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2025-07-03bpf: Reduce stack frame size by using env->insn_buf for bpf insnsYonghong Song
Arnd Bergmann reported an issue ([1]) where clang compiler (less than llvm18) may trigger an error where the stack frame size exceeds the limit. I can reproduce the error like below: kernel/bpf/verifier.c:24491:5: error: stack frame size (2552) exceeds limit (1280) in 'bpf_check' [-Werror,-Wframe-larger-than] kernel/bpf/verifier.c:19921:12: error: stack frame size (1368) exceeds limit (1280) in 'do_check' [-Werror,-Wframe-larger-than] Use env->insn_buf for bpf insns instead of putting these insns on the stack. This can resolve the above 'bpf_check' error. The 'do_check' error will be resolved in the next patch. [1] https://lore.kernel.org/bpf/20250620113846.3950478-1-arnd@kernel.org/ Reported-by: Arnd Bergmann <arnd@kernel.org> Tested-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Jiri Olsa <jolsa@kernel.org> Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/r/20250703141111.1484521-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-03bpf: Simplify assignment to struct bpf_insn pointer in do_misc_fixups()Yonghong Song
In verifier.c, the following code patterns (in two places) struct bpf_insn *patch = &insn_buf[0]; can be simplified to struct bpf_insn *patch = insn_buf; which is easier to understand. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/r/20250703141106.1483216-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-03bpf: Avoid warning on unexpected map for tail callPaul Chaignon
Before handling the tail call in record_func_key(), we check that the map is of the expected type and log a verifier error if it isn't. Such an error however doesn't indicate anything wrong with the verifier. The check for map<>func compatibility is done after record_func_key(), by check_map_func_compatibility(). Therefore, this patch logs the error as a typical reject instead of a verifier error. Fixes: d2e4c1e6c294 ("bpf: Constant map key tracking for prog array pokes") Fixes: 0df1a55afa83 ("bpf: Warn on internal verifier errors") Reported-by: syzbot+efb099d5833bca355e51@syzkaller.appspotmail.com Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com> Acked-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/1f395b74e73022e47e04a31735f258babf305420.1751578055.git.paul.chaignon@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-03Merge branch 'bpf-standard-streams'Alexei Starovoitov
Kumar Kartikeya Dwivedi says: ==================== BPF Standard Streams This set introduces a standard output interface with two streams, namely stdout and stderr, for BPF programs. The idea is that these streams will be written to by BPF programs and the kernel, and serve as standard interfaces for informing user space of any BPF runtime violations. Users can also utilize them for printing normal messages for debugging usage, as is the case with bpf_printk() and trace pipe interface. BPF programs and the kernel can use these streams to output messages. User space can dump these messages using bpftool. The stream interface itself is implemented using a lockless list, so that we can queue messages from any context. Every printk statement into the stream leads to memory allocation. Allocation itself relies on try_alloc_pages() to construct a bespoke bump allocator to carve out elements. If this fails, we finally give up and drop the message. See commit logs for more details. Two scenarios are covered: - Deadlocks and timeouts in rqspinlock. - Timeouts for may_goto. In each we provide the stack trace and source information for the offending BPF programs. Both the C source line and the file and line numbers are printed. The output format is as follows: ERROR: AA or ABBA deadlock detected for bpf_res_spin_lock Attempted lock = 0xff11000108f3a5e0 Total held locks = 1 Held lock[ 0] = 0xff11000108f3a5e0 CPU: 48 UID: 0 PID: 786 Comm: test_progs Call trace: bpf_stream_stage_dump_stack+0xb0/0xd0 bpf_prog_report_rqspinlock_violation+0x10b/0x130 bpf_res_spin_lock+0x8c/0xa0 bpf_prog_3699ea119d1f6ed8_foo+0xe5/0x140 if (!bpf_res_spin_lock(&v2->lock)) @ stream_bpftool.c:62 bpf_prog_9b324ec4a1b2a5c0_stream_bpftool_dump_prog_stream+0x7e/0x2d0 foo(stream); @ stream_bpftool.c:93 bpf_prog_test_run_syscall+0x102/0x240 __sys_bpf+0xd68/0x2bf0 __x64_sys_bpf+0x1e/0x30 do_syscall_64+0x68/0x140 entry_SYSCALL_64_after_hwframe+0x76/0x7e ERROR: Timeout detected for may_goto instruction CPU: 48 UID: 0 PID: 786 Comm: test_progs Call trace: bpf_stream_stage_dump_stack+0xb0/0xd0 bpf_prog_report_may_goto_violation+0x6a/0x90 bpf_check_timed_may_goto+0x4d/0xa0 arch_bpf_timed_may_goto+0x21/0x40 bpf_prog_3699ea119d1f6ed8_foo+0x12f/0x140 while (can_loop) @ stream_bpftool.c:71 bpf_prog_9b324ec4a1b2a5c0_stream_bpftool_dump_prog_stream+0x7e/0x2d0 foo(stream); @ stream_bpftool.c:93 bpf_prog_test_run_syscall+0x102/0x240 __sys_bpf+0xd68/0x2bf0 __x64_sys_bpf+0x1e/0x30 do_syscall_64+0x68/0x140 entry_SYSCALL_64_after_hwframe+0x76/0x7e Changelog: ---------- v4 -> v5 v4: https://lore.kernel.org/bpf/20250702031737.407548-1-memxor@gmail.com * Add acks from Emil. * Address various nits. * Add extra failure tests. * Make deadlock test a little more robust to catch problems. v3 -> v4 v3: https://lore.kernel.org/bpf/20250624031252.2966759-1-memxor@gmail.com * Switch to alloc_pages_nolock(), avoid incorrect memcg accounting. (Alexei) * We will figure out proper accounting later. * Drop error limit logic, restrict stream capacity to 100,000 bytes. (Alexei) * Remove extra invocation of is_bpf_text_address(). (Jiri) * Avoid emitting NULL byte into the stream text, adjust regex in selftests. (Alexei) * Add