Re: [PATCH 08/35] perf buildid-cache: Add guestmount'd files to the build ID cache

[Ian Rogers]

On Mon, Jul 11, 2022 at 2:33 AM Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
>
> When the guestmount option is used, a guest machine's file system mount
> point is recorded in machine->root_dir.
>
> perf already iterates guest machines when adding files to the build ID
> cache, but does not take machine->root_dir into account.
>
> Use machine->root_dir to find files for guest build IDs, and add them to
> the build ID cache using the "proper" name i.e. relative to the guest root
> directory not the host root directory.
>
> Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>

Is it plausible to add a test for this? Our tests create workload but
there's no existing hypervisor way to do this. Perhaps the test can
run in a hypervisor? Or maybe there's a route that doesn't involve
hypervisors.

Acked-by: Ian Rogers <irogers@xxxxxxxxxx>

Thanks,
Ian

> ---
>  tools/perf/util/build-id.c | 67 +++++++++++++++++++++++++++++---------
>  tools/perf/util/build-id.h | 16 ++++++---
>  2 files changed, 63 insertions(+), 20 deletions(-)
>
> diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
> index 4c9093b64d1f..7c9f441936ee 100644
> --- a/tools/perf/util/build-id.c
> +++ b/tools/perf/util/build-id.c
> @@ -625,9 +625,12 @@ static int build_id_cache__add_sdt_cache(const char *sbuild_id,
>  #endif
>
>  static char *build_id_cache__find_debug(const char *sbuild_id,
> -                                       struct nsinfo *nsi)
> +                                       struct nsinfo *nsi,
> +                                       const char *root_dir)
>  {
> +       const char *dirname = "/usr/lib/debug/.build-id/";
>         char *realname = NULL;
> +       char dirbuf[PATH_MAX];
>         char *debugfile;
>         struct nscookie nsc;
>         size_t len = 0;
> @@ -636,8 +639,12 @@ static char *build_id_cache__find_debug(const char *sbuild_id,
>         if (!debugfile)
>                 goto out;
>
> -       len = __symbol__join_symfs(debugfile, PATH_MAX,
> -                                  "/usr/lib/debug/.build-id/");
> +       if (root_dir) {
> +               path__join(dirbuf, PATH_MAX, root_dir, dirname);
> +               dirname = dirbuf;
> +       }
> +
> +       len = __symbol__join_symfs(debugfile, PATH_MAX, dirname);
>         snprintf(debugfile + len, PATH_MAX - len, "%.2s/%s.debug", sbuild_id,
>                  sbuild_id + 2);
>
> @@ -668,14 +675,18 @@ static char *build_id_cache__find_debug(const char *sbuild_id,
>
>  int
>  build_id_cache__add(const char *sbuild_id, const char *name, const char *realname,
> -                   struct nsinfo *nsi, bool is_kallsyms, bool is_vdso)
> +                   struct nsinfo *nsi, bool is_kallsyms, bool is_vdso,
> +                   const char *proper_name, const char *root_dir)
>  {
>         const size_t size = PATH_MAX;
>         char *filename = NULL, *dir_name = NULL, *linkname = zalloc(size), *tmp;
>         char *debugfile = NULL;
>         int err = -1;
>
> -       dir_name = build_id_cache__cachedir(sbuild_id, name, nsi, is_kallsyms,
> +       if (!proper_name)
> +               proper_name = name;
> +
> +       dir_name = build_id_cache__cachedir(sbuild_id, proper_name, nsi, is_kallsyms,
>                                             is_vdso);
>         if (!dir_name)
>                 goto out_free;
> @@ -715,7 +726,7 @@ build_id_cache__add(const char *sbuild_id, const char *name, const char *realnam
>          */
>         if (!is_kallsyms && !is_vdso &&
>             strncmp(".ko", name + strlen(name) - 3, 3)) {
> -               debugfile = build_id_cache__find_debug(sbuild_id, nsi);
> +               debugfile = build_id_cache__find_debug(sbuild_id, nsi, root_dir);
>                 if (debugfile) {
>                         zfree(&filename);
>                         if (asprintf(&filename, "%s/%s", dir_name,
> @@ -781,8 +792,9 @@ build_id_cache__add(const char *sbuild_id, const char *name, const char *realnam
>         return err;
>  }
>
> -int build_id_cache__add_s(const char *sbuild_id, const char *name,
> -                         struct nsinfo *nsi, bool is_kallsyms, bool is_vdso)
> +int __build_id_cache__add_s(const char *sbuild_id, const char *name,
> +                           struct nsinfo *nsi, bool is_kallsyms, bool is_vdso,
> +                           const char *proper_name, const char *root_dir)
>  {
>         char *realname = NULL;
>         int err = -1;
> @@ -796,8 +808,8 @@ int build_id_cache__add_s(const char *sbuild_id, const char *name,
