Re: [PATCH 22/35] perf tools: Automatically use guest kcore_dir if present

Ian Rogers
2022-07-20T00:52:18Z

On Mon, Jul 11, 2022 at 2:33 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
>
> When registering a guest machine using machine_pid from the id index,
> check perf.data for a matching kcore_dir subdirectory and set the
> kallsyms file name accordingly. If set, use it to find the machine's
> kernel symbols and object code (from kcore).
>
> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
> ---
> tools/perf/util/data.c | 19 +++++++++++++++++++
> tools/perf/util/data.h | 1 +
> tools/perf/util/machine.h | 1 +
> tools/perf/util/session.c | 2 ++
> tools/perf/util/symbol.c | 6 ++++--
> 5 files changed, 27 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/util/data.c b/tools/perf/util/data.c
> index 9782ccbe595d..a7f68c309545 100644
> --- a/tools/perf/util/data.c
> +++ b/tools/perf/util/data.c
> @@ -518,6 +518,25 @@ char *perf_data__kallsyms_name(struct perf_data *data)
> return kallsyms_name;
> }
>
> +char *perf_data__guest_kallsyms_name(struct perf_data *data, pid_t machine_pid)
> +{
> + char *kallsyms_name;
> + struct stat st;
> +
> + if (!data->is_dir)
> + return NULL;
> +
> + if (asprintf(&kallsyms_name, "%s/kcore_dir__%d/kallsyms", data->path, machine_pid) < 0)

Is there a missing free for this in perf_data__close ?

Thanks,
Ian

> + return NULL;
> +
> + if (stat(kallsyms_name, &st)) {
> + free(kallsyms_name);
> + return NULL;
> + }
> +
> + return kallsyms_name;
> +}
> +
> bool is_perf_data(const char *path)
> {
> bool ret = false;
> diff --git a/tools/perf/util/data.h b/tools/perf/util/data.h
> index 7de53d6e2d7f..173132d502f5 100644
> --- a/tools/perf/util/data.h
> +++ b/tools/perf/util/data.h
> @@ -101,5 +101,6 @@ unsigned long perf_data__size(struct perf_data *data);
> int perf_data__make_kcore_dir(struct perf_data *data, char *buf, size_t buf_sz);
> bool has_kcore_dir(const char *path);
> char *perf_data__kallsyms_name(struct perf_data *data);
> +char *perf_data__guest_kallsyms_name(struct perf_data *data, pid_t machine_pid);
> bool is_perf_data(const char *path);
> #endif /* __PERF_DATA_H */
> diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h
> index 5d7daf7cb7bc..d40b23c71420 100644
> --- a/tools/perf/util/machine.h
> +++ b/tools/perf/util/machine.h
> @@ -48,6 +48,7 @@ struct machine {
> bool single_address_space;
> char *root_dir;
> char *mmap_name;
> + char *kallsyms_filename;
> struct threads threads[THREADS__TABLE_SIZE];
> struct vdso_info *vdso_info;
> struct perf_env *env;
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index 7ea0b91013ea..98e16659a149 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -2772,6 +2772,8 @@ static int perf_session__register_guest(struct perf_session *session, pid_t mach
> return -ENOMEM;
> thread__put(thread);
>
> + machine->kallsyms_filename = perf_data__guest_kallsyms_name(session->data, machine_pid);
> +
> return 0;
> }
>
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index f72baf636724..a4b22caa7c24 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -2300,11 +2300,13 @@ static int dso__load_kernel_sym(struct dso *dso, struct map *map)
> static int dso__load_guest_kernel_sym(struct dso *dso, struct map *map)
> {
> int err;
> - const char *kallsyms_filename = NULL;
> + const char *kallsyms_filename;
> struct machine *machine = map__kmaps(map)->machine;
> char path[PATH_MAX];
>
> - if (machine__is_default_guest(machine)) {
> + if (machine->kallsyms_filename) {
> + kallsyms_filename = machine->kallsyms_filename;
> + } else if (machine__is_default_guest(machine)) {
> /*
> * if the user specified a vmlinux filename, use it and only
> * it, reporting errors to the user if it cannot be used.
> --
> 2.25.1
>