comment around rcu_read_lock() for bpf_prog_ksym_find. (Alexei) * Tighten stream capacity check selftest. * Add acks from Andrii. v2 -> v3 v2: https://lore.kernel.org/bpf/20250524011849.681425-1-memxor@gmail.com * Fix bug when handling single element stream stage. (Eduard) * Move to mutex for protection of stream read and copy_to_user(). (Alexei) * Split bprintf refactor into its own patch. (Alexei) * Move kfunc definition to common_btf_ids to avoid initcall proliferation. (Alexei) * Return line number by reference in bpf_prog_get_file_line. (Alexei) * Remove NULL checks for BTF name pointer. (Alexei) * Add WARN_ON_ONCE(!rcu_read_lock_held()) in bpf_prog_ksym_find. (Eduard) * Remove hardcoded stream stage from macros. (Alexei, Eduard) * Move refactoring hunks to their own patch. (Alexei) * Add empty opts parameter for future extensibility to libbpf API. (Andrii, Eduard) * Add BPF_STREAM_{STDOUT,STDERR} to UAPI. (Andrii) * Add code to match on backtrace output. (Eduard) * Fix misc nits. * Add acks. v1 -> v2 v1: https://lore.kernel.org/bpf/20250507171720.1958296-1-memxor@gmail.com * Drop arena page fault prints, will be done as follow up. (Alexei) * Defer Andrii's request to reuse code and Alan's suggestion of error counts to follow up. * Drop bpf_dynptr_from_mem_slice patch. * Drop some acks due to heavy reworking. * Fix KASAN splat in bpf_prog_get_file_line. (Eduard) * Collapse bpf_prog_ksym_find and is_bpf_text_address into single call. (Eduard) * Add missing RCU read lock in bpf_prog_ksym_find. * Fix incorrect error handling in dump_stack_cb. * Simplify libbpf macro. (Eduard, Andrii) * Introduce bpf_prog_stream_read() libbpf API. (Eduard, Alexei, Andrii) * Drop BPF prog from the bpftool, use libbpf API. * Rework selftests. RFC v1 -> v1 RFC v1: https://lore.kernel.org/bpf/20250414161443.1146103-1-memxor@gmail.com * Rebase on bpf-next/master. * Change output in dump_stack to also print source line. (Alexei) * Simplify API to single pop() operation. (Eduard, Alexei) * Add kdoc for bpf_dynptr_from_mem_slice. * Fix -EINVAL returned from prog_dump_stream. (Eduard) * Split dump_stack() patch into multiple commits. * Add macro wrapping stream staging API. * Change bpftool command from dump to tracelog. (Quentin) * Add bpftool documentation and bash completion. (Quentin) * Change license of bpftool to Dual BSD/GPL. * Simplify memory allocator. (Alexei) * No overflow into second page. * Remove bpf_mem_alloc() fallback. * Symlink bpftool BPF program and exercise as selftest. (Eduard) * Verify output after dumping from ringbuf. (Eduard) * More failure cases to check API invariants. * Remove patches for dynptr lifetime fixes (split into separate set). * Limit maximum error messages, and add stream capacity. (Eduard) ==================== Link: https://patch.msgid.link/20250703204818.925464-1-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-03selftests/bpf: Add tests for prog streamsKumar Kartikeya Dwivedi
Add selftests to stress test the various facets of the stream API, memory allocation pattern, and ensuring dumping support is tested and functional. Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20250703204818.925464-13-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-03bpftool: Add support for dumping streamsKumar Kartikeya Dwivedi
Add support for printing the BPF stream contents of a program in bpftool. The new bpftool prog tracelog command is extended to take stdout and stderr arguments, and then the prog specification. The bpf_prog_stream_read() API added in previous patch is simply reused to grab data and then it is dumped to the respective file. The stdout data is sent to stdout, and stderr is printed to stderr. Cc: Quentin Monnet <qmo@kernel.org> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20250703204818.925464-12-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-03libbpf: Introduce bpf_prog_stream_read() APIKumar Kartikeya Dwivedi
Introduce a libbpf API so that users can read data from a given BPF stream for a BPF prog fd. For now, only the low-level syscall wrapper is provided, we can add a bpf_program__* accessor as a follow up if needed. Acked-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20250703204818.925464-11-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-03libbpf: Add bpf_stream_printk() macroKumar Kartikeya Dwivedi
Add a convenience macro to print data to the BPF streams. BPF_STDOUT and BPF_STDERR stream IDs in the vmlinux.h can be passed to the macro to print to the respective streams. Acked-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20250703204818.925464-10-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-03bpf: Report rqspinlock deadlocks/timeout to BPF stderrKumar Kartikeya Dwivedi
Begin reporting rqspinlock deadlocks and timeout to BPF program's stderr. Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20250703204818.925464-9-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-03bpf: Report may_goto timeout to BPF stderrKumar Kartikeya Dwivedi
Begin reporting may_goto timeouts to BPF program's stderr stream. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20250703204818.925464-8-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-03bpf: Add dump_stack() analogue to print to BPF stderrKumar Kartikeya Dwivedi
Introduce a kernel function which is the analogue of dump_stack() printing some useful information and the stack trace. This is not exposed to BPF programs yet, but can be made available in the future. When we have a program counter for a BPF program in the stack trace, also additionally output the filename and line number to make the trace helpful. The rest of the trace can be passed into ./decode_stacktrace.sh to obtain the line numbers for kernel symbols. Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20250703204818.925464-7-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-03bpf: Add function to find program from stack traceKumar Kartikeya Dwivedi
