1,11 @@ +=========== +Syscall API +=========== + +The primary info for the bpf syscall is available in the `man-pages`_ +for `bpf(2)`_. For more information about the userspace API, see +Documentation/userspace-api/ebpf/index.rst. + +.. Links: +.. _man-pages: https://www.kernel.org/doc/man-pages/ +.. _bpf(2): https://man7.org/linux/man-pages/man2/bpf.2.html
\ No newline at end of file diff --git a/Documentation/bpf/test_debug.rst b/Documentation/bpf/test_debug.rst new file mode 100644 index 000000000000..ebf0caceb6a6 --- /dev/null +++ b/Documentation/bpf/test_debug.rst @@ -0,0 +1,9 @@ +========================= +Testing and debugging BPF +========================= + +.. toctree:: + :maxdepth: 1 + + drgn + s390 diff --git a/Documentation/bpf/verifier.rst b/Documentation/bpf/verifier.rst new file mode 100644 index 000000000000..fae5f6273bac --- /dev/null +++ b/Documentation/bpf/verifier.rst @@ -0,0 +1,529 @@ + +============= +eBPF verifier +============= + +The safety of the eBPF program is determined in two steps. + +First step does DAG check to disallow loops and other CFG validation. +In particular it will detect programs that have unreachable instructions. +(though classic BPF checker allows them) + +Second step starts from the first insn and descends all possible paths. +It simulates execution of every insn and observes the state change of +registers and stack. + +At the start of the program the register R1 contains a pointer to context +and has type PTR_TO_CTX. +If verifier sees an insn that does R2=R1, then R2 has now type +PTR_TO_CTX as well and can be used on the right hand side of expression. +If R1=PTR_TO_CTX and insn is R2=R1+R1, then R2=SCALAR_VALUE, +since addition of two valid pointers makes invalid pointer. +(In 'secure' mode verifier will reject any type of pointer arithmetic to make +sure that kernel addresses don't leak to unprivileged users) + +If register was never written to, it's not readable:: + + bpf_mov R0 = R2 + bpf_exit + +will be rejected, since R2 is unreadable at the start of the program. + +After kernel function call, R1-R5 are reset to unreadable and +R0 has a return type of the function. + +Since R6-R9 are callee saved, their state is preserved across the call. + +:: + + bpf_mov R6 = 1 + bpf_call foo + bpf_mov R0 = R6 + bpf_exit + +is a correct program. If there was R1 instead of R6, it would have +been rejected. + +load/store instructions are allowed only with registers of valid types, which +are PTR_TO_CTX, PTR_TO_MAP, PTR_TO_STACK. They are bounds and alignment checked. +For example:: + + bpf_mov R1 = 1 + bpf_mov R2 = 2 + bpf_xadd *(u32 *)(R1 + 3) += R2 + bpf_exit + +will be rejected, since R1 doesn't have a valid pointer type at the time of +execution of instruction bpf_xadd. + +At the start R1 type is PTR_TO_CTX (a pointer to generic ``struct bpf_context``) +A callback is used to customize verifier to restrict eBPF program access to only +certain fields within ctx structure with specified size and alignment. + +For example, the following insn:: + + bpf_ld R0 = *(u32 *)(R6 + 8) + +intends to load a word from address R6 + 8 and store it into R0 +If R6=PTR_TO_CTX, via is_valid_access() callback the verifier will know +that offset 8 of size 4 bytes can be accessed for reading, otherwise +the verifier will reject the program. +If R6=PTR_TO_STACK, then access should be aligned and be within +stack bounds, which are [-MAX_BPF_STACK, 0). In this example offset is 8, +so it will fail verification, since it's out of bounds. + +The verifier will allow eBPF program to read data from stack only after +it wrote into it. + +Classic BPF verifier does similar check with M[0-15] memory slots. +For example:: + + bpf_ld R0 = *(u32 *)(R10 - 4) + bpf_exit + +is invalid program. +Though R10 is correct read-only register and has type PTR_TO_STACK +and R10 - 4 is within stack bounds, there were no stores into that location. + +Pointer register spill/fill is tracked as well, since four (R6-R9) +callee saved registers may not be enough for some programs. + +Allowed function calls are customized with bpf_verifier_ops->get_func_proto() +The eBPF verifier will check that registers match argument constraints. +After the call register R0 will be set to return type of the function. + +Function calls is a main mechanism to extend functionality of eBPF programs. +Socket filters may let programs to call one set of functions, whereas tracing +filters may allow completely different set. + +If a function made accessible to eBPF program, it needs to be thought through +from safety point of view. The verifier will guarantee that the function is +called with valid arguments. + +seccomp vs socket filters have different security restrictions for classic BPF. +Seccomp solves this by two stage verifier: classic BPF verifier is followed +by seccomp verifier. In case of eBPF one configurable verifier is shared for +all use cases. + +See details of eBPF verifier in kernel/bpf/verifier.c + +Register value tracking +======================= + +In order to determine the safety of an eBPF program, the verifier must track +the range of possible values in each register and also in each stack slot. +This is done with ``struct bpf_reg_state``, defined in include/linux/ +bpf_verifier.h, which unifies tracking of scalar and pointer values. Each +register state has a type, which is either NOT_INIT (the register has not been +written to), SCALAR_VALUE (some value which is not usable as a pointer), or a +pointer type. The types of pointers describe their base, as follows: + + + PTR_TO_CTX + Pointer to bpf_context. + CONST_PTR_TO_MAP + Pointer to struct bpf_map. "Const" because arithmetic + on these pointers is forbidden. + PTR_TO_MAP_VALUE + Pointer to the value stored in a map element. + PTR_TO_MAP_VALUE_OR_NULL + Either a pointer to a map value, or NULL; map accesses + (see maps.rst) return this type, which becomes a + PTR_TO_MAP_VALUE when checked != NULL. Arithmetic on + these pointers is forbidden. + PTR_TO_STACK + Frame pointer. + PTR_TO_PACKET + skb->data. + PTR_TO_PACKET_END + skb->data + headlen; arithmetic forbidden. + PTR_TO_SOCKET + Pointer to struct bpf_sock_ops, implicitly refcounted. + PTR_TO_SOCKET_OR_NULL + Either a pointer to a socket, or NULL; socket lookup + returns this type, which becomes a PTR_TO_SOCKET when + checked != NULL. PTR_TO_SOCKET is reference-counted, + so programs must release the reference through the + socket release function before the end of the program. + Arithmetic on these pointers is forbidden. + +However, a pointer may be offset from this base (as a result of pointer +arithmetic), and this is tracked in two parts: the 'fixed offset' and 'variable +offset'. The former is used when an exactly-known value (e.g. an immediate +operand) is added to a pointer, while the latter is used for values which are +not exactly known. The variable offset is also used in SCALAR_VALUEs, to track +the range of possible values in the register. + +The verifier's knowledge about the variable offset consists of: + +* minimum and maximum values as unsigned +* minimum and maximum values as signed + +* knowledge of the values of individual bits, in the form of a 'tnum': a u64 + 'mask' and a u64 'value'. 1s in the mask represent bits whose value is unknown; + 1s in the value represent bits known to be 1. Bits known to be 0 have 0 in both + mask and value; no bit should ever be 1 in both. For example, if a byte is read + into a register from memory, the register's top 56 bits are known zero, while + the low 8 are unknown - which is represented as the tnum (0x0; 0xff). If we + then OR this with 0x40, we get (0x40; 0xbf), then if we add 1 we get (0x0; + 0x1ff), because of potential carries. + +Besides arithmetic, the register state can also be updated by conditional +branches. For instance, if a SCALAR_VALUE is compared > 8, in the 'true' branch +it will have a umin_value (unsigned minimum value) of 9, whereas in the 'false' +branch it will have a umax_value of 8. A signed compare (with BPF_JSGT or +BPF_JSGE) would instead update the signed minimum/maximum values. Information +from the signed and unsigned bounds can be combined; for instance if a value is +first tested < 8 and then tested s> 4, the verifier will conclude that the value +is also > 4 and s< 8, since the bounds prevent crossing the sign boundary. + +PTR_TO_PACKETs with a variable offset part have an 'id', which is common to all +pointers sharing that same variable offset. This is important for packet range +checks: after adding a variable to a packet pointer register A, if you then copy +it to another register B and then add a constant 4 to A, both registers will +share the same 'id' but the A will have a fixed offset of +4. Then if A is +bounds-checked and found to be less than a PTR_TO_PACKET_END, the register B is +now known to have a safe range of at least 4 bytes. See 'Direct packet access', +below, for more on PTR_TO_PACKET ranges. + +The 'id' field is also used on PTR_TO_MAP_VALUE_OR_NULL, common to all copies of +the pointer returned from a map lookup. This means that when one copy is +checked and found to be non-NULL, all copies can become PTR_TO_MAP_VALUEs. +As well as range-checking, the tracked information is also used for enforcing +alignment of pointer accesses. For instance, on most systems the packet pointer +is 2 bytes after a 4-byte alignment. If a program adds 14 bytes to that to jump +over the Ethernet header, then reads IHL and addes (IHL * 4), the resulting +pointer will have a variable offset known to be 4n+2 for some n, so adding the 2 +bytes (NET_IP_ALIGN) gives a 4-byte alignment and so word-sized accesses through +that pointer are safe. +The 'id' field is also used on PTR_TO_SOCKET and PTR_TO_SOCKET_OR_NULL, common +to all copies of the pointer returned from a socket lookup. This has similar +behaviour to the handling for PTR_TO_MAP_VALUE_OR_NULL->PTR_TO_MAP_VALUE, but +it also handles reference tracking for the pointer. PTR_TO_SOCKET implicitly +represents a reference to the corresponding ``struct sock``. To ensure that the +reference is not leaked, it is imperative to NULL-check the reference and in +the non-NULL case, and pass the valid reference to the socket release function. + +Direct packet access +==================== + +In cls_bpf and act_bpf programs the verifier allows direct access to the packet +data via skb->data and skb->data_end pointers. +Ex:: + + 1: r4 = *(u32 *)(r1 +80) /* load skb->data_end */ + 2: r3 = *(u32 *)(r1 +76) /* load skb->data */ + 3: r5 = r3 + 4: r5 += 14 + 5: if r5 > r4 goto pc+16 + R1=ctx