perf build-id: Add quirk to deal with perf.data file format breakage

The a1645ce1 changeset:

"perf: 'perf kvm' tool for monitoring guest performance from host"

Added a field to struct build_id_event that broke the file format.

Since the kernel build-id is the first entry, process the table using
the old format if the well known '[kernel.kallsyms]' string for the
kernel build-id has the first 4 characters chopped off (where the pid_t
sits).

Reported-by: Han Pingtian <phan@redhat.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Zhang Yanmin <yanmin_zhang@linux.intel.com>
Cc: stable@kernel.org
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 56 insertions, 1 deletions

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index e5230c0ef95b..93862a8027ea 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -695,13 +695,50 @@ out:
         return err;
 }
 
+static int perf_header__read_build_ids_abi_quirk(struct perf_header *header,
+                                                 int input, u64 offset, u64 size)
+{
+        struct perf_session *session = container_of(header, struct perf_session, header);
+        struct {
+                struct perf_event_header   header;
+                u8                         build_id[ALIGN(BUILD_ID_SIZE, sizeof(u64))];
+                char                       filename[0];
+        } old_bev;
+        struct build_id_event bev;
+        char filename[PATH_MAX];
+        u64 limit = offset + size;
+
+        while (offset < limit) {
+                ssize_t len;
+
+                if (read(input, &old_bev, sizeof(old_bev)) != sizeof(old_bev))
+                        return -1;
+
+                if (header->needs_swap)
+                        perf_event_header__bswap(&old_bev.header);
+
+                len = old_bev.header.size - sizeof(old_bev);
+                if (read(input, filename, len) != len)
+                        return -1;
+
+                bev.header = old_bev.header;
+                bev.pid    = 0;
+                memcpy(bev.build_id, old_bev.build_id, sizeof(bev.build_id));
+                __event_process_build_id(&bev, filename, session);
+
+                offset += bev.header.size;
+        }
+
+        return 0;
+}
+
 static int perf_header__read_build_ids(struct perf_header *header,
                                        int input, u64 offset, u64 size)
 {
         struct perf_session *session = container_of(header, struct perf_session, header);
         struct build_id_event bev;
         char filename[PATH_MAX];
-        u64 limit = offset + size;
+        u64 limit = offset + size, orig_offset = offset;
         int err = -1;
 
         while (offset < limit) {
@@ -716,6 +753,24 @@ static int perf_header__read_build_ids(struct perf_header *header,
                 len = bev.header.size - sizeof(bev);
                 if (read(input, filename, len) != len)
                         goto out;
+                /*
+                 * The a1645ce1 changeset:
+                 *
+                 * "perf: 'perf kvm' tool for monitoring guest performance from host"
+                 *
+                 * Added a field to struct build_id_event that broke the file
+                 * format.
+                 *
+                 * Since the kernel build-id is the first entry, process the
+                 * table using the old format if the well known
+                 * '[kernel.kallsyms]' string for the kernel build-id has the
+                 * first 4 characters chopped off (where the pid_t sits).
+                 */
+                if (memcmp(filename, "nel.kallsyms]", 13) == 0) {
+                        if (lseek(input, orig_offset, SEEK_SET) == (off_t)-1)
+                                return -1;
+                        return perf_header__read_build_ids_abi_quirk(header, input, offset, size);
+                }
 
                 __event_process_build_id(&bev, filename, session);