In preparation of figuring out the closest program that led to the current point in the kernel, implement a function that scans through the stack trace and finds out the closest BPF program when walking down the stack trace. Special care needs to be taken to skip over kernel and BPF subprog frames. We basically scan until we find a BPF main prog frame. The assumption is that if a program calls into us transitively, we'll hit it along the way. If not, we end up returning NULL. Contextually the function will be used in places where we know the program may have called into us. Due to reliance on arch_bpf_stack_walk(), this function only works on x86 with CONFIG_UNWINDER_ORC, arm64, and s390. Remove the warning from arch_bpf_stack_walk as well since we call it outside bpf_throw() context. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20250703204818.925464-6-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-03bpf: Ensure RCU lock is held around bpf_prog_ksym_findKumar Kartikeya Dwivedi
Add a warning to ensure RCU lock is held around tree lookup, and then fix one of the invocations in bpf_stack_walker. The program has an active stack frame and won't disappear. Use the opportunity to remove unneeded invocation of is_bpf_text_address. Fixes: f18b03fabaa9 ("bpf: Implement BPF exceptions") Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20250703204818.925464-5-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-03bpf: Add function to extract program source infoKumar Kartikeya Dwivedi
Prepare a function for use in future patches that can extract the file info, line info, and the source line number for a given BPF program provided it's program counter. Only the basename of the file path is provided, given it can be excessively long in some cases. This will be used in later patches to print source info to the BPF stream. Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20250703204818.925464-4-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-03bpf: Introduce BPF standard streamsKumar Kartikeya Dwivedi
Add support for a stream API to the kernel and expose related kfuncs to BPF programs. Two streams are exposed, BPF_STDOUT and BPF_STDERR. These can be used for printing messages that can be consumed from user space, thus it's similar in spirit to existing trace_pipe interface. The kernel will use the BPF_STDERR stream to notify the program of any errors encountered at runtime. BPF programs themselves may use both streams for writing debug messages. BPF library-like code may use BPF_STDERR to print warnings or errors on misuse at runtime. The implementation of a stream is as follows. Everytime a message is emitted from the kernel (directly, or through a BPF program), a record is allocated by bump allocating from per-cpu region backed by a page obtained using alloc_pages_nolock(). This ensures that we can allocate memory from any context. The eventual plan is to discard this scheme in favor of Alexei's kmalloc_nolock() [0]. This record is then locklessly inserted into a list (llist_add()) so that the printing side doesn't require holding any locks, and works in any context. Each stream has a maximum capacity of 4MB of text, and each printed message is accounted against this limit. Messages from a program are emitted using the bpf_stream_vprintk kfunc, which takes a stream_id argument in addition to working otherwise similar to bpf_trace_vprintk. The bprintf buffer helpers are extracted out to be reused for printing the string into them before copying it into the stream, so that we can (with the defined max limit) format a string and know its true length before performing allocations of the stream element. For consuming elements from a stream, we expose a bpf(2) syscall command named BPF_PROG_STREAM_READ_BY_FD, which allows reading data from the stream of a given prog_fd into a user space buffer. The main logic is implemented in bpf_stream_read(). The log messages are queued in bpf_stream::log by the bpf_stream_vprintk kfunc, and then pulled and ordered correctly in the stream backlog. For this purpose, we hold a lock around bpf_stream_backlog_peek(), as llist_del_first() (if we maintained a second lockless list for the backlog) wouldn't be safe from multiple threads anyway. Then, if we fail to find something in the backlog log, we splice out everything from the lockless log, and place it in the backlog log, and then return the head of the backlog. Once the full length of the element is consumed, we will pop it and free it. The lockless list bpf_stream::log is a LIFO stack. Elements obtained using a llist_del_all() operation are in LIFO order, thus would break the chronological ordering if printed directly. Hence, this batch of messages is first reversed. Then, it is stashed into a separate list in the stream, i.e. the backlog_log. The head of this list is the actual message that should always be returned to the caller. All of this is done in bpf_stream_backlog_fill(). From the kernel side, the writing into the stream will be a bit more involved than the typical printk. First, the kernel typically may print a collection of messages into the stream, and parallel writers into the stream may suffer from interleaving of messages. To ensure each group of messages is visible atomically, we can lift the advantage of using a lockless list for pushing in messages. To enable this, we add a