R3=pkt(id=0,off=0,r=14) R4=pkt_end R5=pkt(id=0,off=14,r=14) R10=fp + 6: r0 = *(u16 *)(r3 +12) /* access 12 and 13 bytes of the packet */ + +this 2byte load from the packet is safe to do, since the program author +did check ``if (skb->data + 14 > skb->data_end) goto err`` at insn #5 which +means that in the fall-through case the register R3 (which points to skb->data) +has at least 14 directly accessible bytes. The verifier marks it +as R3=pkt(id=0,off=0,r=14). +id=0 means that no additional variables were added to the register. +off=0 means that no additional constants were added. +r=14 is the range of safe access which means that bytes [R3, R3 + 14) are ok. +Note that R5 is marked as R5=pkt(id=0,off=14,r=14). It also points +to the packet data, but constant 14 was added to the register, so +it now points to ``skb->data + 14`` and accessible range is [R5, R5 + 14 - 14) +which is zero bytes. + +More complex packet access may look like:: + + + R0=inv1 R1=ctx R3=pkt(id=0,off=0,r=14) R4=pkt_end R5=pkt(id=0,off=14,r=14) R10=fp + 6: r0 = *(u8 *)(r3 +7) /* load 7th byte from the packet */ + 7: r4 = *(u8 *)(r3 +12) + 8: r4 *= 14 + 9: r3 = *(u32 *)(r1 +76) /* load skb->data */ + 10: r3 += r4 + 11: r2 = r1 + 12: r2 <<= 48 + 13: r2 >>= 48 + 14: r3 += r2 + 15: r2 = r3 + 16: r2 += 8 + 17: r1 = *(u32 *)(r1 +80) /* load skb->data_end */ + 18: if r2 > r1 goto pc+2 + R0=inv(id=0,umax_value=255,var_off=(0x0; 0xff)) R1=pkt_end R2=pkt(id=2,off=8,r=8) R3=pkt(id=2,off=0,r=8) R4=inv(id=0,umax_value=3570,var_off=(0x0; 0xfffe)) R5=pkt(id=0,off=14,r=14) R10=fp + 19: r1 = *(u8 *)(r3 +4) + +The state of the register R3 is R3=pkt(id=2,off=0,r=8) +id=2 means that two ``r3 += rX`` instructions were seen, so r3 points to some +offset within a packet and since the program author did +``if (r3 + 8 > r1) goto err`` at insn #18, the safe range is [R3, R3 + 8). +The verifier only allows 'add'/'sub' operations on packet registers. Any other +operation will set the register state to 'SCALAR_VALUE' and it won't be +available for direct packet access. + +Operation ``r3 += rX`` may overflow and become less than original skb->data, +therefore the verifier has to prevent that. So when it sees ``r3 += rX`` +instruction and rX is more than 16-bit value, any subsequent bounds-check of r3 +against skb->data_end will not give us 'range' information, so attempts to read +through the pointer will give "invalid access to packet" error. + +Ex. after insn ``r4 = *(u8 *)(r3 +12)`` (insn #7 above) the state of r4 is +R4=inv(id=0,umax_value=255,var_off=(0x0; 0xff)) which means that upper 56 bits +of the register are guaranteed to be zero, and nothing is known about the lower +8 bits. After insn ``r4 *= 14`` the state becomes +R4=inv(id=0,umax_value=3570,var_off=(0x0; 0xfffe)), since multiplying an 8-bit +value by constant 14 will keep upper 52 bits as zero, also the least significant +bit will be zero as 14 is even. Similarly ``r2 >>= 48`` will make +R2=inv(id=0,umax_value=65535,var_off=(0x0; 0xffff)), since the shift is not sign +extending. This logic is implemented in adjust_reg_min_max_vals() function, +which calls adjust_ptr_min_max_vals() for adding pointer to scalar (or vice +versa) and adjust_scalar_min_max_vals() for operations on two scalars. + +The end result is that bpf program author can access packet directly +using normal C code as:: + + void *data = (void *)(long)skb->data; + void *data_end = (void *)(long)skb->data_end; + struct eth_hdr *eth = data; + struct iphdr *iph = data + sizeof(*eth); + struct udphdr *udp = data + sizeof(*eth) + sizeof(*iph); + + if (data + sizeof(*eth) + sizeof(*iph) + sizeof(*udp) > data_end) + return 0; + if (eth->h_proto != htons(ETH_P_IP)) + return 0; + if (iph->protocol != IPPROTO_UDP || iph->ihl != 5) + return 0; + if (udp->dest == 53 || udp->source == 9) + ...; + +which makes such programs easier to write comparing to LD_ABS insn +and significantly faster. + +Pruning +======= + +The verifier does not actually walk all possible paths through the program. For +each new branch to analyse, the verifier looks at all the states it's previously +been in when at this instruction. If any of them contain the current state as a +subset, the branch is 'pruned' - that is, the fact that the previous state was +accepted implies the current state would be as well. For instance, if in the +previous state, r1 held a packet-pointer, and in the current state, r1 holds a +packet-pointer with a range as long or longer and at least as strict an +alignment, then r1 is safe. Similarly, if r2 was NOT_INIT before then it can't +have been used by any path from that point, so any value in r2 (including +another NOT_INIT) is safe. The implementation is in the function regsafe(). +Pruning considers not only the registers but also the stack (and any spilled +registers it may hold). They must all be safe for the branch to be pruned. +This is implemented in states_equal(). + +Understanding eBPF verifier messages +==================================== + +The following are few examples of invalid eBPF programs and verifier error +messages as seen in the log: + +Program with unreachable instructions:: + + static struct bpf_insn prog[] = { + BPF_EXIT_INSN(), + BPF_EXIT_INSN(), + }; + +Error: + + unreachable insn 1 + +Program that reads uninitialized register:: + + BPF_MOV64_REG(BPF_REG_0, BPF_REG_2), + BPF_EXIT_INSN(), + +Error:: + + 0: (bf) r0 = r2 + R2 !read_ok + +Program that doesn't initialize R0 before exiting:: + + BPF_MOV64_REG(BPF_REG_2, BPF_REG_1), + BPF_EXIT_INSN(), + +Error:: + + 0: (bf) r2 = r1 + 1: (95) exit + R0 !read_ok + +Program that accesses stack out of bounds:: + + BPF_ST_MEM(BPF_DW, BPF_REG_10, 8, 0), + BPF_EXIT_INSN(), + +Error:: + + 0: (7a) *(u64 *)(r10 +8) = 0 + invalid stack off=8 size=8 + +Program that doesn't initialize stack before passing its address into function:: + + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), + BPF_LD_MAP_FD(BPF_REG_1, 0), + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), + BPF_EXIT_INSN(), + +Error:: + + 0: (bf) r2 = r10 + 1: (07) r2 += -8 + 2: (b7) r1 = 0x0 + 3: (85) call 1 + invalid indirect read from stack off -8+0 size 8 + +Program that uses invalid map_fd=0 while calling to map_lookup_elem() function:: + + BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), + BPF_LD_MAP_FD(BPF_REG_1, 0), + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), + BPF_EXIT_INSN(), + +Error:: + + 0: (7a) *(u64 *)(r10 -8) = 0 + 1: (bf) r2 = r10 + 2: (07) r2 += -8 + 3: (b7) r1 = 0x0 + 4: (85) call 1 + fd 0 is not pointing to valid bpf_map + +Program that doesn't check return value of map_lookup_elem() before accessing +map element:: + + BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), + BPF_LD_MAP_FD(BPF_REG_1, 0), + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), + BPF_ST_MEM(BPF_DW, BPF_REG_0, 0, 0), + BPF_EXIT_INSN(), + +Error:: + + 0: (7a) *(u64 *)(r10 -8) = 0 + 1: (bf) r2 = r10 + 2: (07) r2 += -8 + 3: (b7) r1 = 0x0 + 4: (85) call 1 + 5: (7a) *(u64 *)(r0 +0) = 0 + R0 invalid mem access 'map_value_or_null' + +Program that correctly checks map_lookup_elem() returned value for NULL, but +accesses the memory with incorrect alignment:: + + BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), + BPF_LD_MAP_FD(BPF_REG_1, 0), + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), + BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1), + BPF_ST_MEM(BPF_DW, BPF_REG_0, 4, 0), + BPF_EXIT_INSN(), + +Error:: + + 0: (7a) *(u64 *)(r10 -8) = 0 + 1: (bf) r2 = r10 + 2: (07) r2 += -8 + 3: (b7) r1 = 1 + 4: (85) call 1 + 5: (15) if r0 == 0x0 goto pc+1 + R0=map_ptr R10=fp + 6: (7a) *(u64 *)(r0 +4) = 0 + misaligned access off 4 size 8 + +Program that correctly checks map_lookup_elem() returned value for NULL and +accesses memory with correct alignment in one side of 'if' branch, but fails +to do so in the other side of 'if' branch:: + + BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), + BPF_LD_MAP_FD(BPF_REG_1, 0), + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), + BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2), + BPF_ST_MEM(BPF_DW, BPF_REG_0, 0, 0), + BPF_EXIT_INSN(), + BPF_ST_MEM(BPF_DW, BPF_REG_0, 0, 1), + BPF_EXIT_INSN(), + +Error:: + + 0: (7a) *(u64 *)(r10 -8) = 0 + 1: (bf) r2 = r10 + 2: (07) r2 += -8 + 3: (b7) r1 = 1 + 4: (85) call 1 + 5: (15) if r0 == 0x0 goto pc+2 + R0=map_ptr R10=fp + 6: (7a) *(u64 *)(r0 +0) = 0 + 7: (95) exit + + from 5 to 8: R0=imm0 R10=fp + 8: (7a) *(u64 *)(r0 +0) = 1 + R0 invalid mem access 'imm' + +Program that performs a socket lookup then sets the pointer to NULL without +checking it:: + + BPF_MOV64_IMM(BPF_REG_2, 0), + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_2, -8), + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), + BPF_MOV64_IMM(BPF_REG_3, 4), + BPF_MOV64_IMM(BPF_REG_4, 0), + BPF_MOV64_IMM(BPF_REG_5, 0), + BPF_EMIT_CALL(BPF_FUNC_sk_lookup_tcp), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + +Error:: + + 0: (b7) r2 = 0 + 1: (63) *(u32 *)(r10 -8) = r2 + 2: (bf) r2 = r10 + 3: (07) r2 += -8 + 4: (b7) r3 = 4 + 5: (b7) r4 = 0 + 6: (b7) r5 = 0 + 7: (85) call bpf_sk_lookup_tcp#65 + 8: (b7) r0 = 0 + 9: (95) exit + Unreleased reference id=1, alloc_insn=7 + +Program that performs a socket lookup but does not NULL-check the returned +value:: + + BPF_MOV64_IMM(BPF_REG_2, 0), + BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_2, -8), + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), + BPF_MOV64_IMM(BPF_REG_3, 4), + BPF_MOV64_IMM(BPF_REG_4, 0), + BPF_MOV64_IMM(BPF_REG_5, 0), + BPF_EMIT_CALL(BPF_FUNC_sk_lookup_tcp), + BPF_EXIT_INSN(), + +Error:: + + 0: (b7) r2 = 0 + 1: (63) *(u32 *)(r10 -8) = r2 + 2: (bf) r2 = r10 + 3: (07) r2 += -8 + 4: (b7) r3 = 4 + 5: (b7) r4 = 0 + 6: (b7) r5 = 0 + 7: (85) call bpf_sk_lookup_tcp#65 + 8: (95) exit + Unreleased reference id=1, alloc_insn=7 diff --git a/Documentation/conf.py b/Documentation/conf.py index 17f7cee56987..76e5eb5cb62b 100644 --- a/Documentation/conf.py +++ b/Documentation/conf.py @@ -249,11 +249,16 @@ except ImportError: html_static_path = ['sphinx-static'] -html_context = { - 'css_files': [ - '_static/theme_overrides.css', - ], -} +html_css_files = [ + 'theme_overrides.css', +] + +if major <= 1 and minor < 8: + html_context = { + 'css_files': [ + '_static/theme_overrides.css', + ], + } # Add any extra paths that contain custom files (such as robots.txt or # .htaccess) here, relative to this directory. These files are copied diff --git a/Documentation/cpu-freq/core.rst b/Documentation/cpu-freq/core.rst index 33cb90bd1d8f..4ceef8e7217c 100644 --- a/Documentation/cpu-freq/core.rst +++ b/Documentation/cpu-freq/core.rst @@ -73,12 +73,12 @@ CPUFREQ_POSTCHANGE. The third argument is a struct cpufreq_freqs with the following values: -===== =========================== -cpu number of the affected CPU +====== ====================================== +policy a pointer to the struct cpufreq_policy old old frequency new new frequency flags flags of the cpufreq driver -===== =========================== +====== ====================================== 3. CPUFreq Table Generation with Operating Performance Point (OPP) ================================================================== diff --git a/Documentation/devicetree/bindings/net/can/allwinner,sun4i-a10-can.yaml b/Documentation/devicetree/bindings/net/can/allwinner,sun4i-a10-can.yaml index a95960ee3feb..c93fe9d3ea82 100644 --- a/Documentation/devicetree/bindings/net/can/allwinner,sun4i-a10-can.yaml +++ b/Documentation/devicetree/bindings/net/can/allwinner,sun4i-a10-can.yaml @@ -17,6 +17,7 @@ properties: - const: allwinner,sun7i-a20-can - const: allwinner,sun4i-a10-can - const: allwinner,sun4i-a10-can + - const: allwinner,sun8i-r40-can reg: maxItems: 1 @@ -27,6 +28,19 @@ properties: clocks: maxItems: 1 + resets: + maxItems: 1 + +if: + properties: + compatible: + contains: + const: allwinner,sun8i-r40-can + +then: + required: + - resets + required: - compatible - reg @@ -47,5 +61,15 @@ examples: interrupts = <GIC_SPI 26 IRQ_TYPE_LEVEL_HIGH>; clocks = <&ccu CLK_APB1_CAN>; }; + - | + #define RST_BUS_CAN 68 + #define CLK_BUS_CAN 91 + can1: can@1c2bc00 { + compatible = "allwinner,sun8i-r40-can"; + reg = <0x01c2bc00 0x400>; + interrupts = <GIC_SPI 26 IRQ_TYPE_LEVEL_HIGH>; + clocks = <&ccu CLK_BUS_CAN>; + resets = <&ccu RST_BUS_CAN>; + }; ... diff --git a/Documentation/devicetree/bindings/net/dsa/dsa-port.yaml b/Documentation/devicetree/bindings/net/dsa/dsa-port.yaml new file mode 100644 index 000000000000..702df848a71d --- /dev/null +++ b/Documentation/devicetree/bindings/net/dsa/dsa-port.yaml @@ -0,0 +1,77 @@ +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/net/dsa/dsa-port.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: Ethernet Switch port Device Tree Bindings + +maintainers: + - Andrew Lunn <andrew@lunn.ch> + - Florian Fainelli <f.fainelli@gmail.com> + - Vivien Didelot <vivien.didelot@gmail.com> + +description: + Ethernet switch port Description + +allOf: + - $ref: "http://devicetree.org/schemas/net/ethernet-controller.yaml#" + +properties: + reg: + description: Port number + + label: + description: + Describes the label associated with this port, which will become + the netdev name + $ref: /schemas/types.yaml#/definitions/string + + link: + description: + Should be a list of phandles to other switch's DSA port. This + port is used as the outgoing port towards the phandle ports. The + full routing information must be given, not just the one hop + routes to neighbouring switches + $ref: /schemas/types.yaml#/definitions/phandle-array + + ethernet: + description: + Should be a phandle to a valid Ethernet device node. This host + device is what the switch port is connected to + $ref: /schemas/types.yaml#/definitions/phandle + + dsa-tag-protocol: + description: + Instead of the default, the switch will use this tag protocol if + possible. Useful when a device supports multiple protocols and + the default is incompatible with the Ethernet device. + enum: + - dsa + - edsa + - ocelot + - ocelot-8021q + - seville + + phy-handle: true + + phy-mode: true + + fixed-link: true + + mac-address: true + + sfp: true + + managed: true + + rx-internal-delay-ps: true + + tx-internal-delay-ps: true + +required: + - reg + +additionalProperties: true + +... diff --git a/Documentation/devicetree/bindings/net/dsa/dsa.yaml b/Documentation/devicetree/bindings/net/dsa/dsa.yaml index 2ad7f79ad371..b9d48e357e77 100644 --- a/Documentation/devicetree/bindings/net/dsa/dsa.yaml +++ b/Documentation/devicetree/bindings/net/dsa/dsa.yaml @@ -46,65 +46,9 @@ patternProperties: type: object description: Ethernet switch ports - allOf: - - $ref: "http://devicetree.org/schemas/net/ethernet-controller.yaml#" + $ref: dsa-port.yaml# - properties: - reg: - description: Port number - - label: - description: - Describes the label associated with this port, which will become - the netdev name - $ref: /schemas/types.yaml#/definitions/string - - link: - description: - Should be a list of phandles to other switch's DSA port. This - port is used as the outgoing port towards the phandle ports. The - full routing information must be given, not just the one hop - routes to neighbouring switches - $ref: /schemas/types.yaml#/definitions/phandle-array - - ethernet: - description: - Should be a phandle to a valid Ethernet device node. This host - device is what the switch port is connected to - $ref: /schemas/types.yaml#/definitions/phandle - - dsa-tag-protocol: - description: - Instead of the default, the switch will use this tag protocol if - possible. Useful when a device supports multiple protocols and - the default is incompatible with the Ethernet device. - enum: - - dsa - - edsa - - ocelot - - ocelot-8021q - - seville - - phy-handle: true - - phy-mode: true - - fixed-link: true - - mac-address: true - - sfp: true - - managed: true - - rx-internal-delay-ps: true - - tx-internal-delay-ps: true - - required: - - reg - - additionalProperties: false + unevaluatedProperties: false oneOf: - required: diff --git a/Documentation/devicetree/bindings/net/dsa/qca8k.yaml b/Documentation/devicetree/bindings/net/dsa/qca8k.yaml index 48de0ace265d..89c21b289447 100644 --- a/Documentation/devicetree/bindings/net/dsa/qca8k.yaml +++ b/Documentation/devicetree/bindings/net/dsa/qca8k.yaml @@ -99,40 +99,9 @@ patternProperties: type: object description: Ethernet switch ports - properties: - reg: - description: Port number - - label: - description: - Describes the label associated with this port, which will become - the netdev name - $ref: /schemas/types.yaml#/definitions/string - - link: - description: - Should be a list of phandles to other switch's DSA port. This - port is used as the outgoing port towards the phandle ports. The - full routing information must be given, not just the one hop - routes to neighbouring switches - $ref: /schemas/types.yaml#/definitions/phandle-array - - ethernet: - description: - Should be a phandle to a valid Ethernet device node. This host - device is what the switch port is connected to - $ref: /schemas/types.yaml#/definitions/phandle - - phy-handle: true - - phy-mode: true - - fixed-link: true - - mac-address: true - - sfp: true + $ref: dsa-port.yaml# + properties: qca,sgmii-rxclk-falling-edge: $ref: /schemas/types.yaml#/definitions/flag description: @@ -154,10 +123,7 @@ patternProperties: SGMII on the QCA8337, it is advised to set this unless a communication issue is observed. - required: - - reg - - additionalProperties: false + unevaluatedProperties: false oneOf: - required: diff --git a/Documentation/devicetree/bindings/net/microchip,lan966x-switch.yaml b/Documentation/devicetree/bindings/net/microchip,lan966x-switch.yaml index d54dc183a033..5bee665d5fcf 100644 --- a/Documentation/devicetree/bindings/net/microchip,lan966x-switch.yaml +++ b/Documentation/devicetree/bindings/net/microchip,lan966x-switch.yaml @@ -56,12 +56,21 @@ properties: ethernet-ports: type: object + + properties: + '#address-cells': + const: 1 + '#size-cells': + const: 0 + + additionalProperties: false + patternProperties: "^port@[0-9a-f]+$": type: object - allOf: - - $ref: "http://devicetree.org/schemas/net/ethernet-controller.yaml#" + $ref: "/schemas/net/ethernet-controller.yaml#" + unevaluatedProperties: false properties: '#address-cells': diff --git a/Documentation/devicetree/bindings/net/vertexcom-mse102x.yaml b/Documentation/devicetree/bindings/net/vertexcom-mse102x.yaml new file mode 100644 index 000000000000..8156a9aeb589 --- /dev/null +++ b/Documentation/devicetree/bindings/net/vertexcom-mse102x.yaml @@ -0,0 +1,71 @@ +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) +%YAML 1.2 +--- +$id: "http://devicetree.org/schemas/net/vertexcom-mse102x.yaml#" +$schema: "http://devicetree.org/meta-schemas/core.yaml#" + +title: The Vertexcom MSE102x (SPI) Device Tree Bindings + +maintainers: + - Stefan Wahren <stefan.wahren@in-tech.com> + +description: + Vertexcom's MSE102x are a family of HomePlug GreenPHY chips. + They can be connected either via RGMII, RMII or SPI to a host CPU. + + In order to use a MSE102x chip as SPI device, it must be defined as + a child of an SPI master device in the device tree. + + More information can be found at + http://www.vertexcom.com/doc/MSE1022%20Product%20Brief.pdf + +allOf: + - $ref: ethernet-controller.yaml# + +properties: + compatible: + enum: + - vertexcom,mse1021 + - vertexcom,mse1022 + + reg: + maxItems: 1 + + interrupts: + maxItems: 1 + + spi-cpha: true + + spi-cpol: true + + spi-max-frequency: + minimum: 6000000 + maximum: 7142857 + +required: + - compatible + - reg + - interrupts + - spi-cpha + - spi-cpol + - spi-max-frequency + +additionalProperties: false + +examples: + - | + #include <dt-bindings/interrupt-controller/irq.h> + spi0 { + #address-cells = <1>; + #size-cells = <0>; + + ethernet@0 { + compatible = "vertexcom,mse1021"; + reg = <0>; + interrupt-parent = <&gpio>; + interrupts = <23 IRQ_TYPE_EDGE_RISING>; + spi-cpha; + spi-cpol; + spi-max-frequency = <7142857>; + }; + }; diff --git a/Documentation/devicetree/bindings/spi/spi-rockchip.yaml b/Documentation/devicetree/bindings/spi/spi-rockchip.yaml index 7f987e79337c..52a78a2e362e 100644 --- a/Documentation/devicetree/bindings/spi/spi-rockchip.yaml +++ b/Documentation/devicetree/bindings/spi/spi-rockchip.yaml @@ -33,6 +33,7 @@ properties: - rockchip,rk3328-spi - rockchip,rk3368-spi - rockchip,rk3399-spi + - rockchip,rk3568-spi - rockchip,rv1126-spi - const: rockchip,rk3066-spi diff --git a/Documentation/devicetree/bindings/vendor-prefixes.yaml b/Documentation/devicetree/bindings/vendor-prefixes.yaml index 5f4ca46bfb13..0d1679b4ff99 100644 --- a/Documentation/devicetree/bindings/vendor-prefixes.yaml +++ b/Documentation/devicetree/bindings/vendor-prefixes.yaml @@ -1274,6 +1274,8 @@ patternProperties: description: Variscite Ltd. "^vdl,.*": description: Van der Laan b.v. + "^vertexcom,.*": + description: Vertexcom Technologies, Inc. "^via,.*": description: VIA Technologies, Inc. "^videostrong,.