linux-kernel - Re: [PATCH 21/35] perf tools: Make has_kcore_dir() work also for guest kcore

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Message-ID: <CAP-5=fUKkR_coQQX-pce41OYCG4BuLxmidduXy53XKX4Jy+67g@mail.gmail.com>
Date:   Tue, 19 Jul 2022 17:49:03 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH 21/35] perf tools: Make has_kcore_dir() work also for
 guest kcore_dir

On Mon, Jul 11, 2022 at 2:33 AM Adrian Hunter <adrian.hunter@...el.com> wrote:
>
> Copies of /proc/kallsyms, /proc/modules and an extract of /proc/kcore can
> be stored in the perf.data output directory under the subdirectory named
> kcore_dir. Guest machines will have their files also under subdirectories
> beginning kcore_dir__ followed by the machine pid. Make has_kcore_dir()
> return true also if there is a guest machine kcore_dir.
>
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>

Acked-by: Ian Rogers <irogers@...gle.com>

Thanks,
Ian

> ---
>  tools/perf/util/data.c | 24 +++++++++++++++---------
>  1 file changed, 15 insertions(+), 9 deletions(-)
>
> diff --git a/tools/perf/util/data.c b/tools/perf/util/data.c
> index caabeac24c69..9782ccbe595d 100644
> --- a/tools/perf/util/data.c
> +++ b/tools/perf/util/data.c
> @@ -3,6 +3,7 @@
>  #include <linux/kernel.h>
>  #include <linux/string.h>
>  #include <linux/zalloc.h>
> +#include <linux/err.h>
>  #include <sys/types.h>
>  #include <sys/stat.h>
>  #include <errno.h>
> @@ -481,16 +482,21 @@ int perf_data__make_kcore_dir(struct perf_data *data, char *buf, size_t buf_sz)
>
>  bool has_kcore_dir(const char *path)
>  {
> -       char *kcore_dir;
> -       int ret;
> -
> -       if (asprintf(&kcore_dir, "%s/kcore_dir", path) < 0)
> -               return false;
> -
> -       ret = access(kcore_dir, F_OK);
> +       struct dirent *d = ERR_PTR(-EINVAL);
> +       const char *name = "kcore_dir";
> +       DIR *dir = opendir(path);
> +       size_t n = strlen(name);
> +       bool result = false;
> +
> +       if (dir) {
> +               while (d && !result) {
> +                       d = readdir(dir);
> +                       result = d ? strncmp(d->d_name, name, n) : false;
> +               }
> +               closedir(dir);
> +       }
>
> -       free(kcore_dir);
> -       return !ret;
> +       return result;
>  }
>
>  char *perf_data__kallsyms_name(struct perf_data *data)
> --
> 2.25.1
>