bpf_stream_stage() macro, and require kernel users to use bpf_stream_printk statements for the passed expression to write into the stream. Underneath the macro, we have a message staging API, where a bpf_stream_stage object on the stack accumulates the messages being printed into a local llist_head, and then a commit operation splices the whole batch into the stream's lockless log list. This is especially pertinent for rqspinlock deadlock messages printed to program streams. After this change, we see each deadlock invocation as a non-interleaving contiguous message without any confusion on the reader's part, improving their user experience in debugging the fault. While programs cannot benefit from this staged stream writing API, they could just as well hold an rqspinlock around their print statements to serialize messages, hence this is kept kernel-internal for now. Overall, this infrastructure provides NMI-safe any context printing of messages to two dedicated streams. Later patches will add support for printing splats in case of BPF arena page faults, rqspinlock deadlocks, and cond_break timeouts, and integration of this facility into bpftool for dumping messages to user space. [0]: https://lore.kernel.org/bpf/20250501032718.65476-1-alexei.starovoitov@gmail.com Reviewed-by: Eduard Zingerman <eddyz87@gmail.com> Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20250703204818.925464-3-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-03bpf: Refactor bprintf buffer supportKumar Kartikeya Dwivedi
Refactor code to be able to get and put bprintf buffers and use bpf_printf_prepare independently. This will be used in the next patch to implement BPF streams support, particularly as a staging buffer for strings that need to be formatted and then allocated and pushed into a stream. Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20250703204818.925464-2-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-03bpf: Add show_fdinfo for kprobe_multiTao Chen
Show kprobe_multi link info with fdinfo, the info as follows: link_type: kprobe_multi link_id: 1 prog_tag: a69740b9746f7da8 prog_id: 21 kprobe_cnt: 8 missed: 0 cookie func 1 bpf_fentry_test1+0x0/0x20 7 bpf_fentry_test2+0x0/0x20 2 bpf_fentry_test3+0x0/0x20 3 bpf_fentry_test4+0x0/0x20 4 bpf_fentry_test5+0x0/0x20 5 bpf_fentry_test6+0x0/0x20 6 bpf_fentry_test7+0x0/0x20 8 bpf_fentry_test8+0x0/0x10 Signed-off-by: Tao Chen <chen.dylane@linux.dev> Link: https://lore.kernel.org/r/20250702153958.639852-3-chen.dylane@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-03bpf: Add show_fdinfo for uprobe_multiTao Chen
Show uprobe_multi link info with fdinfo, the info as follows: link_type: uprobe_multi link_id: 9 prog_tag: e729f789e34a8eca prog_id: 39 uprobe_cnt: 3 pid: 0 path: /home/dylane/bpf/tools/testing/selftests/bpf/test_progs cookie offset ref_ctr_offset 3 0xa69f13 0x0 1 0xa69f1e 0x0 2 0xa69f29 0x0 Signed-off-by: Tao Chen <chen.dylane@linux.dev> Link: https://lore.kernel.org/r/20250702153958.639852-2-chen.dylane@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-03bpf: Show precise link_type for {uprobe,kprobe}_multi fdinfoTao Chen
Alexei suggested, 'link_type' can be more precise and differentiate for human in fdinfo. In fact BPF_LINK_TYPE_KPROBE_MULTI includes kretprobe_multi type, the same as BPF_LINK_TYPE_UPROBE_MULTI, so we can show it more concretely. link_type: kprobe_multi link_id: 1 prog_tag: d2b307e915f0dd37 ... link_type: kretprobe_multi link_id: 2 prog_tag: ab9ea0545870781d ... link_type: uprobe_multi link_id: 9 prog_tag: e729f789e34a8eca ... link_type: uretprobe_multi link_id: 10 prog_tag: 7db356c03e61a4d4 Co-developed-by: Jiri Olsa <jolsa@kernel.org> Signed-off-by: Jiri Olsa <jolsa@kernel.org> Signed-off-by: Tao Chen <chen.dylane@linux.dev> Link: https://lore.kernel.org/r/20250702153958.639852-1-chen.dylane@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-03Merge branch 'bpf-add-bpf_dynptr_memset-kfunc'Andrii Nakryiko
Ihor Solodrai says: ==================== bpf: add bpf_dynptr_memset() kfunc Implement bpf_dynptr_memset() kfunc and add tests for it. v3->v4: * do error checks after slice, nits v2->v3: * nits and slow-path loop rewrite (Andrii) * simplify xdp chunks test (Mykyta) v1->v2: * handle non-linear buffers with bpf_dynptr_write() * change function signature to include offset arg * add more test cases v3: https://lore.kernel.org/bpf/20250630212113.573097-1-isolodrai@meta.com/ v2: https://lore.kernel.org/bpf/20250624205240.1311453-1-isolodrai@meta.com/ v1: https://lore.kernel.org/bpf/20250618223310.3684760-1-isolodrai@meta.com/ ==================== Link: https://patch.msgid.link/20250702210309.3115903-1-isolodrai@meta.com Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
2025-07-03selftests/bpf: Add test cases for bpf_dynptr_memset()Ihor Solodrai
Add tests to verify the behavior of bpf_dynptr_memset(): * normal memset 0 * normal memset non-0 * memset with an offset * memset in dynptr that was adjusted * error: size overflow * error: offset+size overflow * error: readonly dynptr * memset into non-linear xdp dynptr Signed-off-by: Ihor Solodrai <isolodrai@meta.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Mykyta Yatsenko <yatsenko@meta.com> Link: https://lore.kernel.org/bpf/20250702210309.3115903-3-isolodrai@meta.com
2025-07-03bpf: Add bpf_dynptr_memset() kfuncIhor Solodrai
Currently there is no straightforward way to fill dynptr memory with a value (most commonly zero). One can do it with bpf_dynptr_write(), but a temporary buffer is necessary for that. Implement bpf_dynptr_memset() - an analogue of memset() from libc. Signed-off-by: Ihor Solodrai <isolodrai@meta.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20250702210309.3115903-2-isolodrai@meta.com