*": diff --git a/Documentation/filesystems/cifs/ksmbd.rst b/Documentation/filesystems/cifs/ksmbd.rst index a1326157d53f..b0d354fd8066 100644 --- a/Documentation/filesystems/cifs/ksmbd.rst +++ b/Documentation/filesystems/cifs/ksmbd.rst @@ -50,11 +50,11 @@ ksmbd.mountd (user space daemon) -------------------------------- ksmbd.mountd is userspace process to, transfer user account and password that -are registered using ksmbd.adduser(part of utils for user space). Further it +are registered using ksmbd.adduser (part of utils for user space). Further it allows sharing information parameters that parsed from smb.conf to ksmbd in kernel. For the execution part it has a daemon which is continuously running and connected to the kernel interface using netlink socket, it waits for the -requests(dcerpc and share/user info). It handles RPC calls (at a minimum few +requests (dcerpc and share/user info). It handles RPC calls (at a minimum few dozen) that are most important for file server from NetShareEnum and NetServerGetInfo. Complete DCE/RPC response is prepared from the user space and passed over to the associated kernel thread for the client. @@ -154,11 +154,11 @@ Each layer 1. Enable all component prints # sudo ksmbd.control -d "all" -2. Enable one of components(smb, auth, vfs, oplock, ipc, conn, rdma) +2. Enable one of components (smb, auth, vfs, oplock, ipc, conn, rdma) # sudo ksmbd.control -d "smb" -3. Show what prints are enable. - # cat/sys/class/ksmbd-control/debug +3. Show what prints are enabled. + # cat /sys/class/ksmbd-control/debug [smb] auth vfs oplock ipc conn [rdma] 4. Disable prints: diff --git a/Documentation/filesystems/netfs_library.rst b/Documentation/filesystems/netfs_library.rst index bb68d39f03b7..375baca7edcd 100644 --- a/Documentation/filesystems/netfs_library.rst +++ b/Documentation/filesystems/netfs_library.rst @@ -1,7 +1,7 @@ .. SPDX-License-Identifier: GPL-2.0 ================================= -NETWORK FILESYSTEM HELPER LIBRARY +Network Filesystem Helper Library ================================= .. Contents: @@ -37,22 +37,22 @@ into a common call framework. The following services are provided: - * Handles transparent huge pages (THPs). + * Handle folios that span multiple pages. - * Insulates the netfs from VM interface changes. + * Insulate the netfs from VM interface changes. - * Allows the netfs to arbitrarily split reads up into pieces, even ones that - don't match page sizes or page alignments and that may cross pages. + * Allow the netfs to arbitrarily split reads up into pieces, even ones that + don't match folio sizes or folio alignments and that may cross folios. - * Allows the netfs to expand a readahead request in both directions to meet - its needs. + * Allow the netfs to expand a readahead request in both directions to meet its + needs. - * Allows the netfs to partially fulfil a read, which will then be resubmitted. + * Allow the netfs to partially fulfil a read, which will then be resubmitted. - * Handles local caching, allowing cached data and server-read data to be + * Handle local caching, allowing cached data and server-read data to be interleaved for a single request. - * Handles clearing of bufferage that aren't on the server. + * Handle clearing of bufferage that aren't on the server. * Handle retrying of reads that failed, switching reads from the cache to the server as necessary. @@ -70,22 +70,22 @@ Read Helper Functions Three read helpers are provided:: - * void netfs_readahead(struct readahead_control *ractl, - const struct netfs_read_request_ops *ops, - void *netfs_priv);`` - * int netfs_readpage(struct file *file, - struct page *page, - const struct netfs_read_request_ops *ops, - void *netfs_priv); - * int netfs_write_begin(struct file *file, - struct address_space *mapping, - loff_t pos, - unsigned int len, - unsigned int flags, - struct page **_page, - void **_fsdata, - const struct netfs_read_request_ops *ops, - void *netfs_priv); + void netfs_readahead(struct readahead_control *ractl, + const struct netfs_read_request_ops *ops, + void *netfs_priv); + int netfs_readpage(struct file *file, + struct folio *folio, + const struct netfs_read_request_ops *ops, + void *netfs_priv); + int netfs_write_begin(struct file *file, + struct address_space *mapping, + loff_t pos, + unsigned int len, + unsigned int flags, + struct folio **_folio, + void **_fsdata, + const struct netfs_read_request_ops *ops, + void *netfs_priv); Each corresponds to a VM operation, with the addition of a couple of parameters for the use of the read helpers: @@ -103,8 +103,8 @@ Both of these values will be stored into the read request structure. For ->readahead() and ->readpage(), the network filesystem should just jump into the corresponding read helper; whereas for ->write_begin(), it may be a little more complicated as the network filesystem might want to flush -conflicting writes or track dirty data and needs to put the acquired page if an -error occurs after calling the helper. +conflicting writes or track dirty data and needs to put the acquired folio if +an error occurs after calling the helper. The helpers manage the read request, calling back into the network filesystem through the suppplied table of operations. Waits will be performed as @@ -253,7 +253,7 @@ through which it can issue requests and negotiate:: void (*issue_op)(struct netfs_read_subrequest *subreq); bool (*is_still_valid)(struct netfs_read_request *rreq); int (*check_write_begin)(struct file *file, loff_t pos, unsigned len, - struct page *page, void **_fsdata); + struct folio *folio, void **_fsdata); void (*done)(struct netfs_read_request *rreq); void (*cleanup)(struct address_space *mapping, void *netfs_priv); }; @@ -313,13 +313,14 @@ The operations are as follows: There is no return value; the netfs_subreq_terminated() function should be called to indicate whether or not the operation succeeded and how much data - it transferred. The filesystem also should not deal with setting pages + it transferred. The filesystem also should not deal with setting folios uptodate, unlocking them or dropping their refs - the helpers need to deal with this as they have to coordinate with copying to the local cache. - Note that the helpers have the pages locked, but not pinned. It is possible - to use the ITER_XARRAY iov iterator to refer to the range of the inode that - is being operated upon without the need to allocate large bvec tables. + Note that the helpers have the folios locked, but not pinned. It is + possible to use the ITER_XARRAY iov iterator to refer to the range of the + inode that is being operated upon without the need to allocate large bvec + tables. * ``is_still_valid()`` @@ -330,15 +331,15 @@ The operations are as follows: * ``check_write_begin()`` [Optional] This is called from the netfs_write_begin() helper once it has - allocated/grabbed the page to be modified to allow the filesystem to flush + allocated/grabbed the folio to be modified to allow the filesystem to flush conflicting state before allowing it to be modified. - It should return 0 if everything is now fine, -EAGAIN if the page should be + It should return 0 if everything is now fine, -EAGAIN if the folio should be regrabbed and any other error code to abort the operation. * ``done`` - [Optional] This is called after the pages in the request have all been + [Optional] This is called after the folios in the request have all been unlocked (and marked uptodate if applicable). * ``cleanup`` @@ -390,7 +391,7 @@ The read helpers work by the following general procedure: * If NETFS_SREQ_CLEAR_TAIL was set, a short read will be cleared to the end of the slice instead of reissuing. - * Once the data is read, the pages that have been fully read/cleared: + * Once the data is read, the folios that have been fully read/cleared: * Will be marked uptodate. @@ -398,11 +399,11 @@ The read helpers work by the following general procedure: * Unlocked - * Any pages that need writing to the cache will then have DIO writes issued. + * Any folios that need writing to the cache will then have DIO writes issued. * Synchronous operations will wait for reading to be complete. - * Writes to the cache will proceed asynchronously and the pages will have the + * Writes to the cache will proceed asynchronously and the folios will have the PG_fscache mark removed when that completes. * The request structures will be cleaned up when everything has completed. @@ -452,6 +453,9 @@ operation table looks like the following:: netfs_io_terminated_t term_func, void *term_func_priv); + int (*prepare_write)(struct netfs_cache_resources *cres, + loff_t *_start, size_t *_len, loff_t i_size); + int (*write)(struct netfs_cache_resources *cres, loff_t start_pos, struct iov_iter *iter, @@ -509,6 +513,14 @@ The methods defined in the table are: indicating whether the termination is definitely happening in the caller's context. + * ``prepare_write()`` + + [Required] Called to adjust a write to the cache and check that there is + sufficient space in the cache. The start and length values indicate the + size of the write that netfslib is proposing, and this can be adjusted by + the cache to respect DIO boundaries. The file size is passed for + information. + * ``write()`` [Required] Called to write to the cache. The start file offset is given @@ -525,4 +537,9 @@ not the read request structure as they could be used in other situations where there isn't a read request structure as well, such as writing dirty data to the cache. + +API Function Reference +====================== + .. kernel-doc:: include/linux/netfs.h +.. kernel-doc:: fs/netfs/read_helper.c diff --git a/Documentation/locking/locktypes.rst b/Documentation/locking/locktypes.rst index ddada4a53749..4fd7b70fcde1 100644 --- a/Documentation/locking/locktypes.rst +++ b/Documentation/locking/locktypes.rst @@ -439,11 +439,9 @@ preemption. The following substitution works on both kernels:: spin_lock(&p->lock); p->count += this_cpu_read(var2); -On a non-PREEMPT_RT kernel migrate_disable() maps to preempt_disable() -which makes the above code fully equivalent. On a PREEMPT_RT kernel migrate_disable() ensures that the task is pinned on the current CPU which in turn guarantees that the per-CPU access to var1 and var2 are staying on -the same CPU. +the same CPU while the task remains preemptible. The migrate_disable() substitution is not valid for the following scenario:: @@ -456,9 +454,8 @@ scenario:: p = this_cpu_ptr(&var1); p->val = func2(); -While correct on a non-PREEMPT_RT kernel, this breaks on PREEMPT_RT because -here migrate_disable() does not protect against reentrancy from a -preempting task. A correct substitution for this case is:: +This breaks because migrate_disable() does not protect against reentrancy from +a preempting task. A correct substitution for