diff options
Diffstat (limited to 'Documentation/networking/filter.txt')
| -rw-r--r-- | Documentation/networking/filter.txt | 31 |
1 files changed, 17 insertions, 14 deletions
diff --git a/Documentation/networking/filter.txt b/Documentation/networking/filter.txt index 2196b824e96c..b5e060edfc38 100644 --- a/Documentation/networking/filter.txt +++ b/Documentation/networking/filter.txt @@ -464,10 +464,11 @@ breakpoints: 0 1 JIT compiler ------------ -The Linux kernel has a built-in BPF JIT compiler for x86_64, SPARC, PowerPC, -ARM, ARM64, MIPS and s390 and can be enabled through CONFIG_BPF_JIT. The JIT -compiler is transparently invoked for each attached filter from user space -or for internal kernel users if it has been previously enabled by root: +The Linux kernel has a built-in BPF JIT compiler for x86_64, SPARC, +PowerPC, ARM, ARM64, MIPS, RISC-V and s390 and can be enabled through +CONFIG_BPF_JIT. The JIT compiler is transparently invoked for each +attached filter from user space or for internal kernel users if it has +been previously enabled by root: echo 1 > /proc/sys/net/core/bpf_jit_enable @@ -603,9 +604,10 @@ got from bpf_prog_create(), and 'ctx' the given context (e.g. skb pointer). All constraints and restrictions from bpf_check_classic() apply before a conversion to the new layout is being done behind the scenes! -Currently, the classic BPF format is being used for JITing on most 32-bit -architectures, whereas x86-64, aarch64, s390x, powerpc64, sparc64, arm32 perform -JIT compilation from eBPF instruction set. +Currently, the classic BPF format is being used for JITing on most +32-bit architectures, whereas x86-64, aarch64, s390x, powerpc64, +sparc64, arm32, riscv (RV64G) perform JIT compilation from eBPF +instruction set. Some core changes of the new internal format: @@ -865,7 +867,7 @@ Three LSB bits store instruction class which is one of: BPF_STX 0x03 BPF_STX 0x03 BPF_ALU 0x04 BPF_ALU 0x04 BPF_JMP 0x05 BPF_JMP 0x05 - BPF_RET 0x06 [ class 6 unused, for future if needed ] + 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 ... @@ -902,9 +904,9 @@ If BPF_CLASS(code) == BPF_ALU or BPF_ALU64 [ in eBPF ], BPF_OP(code) is one of: BPF_ARSH 0xc0 /* eBPF only: sign extending shift right */ BPF_END 0xd0 /* eBPF only: endianness conversion */ -If BPF_CLASS(code) == BPF_JMP, BPF_OP(code) is one of: +If BPF_CLASS(code) == BPF_JMP or BPF_JMP32 [ in eBPF ], BPF_OP(code) is one of: - BPF_JA 0x00 + BPF_JA 0x00 /* BPF_JMP only */ BPF_JEQ 0x10 BPF_JGT 0x20 BPF_JGE 0x30 @@ -912,8 +914,8 @@ If BPF_CLASS(code) == BPF_JMP, BPF_OP(code) is one of: BPF_JNE 0x50 /* eBPF only: jump != */ BPF_JSGT 0x60 /* eBPF only: signed '>' */ BPF_JSGE 0x70 /* eBPF only: signed '>=' */ - BPF_CALL 0x80 /* eBPF only: function call */ - BPF_EXIT 0x90 /* eBPF only: function return */ + 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 '<' */ @@ -936,8 +938,9 @@ 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 currently -unused and reserved for future use. +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: |