2025-07-02selftests/bpf: Allow veristat compile standaloneMykyta Yatsenko
Veristat is synced into the standalone repo, where it compiles without kernel private dependencies. This patch fixes compilation errors in standalone veristat. Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20250702175622.358405-1-mykyta.yatsenko5@gmail.com
2025-07-02bpf: Avoid warning on multiple referenced args in callPaul Chaignon
The description of full helper calls in syzkaller [1] and the addition of kernel warnings in commit 0df1a55afa83 ("bpf: Warn on internal verifier errors") allowed syzbot to reach a verifier state that was thought to indicate a verifier bug [2]: 12: (85) call bpf_tcp_raw_gen_syncookie_ipv4#204 verifier bug: more than one arg with ref_obj_id R2 2 2 This error can be reproduced with the program from the previous commit: 0: (b7) r2 = 20 1: (b7) r3 = 0 2: (18) r1 = 0xffff92cee3cbc600 4: (85) call bpf_ringbuf_reserve#131 5: (55) if r0 == 0x0 goto pc+3 6: (bf) r1 = r0 7: (bf) r2 = r0 8: (85) call bpf_tcp_raw_gen_syncookie_ipv4#204 9: (95) exit bpf_tcp_raw_gen_syncookie_ipv4 expects R1 and R2 to be ARG_PTR_TO_FIXED_SIZE_MEM (with a size of at least sizeof(struct iphdr) for R1). R0 is a ring buffer payload of 20B and therefore matches this requirement. The verifier reaches the check on ref_obj_id while verifying R2 and rejects the program because the helper isn't supposed to take two referenced arguments. This case is a legitimate rejection and doesn't indicate a kernel bug, so we shouldn't log it as such and shouldn't emit a kernel warning. Link: https://github.com/google/syzkaller/pull/4313 [1] Link: https://lore.kernel.org/all/686491d6.a70a0220.3b7e22.20ea.GAE@google.com/T/ [2] Fixes: 457f44363a88 ("bpf: Implement BPF ring buffer and verifier support for it") Fixes: 0df1a55afa83 ("bpf: Warn on internal verifier errors") Reported-by: syzbot+69014a227f8edad4d8c6@syzkaller.appspotmail.com Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com> Link: https://lore.kernel.org/r/cd09afbfd7bef10bbc432d72693f78ffdc1e8ee5.1751463262.git.paul.chaignon@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
2025-07-02selftests/bpf: Negative test case for ref_obj_id in argsPaul Chaignon
This patch adds a test case, as shown below, for the verifier error "more than one arg with ref_obj_id". 0: (b7) r2 = 20 1: (b7) r3 = 0 2: (18) r1 = 0xffff92cee3cbc600 4: (85) call bpf_ringbuf_reserve#131 5: (55) if r0 == 0x0 goto pc+3 6: (bf) r1 = r0 7: (bf) r2 = r0 8: (85) call bpf_tcp_raw_gen_syncookie_ipv4#204 9: (95) exit This error is currently incorrectly reported as a verifier bug, with a warning. The next patch in this series will address that. Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com> Link: https://lore.kernel.org/r/3ba78e6cda47ccafd6ea70dadbc718d020154664.1751463262.git.paul.chaignon@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
2025-07-02selftests/bpf: null checks for rdonly_untrusted_mem should be preservedEduard Zingerman
Test case checking that verifier does not assume rdonly_untrusted_mem values as not null. Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20250702073620.897517-2-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
2025-07-02bpf: avoid jump misprediction for PTR_TO_MEM | PTR_UNTRUSTEDEduard Zingerman
Commit f2362a57aeff ("bpf: allow void* cast using bpf_rdonly_cast()") added a notion of PTR_TO_MEM | MEM_RDONLY | PTR_UNTRUSTED type. This simultaneously introduced a bug in jump prediction logic for situations like below: p = bpf_rdonly_cast(..., 0); if (p) a(); else b(); Here verifier would wrongly predict that else branch cannot be taken. This happens because: - Function reg_not_null() assumes that PTR_TO_MEM w/o PTR_MAYBE_NULL flag cannot be zero. - The call to bpf_rdonly_cast() returns a rdonly_untrusted_mem value w/o PTR_MAYBE_NULL flag. Tracking of PTR_MAYBE_NULL flag for untrusted PTR_TO_MEM does not make sense, as the main purpose of the flag is to catch null pointer access errors. Such errors are not possible on load of PTR_UNTRUSTED values and verifier makes sure that PTR_UNTRUSTED can't be passed to helpers or kfuncs. Hence, modify reg_not_null() to assume that nullness of untrusted PTR_TO_MEM is not known. Fixes: f2362a57aeff ("bpf: allow void* cast using bpf_rdonly_cast()") Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com> Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20250702073620.897517-1-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
2025-07-02selftests/bpf: Don't call fsopen() as privileged userMatteo Croce
In the BPF token example, the fsopen() syscall is called as privileged user. This is unneeded because fsopen() can be called also as unprivileged user from the user namespace. As the `fs_fd` file descriptor which was sent back and forth is still the same, keep it open instead of cloning and closing it twice via SCM_RIGHTS. cfr. https://github.com/systemd/systemd/pull/36134 Signed-off-by: Matteo Croce <teknoraver@meta.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Christian Brauner <brauner@kernel.org> Link: https://lore.kernel.org/bpf/20250701183123.31781-1-technoboy85@gmail.com
2025-07-01selftests/bpf: Fix spelling mistake "subtration" -> "subtraction"Colin Ian King
There are spelling mistakes in description text. Fix these. Signed-off-by: Colin Ian King <colin.i.king@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20250630125528.563077-1-colin.i.king@gmail.com
2025-07-01selftests/bpf: Enable dynptr/test_probe_read_user_str_dynptrMykyta Yatsenko
