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Commit 69996df4 authored by Stephane Eranian's avatar Stephane Eranian Committed by Ingo Molnar
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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a perf.data file which is using a newer version of the ABI than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: default avatarStephane 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: default avatarIngo Molnar <mingo@elte.hu>
parent cb5d7699

tools/perf/util/header.c

+48 −5
Original line number Diff line number Diff line
@@ -1973,6 +1973,51 @@ static int perf_header__read_pipe(struct perf_session *session, int fd) 
	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 @@ int perf_session__read_header(struct perf_session *session, int fd) 
	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)

tools/perf/util/session.c

+2 −2
Original line number Diff line number Diff line
@@ -24,7 +24,7 @@ static int perf_session__open(struct perf_session *self, bool force) 
		self->fd = STDIN_FILENO;



		if (perf_session__read_header(self, self->fd) < 0)

			pr_err("incompatible file format");

			pr_err("incompatible file format (rerun with -v to learn more)");



		return 0;

	}
@@ -56,7 +56,7 @@ static int perf_session__open(struct perf_session *self, bool force) 
	}



	if (perf_session__read_header(self, self->fd) < 0) {

		pr_err("incompatible file format");

		pr_err("incompatible file format (rerun with -v to learn more)");

		goto out_close;

	}