this case is:: func() { diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst index ce2b8e8bb9ab..43cdc4d34745 100644 --- a/Documentation/networking/filter.rst +++ b/Documentation/networking/filter.rst @@ -6,6 +6,13 @@ Linux Socket Filtering aka Berkeley Packet Filter (BPF) ======================================================= +Notice +------ + +This file used to document the eBPF format and mechanisms even when not +related to socket filtering. The ../bpf/index.rst has more details +on eBPF. + Introduction ------------ @@ -617,15 +624,11 @@ format with similar underlying principles from BPF described in previous paragraphs is being used. However, the instruction set format is modelled closer to the underlying architecture to mimic native instruction sets, so that a better performance can be achieved (more details later). This new -ISA is called 'eBPF' or 'internal BPF' interchangeably. (Note: eBPF which +ISA is called eBPF. See the ../bpf/index.rst for details. (Note: eBPF which originates from [e]xtended BPF is not the same as BPF extensions! While eBPF is an ISA, BPF extensions date back to classic BPF's 'overloading' of BPF_LD | BPF_{B,H,W} | BPF_ABS instruction.) -It is designed to be JITed with one to one mapping, which can also open up -the possibility for GCC/LLVM compilers to generate optimized eBPF code through -an eBPF backend that performs almost as fast as natively compiled code. - The new instruction set was originally designed with the possible goal in mind to write programs in "restricted C" and compile into eBPF with a optional GCC/LLVM backend, so that it can just-in-time map to modern 64-bit CPUs with @@ -650,1032 +653,11 @@ Currently, the classic BPF format is being used for JITing on most sparc64, arm32, riscv64, riscv32 perform JIT compilation from eBPF instruction set. -Some core changes of the new internal format: - -- Number of registers increase from 2 to 10: - - The old format had two registers A and X, and a hidden frame pointer. The - new layout extends this to be 10 internal registers and a read-only frame - pointer. Since 64-bit CPUs are passing arguments to functions via registers - the number of args from eBPF program to in-kernel function is restricted - to 5 and one register is used to accept return value from an in-kernel - function. Natively, x86_64 passes first 6 arguments in registers, aarch64/ - sparcv9/mips64 have 7 - 8 registers for arguments; x86_64 has 6 callee saved - registers, and aarch64/sparcv9/mips64 have 11 or more callee saved registers. - - Therefore, eBPF calling convention is defined as: - - * R0 - return value from in-kernel function, and exit value for eBPF program - * R1 - R5 - arguments from eBPF program to in-kernel function - * R6 - R9 - callee saved registers that in-kernel function will preserve - * R10 - read-only frame pointer to access stack - - Thus, all eBPF registers map one to one to HW registers on x86_64, aarch64, - etc, and eBPF calling convention maps directly to ABIs used by the kernel on - 64-bit architectures. - - On 32-bit architectures JIT may map programs that use only 32-bit arithmetic - and may let more complex programs to be interpreted. - - R0 - R5 are scratch registers and eBPF program needs spill/fill them if - necessary across calls. Note that there is only one eBPF program (== one - eBPF main routine) and it cannot call other eBPF functions, it can only - call predefined in-kernel functions, though. - -- Register width increases from 32-bit to 64-bit: - - Still, the semantics of the original 32-bit ALU operations are preserved - via 32-bit subregisters. All eBPF registers are 64-bit with 32-bit lower - subregisters that zero-extend into 64-bit if they are being written to. - That behavior maps directly to x86_64 and arm64 subregister definition, but - makes other JITs more difficult. - - 32-bit architectures run 64-bit internal BPF programs via interpreter. - Their JITs may convert BPF programs that only use 32-bit subregisters into - native instruction set and let the rest being interpreted. - - Operation is 64-bit, because on 64-bit architectures, pointers are also - 64-bit wide, and we want to pass 64-bit values in/out of kernel functions, - so 32-bit eBPF registers would otherwise require to define register-pair - ABI, thus, there won't be able to use a direct eBPF register to HW register - mapping and JIT would need to do combine/split/move operations for every - register in and out of the function, which is complex, bug prone and slow. - Another reason is the use of atomic 64-bit counters. - -- Conditional jt/jf targets replaced with jt/fall-through: - - While the original design has constructs such as ``if (cond) jump_true; - else jump_false;``, they are being replaced into alternative constructs like - ``if (cond) jump_true; /* else fall-through */``. - -- Introduces bpf_call insn and register passing convention for zero overhead - calls from/to other kernel functions: - - Before an in-kernel function call, the internal BPF program needs to - place function arguments into R1 to R5 registers to satisfy calling - convention, then the interpreter will take them from registers and pass - to in-kernel function. If R1 - R5 registers are mapped to CPU registers - that are used for argument passing on given architecture, the JIT compiler - doesn't need to emit extra moves. Function arguments will be in the correct - registers and BPF_CALL instruction will be JITed as single 'call' HW - instruction. This calling convention was picked to cover common call - situations without performance penalty. - - After an in-kernel function call, R1 - R5 are reset to unreadable and R0 has - a return value of the function. Since R6 - R9 are callee saved, their state - is preserved across the call. - - For example, consider three C functions:: - - u64 f1() { return (*_f2)(1); } - u64 f2(u64 a) { return f3(a + 1, a); } - u64 f3(u64 a, u64 b) { return a - b; } - - GCC can compile f1, f3 into x86_64:: - - f1: - movl $1, %edi - movq _f2(%rip), %rax - jmp *%rax - f3: - movq %rdi, %rax - subq %rsi, %rax - ret - - Function f2 in eBPF may look like:: - - f2: - bpf_mov R2, R1 - bpf_add R1, 1 - bpf_call f3 - bpf_exit - - If f2 is JITed and the pointer stored to ``_f2``. The calls f1 -> f2 -> f3 and - returns will be seamless. Without JIT, __bpf_prog_run() interpreter needs to - be used to call into f2. - - For practical reasons all eBPF programs have only one argument 'ctx' which is - already placed into R1 (e.g. on __bpf_prog_run() startup) and the programs - can call kernel functions with up to 5 arguments. Calls with 6 or more arguments - are currently not supported, but these restrictions can be lifted if necessary - in the future. - - On 64-bit architectures all register map to HW registers one to one. For - example, x86_64 JIT compiler can map them as ... - - :: - - R0 - rax - R1 - rdi - R2 - rsi - R3 - rdx - R4 - rcx - R5 - r8 - R6 - rbx - R7 - r13 - R8 - r14 - R9 - r15 - R10 - rbp - - ... since x86_64 ABI mandates rdi, rsi, rdx, rcx, r8, r9 for argument passing - and rbx, r12 - r15 are callee saved. - - Then the following internal BPF pseudo-program:: - - bpf_mov R6, R1 /* save ctx */ - bpf_mov R2, 2 - bpf_mov R3, 3 - bpf_mov R4, 4 - bpf_mov R5, 5 - bpf_call foo - bpf_mov R7, R0 /* save foo() return value */ - bpf_mov R1, R6 /* restore ctx for next call */ - bpf_mov R2, 6 - bpf_mov R3, 7 - bpf_mov R4, 8 - bpf_mov R5, 9 - bpf_call bar - bpf_add R0, R7 - bpf_exit - - After JIT to x86_64 may look like:: - - push %rbp - mov %rsp,%rbp - sub $0x228,%rsp - mov %rbx,-0x228(%rbp) - mov %r13,-0x220(%rbp) - mov %rdi,%rbx - mov $0x2,%esi - mov $0x3,%edx - mov $0x4,%ecx - mov $0x5,%r8d - callq foo - mov %rax,%r13 - mov %rbx,%rdi - mov $0x6,%esi - mov $0x7,%edx - mov $0x8,%ecx - mov $0x9,%r8d - callq bar - add %r13,%rax - mov -0x228(%rbp),%rbx - mov -0x220(%rbp),%r13 - leaveq - retq - - Which is in this example equivalent in C to:: - - u64 bpf_filter(u64 ctx) - { - return foo(ctx, 2, 3, 4, 5) + bar(ctx, 6, 7, 8, 9); - } - - In-kernel functions foo() and bar() with prototype: u64 (*)(u64 arg1, u64 - arg2, u64 arg3, u64 arg4, u64 arg5); will receive arguments in proper - registers and place their return value into ``%rax`` which is R0 in eBPF. - Prologue and epilogue are emitted by JIT and are implicit in the - interpreter. R0-R5 are scratch registers, so eBPF program needs to preserve - them across the calls as defined by calling convention. - - For example the following program is invalid:: - - bpf_mov R1, 1 - bpf_call foo - bpf_mov R0, R1 - bpf_exit - - After the call the registers R1-R5 contain junk values and cannot be read. - An in-kernel eBPF verifier is used to validate internal BPF programs. - -Also in the new design, eBPF is limited to 4096 insns, which means that any -program will terminate quickly and will only call a fixed number of kernel -functions. Original BPF and the new format are two operand instructions, -which helps to do one-to-one mapping between eBPF insn and x86 insn during JIT. - -The input context pointer for invoking the interpreter function is generic, -its content is defined by a specific use case. For seccomp register R1 points -to seccomp_data, for converted BPF filters R1 points to a skb. - -A program, that is translated internally consists of the following elements:: - - op:16, jt:8, jf:8, k:32 ==> op:8, dst_reg:4, src_reg:4, off:16, imm:32 - -So far 87 internal BPF instructions were implemented. 