perf tools: Enable reading of perf.data files from different ABI rev
This patch allows perf to process perf.data files generated
using an ABI that has a different perf_event_attr struct size,
i.e., a different ABI version.
The perf_event_attr can be extended, yet perf needs to cope with
older perf.data files. Similarly, perf must be able to cope with
a perf.data file which is using a newer version of the ABI than
what it knows about.
This patch adds read_attr(), a routine that reads a
perf_event_attr struct from a file incrementally based on its
advertised size. If the on-file struct is smaller than what perf
knows, then the extra fields are zeroed. If the on-file struct
is bigger, then perf only uses what it knows about, the rest is
skipped.
Signed-off-by: Stephane Eranian <eranian@google.com>
Cc: peterz@infradead.org
Cc: acme@redhat.com
Cc: robert.richter@amd.com
Cc: ming.m.lin@intel.com
Cc: andi@firstfloor.org
Cc: asharma@fb.com
Cc: ravitillo@lbl.gov
Cc: vweaver1@eecs.utk.edu
Cc: khandual@linux.vnet.ibm.com
Cc: dsahern@gmail.com
Link: http://lkml.kernel.org/r/1328826068-11713-17-git-send-email-eranian@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 9f867d9..666f189 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -1973,6 +1973,51 @@
return 0;
}
+static int read_attr(int fd, struct perf_header *ph,
+ struct perf_file_attr *f_attr)
+{
+ struct perf_event_attr *attr = &f_attr->attr;
+ size_t sz, left;
+ size_t our_sz = sizeof(f_attr->attr);
+ int ret;
+
+ memset(f_attr, 0, sizeof(*f_attr));
+
+ /* read minimal guaranteed structure */
+ ret = readn(fd, attr, PERF_ATTR_SIZE_VER0);
+ if (ret <= 0) {
+ pr_debug("cannot read %d bytes of header attr\n",
+ PERF_ATTR_SIZE_VER0);
+ return -1;
+ }
+
+ /* on file perf_event_attr size */
+ sz = attr->size;
+ if (ph->needs_swap)
+ sz = bswap_32(sz);
+
+ if (sz == 0) {
+ /* assume ABI0 */
+ sz = PERF_ATTR_SIZE_VER0;
+ } else if (sz > our_sz) {
+ pr_debug("file uses a more recent and unsupported ABI"
+ " (%zu bytes extra)\n", sz - our_sz);
+ return -1;
+ }
+ /* what we have not yet read and that we know about */
+ left = sz - PERF_ATTR_SIZE_VER0;
+ if (left) {
+ void *ptr = attr;
+ ptr += PERF_ATTR_SIZE_VER0;
+
+ ret = readn(fd, ptr, left);
+ }
+ /* read perf_file_section, ids are read in caller */
+ ret = readn(fd, &f_attr->ids, sizeof(f_attr->ids));
+
+ return ret <= 0 ? -1 : 0;
+}
+
int perf_session__read_header(struct perf_session *session, int fd)
{
struct perf_header *header = &session->header;
@@ -1988,19 +2033,17 @@
if (session->fd_pipe)
return perf_header__read_pipe(session, fd);
- if (perf_file_header__read(&f_header, header, fd) < 0) {
- pr_debug("incompatible file format\n");
+ if (perf_file_header__read(&f_header, header, fd) < 0)
return -EINVAL;
- }
- nr_attrs = f_header.attrs.size / sizeof(f_attr);
+ nr_attrs = f_header.attrs.size / f_header.attr_size;
lseek(fd, f_header.attrs.offset, SEEK_SET);
for (i = 0; i < nr_attrs; i++) {
struct perf_evsel *evsel;
off_t tmp;
- if (readn(fd, &f_attr, sizeof(f_attr)) <= 0)
+ if (read_attr(fd, header, &f_attr) < 0)
goto out_errno;
if (header->needs_swap)