From: Hou Tao houtao1@huawei.com
[ Upstream commit 47df8a2f78bc34ff170d147d05b121f84e252b85 ]
Since commit bfea9a8574f3 ("bpf: Add name to struct bpf_ksym"), when reporting subprog ksymbol to perf, prog name instead of subprog name is used. The backtrace of bpf program with subprogs will be incorrect as shown below:
ffffffffc02deace bpf_prog_e44a3057dcb151f8_overwrite+0x66 ffffffffc02de9f7 bpf_prog_e44a3057dcb151f8_overwrite+0x9f ffffffffa71d8d4e trace_call_bpf+0xce ffffffffa71c2938 perf_call_bpf_enter.isra.0+0x48
overwrite is the entry program and it invokes the overwrite_htab subprog through bpf_loop, but in above backtrace, overwrite program just jumps inside itself.
Fixing it by using subprog name when reporting subprog ksymbol. After the fix, the output of perf script will be correct as shown below:
ffffffffc031aad2 bpf_prog_37c0bec7d7c764a4_overwrite_htab+0x66 ffffffffc031a9e7 bpf_prog_c7eb827ef4f23e71_overwrite+0x9f ffffffffa3dd8d4e trace_call_bpf+0xce ffffffffa3dc2938 perf_call_bpf_enter.isra.0+0x48
Fixes: bfea9a8574f3 ("bpf: Add name to struct bpf_ksym") Signed-off-by: Hou Tao houtao1@huawei.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Acked-by: Jiri Olsa jolsa@kernel.org Link: https://lore.kernel.org/bpf/20221114095733.158588-1-houtao@huaweicloud.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/events/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c index bec18d81b116..8dcbefd90b7f 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -9006,7 +9006,7 @@ static void perf_event_bpf_emit_ksymbols(struct bpf_prog *prog, PERF_RECORD_KSYMBOL_TYPE_BPF, (u64)(unsigned long)subprog->bpf_func, subprog->jited_len, unregister, - prog->aux->ksym.name); + subprog->aux->ksym.name); } } }