diff options
| author | Yonghong Song <yonghong.song@linux.dev> | 2023-08-26 13:08:43 -0700 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2023-08-30 08:36:17 +0200 |
| commit | 32337c0a28242f725c2c499c15100d67a4133050 (patch) | |
| tree | 412a11f4026479c82b08c9e29dae6a783097de7e /net/bpf | |
| parent | bd6c11bc43c496cddfc6cf603b5d45365606dbd5 (diff) | |
bpf: Prevent inlining of bpf_fentry_test7()
With latest clang18, I hit test_progs failures for the following test:
#13/2 bpf_cookie/multi_kprobe_link_api:FAIL
#13/3 bpf_cookie/multi_kprobe_attach_api:FAIL
#13 bpf_cookie:FAIL
#75 fentry_fexit:FAIL
#76/1 fentry_test/fentry:FAIL
#76 fentry_test:FAIL
#80/1 fexit_test/fexit:FAIL
#80 fexit_test:FAIL
#110/1 kprobe_multi_test/skel_api:FAIL
#110/2 kprobe_multi_test/link_api_addrs:FAIL
#110/3 kprobe_multi_test/link_api_syms:FAIL
#110/4 kprobe_multi_test/attach_api_pattern:FAIL
#110/5 kprobe_multi_test/attach_api_addrs:FAIL
#110/6 kprobe_multi_test/attach_api_syms:FAIL
#110 kprobe_multi_test:FAIL
For example, for #13/2, the error messages are:
[...]
kprobe_multi_test_run:FAIL:kprobe_test7_result unexpected kprobe_test7_result: actual 0 != expected 1
[...]
kprobe_multi_test_run:FAIL:kretprobe_test7_result unexpected kretprobe_test7_result: actual 0 != expected 1
clang17 does not have this issue.
Further investigation shows that kernel func bpf_fentry_test7(), used in
the above tests, is inlined by the compiler although it is marked as
noinline.
int noinline bpf_fentry_test7(struct bpf_fentry_test_t *arg)
{
return (long)arg;
}
It is known that for simple functions like the above (e.g. just returning
a constant or an input argument), the clang compiler may still do inlining
for a noinline function. Adding 'asm volatile ("")' in the beginning of the
bpf_fentry_test7() can prevent inlining.
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20230826200843.2210074-1-yonghong.song@linux.dev
Diffstat (limited to 'net/bpf')
| -rw-r--r-- | net/bpf/test_run.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c index 57a7a64b84ed..0841f8d82419 100644 --- a/net/bpf/test_run.c +++ b/net/bpf/test_run.c @@ -543,6 +543,7 @@ struct bpf_fentry_test_t { int noinline bpf_fentry_test7(struct bpf_fentry_test_t *arg) { + asm volatile (""); return (long)arg; } |