Commit 9ef40511 authored by Hou Tao's avatar Hou Tao Committed by Tengda Wu
Browse files

bpf, events: Use prog to emit ksymbol event for main program 

mainline inclusion
from mainline-v6.11-rc1
commit 0be9ae5486cd9e767138c13638820d240713f5f1
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IAHA5K

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0be9ae5486cd9e767138c13638820d240713f5f1



--------------------------------

Since commit 0108a4e9 ("bpf: ensure main program has an extable"),
prog->aux->func[0]->kallsyms is left as uninitialized. For BPF programs
with subprogs, the symbol for the main program is missing just as shown
in the output of perf script below:

 ffffffff81284b69 qp_trie_lookup_elem+0xb9 ([kernel.kallsyms])
 ffffffffc0011125 bpf_prog_a4a0eb0651e6af8b_lookup_qp_trie+0x5d (bpf...)
 ffffffff8127bc2b bpf_for_each_array_elem+0x7b ([kernel.kallsyms])
 ffffffffc00110a1 +0x25 ()
 ffffffff8121a89a trace_call_bpf+0xca ([kernel.kallsyms])

Fix it by always using prog instead prog->aux->func[0] to emit ksymbol
event for the main program. After the fix, the output of perf script
will be correct:

 ffffffff81284b96 qp_trie_lookup_elem+0xe6 ([kernel.kallsyms])
 ffffffffc001382d bpf_prog_a4a0eb0651e6af8b_lookup_qp_trie+0x5d (bpf...)
 ffffffff8127bc2b bpf_for_each_array_elem+0x7b ([kernel.kallsyms])
 ffffffffc0013779 bpf_prog_245c55ab25cfcf40_qp_trie_lookup+0x25 (bpf...)
 ffffffff8121a89a trace_call_bpf+0xca ([kernel.kallsyms])

Fixes: 0108a4e9 ("bpf: ensure main program has an extable")
Signed-off-by: default avatarHou Tao <houtao1@huawei.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Tested-by: default avatarYonghong Song <yonghong.song@linux.dev>
Reviewed-by: default avatarKrister Johansen <kjlx@templeofstupid.com>
Reviewed-by: default avatarJiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20240714065533.1112616-1-houtao@huaweicloud.com


Signed-off-by: default avatarTengda Wu <wutengda2@huawei.com>
parent 8f97cc1b

kernel/events/core.c

+13 −15
Original line number Diff line number Diff line
@@ -8733,13 +8733,12 @@ static void perf_event_bpf_emit_ksymbols(struct bpf_prog *prog, 
	bool unregister = type == PERF_BPF_EVENT_PROG_UNLOAD;

	int i;



	if (prog->aux->func_cnt == 0) {

	perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF,

			   (u64)(unsigned long)prog->bpf_func,

			   prog->jited_len, unregister,

			   prog->aux->ksym.name);

	} else {

		for (i = 0; i < prog->aux->func_cnt; i++) {



	for (i = 1; i < prog->aux->func_cnt; i++) {

		struct bpf_prog *subprog = prog->aux->func[i];



		perf_event_ksymbol(
@@ -8749,7 +8748,6 @@ static void perf_event_bpf_emit_ksymbols(struct bpf_prog *prog, 
			subprog->aux->ksym.name);

	}

}

}



void perf_event_bpf_event(struct bpf_prog *prog,

			  enum perf_bpf_event_type type,