Patch "bpf, events: Use prog to emit ksymbol event for main program" has been added to the 6.1-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

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

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     bpf-events-use-prog-to-emit-ksymbol-event-for-main-p.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 00580d6b26ad1f6fffd4627b6f8c1680fd2711ff
Author: Hou Tao <houtao1@xxxxxxxxxx>
Date:   Sun Jul 14 14:55:33 2024 +0800

    bpf, events: Use prog to emit ksymbol event for main program
    
    [ Upstream commit 0be9ae5486cd9e767138c13638820d240713f5f1 ]
    
    Since commit 0108a4e9f358 ("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: 0108a4e9f358 ("bpf: ensure main program has an extable")
    Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
    Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
    Tested-by: Yonghong Song <yonghong.song@xxxxxxxxx>
    Reviewed-by: Krister Johansen <kjlx@xxxxxxxxxxxxxxxxxx>
    Reviewed-by: Jiri Olsa <jolsa@xxxxxxxxxx>
    Link: https://lore.kernel.org/bpf/20240714065533.1112616-1-houtao@xxxxxxxxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/kernel/events/core.c b/kernel/events/core.c
index b8333b8e6a782..d92ee56a2a768 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -9097,21 +9097,19 @@ 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++) {
-			struct bpf_prog *subprog = prog->aux->func[i];
-
-			perf_event_ksymbol(
-				PERF_RECORD_KSYMBOL_TYPE_BPF,
-				(u64)(unsigned long)subprog->bpf_func,
-				subprog->jited_len, unregister,
-				subprog->aux->ksym.name);
-		}
+	perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF,
+			   (u64)(unsigned long)prog->bpf_func,
+			   prog->jited_len, unregister,
+			   prog->aux->ksym.name);
+
+	for (i = 1; i < prog->aux->func_cnt; i++) {
+		struct bpf_prog *subprog = prog->aux->func[i];
+
+		perf_event_ksymbol(
+			PERF_RECORD_KSYMBOL_TYPE_BPF,
+			(u64)(unsigned long)subprog->bpf_func,
+			subprog->jited_len, unregister,
+			subprog->aux->ksym.name);
 	}
 }