[PATCH bpf-next] libbpf: fix return value for PERF_EVENT __arg_ctx type fix up check

[PATCH bpf-next] libbpf: fix return value for PERF_EVENT __arg_ctx type fix up check

[Andrii Nakryiko]

If PERF_EVENT program has __arg_ctx argument with matching
architecture-specific pt_regs/user_pt_regs/user_regs_struct pointer
type, libbpf should still perform type rewrite for old kernels, but not
emit the warning. Fix copy/paste from kernel code where 0 is meant to
signify "no error" condition. For libbpf we need to return "true" to
proceed with type rewrite (which for PERF_EVENT program will be
a canonical `struct bpf_perf_event_data *` type).

Fixes: 9eea8fafe33e ("libbpf: fix __arg_ctx type enforcement for perf_event programs")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/lib/bpf/libbpf.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 6932f2c4ddfd..01f407591a92 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -6404,13 +6404,13 @@ static bool need_func_arg_type_fixup(const struct btf *btf, const struct bpf_pro
 	case BPF_PROG_TYPE_PERF_EVENT:
 		if (__builtin_types_compatible_p(bpf_user_pt_regs_t, struct pt_regs) &&
 		    btf_is_struct(t) && strcmp(tname, "pt_regs") == 0)
-			return 0;
+			return true;
 		if (__builtin_types_compatible_p(bpf_user_pt_regs_t, struct user_pt_regs) &&
 		    btf_is_struct(t) && strcmp(tname, "user_pt_regs") == 0)
-			return 0;
+			return true;
 		if (__builtin_types_compatible_p(bpf_user_pt_regs_t, struct user_regs_struct) &&
 		    btf_is_struct(t) && strcmp(tname, "user_regs_struct") == 0)
-			return 0;
+			return true;
 		break;
 	case BPF_PROG_TYPE_RAW_TRACEPOINT:
 	case BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE:
-- 
2.34.1

Re: [PATCH bpf-next] libbpf: fix return value for PERF_EVENT __arg_ctx type fix up check

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Mon,  5 Feb 2024 16:22:43 -0800 you wrote:
> If PERF_EVENT program has __arg_ctx argument with matching
> architecture-specific pt_regs/user_pt_regs/user_regs_struct pointer
> type, libbpf should still perform type rewrite for old kernels, but not
> emit the warning. Fix copy/paste from kernel code where 0 is meant to
> signify "no error" condition. For libbpf we need to return "true" to
> proceed with type rewrite (which for PERF_EVENT program will be
> a canonical `struct bpf_perf_event_data *` type).
> 
> [...]

Here is the summary with links:
  - [bpf-next] libbpf: fix return value for PERF_EVENT __arg_ctx type fix up check
    https://git.kernel.org/bpf/bpf-next/c/d7bc416aa5cc

You are awesome, thank you!
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