Re: [PATCHv2 bpf-next] selftests/bpf: Fix d_path test

Song Liu
2023-09-01T23:09:46Z

On Thu, Aug 31, 2023 at 8:21 AM Daniel Borkmann <daniel@iogearbox.net> wrote:
>
> On 8/31/23 4:11 PM, Jiri Olsa wrote:
> > Recent commit [1] broken d_path test, because now filp_close is not called
> > directly from sys_close, but eventually later when the file is finally
> > released.
> >
> > As suggested by Hou Tao we don't need to re-hook the bpf program, but just
> > instead we can use sys_close_range to trigger filp_close synchronously.
> >
> > [1] 021a160abf62 ("fs: use __fput_sync in close(2)")
> > Suggested-by: Hou Tao <houtao@huaweicloud.com>
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
>
> That did the trick, thanks everyone, applied!

I guess I am a bit late. But how about we use something like the following?
I like this one better because it tests bpf_d_path() from retval at fexit.

Thanks,
Song

diff --git i/kernel/trace/bpf_trace.c w/kernel/trace/bpf_trace.c
index a7264b2c17ad..fe91836cedcd 100644
--- i/kernel/trace/bpf_trace.c
+++ w/kernel/trace/bpf_trace.c
@@ -941,6 +941,7 @@ BTF_ID(func, vfs_fallocate)
BTF_ID(func, dentry_open)
BTF_ID(func, vfs_getattr)
BTF_ID(func, filp_close)
+BTF_ID(func, close_fd_get_file)
BTF_SET_END(btf_allowlist_d_path)

static bool bpf_d_path_allowed(const struct bpf_prog *prog)
diff --git i/tools/testing/selftests/bpf/progs/test_d_path.c
w/tools/testing/selftests/bpf/progs/test_d_path.c
index 84e1f883f97b..c880cfc95737 100644
--- i/tools/testing/selftests/bpf/progs/test_d_path.c
+++ w/tools/testing/selftests/bpf/progs/test_d_path.c
@@ -40,8 +40,8 @@ int BPF_PROG(prog_stat, struct path *path, struct kstat *stat,
return 0;
}

-SEC("fentry/filp_close")
-int BPF_PROG(prog_close, struct file *file, void *id)
+SEC("fexit/close_fd_get_file")
+int BPF_PROG(close_fd_get_file, int fd, struct file *file /* retval */)
{
pid_t pid = bpf_get_current_pid_tgid() >> 32;
__u32 cnt = cnt_close;