>                         goto out_free;
>         }
>
> -       err = build_id_cache__add(sbuild_id, name, realname, nsi, is_kallsyms, is_vdso);
> -
> +       err = build_id_cache__add(sbuild_id, name, realname, nsi,
> +                                 is_kallsyms, is_vdso, proper_name, root_dir);
>  out_free:
>         if (!is_kallsyms)
>                 free(realname);
> @@ -806,14 +818,16 @@ int build_id_cache__add_s(const char *sbuild_id, const char *name,
>
>  static int build_id_cache__add_b(const struct build_id *bid,
>                                  const char *name, struct nsinfo *nsi,
> -                                bool is_kallsyms, bool is_vdso)
> +                                bool is_kallsyms, bool is_vdso,
> +                                const char *proper_name,
> +                                const char *root_dir)
>  {
>         char sbuild_id[SBUILD_ID_SIZE];
>
>         build_id__sprintf(bid, sbuild_id);
>
> -       return build_id_cache__add_s(sbuild_id, name, nsi, is_kallsyms,
> -                                    is_vdso);
> +       return __build_id_cache__add_s(sbuild_id, name, nsi, is_kallsyms,
> +                                      is_vdso, proper_name, root_dir);
>  }
>
>  bool build_id_cache__cached(const char *sbuild_id)
> @@ -896,6 +910,10 @@ static int dso__cache_build_id(struct dso *dso, struct machine *machine,
>         bool is_kallsyms = dso__is_kallsyms(dso);
>         bool is_vdso = dso__is_vdso(dso);
>         const char *name = dso->long_name;
> +       const char *proper_name = NULL;
> +       const char *root_dir = NULL;
> +       char *allocated_name = NULL;
> +       int ret = 0;
>
>         if (!dso->has_build_id)
>                 return 0;
> @@ -905,11 +923,28 @@ static int dso__cache_build_id(struct dso *dso, struct machine *machine,
>                 name = machine->mmap_name;
>         }
>
> +       if (!machine__is_host(machine)) {
> +               if (*machine->root_dir) {
> +                       root_dir = machine->root_dir;
> +                       ret = asprintf(&allocated_name, "%s/%s", root_dir, name);
> +                       if (ret < 0)
> +                               return ret;
> +                       proper_name = name;
> +                       name = allocated_name;
> +               } else if (is_kallsyms) {
> +                       /* Cannot get guest kallsyms */
> +                       return 0;
> +               }
> +       }
> +
>         if (!is_kallsyms && dso__build_id_mismatch(dso, name))
> -               return 0;
> +               goto out_free;
>
> -       return build_id_cache__add_b(&dso->bid, name, dso->nsinfo,
> -                                    is_kallsyms, is_vdso);
> +       ret = build_id_cache__add_b(&dso->bid, name, dso->nsinfo,
> +                                   is_kallsyms, is_vdso, proper_name, root_dir);
> +out_free:
> +       free(allocated_name);
> +       return ret;
>  }
>
>  static int
> diff --git a/tools/perf/util/build-id.h b/tools/perf/util/build-id.h
> index c19617151670..4e3a1169379b 100644
> --- a/tools/perf/util/build-id.h
> +++ b/tools/perf/util/build-id.h
> @@ -66,10 +66,18 @@ int build_id_cache__list_build_ids(const char *pathname, struct nsinfo *nsi,
>                                    struct strlist **result);
>  bool build_id_cache__cached(const char *sbuild_id);
>  int build_id_cache__add(const char *sbuild_id, const char *name, const char *realname,
> -                       struct nsinfo *nsi, bool is_kallsyms, bool is_vdso);
> -int build_id_cache__add_s(const char *sbuild_id,
> -                         const char *name, struct nsinfo *nsi,
> -                         bool is_kallsyms, bool is_vdso);
> +                       struct nsinfo *nsi, bool is_kallsyms, bool is_vdso,
> +                       const char *proper_name, const char *root_dir);
> +int __build_id_cache__add_s(const char *sbuild_id,
> +                           const char *name, struct nsinfo *nsi,
> +                           bool is_kallsyms, bool is_vdso,
> +                           const char *proper_name, const char *root_dir);
> +static inline int build_id_cache__add_s(const char *sbuild_id,
> +                                       const char *name, struct nsinfo *nsi,
> +                                       bool is_kallsyms, bool is_vdso)
> +{
> +       return __build_id_cache__add_s(sbuild_id, name, nsi, is_kallsyms, is_vdso, NULL, NULL);
> +}
>  int build_id_cache__remove_s(const char *sbuild_id);
>
>  extern char buildid_dir[];
> --
> 2.25.1
>