8-bit 'op' opcode field -has room for new instructions. Some of them may use 16/24/32 byte encoding. New -instructions must be multiple of 8 bytes to preserve backward compatibility. - -Internal BPF is a general purpose RISC instruction set. Not every register and -every instruction are used during translation from original BPF to new format. -For example, socket filters are not using ``exclusive add`` instruction, but -tracing filters may do to maintain counters of events, for example. Register R9 -is not used by socket filters either, but more complex filters may be running -out of registers and would have to resort to spill/fill to stack. - -Internal BPF can be used as a generic assembler for last step performance -optimizations, socket filters and seccomp are using it as assembler. Tracing -filters may use it as assembler to generate code from kernel. In kernel usage -may not be bounded by security considerations, since generated internal BPF code -may be optimizing internal code path and not being exposed to the user space. -Safety of internal BPF can come from a verifier (TBD). In such use cases as -described, it may be used as safe instruction set. - -Just like the original BPF, the new format runs within a controlled environment, -is deterministic and the kernel can easily prove that. The safety of the program -can be determined in two steps: first step does depth-first-search to disallow -loops and other CFG validation; second step starts from the first insn and -descends all possible paths. It simulates execution of every insn and observes -the state change of registers and stack. - -eBPF opcode encoding --------------------- - -eBPF is reusing most of the opcode encoding from classic to simplify conversion -of classic BPF to eBPF. For arithmetic and jump instructions the 8-bit 'code' -field is divided into three parts:: - - +----------------+--------+--------------------+ - | 4 bits | 1 bit | 3 bits | - | operation code | source | instruction class | - +----------------+--------+--------------------+ - (MSB) (LSB) - -Three LSB bits store instruction class which is one of: - - =================== =============== - Classic BPF classes eBPF classes - =================== =============== - BPF_LD 0x00 BPF_LD 0x00 - BPF_LDX 0x01 BPF_LDX 0x01 - BPF_ST 0x02 BPF_ST 0x02 - BPF_STX 0x03 BPF_STX 0x03 - BPF_ALU 0x04 BPF_ALU 0x04 - BPF_JMP 0x05 BPF_JMP 0x05 - BPF_RET 0x06 BPF_JMP32 0x06 - BPF_MISC 0x07 BPF_ALU64 0x07 - =================== =============== - -When BPF_CLASS(code) == BPF_ALU or BPF_JMP, 4th bit encodes source operand ... - - :: - - BPF_K 0x00 - BPF_X 0x08 - - * in classic BPF, this means:: - - BPF_SRC(code) == BPF_X - use register X as source operand - BPF_SRC(code) == BPF_K - use 32-bit immediate as source operand - - * in eBPF, this means:: - - BPF_SRC(code) == BPF_X - use 'src_reg' register as source operand - BPF_SRC(code) == BPF_K - use 32-bit immediate as source operand - -... and four MSB bits store operation code. - -If BPF_CLASS(code) == BPF_ALU or BPF_ALU64 [ in eBPF ], BPF_OP(code) is one of:: - - BPF_ADD 0x00 - BPF_SUB 0x10 - BPF_MUL 0x20 - BPF_DIV 0x30 - BPF_OR 0x40 - BPF_AND 0x50 - BPF_LSH 0x60 - BPF_RSH 0x70 - BPF_NEG 0x80 - BPF_MOD 0x90 - BPF_XOR 0xa0 - BPF_MOV 0xb0 /* eBPF only: mov reg to reg */ - BPF_ARSH 0xc0 /* eBPF only: sign extending shift right */ - BPF_END 0xd0 /* eBPF only: endianness conversion */ - -If BPF_CLASS(code) == BPF_JMP or BPF_JMP32 [ in eBPF ], BPF_OP(code) is one of:: - - BPF_JA 0x00 /* BPF_JMP only */ - BPF_JEQ 0x10 - BPF_JGT 0x20 - BPF_JGE 0x30 - BPF_JSET 0x40 - BPF_JNE 0x50 /* eBPF only: jump != */ - BPF_JSGT 0x60 /* eBPF only: signed '>' */ - BPF_JSGE 0x70 /* eBPF only: signed '>=' */ - BPF_CALL 0x80 /* eBPF BPF_JMP only: function call */ - BPF_EXIT 0x90 /* eBPF BPF_JMP only: function return */ - BPF_JLT 0xa0 /* eBPF only: unsigned '<' */ - BPF_JLE 0xb0 /* eBPF only: unsigned '<=' */ - BPF_JSLT 0xc0 /* eBPF only: signed '<' */ - BPF_JSLE 0xd0 /* eBPF only: signed '<=' */ - -So BPF_ADD | BPF_X | BPF_ALU means 32-bit addition in both classic BPF -and eBPF. There are only two registers in classic BPF, so it means A += X. -In eBPF it means dst_reg = (u32) dst_reg + (u32) src_reg; similarly, -BPF_XOR | BPF_K | BPF_ALU means A ^= imm32 in classic BPF and analogous -src_reg = (u32) src_reg ^ (u32) imm32 in eBPF. - -Classic BPF is using BPF_MISC class to represent A = X and X = A moves. -eBPF is using BPF_MOV | BPF_X | BPF_ALU code instead. Since there are no -BPF_MISC operations in eBPF, the class 7 is used as BPF_ALU64 to mean -exactly the same operations as BPF_ALU, but with 64-bit wide operands -instead. So BPF_ADD | BPF_X | BPF_ALU64 means 64-bit addition, i.e.: -dst_reg = dst_reg + src_reg - -Classic BPF wastes the whole BPF_RET class to represent a single ``ret`` -operation. Classic BPF_RET | BPF_K means copy imm32 into return register -and perform function exit. eBPF is modeled to match CPU, so BPF_JMP | BPF_EXIT -in eBPF means function exit only. The eBPF program needs to store return -value into register R0 before doing a BPF_EXIT. Class 6 in eBPF is used as -BPF_JMP32 to mean exactly the same operations as BPF_JMP, but with 32-bit wide -operands for the comparisons instead. - -For load and store instructions the 8-bit 'code' field is divided as:: - - +--------+--------+-------------------+ - | 3 bits | 2 bits | 3 bits | - | mode | size | instruction class | - +--------+--------+-------------------+ - (MSB) (LSB) - -Size modifier is one of ... - -:: - - BPF_W 0x00 /* word */ - BPF_H 0x08 /* half word */ - BPF_B 0x10 /* byte */ - BPF_DW 0x18 /* eBPF only, double word */ - -... which encodes size of load/store operation:: - - B - 1 byte - H - 2 byte - W - 4 byte - DW - 8 byte (eBPF only) - -Mode modifier is one of:: - - BPF_IMM 0x00 /* used for 32-bit mov in classic BPF and 64-bit in eBPF */ - BPF_ABS 0x20 - BPF_IND 0x40 - BPF_MEM 0x60 - BPF_LEN 0x80 /* classic BPF only, reserved in eBPF */ - BPF_MSH 0xa0 /* classic BPF only, reserved in eBPF */ - BPF_ATOMIC 0xc0 /* eBPF only, atomic operations */ - -eBPF has two non-generic instructions: (BPF_ABS | <size> | BPF_LD) and -(BPF_IND | <size> | BPF_LD) which are used to access packet data. - -They had to be carried over from classic to have strong performance of -socket filters running in eBPF interpreter. These instructions can only -be used when interpreter context is a pointer to ``struct sk_buff`` and -have seven implicit operands. Register R6 is an implicit input that must -contain pointer to sk_buff. Register R0 is an implicit output which contains -the data fetched from the packet. Registers R1-R5 are scratch registers -and must not be used to store the data across BPF_ABS | BPF_LD or -BPF_IND | BPF_LD instructions. - -These instructions have implicit program exit condition as well. When -eBPF program is trying to access the data beyond the packet boundary, -the interpreter will abort the execution of the program. JIT compilers -therefore must preserve this property. src_reg and imm32 fields are -explicit inputs to these instructions. - -For example:: - - BPF_IND | BPF_W | BPF_LD means: - - R0 = ntohl(*(u32 *) (((struct sk_buff *) R6)->data + src_reg + imm32)) - and R1 - R5 were scratched. - -Unlike classic BPF instruction set, eBPF has generic load/store operations:: - - BPF_MEM | <size> | BPF_STX: *(size *) (dst_reg + off) = src_reg - BPF_MEM | <size> | BPF_ST: *(size *) (dst_reg + off) = imm32 - BPF_MEM | <size> | BPF_LDX: dst_reg = *(size *) (src_reg + off) - -Where size is one of: BPF_B or BPF_H or BPF_W or BPF_DW. - -It also includes atomic operations, which use the immediate field for extra -encoding:: - - .imm = BPF_ADD, .code = BPF_ATOMIC | BPF_W | BPF_STX: lock xadd *(u32 *)(dst_reg + off16) += src_reg - .imm = BPF_ADD, .code = BPF_ATOMIC | BPF_DW | BPF_STX: lock xadd *(u64 *)(dst_reg + off16) += src_reg - -The basic atomic operations supported are:: - - BPF_ADD - BPF_AND - BPF_OR - BPF_XOR - -Each having equivalent semantics with the ``BPF_ADD`` example, that is: the -memory location addresed by ``dst_reg + off`` is atomically modified, with -``src_reg`` as the other operand. If the ``BPF_FETCH`` flag is set in the -immediate, then these operations also overwrite ``src_reg`` with the -value that was in memory before it was modified. - -The more special operations are:: - - BPF_XCHG - -This atomically exchanges ``src_reg`` with the value addressed by ``dst_reg + -off``. :: - - BPF_CMPXCHG - -This atomically compares the value addressed by ``dst_reg + off`` with -``R0``. If they match it is replaced with ``src_reg``. In either case, the -value that was there before is zero-extended and loaded back to ``R0``. - -Note that 1 and 2 byte atomic operations are not supported. - -Clang can generate atomic instructions by default when ``-mcpu=v3`` is -enabled. If a lower version for ``-mcpu`` is set, the only atomic instruction -Clang can generate is ``BPF_ADD`` *without* ``BPF_FETCH``. If you need to enable -the atomics features, while keeping a lower ``-mcpu`` version, you can use -``-Xclang -target-feature -Xclang +alu32``. - -You may encounter ``BPF_XADD`` - this is a legacy name for ``BPF_ATOMIC``, -referring to the exclusive-add operation encoded when the immediate field is -zero. - -eBPF has one 16-byte instruction: ``BPF_LD | BPF_DW | BPF_IMM`` which consists -of two consecutive ``struct bpf_insn`` 8-byte blocks and interpreted as single -instruction that loads 64-bit immediate value into a dst_reg. -Classic BPF has similar instruction: ``BPF_LD | BPF_W | BPF_IMM`` which loads -32-bit immediate value into a register. - -eBPF verifier -------------- -The safety of the eBPF program is determined in two steps. - -First step does DAG check to disallow loops and other CFG validation. -In particular it will detect programs that have unreachable instructions. -(though classic BPF checker allows them) - -Second step starts from the first insn and descends all possible paths. -It simulates execution of every insn and observes the state change of -registers and stack. - -At the start of the program the register R1 contains a pointer to context -and has type PTR_TO_CTX. -If verifier sees an insn that does R2=R1, then R2 has now type -PTR_TO_CTX as well and can be used on the right hand side of expression. -If R1=PTR_TO_CTX and insn is R2=R1+R1, then R2=SCALAR_VALUE, -since addition of two valid pointers makes invalid pointer. -(In 'secure' mode verifier will reject any type of pointer arithmetic to make -sure that kernel addresses don't leak to unprivileged users) - -If register was never written to, it's not readable:: - - bpf_mov R0 = R2 - bpf_exit - -will be rejected, since R2 is unreadable at the start of the program. - -After kernel function call, R1-R5 are reset to unreadable and -R0 has a return type of the function. - -Since R6-R9 are callee saved, their state is preserved across the call. - -:: - - bpf_mov R6 = 1 - bpf_call foo - bpf_mov R0 = R6 - bpf_exit - -is a correct program. If there was R1 instead of R6, it would have -been rejected. - -load/store instructions are allowed only with registers of valid types, which -are PTR_TO_CTX, PTR_TO_MAP, PTR_TO_STACK. They are bounds and alignment checked. -For example:: - - bpf_mov R1 = 1 - bpf_mov R2 = 2 - bpf_xadd *(u32 *)(R1 + 3) += R2 - bpf_exit - -will be rejected, since R1 doesn't have a valid pointer type at the time of -execution of instruction bpf_xadd. - -At the start R1 type is PTR_TO_CTX (a pointer to generic ``struct bpf_context``) -A callback is used to customize verifier to restrict eBPF program access to only -certain fields within ctx structure with specified size and alignment. - -For example, the following insn:: - - bpf_ld R0 = *(u32 *)(R6 + 