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
Unified · Split
| @@ -1404,9 +1404,6 @@ static const struct bpf_func_proto bpf_perf_prog_read_value_proto = { · 1403 unmodified lines | ||
| 1404 | 1404 | BPF_CALL_4(bpf_read_branch_records, struct bpf_perf_event_data_kern *, ctx, |
| 1405 | 1405 | void *, buf, u32, size, u64, flags) |
| 1406 | 1406 | { |
| 1407 | −#ifndef CONFIG_X86 | |
| 1408 | − return -ENOENT; | |
| 1409 | −#else | |
| 1410 | 1407 | static const u32 br_entry_size = sizeof(struct perf_branch_entry); |
| 1411 | 1408 | struct perf_branch_stack *br_stack = ctx->data->br_stack; |
| 1412 | 1409 | u32 to_copy; |
| @@ -1415,7 +1412,7 @@ BPF_CALL_4(bpf_read_branch_records, struct bpf_perf_event_data_kern *, ctx, · 2 unmodified lines | ||
| 1415 | 1412 | return -EINVAL; |
| 1416 | 1413 | |
| 1417 | 1414 | if (unlikely(!br_stack)) |
| 1418 | − return -EINVAL; | |
| 1415 | + return -ENOENT; | |
| 1419 | 1416 | |
| 1420 | 1417 | if (flags & BPF_F_GET_BRANCH_RECORDS_SIZE) |
| 1421 | 1418 | return br_stack->nr * br_entry_size; |
| @@ -1427,7 +1424,6 @@ BPF_CALL_4(bpf_read_branch_records, struct bpf_perf_event_data_kern *, ctx, · 5 unmodified lines | ||
| 1427 | 1424 | memcpy(buf, br_stack->entries, to_copy); |
| 1428 | 1425 | |
| 1429 | 1426 | return to_copy; |
| 1430 | −#endif | |
| 1431 | 1427 | } |
| 1432 | 1428 | |
| 1433 | 1429 | static const struct bpf_func_proto bpf_read_branch_records_proto = { |