From: Kajol Jain kjain@linux.ibm.com
[ Upstream commit db52f57211b4e45f0ebb274e2c877b211dc18591 ]
Branch data available to BPF programs can be very useful to get stack traces out of userspace application.
Commit fff7b64355ea ("bpf: Add bpf_read_branch_records() helper") added BPF support to capture branch records in x86. Enable this feature also for other architectures as well by removing checks specific to x86.
If an architecture doesn't support branch records, bpf_read_branch_records() still has appropriate checks and it will return an -EINVAL in that scenario. Based on UAPI helper doc in include/uapi/linux/bpf.h, unsupported architectures should return -ENOENT in such case. Hence, update the appropriate check to return -ENOENT instead.
Selftest 'perf_branches' result on power9 machine which has the branch stacks support:
- Before this patch:
[command]# ./test_progs -t perf_branches #88/1 perf_branches/perf_branches_hw:FAIL #88/2 perf_branches/perf_branches_no_hw:OK #88 perf_branches:FAIL Summary: 0/1 PASSED, 0 SKIPPED, 1 FAILED
- After this patch:
[command]# ./test_progs -t perf_branches #88/1 perf_branches/perf_branches_hw:OK #88/2 perf_branches/perf_branches_no_hw:OK #88 perf_branches:OK Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED
Selftest 'perf_branches' result on power9 machine which doesn't have branch stack report:
- After this patch:
[command]# ./test_progs -t perf_branches #88/1 perf_branches/perf_branches_hw:SKIP #88/2 perf_branches/perf_branches_no_hw:OK #88 perf_branches:OK Summary: 1/1 PASSED, 1 SKIPPED, 0 FAILED
Fixes: fff7b64355eac ("bpf: Add bpf_read_branch_records() helper") Suggested-by: Peter Zijlstra peterz@infradead.org Signed-off-by: Kajol Jain kjain@linux.ibm.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Link: https://lore.kernel.org/bpf/20211206073315.77432-1-kjain@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/trace/bpf_trace.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index ae9755037b7ee..e36d184615fb7 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -1400,9 +1400,6 @@ static const struct bpf_func_proto bpf_perf_prog_read_value_proto = { BPF_CALL_4(bpf_read_branch_records, struct bpf_perf_event_data_kern *, ctx, void *, buf, u32, size, u64, flags) { -#ifndef CONFIG_X86 - return -ENOENT; -#else static const u32 br_entry_size = sizeof(struct perf_branch_entry); struct perf_branch_stack *br_stack = ctx->data->br_stack; u32 to_copy; @@ -1411,7 +1408,7 @@ BPF_CALL_4(bpf_read_branch_records, struct bpf_perf_event_data_kern *, ctx, return -EINVAL;
if (unlikely(!br_stack)) - return -EINVAL; + return -ENOENT;
if (flags & BPF_F_GET_BRANCH_RECORDS_SIZE) return br_stack->nr * br_entry_size; @@ -1423,7 +1420,6 @@ BPF_CALL_4(bpf_read_branch_records, struct bpf_perf_event_data_kern *, ctx, memcpy(buf, br_stack->entries, to_copy);
return to_copy; -#endif }
static const struct bpf_func_proto bpf_read_branch_records_proto = {