8) - -intends to load a word from address R6 + 8 and store it into R0 -If R6=PTR_TO_CTX, via is_valid_access() callback the verifier will know -that offset 8 of size 4 bytes can be accessed for reading, otherwise -the verifier will reject the program. -If R6=PTR_TO_STACK, then access should be aligned and be within -stack bounds, which are [-MAX_BPF_STACK, 0). In this example offset is 8, -so it will fail verification, since it's out of bounds. - -The verifier will allow eBPF program to read data from stack only after -it wrote into it. - -Classic BPF verifier does similar check with M[0-15] memory slots. -For example:: - - bpf_ld R0 = *(u32 *)(R10 - 4) - bpf_exit - -is invalid program. -Though R10 is correct read-only register and has type PTR_TO_STACK -and R10 - 4 is within stack bounds, there were no stores into that location. - -Pointer register spill/fill is tracked as well, since four (R6-R9) -callee saved registers may not be enough for some programs. - -Allowed function calls are customized with bpf_verifier_ops->get_func_proto() -The eBPF verifier will check that registers match argument constraints. -After the call register R0 will be set to return type of the function. - -Function calls is a main mechanism to extend functionality of eBPF programs. -Socket filters may let programs to call one set of functions, whereas tracing -filters may allow completely different set. - -If a function made accessible to eBPF program, it needs to be thought through -from safety point of view. The verifier will guarantee that the function is -called with valid arguments. - -seccomp vs socket filters have different security restrictions for classic BPF. -Seccomp solves this by two stage verifier: classic BPF verifier is followed -by seccomp verifier. In case of eBPF one configurable verifier is shared for -all use cases. - -See details of eBPF verifier in kernel/bpf/verifier.c - -Register value tracking ------------------------ -In order to determine the safety of an eBPF program, the verifier must track -the range of possible values in each register and also in each stack slot. -This is done with ``struct bpf_reg_state``, defined in include/linux/ -bpf_verifier.h, which unifies tracking of scalar and pointer values. Each -register state has a type, which is either NOT_INIT (the register has not been -written to), SCALAR_VALUE (some value which is not usable as a pointer), or a -pointer type. The types of pointers describe their base, as follows: - - - PTR_TO_CTX - Pointer to bpf_context. - CONST_PTR_TO_MAP - Pointer to struct bpf_map. "Const" because arithmetic - on these pointers is forbidden. - PTR_TO_MAP_VALUE - Pointer to the value stored in a map element. - PTR_TO_MAP_VALUE_OR_NULL - Either a pointer to a map value, or NULL; map accesses - (see section 'eBPF maps', below) return this type, - which becomes a PTR_TO_MAP_VALUE when checked != NULL. - Arithmetic on these pointers is forbidden. - PTR_TO_STACK - Frame pointer. - PTR_TO_PACKET - skb->data. - PTR_TO_PACKET_END - skb->data + headlen; arithmetic forbidden. - PTR_TO_SOCKET - Pointer to struct bpf_sock_ops, implicitly refcounted. - PTR_TO_SOCKET_OR_NULL - Either a pointer to a socket, or NULL; socket lookup - returns this type, which becomes a PTR_TO_SOCKET when - checked != NULL. PTR_TO_SOCKET is reference-counted, - so programs must release the reference through the - socket release function before the end of the program. - Arithmetic on these pointers is forbidden. - -However, a pointer may be offset from this base (as a result of pointer -arithmetic), and this is tracked in two parts: the 'fixed offset' and 'variable -offset'. The former is used when an exactly-known value (e.g. an immediate -operand) is added to a pointer, while the latter is used for values which are -not exactly known. The variable offset is also used in SCALAR_VALUEs, to track -the range of possible values in the register. - -The verifier's knowledge about the variable offset consists of: - -* minimum and maximum values as unsigned -* minimum and maximum values as signed - -* knowledge of the values of individual bits, in the form of a 'tnum': a u64 - 'mask' and a u64 'value'. 1s in the mask represent bits whose value is unknown; - 1s in the value represent bits known to be 1. Bits known to be 0 have 0 in both - mask and value; no bit should ever be 1 in both. For example, if a byte is read - into a register from memory, the register's top 56 bits are known zero, while - the low 8 are unknown - which is represented as the tnum (0x0; 0xff). If we - then OR this with 0x40, we get (0x40; 0xbf), then if we add 1 we get (0x0; - 0x1ff), because of potential carries. - -Besides arithmetic, the register state can also be updated by conditional -branches. For instance, if a SCALAR_VALUE is compared > 8, in the 'true' branch -it will have a umin_value (unsigned minimum value) of 9, whereas in the 'false' -branch it will have a umax_value of 8. A signed compare (with BPF_JSGT or -BPF_JSGE) would instead update the signed minimum/maximum values. Information -from the signed and unsigned bounds can be combined; for instance if a value is -first tested < 8 and then tested s> 4, the verifier will conclude that the value -is also > 4 and s< 8, since the bounds prevent crossing the sign boundary. - -PTR_TO_PACKETs with a variable offset part have an 'id', which is common to all -pointers sharing that same variable offset. This is important for packet range -checks: after adding a variable to a packet pointer register A, if you then copy -it to another register B and then add a constant 4 to A, both registers will -share the same 'id' but the A will have a fixed offset of +4. Then if A is -bounds-checked and found to be less than a PTR_TO_PACKET_END, the register B is -now known to have a safe range of at least 4 bytes. See 'Direct packet access', -below, for more on PTR_TO_PACKET ranges. - -The 'id' field is also used on PTR_TO_MAP_VALUE_OR_NULL, common to all copies of -the pointer returned from a map lookup. This means that when one copy is -checked and found to be non-NULL, all copies can become PTR_TO_MAP_VALUEs. -As well as range-checking, the tracked information is also used for enforcing -alignment of pointer accesses. For instance, on most systems the packet pointer -is 2 bytes after a 4-byte alignment. If a program adds 14 bytes to that to jump -over the Ethernet header, then reads IHL and addes (IHL * 4), the resulting -pointer will have a variable offset known to be 4n+2 for some n, so adding the 2 -bytes (NET_IP_ALIGN) gives a 4-byte alignment and so word-sized accesses through -that pointer are safe. -The 'id' field is also used on PTR_TO_SOCKET and PTR_TO_SOCKET_OR_NULL, common -to all copies of the pointer returned from a socket lookup. This has similar -behaviour to the handling for PTR_TO_MAP_VALUE_OR_NULL->PTR_TO_MAP_VALUE, but -it also handles reference tracking for the pointer. PTR_TO_SOCKET implicitly -represents a reference to the corresponding ``struct sock``. To ensure that the -reference is not leaked, it is imperative to NULL-check the reference and in -the non-NULL case, and pass the valid reference to the socket release function. - -Direct packet access --------------------- -In cls_bpf and act_bpf programs the verifier allows direct access to the packet -data via skb->data and skb->data_end pointers. -Ex:: - - 1: r4 = *(u32 *)(r1 +80) /* load skb->data_end */ - 2: r3 = *(u32 *)(r1 +76) /* load skb->data */ - 3: r5 = r3 - 4: r5 += 14 - 5: if r5 > r4 goto pc+16 - R1=ctx R3=pkt(id=0,off=0,r=14) R4=pkt_end R5=pkt(id=0,off=14,r=14) R10=fp - 6: r0 = *(u16 *)(r3 +12) /* access 12 and 13 bytes of the packet */ - -this 2byte load from the packet is safe to do, since the program author -did check ``if (skb->data + 14 > skb->data_end) goto err`` at insn #5 which -means that in the fall-through case the register R3 (which points to skb->data) -has at least 14 directly accessible bytes. The verifier marks it -as R3=pkt(id=0,off=0,r=14). -id=0 means that no additional variables were added to the register. -off=0 means that no additional constants were added. -r=14 is the range of safe access which means that bytes [R3, R3 + 14) are ok. -Note that R5 is marked as R5=pkt(id=0,off=14,r=14). It also points -to the packet data, but constant 14 was added to the register, so -it now points to ``skb->data + 14`` and accessible range is [R5, R5 + 14 - 14) -which is zero bytes. - -More complex packet access may look like:: - - - R0=inv1 R1=ctx R3=pkt(id=0,off=0,r=14) R4=pkt_end R5=pkt(id=0,off=14,r=14) R10=fp - 6: r0 = *(u8 *)(r3 +7) /* load 7th byte from the packet */ - 7: r4 = *(u8 *)(r3 +12) - 8: r4 *= 14 - 9: r3 = *(u32 *)(r1 +76) /* load skb->data */ - 10: r3 += r4 - 11: r2 = r1 - 12: r2 <<= 48 - 13: r2 >>= 48 - 14: r3 += r2 - 15: r2 = r3 - 16: r2 += 8 - 17: r1 = *(u32 *)(r1 +80) /* load skb->data_end */ - 18: if r2 > r1 goto pc+2 - R0=inv(id=0,umax_value=255,var_off=(0x0; 0xff)) R1=pkt_end R2=pkt(id=2,off=8,r=8) R3=pkt(id=2,off=0,r=8) R4=inv(id=0,umax_value=3570,var_off=(0x0; 0xfffe)) R5=pkt(id=0,off=14,r=14) R10=fp - 19: r1 = *(u8 *)(r3 +4) - -The state of the register R3 is R3=pkt(id=2,off=0,r=8) -id=2 means that two ``r3 += rX`` instructions were seen, so r3 points to some -offset within a packet and since the program author did -``if (r3 + 8 > r1) goto err`` at insn #18, the safe range is [R3, R3 + 8). -The verifier only allows 'add'/'sub' operations on packet registers. Any other -operation will set the register state to 'SCALAR_VALUE' and it won't be -available for direct packet access. - -Operation ``r3 += rX`` may overflow and become less than original skb->data, -therefore the verifier has to prevent that. So when it sees ``r3 += rX`` -instruction and rX is more than 16-bit value, any subsequent bounds-check of r3 -against skb->data_end will not give us 'range' information, so attempts to read -through the pointer will give "invalid access to packet" error. - -Ex. after insn ``r4 = *(u8 *)(r3 +12)`` (insn #7 above) the state of r4 is -R4=inv(id=0,umax_value=255,var_off=(0x0; 0xff)) which means that upper 56 bits -of the register are guaranteed to be zero, and nothing is known about the lower -8 bits. After insn ``r4 *= 14`` the state becomes -R4=inv(id=0,umax_value=3570,var_off=(0x0; 0xfffe)), since multiplying an 8-bit -value by constant 14 will keep upper 52 bits as zero, also the least significant -bit will be zero as 14 is even. Similarly ``r2 >>= 48`` will make -R2=inv(id=0,umax_value=65535,var_off=(0x0; 0xffff)), since the shift is not sign -extending. This logic is implemented