Enable previously disabled dynptr/test_probe_read_user_str_dynptr test, after the fix it depended on was merged into bpf-next. Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/bpf/20250630133515.1108325-1-mykyta.yatsenko5@gmail.com
2025-07-01bpf: Warn on internal verifier errorsPaul Chaignon
This patch is a follow up to commit 1cb0f56d9618 ("bpf: WARN_ONCE on verifier bugs"). It generalizes the use of verifier_error throughout the verifier, in particular for logs previously marked "verifier internal error". As a consequence, all of those verifier bugs will now come with a kernel warning (under CONFIG_DBEUG_KERNEL) detectable by fuzzers. While at it, some error messages that were too generic (ex., "bpf verifier is misconfigured") have been reworded. Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com> Link: https://lore.kernel.org/r/aGQqnzMyeagzgkCK@Tunnel Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-01Merge branch 's390-bpf-describe-the-frame-using-a-struct-instead-of-constants'Alexei Starovoitov
Ilya Leoshkevich says: ==================== s390/bpf: Describe the frame using a struct instead of constants Hi, This series contains two small refactorings without functional changes. The first one removes the code duplication around calculating the distance from %r15 to the stack frame. The second one simplifies how offsets to various values stored inside the frame are calculated. Best regards, Ilya ==================== Link: https://patch.msgid.link/20250624121501.50536-1-iii@linux.ibm.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-01s390/bpf: Describe the frame using a struct instead of constantsIlya Leoshkevich
Currently the caller-allocated portion of the stack frame is described using constants, hardcoded values, and an ASCII drawing, making it harder than necessary to ensure that everything is in sync. Declare a struct and use offsetof() and offsetofend() macros to refer to various values stored within the frame. Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> Link: https://lore.kernel.org/r/20250624121501.50536-3-iii@linux.ibm.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-07-01s390/bpf: Centralize frame offset calculationsIlya Leoshkevich
The calculation of the distance from %r15 to the caller-allocated portion of the stack frame is copy-pasted into multiple places in the JIT code. Move it to bpf_jit_prog() and save the result into bpf_jit::frame_off, so that the other parts of the JIT can use it. Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> Link: https://lore.kernel.org/r/20250624121501.50536-2-iii@linux.ibm.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-06-27selftests/bpf: bpf_rdonly_cast u{8,16,32,64} access testsEduard Zingerman
Tests with aligned and misaligned memory access of different sizes via pointer returned by bpf_rdonly_cast(). Suggested-by: Andrii Nakryiko <andrii.nakryiko@gmail.com> Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20250627015539.1439656-1-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-06-27selftests/bpf: improve error messages in veristatMykyta Yatsenko
Return error if preset parsing fails. Avoid proceeding with veristat run if preset does not parse. Before: ``` ./veristat set_global_vars.bpf.o -G "arr[999999999999999999999] = 1" Failed to parse value '999999999999999999999' Processing 'set_global_vars.bpf.o'... File Program Verdict Duration (us) Insns States Program size Jited size --------------------- ---------------- ------- ------------- ----- ------ ------------ ---------- set_global_vars.bpf.o test_set_globals success 27 64 0 82 0 --------------------- ---------------- ------- ------------- ----- ------ ------------ ---------- Done. Processed 1 files, 0 programs. Skipped 1 files, 0 programs. ``` After: ``` ./veristat set_global_vars.bpf.o -G "arr[999999999999999999999] = 1" Failed to parse value '999999999999999999999' Failed to parse global variable presets: arr[999999999999999999999] = 1 ``` Improve error messages: * If preset struct member can't be found. * Array index out of bounds Extract rtrim function. Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com> Acked-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20250627144342.686896-1-mykyta.yatsenko5@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-06-27selftests/bpf: Fix cgroup_xattr/read_cgroupfs_xattrSong Liu
cgroup_xattr/read_cgroupfs_xattr has two issues: 1. cgroup_xattr/read_cgroupfs_xattr messes up lo without creating a netns first. This causes issue with other tests. Fix this by using a different hook (lsm.s/file_open) and not messing with lo. 2. cgroup_xattr/read_cgroupfs_xattr sets up cgroups without proper mount namespaces. Fix this by using the existing cgroup helpers. A new helper set_cgroup_xattr() is added to set xattr on cgroup files. Fixes: f4fba2d6d282 ("selftests/bpf: Add tests for bpf_cgroup_read_xattr") Reported-by: Alexei Starovoitov <ast@kernel.org> Closes: https://lore.kernel.org/bpf/CAADnVQ+iqMi2HEj_iH7hsx+XJAsqaMWqSDe4tzcGAnehFWA9Sw@mail.gmail.com/ Signed-off-by: Song Liu <song@kernel.org> Tested-by: Eduard Zingerman <eddyz87@gmail.com> Tested-by: Ihor Solodrai <ihor.solodrai@linux.dev> Link: https://lore.kernel.org/r/20250627191221.765921-1-song@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-06-27bpf: guard BTF_ID_FLAGS(bpf_cgroup_read_xattr) with CONFIG_BPF_LSMEduard Zingerman
