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

[Jiri Olsa <olsajiri@gmail.com>]

On Thu, Aug 31, 2023 at 08:37:52PM +0800, Hou Tao wrote:
> Hi,
> 
> On 8/31/2023 7:46 PM, Daniel Borkmann wrote:
> > On 8/31/23 1:00 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>
> >> ---
> >>   tools/testing/selftests/bpf/prog_tests/d_path.c | 8 +++++++-
> >>   1 file changed, 7 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/tools/testing/selftests/bpf/prog_tests/d_path.c
> >> b/tools/testing/selftests/bpf/prog_tests/d_path.c
> >> index 911345c526e6..81e34a4a05d1 100644
> >> --- a/tools/testing/selftests/bpf/prog_tests/d_path.c
> >> +++ b/tools/testing/selftests/bpf/prog_tests/d_path.c
> >> @@ -90,7 +90,11 @@ static int trigger_fstat_events(pid_t pid)
> >>       fstat(indicatorfd, &fileStat);
> >>     out_close:
> >> -    /* triggers filp_close */
> >> +    /* sys_close no longer triggers filp_close, but we can
> >> +     * call sys_close_range instead which still does
> >> +     */
> >> +#define close(fd) close_range(fd, fd, 0)
> >> +
> >
> > The BPF CI selftest build says:
> >
> >     [...]
> >     TEST-OBJ [test_progs] lookup_key.test.o
> >     TEST-OBJ [test_progs] migrate_reuseport.test.o
> >     TEST-OBJ [test_progs] user_ringbuf.test.o
> >   /tmp/work/bpf/bpf/tools/testing/selftests/bpf/prog_tests/d_path.c:
> > In function ‘trigger_fstat_events’:
> >  
> > /tmp/work/bpf/bpf/tools/testing/selftests/bpf/prog_tests/d_path.c:96:19:
> > error: implicit declaration of function ‘close_range’
> > [-Werror=implicit-function-declaration]
> >      96 | #define close(fd) close_range(fd, fd, 0)
> >         |                   ^~~~~~~~~~~
> >  
> > /tmp/work/bpf/bpf/tools/testing/selftests/bpf/prog_tests/d_path.c:98:2:
> > note: in expansion of macro ‘close’
> >      98 |  close(pipefd[0]);
> >         |  ^~~~~
> >     TEST-OBJ [test_progs] task_pt_regs.test.o
> >     [...]
> >
> > Perhaps #include <linux/close_range.h> missing ?
> 
> Including <linux/close_range.h> doesn't help because it only defines two
> macros.

right, just saw that ;-)

> 
> I got the same error when testing locally. It seems close_range() was
> introduced by glibc 2.34 [1] and it was defined in <unistd.h>, but the
> version of glibc in my local VM is 2.29. I modify d_path locally to call
> close_range through syscall():
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/d_path.c
> b/tools/testing/selftests/bpf/prog_tests/d_path.c
> index 81e34a4a05d1..c5811843ce7e 100644
> --- a/tools/testing/selftests/bpf/prog_tests/d_path.c
> +++ b/tools/testing/selftests/bpf/prog_tests/d_path.c
> @@ -12,6 +12,14 @@
>  #include "test_d_path_check_rdonly_mem.skel.h"
>  #include "test_d_path_check_types.skel.h"
> 
> +#ifndef __NR_close_range
> +#ifdef __alpha__
> +#define __NR_close_range 546
> +#else
> +#define __NR_close_range 436
> +#endif
> +#endif
> +
>  static int duration;
> 
>  static struct {
> @@ -93,7 +101,7 @@ static int trigger_fstat_events(pid_t pid)
>         /* sys_close no longer triggers filp_close, but we can
>          * call sys_close_range instead which still does
>          */
> -#define close(fd) close_range(fd, fd, 0)
> +#define close(fd) syscall(__NR_close_range, fd, fd, 0)
> 
> [1]: 9b4feb630e8e arch: wire-up close_range()

nice, thanks for all the info

jirka

> 
> 
> >
> >>       close(pipefd[0]);
> >>       close(pipefd[1]);
> >>       close(sockfd);
> >> @@ -98,6 +102,8 @@ static int trigger_fstat_events(pid_t pid)
> >>       close(devfd);
> >>       close(localfd);
> >>       close(indicatorfd);
> >> +
> >> +#undef close
> >>       return ret;
> >>   }
> >>  
>