On Wed, Jun 14, 2023 at 7:09 AM Yonghong Song yhs@meta.com wrote:

On 6/14/23 12:42 AM, wuyonggang001@208suo.com wrote:

...

Fix the following coccicheck error:

tools/testing/selftests/bpf/progs/test_ksyms_weak.c:53:6-20: ERROR: test of a variable/field address

I didn't see clang/gcc compiler warns about this. Maybe need some additional flags beyond what current selftest/bpf already has in order to trigger this warning? If you feel this warning has some merit, could you propose it to gcc/llvm community?

bpf_link_fops2 is a weak symbol, this check is totally valid and reasonable.

There are two problems here, though:

a) coccicheck shouldn't warn about "test of a variable/field address" for weak symbols, because they can be NULL.

b) this patch is not even fixing that warning, it does a no-op change from implicit non-NULL check to explicit non-NULL check. And the former is actually the preferred style.

So this patch is doubly wrong.

...

Signed-off-by: Yonggang Wu wuyonggang001@208suo.com

tools/testing/selftests/bpf/progs/test_ksyms_weak.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/progs/test_ksyms_weak.c b/tools/testing/selftests/bpf/progs/test_ksyms_weak.c index d00268c91e19..768a4d6ee6f5 100644 --- a/tools/testing/selftests/bpf/progs/test_ksyms_weak.c +++ b/tools/testing/selftests/bpf/progs/test_ksyms_weak.c @@ -50,7 +50,7 @@ int pass_handler(const void *ctx) /* tests non-existent symbols. */ out__non_existent_typed = (__u64)&bpf_link_fops2;

• if (&bpf_link_fops2) /* can't happen */

• if (&bpf_link_fops2 != NULL) /* can't happen */ out__non_existent_typed =

(__u64)bpf_per_cpu_ptr(&bpf_link_fops2, 0);

  if (!bpf_ksym_exists(bpf_task_acquire))