Function bpf_cgroup_read_xattr is defined in fs/bpf_fs_kfuncs.c, which is compiled only when CONFIG_BPF_LSM is set. Add CONFIG_BPF_LSM check to bpf_cgroup_read_xattr spec in common_btf_ids in kernel/bpf/helpers.c to avoid build failures for configs w/o CONFIG_BPF_LSM. Build failure example: BTF .tmp_vmlinux1.btf.o btf_encoder__tag_kfunc: failed to find kfunc 'bpf_cgroup_read_xattr' in BTF ... WARN: resolve_btfids: unresolved symbol bpf_cgroup_read_xattr make[2]: *** [scripts/Makefile.vmlinux:91: vmlinux.unstripped] Error 255 Fixes: 535b070f4a80 ("bpf: Introduce bpf_cgroup_read_xattr to read xattr of cgroup's node") Reported-by: Jake Hillion <jakehillion@meta.com> Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20250627175309.2710973-1-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-06-27bpf: Fix string kfuncs names in doc commentsViktor Malik
Documentation comments for bpf_strnlen and bpf_strcspn contained incorrect function names. Fixes: e91370550f1f ("bpf: Add kfuncs for read-only string operations") Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Closes: https://lore.kernel.org/bpf/20250627174759.3a435f86@canb.auug.org.au/T/#u Signed-off-by: Viktor Malik <vmalik@redhat.com> Link: https://lore.kernel.org/r/20250627082001.237606-1-vmalik@redhat.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-06-26Merge branch 'vfs-6.17.bpf' of ↵Alexei Starovoitov
https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs Merge branch 'vfs-6.17.bpf' from vfs tree into bpf-next/master and resolve conflicts. Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-06-26Merge branch 'support-array-presets-in-veristat'Andrii Nakryiko
Mykyta Yatsenko says: ==================== Support array presets in veristat From: Mykyta Yatsenko <yatsenko@meta.com> This patch series implements support for array variable presets in veristat. Currently users can set values to global variables before loading BPF program, but not for arrays. With this change array elements are supported as well, for example: ``` sudo ./veristat set_global_vars.bpf.o -G "arr[0] = 1" ``` v4 -> v5 * Simplify array elements offset calculation using btf__resolve_size * Support white spaces in array indexes, e.g. arr [ 0 ] * Rename btf_find_member into adjust_var_secinfo_member v3 -> v4 * Rework implementation to support multi dimensional arrays * Rework data structures for storing parsed presets v2 -> v3 * Added more negative tests * Fix mem leak * Other small fixes v1 -> v2 * Support enums as indexes * Separating parsing logic from preset processing * Add more tests ==================== Link: https://patch.msgid.link/20250625165904.87820-1-mykyta.yatsenko5@gmail.com Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
2025-06-26selftests/bpf: Test array presets in veristatMykyta Yatsenko
Modify existing veristat tests to verify that array presets are applied as expected. Introduce few negative tests as well to check that common error modes are handled. Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/bpf/20250625165904.87820-4-mykyta.yatsenko5@gmail.com
2025-06-26selftests/bpf: Support array presets in veristatMykyta Yatsenko
Implement support for presetting values for array elements in veristat. For example: ``` sudo ./veristat set_global_vars.bpf.o -G "arr[3] = 1" ``` Arrays of structures and structure of arrays work, but each individual scalar value has to be set separately: `foo[1].bar[2] = value`. Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/bpf/20250625165904.87820-3-mykyta.yatsenko5@gmail.com
2025-06-26selftests/bpf: Separate var preset parsing in veristatMykyta Yatsenko
Refactor var preset parsing in veristat to simplify implementation. Prepare parsed variable beforehand so that parsing logic is separated from functionality of calculating offsets and searching fields. Introduce rvalue struct, storing either int or enum (string value), will be reused in the next patch, extract parsing rvalue into a separate function. Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/bpf/20250625165904.87820-2-mykyta.yatsenko5@gmail.com
2025-06-26Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf after rc3Alexei Starovoitov
Cross-merge BPF, perf and other fixes after downstream PRs. It restores BPF CI to green after critical fix commit bc4394e5e79c ("perf: Fix the throttle error of some clock events") No conflicts. Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-06-26Merge branch 'bpf-add-kfuncs-for-read-only-string-operations'Alexei Starovoitov
Viktor Malik says: ==================== bpf: Add kfuncs for read-only string operations String operations are commonly used in programming and BPF programs are no exception. Since it is cumbersome to reimplement them over and over, this series introduce kfuncs which provide the most common operations. For now, we only limit ourselves to functions which do not copy memory since these usually introduce undefined behaviour in case the source/destination buffers overlap which would have to be prevented by the verifier. The kernel already contains implementations for all of these, however, it is not possible to use them from BPF context. The main reason is that the verifier is not able to check that it is safe to access the entire string and that the string is null-terminated and the function won't loop forever. Therefore, the operations are open-coded using __get_kernel_nofault instead of plain dereference and bounded to at most XATTR_SIZE_MAX characters to make them safe. That allows to skip all the verfier checks for the passed-in strings as safety is ensured dynamically. All of the proposed functions return integers, even those that normally (in the kernel or libc) return pointers into the strings. The reason is that since the strings are generally treated as unsafe, the pointers couldn't be dereferenced anyways. So, instead, we return an index to the string and let user decide what to do with it. The integer APIs also allow to return various error codes when unexpected situations happen while processing the strings. The series