perf tools: Automatically use guest kcore_dir if present

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>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: kvm@vger.kernel.org
Link: https://lore.kernel.org/r/20220711093218.10967-23-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/data.c b/tools/perf/util/data.c
index 9782ccb..a7f68c3 100644 (file)
--- 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)
+               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 7de53d6..173132d 100644 (file)
--- 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 e147634..199807a 100644 (file)
--- 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 7ea0b91..98e1665 100644 (file)
--- 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 f72baf6..a4b22ca 100644 (file)
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -2300,11 +2300,13 @@ do_kallsyms:
 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.