netdev - Re: [PATCH v3 bpf-next 3/4] selftests/bpf: add get_lib

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Message-ID: <CAEf4BzbyWd6bfWFGLX-c7s2YLjFTQXAc=NOEFChwu2ApvJNeFQ@mail.gmail.com>
Date:   Fri, 4 Feb 2022 11:24:17 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Alan Maguire <alan.maguire@...cle.com>
Cc:     Andrii Nakryiko <andrii@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin Lau <kafai@...com>, Song Liu <songliubraving@...com>,
        Yonghong Song <yhs@...com>,
        john fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
        Yucong Sun <sunyucong@...il.com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH v3 bpf-next 3/4] selftests/bpf: add get_lib_path() helper

On Mon, Jan 31, 2022 at 8:13 AM Alan Maguire <alan.maguire@...cle.com> wrote:
>
> get_lib_path(path_substr) returns full path to a library
> containing path_substr (such as "libc-") found via
> /proc/self/maps.  Caller is responsible for freeing
> the returned string.
>
> Signed-off-by: Alan Maguire <alan.maguire@...cle.com>
> ---
>  tools/testing/selftests/bpf/trace_helpers.c | 17 +++++++++++++++++
>  tools/testing/selftests/bpf/trace_helpers.h |  2 ++
>  2 files changed, 19 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c
> index ca6abae..49e5f0d 100644
> --- a/tools/testing/selftests/bpf/trace_helpers.c
> +++ b/tools/testing/selftests/bpf/trace_helpers.c
> @@ -216,3 +216,20 @@ ssize_t get_rel_offset(uintptr_t addr)
>         fclose(f);
>         return -EINVAL;
>  }
> +
> +char *get_lib_path(const char *path_substr)
> +{
> +       char *found = NULL;
> +       char lib_path[512];
> +       FILE *f;
> +
> +       f = fopen("/proc/self/maps", "r");
> +       while (fscanf(f, "%*s %*s %*s %*s %*s %[^\n]", lib_path) == 1) {

I think it can be followed by " (deleted)", right? Do we want to
detect that and do something about it?

> +               if (strstr(lib_path, path_substr) == NULL)
> +                       continue;
> +               found = strdup(lib_path);
> +               break;
> +       }
> +       fclose(f);
> +       return found;
> +}
> diff --git a/tools/testing/selftests/bpf/trace_helpers.h b/tools/testing/selftests/bpf/trace_helpers.h
> index 238a9c9..ff379f6 100644
> --- a/tools/testing/selftests/bpf/trace_helpers.h
> +++ b/tools/testing/selftests/bpf/trace_helpers.h
> @@ -20,5 +20,7 @@ struct ksym {
>
>  ssize_t get_uprobe_offset(const void *addr);
>  ssize_t get_rel_offset(uintptr_t addr);
> +/* Return allocated string path to library that contains path_substr. */
> +char *get_lib_path(const char *path_substr);
>
>  #endif
> --
> 1.8.3.1
>