include both positive and negative tests using the kfuncs. Changelog --------- Changes in v8: - Return -ENOENT (instead of -1) when "item not found" for relevant functions (Alexei). - Small adjustments of the string algorithms (Andrii). - Adapt comments to kernel style (Alexei). Changes in v7: - Disable negative tests passing NULL and 0x1 to kfuncs on s390 as they aren't relevant (see comment in string_kfuncs_failure1.c for details). Changes in v6: - Improve the third patch which allows to use macros in __retval in selftests. The previous solution broke several tests. Changes in v5: - Make all kfuncs return integers (Andrii). - Return -ERANGE when passing non-kernel pointers on arches with non-overlapping address spaces (Alexei). - Implement "unbounded" variants using the bounded ones (Andrii). - Add more negative test cases. Changes in v4 (all suggested by Andrii): - Open-code all the kfuncs, not just the unbounded variants. - Introduce `pagefault` lock guard to simplify the implementation - Return appropriate error codes (-E2BIG and -EFAULT) on failures - Const-ify all arguments and return values - Add negative test-cases Changes in v3: - Open-code unbounded variants with __get_kernel_nofault instead of dereference (suggested by Alexei). - Use the __sz suffix for size parameters in bounded variants (suggested by Eduard and Alexei). - Make tests more compact (suggested by Eduard). - Add benchmark. ==================== Link: https://patch.msgid.link/cover.1750917800.git.vmalik@redhat.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-06-26selftests/bpf: Add tests for string kfuncsViktor Malik
Add both positive and negative tests cases using string kfuncs added in the previous patches. Positive tests check that the functions work as expected. Negative tests pass various incorrect strings to the kfuncs and check for the expected error codes: -E2BIG when passing too long strings -EFAULT when trying to read inaccessible kernel memory -ERANGE when passing userspace pointers on arches with non-overlapping address spaces A majority of the tests use the RUN_TESTS helper which executes BPF programs with BPF_PROG_TEST_RUN and check for the expected return value. An exception to this are tests for long strings as we need to memset the long string from userspace (at least I haven't found an ergonomic way to memset it from a BPF program), which cannot be done using the RUN_TESTS infrastructure. Suggested-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Viktor Malik <vmalik@redhat.com> Link: https://lore.kernel.org/r/090451a2e60c9ae1dceb4d1bfafa3479db5c7481.1750917800.git.vmalik@redhat.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-06-26selftests/bpf: Allow macros in __retvalViktor Malik
Allow macro expansion for values passed to the `__retval` and `__retval_unpriv` attributes. This is especially useful for testing programs which return various error codes. With this change, the code for parsing special literals can be made simpler, as the literals are defined via macros. The only exception is INT_MIN which expands to (-INT_MAX -1), which is not single number and cannot be parsed by strtol. So, we instead use a prefixed literal _INT_MIN in __retval and handle it separately (assign the expected return to INT_MIN). Also, strtol cannot handle the "ll" suffix so change the value of POINTER_VALUE from 0xcafe4all to 0xbadcafe. Signed-off-by: Viktor Malik <vmalik@redhat.com> Link: https://lore.kernel.org/r/a6c6b551ae0575351faa7b7a1df52f9341a5cbe8.1750917800.git.vmalik@redhat.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-06-26bpf: Add kfuncs for read-only string operationsViktor Malik
String operations are commonly used so this exposes the most common ones to BPF programs. For now, we limit ourselves to operations which do not copy memory around. Unfortunately, most in-kernel implementations assume that strings are %NUL-terminated, which is not necessarily true, and therefore we cannot use them directly in the BPF context. Instead, we open-code them using __get_kernel_nofault instead of plain dereference to make them safe and limit the strings length to XATTR_SIZE_MAX to make sure the functions terminate. When __get_kernel_nofault fails, functions return -EFAULT. Similarly, when the size bound is reached, the functions return -E2BIG. In addition, we return -ERANGE when the passed strings are outside of the kernel address space. Note that thanks to these dynamic safety checks, no other constraints are put on the kfunc args (they are marked with the "__ign" suffix to skip any verifier checks for them). All of the functions return integers, including functions which normally (in kernel or libc) return pointers to the strings. The reason is that since the strings are generally treated as unsafe, the pointers couldn't be dereferenced anyways. So, instead, we return an index to the string and let user decide what to do with it. This also nicely fits with returning various error codes when necessary (see above). Suggested-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Viktor Malik <vmalik@redhat.com> Link: https://lore.kernel.org/r/4b008a6212852c1b056a413f86e3efddac73551c.1750917800.git.vmalik@redhat.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2025-06-26uaccess: Define pagefault lock guardViktor Malik
Define a pagefault lock guard which allows to simplify functions that need to disable page faults. Signed-off-by: Viktor Malik <vmalik@redhat.com> Link: https://lore.kernel.org/r/8a01beb0b671923976f08297d81242bb2129881d.1750917800.git.vmalik@redhat.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
generated by cgit (git 2.34.1) at 2025-09-07 21:38:20 +0000