kernel/tools/testing/selftests/bpf/progs/exhandler_kern.c, branch linux-6.2.y

libbpf: Provide barrier() and barrier_var() in bpf_helpers.h

2022-05-09T15:15:32Z

Add barrier() and barrier_var() macros into bpf_helpers.h to be used by end users. While a bit advanced and specialized instruments, they are sometimes indispensable. Instead of requiring each user to figure out exact asm volatile incantations for themselves, provide them from bpf_helpers.h. Also remove conflicting definitions from selftests. Some tests rely on barrier_var() definition being nothing, those will still work as libbpf does the #ifndef/#endif guarding for barrier() and barrier_var(), allowing users to redefine them, if necessary. Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20220509004148.1801791-8-andrii@kernel.org

selftests/bpf: Workaround a verifier issue for test exhandler

2022-04-19T17:22:19Z

The llvm patch [1] enabled opaque pointer which caused selftest 'exhandler' failure. ... ; work = task->task_works; 7: (79) r1 = *(u64 *)(r6 +2120) ; R1_w=ptr_callback_head(off=0,imm=0) R6_w=ptr_task_struct(off=0,imm=0) ; func = work->func; 8: (79) r2 = *(u64 *)(r1 +8) ; R1_w=ptr_callback_head(off=0,imm=0) R2_w=scalar() ; if (!work && !func) 9: (4f) r1 |= r2 math between ptr_ pointer and register with unbounded min value is not allowed below is insn 10 and 11 10: (55) if r1 != 0 goto +5 11: (18) r1 = 0 ll ... In llvm, the code generation of 'r1 |= r2' happened in codegen selectiondag phase due to difference of opaque pointer vs. non-opaque pointer. Without [1], the related code looks like: r2 = *(u64 *)(r6 + 2120) r1 = *(u64 *)(r2 + 8) if r2 != 0 goto +6 if r1 != 0 goto +5 r1 = 0 ll ... I haven't found a good way in llvm to fix this issue. So let us workaround the problem first so bpf CI won't be blocked. [1] https://reviews.llvm.org/D123300 Signed-off-by: Yonghong Song Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20220419050900.3136024-1-yhs@fb.com

selftests/bpf: Add exception handling selftests for tp_bpf program

2021-11-08T21:17:55Z

Exception handling is triggered in BPF tracing programs when a NULL pointer is dereferenced; the exception handler zeroes the target register and execution of the BPF program progresses. To test exception handling then, we need to trigger a NULL pointer dereference for a field which should never be zero; if it is, the only explanation is the exception handler ran. task->task_works is the NULL pointer chosen (for a new task from fork() no work is associated), and the task_works->func field should not be zero if task_works is non-NULL. The test verifies that task_works and task_works->func are 0. Signed-off-by: Alan Maguire Signed-off-by: Daniel Borkmann Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/1636131046-5982-3-git-send-email-alan.maguire@oracle.com