perf tools: Split up build id saving into fetch and write

We are saving the build id once we stop the profiling. And only
after doing that we know if we need to set that feature in the
header through the feature bitmap.

But if we want a proper feature support in the headers, using a
rule of offset/size pairs in sections, we need to know in
advance how many features we need to set in the headers, so that
we can reserve rooms for their section headers.

The current state doesn't allow that, as it forces us to first
save the build-ids to the file right after the datas instead of
planning any structured layout.

That's why this splits up the build-ids processing in two parts:
one that fetches the build-ids from the Dso objects, and one
that saves them into the file.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp>
LKML-Reference: <1257911467-28276-3-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

4 files changed, 59 insertions, 24 deletions

diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h
index 34c6fcb82d92..1f771ce3a957 100644
--- a/tools/perf/util/event.h
+++ b/tools/perf/util/event.h
@@ -69,6 +69,13 @@ struct build_id_event {
         char                     filename[];
 };
 
+struct build_id_list {
+        struct build_id_event   event;
+        struct list_head        list;
+        const char              *dso_name;
+        int                     len;
+};
+
 typedef union event_union {
         struct perf_event_header        header;
         struct ip_event                 ip;
diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index a4d0bbef9a43..2f702c23f71a 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -174,29 +174,18 @@ static void do_write(int fd, void *buf, size_t size)
         }
 }
 
-static bool write_buildid_table(int fd)
+static void write_buildid_table(int fd, struct list_head *id_head)
 {
-        struct dso *pos;
-        bool have_buildid = false;
-
-        list_for_each_entry(pos, &dsos, node) {
-                struct build_id_event b;
-                size_t len;
-
-                if (filename__read_build_id(pos->long_name,
-                                            &b.build_id,
-                                            sizeof(b.build_id)) < 0)
-                        continue;
-                have_buildid = true;
-                memset(&b.header, 0, sizeof(b.header));
-                len = strlen(pos->long_name) + 1;
-                len = ALIGN(len, 64);
-                b.header.size = sizeof(b) + len;
-                do_write(fd, &b, sizeof(b));
-                do_write(fd, pos->long_name, len);
-        }
+        struct build_id_list *iter, *next;
+
+        list_for_each_entry_safe(iter, next, id_head, list) {
+                struct build_id_event *b = &iter->event;
 
-        return have_buildid;
+                do_write(fd, b, sizeof(*b));
+                do_write(fd, (void *)iter->dso_name, iter->len);
+                list_del(&iter->list);
+                free(iter);
+        }
 }
 
 static void
@@ -226,10 +215,14 @@ perf_header__adds_write(struct perf_header *self, int fd, bool at_exit)
         }
 
         if (at_exit) {
-                lseek(fd, self->data_offset + self->data_size, SEEK_SET);
-                if (write_buildid_table(fd))
+                LIST_HEAD(id_list);
+
+                if (fetch_build_id_table(&id_list)) {
+                        lseek(fd, self->data_offset + self->data_size, SEEK_SET);
                         perf_header__set_feat(self, HEADER_BUILD_ID);
-                lseek(fd, cur_offset, SEEK_SET);
+                        write_buildid_table(fd, &id_list);
+                        lseek(fd, cur_offset, SEEK_SET);
+                }
         }
 };
 
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index a2e95ce1f223..9c286db62003 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -851,6 +851,40 @@ out_close:
         return err;
 }
 
+bool fetch_build_id_table(struct list_head *head)
+{
+        bool have_buildid = false;
+        struct dso *pos;
+
+        list_for_each_entry(pos, &dsos, node) {
+                struct build_id_list *new;
+                struct build_id_event b;
+                size_t len;
+
+                if (filename__read_build_id(pos->long_name,
+                                            &b.build_id,
+                                            sizeof(b.build_id)) < 0)
+                        continue;
+                have_buildid = true;
+                memset(&b.header, 0, sizeof(b.header));
+                len = strlen(pos->long_name) + 1;
+                len = ALIGN(len, 64);
+                b.header.size = sizeof(b) + len;
+
+                new = malloc(sizeof(*new));
+                if (!new)
+                        die("No memory\n");
+
+                memcpy(&new->event, &b, sizeof(b));
+                new->dso_name = pos->long_name;
+                new->len = len;
+
+                list_add_tail(&new->list, head);
+        }
+
+        return have_buildid;
+}
+
 int filename__read_build_id(const char *filename, void *bf, size_t size)
 {
         int fd, err = -1;
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index f8c1899af483..0a34a5493f1b 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -86,6 +86,7 @@ char dso__symtab_origin(const struct dso *self);
 void dso__set_build_id(struct dso *self, void *build_id);
 
 int filename__read_build_id(const char *filename, void *bf, size_t size);
+bool fetch_build_id_table(struct list_head *head);
 int build_id__sprintf(u8 *self, int len, char *bf);
 
 int load_kernel(symbol_filter_t filter);