in adjust_reg_min_max_vals() function, -which calls adjust_ptr_min_max_vals() for adding pointer to scalar (or vice -versa) and adjust_scalar_min_max_vals() for operations on two scalars. - -The end result is that bpf program author can access packet directly -using normal C code as:: - - void *data = (void *)(long)skb->data; - void *data_end = (void *)(long)skb->data_end; - struct eth_hdr *eth = data; - struct iphdr *iph = data + sizeof(*eth); - struct udphdr *udp = data + sizeof(*eth) + sizeof(*iph); - - if (data + sizeof(*eth) + sizeof(*iph) + sizeof(*udp) > data_end) - return 0; - if (eth->h_proto != htons(ETH_P_IP)) - return 0; - if (iph->protocol != IPPROTO_UDP || iph->ihl != 5) - return 0; - if (udp->dest == 53 || udp->source == 9) - ...; - -which makes such programs easier to write comparing to LD_ABS insn -and significantly faster. - -eBPF maps ---------- -'maps' is a generic storage of different types for sharing data between kernel -and userspace. - -The maps are accessed from user space via BPF syscall, which has commands: - -- create a map with given type and attributes - ``map_fd = bpf(BPF_MAP_CREATE, union bpf_attr *attr, u32 size)`` - using attr->map_type, attr->key_size, attr->value_size, attr->max_entries - returns process-local file descriptor or negative error - -- lookup key in a given map - ``err = bpf(BPF_MAP_LOOKUP_ELEM, union bpf_attr *attr, u32 size)`` - using attr->map_fd, attr->key, attr->value - returns zero and stores found elem into value or negative error - -- create or update key/value pair in a given map - ``err = bpf(BPF_MAP_UPDATE_ELEM, union bpf_attr *attr, u32 size)`` - using attr->map_fd, attr->key, attr->value - returns zero or negative error - -- find and delete element by key in a given map - ``err = bpf(BPF_MAP_DELETE_ELEM, union bpf_attr *attr, u32 size)`` - using attr->map_fd, attr->key - -- to delete map: close(fd) - Exiting process will delete maps automatically - -userspace programs use this syscall to create/access maps that eBPF programs -are concurrently updating. - -maps can have different types: hash, array, bloom filter, radix-tree, etc. - -The map is defined by: - - - type - - max number of elements - - key size in bytes - - value size in bytes - -Pruning -------- -The verifier does not actually walk all possible paths through the program. For -each new branch to analyse, the verifier looks at all the states it's previously -been in when at this instruction. If any of them contain the current state as a -subset, the branch is 'pruned' - that is, the fact that the previous state was -accepted implies the current state would be as well. For instance, if in the -previous state, r1 held a packet-pointer, and in the current state, r1 holds a -packet-pointer with a range as long or longer and at least as strict an -alignment, then r1 is safe. Similarly, if r2 was NOT_INIT before then it can't -have been used by any path from that point, so any value in r2 (including -another NOT_INIT) is safe. The implementation is in the function regsafe(). -Pruning considers not only the registers but also the stack (and any spilled -registers it may hold). They must all be safe for the branch to be pruned. -This is implemented in states_equal(). - -Understanding eBPF verifier messages ------------------------------------- - -The following are few examples of invalid eBPF programs and verifier error -messages as seen in the log: - -Program with unreachable instructions:: - - static struct bpf_insn prog[] = { - BPF_EXIT_INSN(), - BPF_EXIT_INSN(), - }; - -Error: - - unreachable insn 1 - -Program that reads uninitialized register:: - - BPF_MOV64_REG(BPF_REG_0, BPF_REG_2), - BPF_EXIT_INSN(), - -Error:: - - 0: (bf) r0 = r2 - R2 !read_ok - -Program that doesn't initialize R0 before exiting:: - - BPF_MOV64_REG(BPF_REG_2, BPF_REG_1), - BPF_EXIT_INSN(), - -Error:: - - 0: (bf) r2 = r1 - 1: (95) exit - R0 !read_ok - -Program that accesses stack out of bounds:: - - BPF_ST_MEM(BPF_DW, BPF_REG_10, 8, 0), - BPF_EXIT_INSN(), - -Error:: - - 0: (7a) *(u64 *)(r10 +8) = 0 - invalid stack off=8 size=8 - -Program that doesn't initialize stack before passing its address into function:: - - BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), - BPF_LD_MAP_FD(BPF_REG_1, 0), - BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), - BPF_EXIT_INSN(), - -Error:: - - 0: (bf) r2 = r10 - 1: (07) r2 += -8 - 2: (b7) r1 = 0x0 - 3: (85) call 1 - invalid indirect read from stack off -8+0 size 8 - -Program that uses invalid map_fd=0 while calling to map_lookup_elem() function:: - - BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), - BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), - BPF_LD_MAP_FD(BPF_REG_1, 0), - BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), - BPF_EXIT_INSN(), - -Error:: - - 0: (7a) *(u64 *)(r10 -8) = 0 - 1: (bf) r2 = r10 - 2: (07) r2 += -8 - 3: (b7) r1 = 0x0 - 4: (85) call 1 - fd 0 is not pointing to valid bpf_map - -Program that doesn't check return value of map_lookup_elem() before accessing -map element:: - - BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), - BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), - BPF_LD_MAP_FD(BPF_REG_1, 0), - BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), - BPF_ST_MEM(BPF_DW, BPF_REG_0, 0, 0), - BPF_EXIT_INSN(), - -Error:: - - 0: (7a) *(u64 *)(r10 -8) = 0 - 1: (bf) r2 = r10 - 2: (07) r2 += -8 - 3: (b7) r1 = 0x0 - 4: (85) call 1 - 5: (7a) *(u64 *)(r0 +0) = 0 - R0 invalid mem access 'map_value_or_null' - -Program that correctly checks map_lookup_elem() returned value for NULL, but -accesses the memory with incorrect alignment:: - - BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), - BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), - BPF_LD_MAP_FD(BPF_REG_1, 0), - BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), - BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1), - BPF_ST_MEM(BPF_DW, BPF_REG_0, 4, 0), - BPF_EXIT_INSN(), - -Error:: - - 0: (7a) *(u64 *)(r10 -8) = 0 - 1: (bf) r2 = r10 - 2: (07) r2 += -8 - 3: (b7) r1 = 1 - 4: (85) call 1 - 5: (15) if r0 == 0x0 goto pc+1 - R0=map_ptr R10=fp - 6: (7a) *(u64 *)(r0 +4) = 0 - misaligned access off 4 size 8 - -Program that correctly checks map_lookup_elem() returned value for NULL and -accesses memory with correct alignment in one side of 'if' branch, but fails -to do so in the other side of 'if' branch:: - - BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), - BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), - BPF_LD_MAP_FD(BPF_REG_1, 0), - BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), - BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2), - BPF_ST_MEM(BPF_DW, BPF_REG_0, 0, 0), - BPF_EXIT_INSN(), - BPF_ST_MEM(BPF_DW, BPF_REG_0, 0, 1), - BPF_EXIT_INSN(), - -Error:: - - 0: (7a) *(u64 *)(r10 -8) = 0 - 1: (bf) r2 = r10 - 2: (07) r2 += -8 - 3: (b7) r1 = 1 - 4: (85) call 1 - 5: (15) if r0 == 0x0 goto pc+2 - R0=map_ptr R10=fp - 6: (7a) *(u64 *)(r0 +0) = 0 - 7: (95) exit - - from 5 to 8: R0=imm0 R10=fp - 8: (7a) *(u64 *)(r0 +0) = 1 - R0 invalid mem access 'imm' - -Program that performs a socket lookup then sets the pointer to NULL without -checking it:: - - BPF_MOV64_IMM(BPF_REG_2, 0), - BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_2, -8), - BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), - BPF_MOV64_IMM(BPF_REG_3, 4), - BPF_MOV64_IMM(BPF_REG_4, 0), - BPF_MOV64_IMM(BPF_REG_5, 0), - BPF_EMIT_CALL(BPF_FUNC_sk_lookup_tcp), - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_EXIT_INSN(), - -Error:: - - 0: (b7) r2 = 0 - 1: (63) *(u32 *)(r10 -8) = r2 - 2: (bf) r2 = r10 - 3: (07) r2 += -8 - 4: (b7) r3 = 4 - 5: (b7) r4 = 0 - 6: (b7) r5 = 0 - 7: (85) call bpf_sk_lookup_tcp#65 - 8: (b7) r0 = 0 - 9: (95) exit - Unreleased reference id=1, alloc_insn=7 - -Program that performs a socket lookup but does not NULL-check the returned -value:: - - BPF_MOV64_IMM(BPF_REG_2, 0), - BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_2, -8), - BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), - BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), - BPF_MOV64_IMM(BPF_REG_3, 4), - BPF_MOV64_IMM(BPF_REG_4, 0), - BPF_MOV64_IMM(BPF_REG_5, 0), - BPF_EMIT_CALL(BPF_FUNC_sk_lookup_tcp), - BPF_EXIT_INSN(), - -Error:: - - 0: (b7) r2 = 0 - 1: (63) *(u32 *)(r10 -8) = r2 - 2: (bf) r2 = r10 - 3: (07) r2 += -8 - 4: (b7) r3 = 4 - 5: (b7) r4 = 0 - 6: (b7) r5 = 0 - 7: (85) call bpf_sk_lookup_tcp#65 - 8: (95) exit - Unreleased reference id=1, alloc_insn=7 - Testing ------- Next to the BPF toolchain, the kernel also ships a test module that contains -various test cases for classic and internal BPF that can be executed against +various test cases for classic and eBPF that can be executed against the BPF interpreter and JIT compiler. It can be found in lib/test_bpf.c and enabled via Kconfig:: diff --git a/Documentation/process/changes.rst b/Documentation/process/changes.rst index b398b8576417..cf908d79666e 100644 --- a/Documentation/process/changes.rst +++ b/Documentation/process/changes.rst @@ -35,6 +35,7 @@ GNU make 3.81 make --version binutils 2.23 ld -v flex 2.5.35 flex --version bison 2.0 bison --version +pahole 1.16 pahole --version util-linux 2.10o fdformat --version kmod 13 depmod -V e2fsprogs 1.41.4 e2fsck -V @@ -108,6 +109,16 @@ Bison Since Linux 4.16, the build system generates parsers during build. This requires bison 2.0 or later. +pahole: +------- + +Since Linux 5.2, if CONFIG_DEBUG_INFO_BTF is selected, the build system +generates BTF (BPF Type Format) from DWARF in vmlinux, a bit later from kernel +modules as well. This requires pahole v1.16 or later. + +It is found in the 'dwarves' or 'pahole' distro packages or from +https://fedorapeople.org/~acme/dwarves/. + Perl ---- diff --git a/Documentation/process/submitting-patches.rst b/Documentation/process/submitting-patches.rst index da085d63af9b..6b3aaed66fba 100644 --- a/Documentation/process/submitting-patches.rst +++ b/Documentation/process/submitting-patches.rst @@ -14,7 +14,8 @@ works, see Documentation/process/development-process.rst. Also, read Documentation/process/submit-checklist.rst for a list of items to check before submitting code. If you are submitting a driver, also read Documentation/process/submitting-drivers.rst; for device -tree binding patches, read Documentation/process/submitting-patches.rst. +tree binding patches, read +Documentation/devicetree/bindings/submitting-patches.rst. This documentation assumes that you're using ``git`` to prepare your patches. If you're unfamiliar with ``git``, you would be well-advised to learn how to |