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

Ian Rogers
2022-07-19T17:42:03Z

On Mon, Jul 11, 2022 at 2:33 AM Adrian Hunter <adrian.hunter@intel.com> 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@intel.com>

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@google.com>

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
>