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Commit 114382a0 authored by Stephane Eranian's avatar Stephane Eranian Committed by Ingo Molnar
Browse files

perf tools: Make perf able to read files from older ABIs 



This patches provides a way to handle legacy perf.data
files.  Legacy files are those using the older PERFFILE
signature.

For those, it is still necessary to detect endianness but
without comparing their header->attr_size with the
tool's own version as it may be different. Instead, we use
a reference table for all known sizes from the legacy era.

We try all the combinations for sizes and endianness. If we find
a match, we proceed, otherwise we return: "incompatible file
format".

This is also done for the pipe-mode file format.

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/1328826068-11713-19-git-send-email-eranian@google.com


Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 62db9068

tools/perf/util/header.c

+94 −28
Original line number Diff line number Diff line
@@ -1803,35 +1803,101 @@ int perf_header__process_sections(struct perf_header *header, int fd, 
	return err;

}



static int check_magic_endian(u64 *magic, struct perf_file_header *header,

			      struct perf_header *ph)

static const int attr_file_abi_sizes[] = {

	[0] = PERF_ATTR_SIZE_VER0,

	[1] = PERF_ATTR_SIZE_VER1,

	0,

};



/*

 * In the legacy file format, the magic number is not used to encode endianness.

 * hdr_sz was used to encode endianness. But given that hdr_sz can vary based

 * on ABI revisions, we need to try all combinations for all endianness to

 * detect the endianness.

 */

static int try_all_file_abis(uint64_t hdr_sz, struct perf_header *ph)

{

	int ret;

	uint64_t ref_size, attr_size;

	int i;



	/* check for legacy format */

	ret = memcmp(magic, __perf_magic1, sizeof(*magic));

	if (ret == 0) {

		pr_debug("legacy perf.data format\n");

		if (!header)

	for (i = 0 ; attr_file_abi_sizes[i]; i++) {

		ref_size = attr_file_abi_sizes[i]

			 + sizeof(struct perf_file_section);

		if (hdr_sz != ref_size) {

			attr_size = bswap_64(hdr_sz);

			if (attr_size != ref_size)

				continue;



			ph->needs_swap = true;

		}

		pr_debug("ABI%d perf.data file detected, need_swap=%d\n",

			 i,

			 ph->needs_swap);

		return 0;

	}

	/* could not determine endianness */

	return -1;

}



		if (header->attr_size != sizeof(struct perf_file_attr)) {

			u64 attr_size = bswap_64(header->attr_size);

#define PERF_PIPE_HDR_VER0	16



			if (attr_size != sizeof(struct perf_file_attr))

				return -1;

static const size_t attr_pipe_abi_sizes[] = {

	[0] = PERF_PIPE_HDR_VER0,

	0,

};



/*

 * In the legacy pipe format, there is an implicit assumption that endiannesss

 * between host recording the samples, and host parsing the samples is the

 * same. This is not always the case given that the pipe output may always be

 * redirected into a file and analyzed on a different machine with possibly a

 * different endianness and perf_event ABI revsions in the perf tool itself.

 */

static int try_all_pipe_abis(uint64_t hdr_sz, struct perf_header *ph)

{

	u64 attr_size;

	int i;



	for (i = 0 ; attr_pipe_abi_sizes[i]; i++) {

		if (hdr_sz != attr_pipe_abi_sizes[i]) {

			attr_size = bswap_64(hdr_sz);

			if (attr_size != hdr_sz)

				continue;



			ph->needs_swap = true;

		}

		pr_debug("Pipe ABI%d perf.data file detected\n", i);

		return 0;

	}

	return -1;

}



static int check_magic_endian(u64 magic, uint64_t hdr_sz,

			      bool is_pipe, struct perf_header *ph)

{

	int ret;



	/* check for legacy format */

	ret = memcmp(&magic, __perf_magic1, sizeof(magic));

	if (ret == 0) {

		pr_debug("legacy perf.data format\n");

		if (is_pipe)

			return try_all_pipe_abis(hdr_sz, ph);



		return try_all_file_abis(hdr_sz, ph);

	}

	/*

	 * the new magic number serves two purposes:

	 * - unique number to identify actual perf.data files

	 * - encode endianness of file

	 */



	/* check magic number with same endianness */

	if (*magic == __perf_magic2)

	/* check magic number with one endianness */

	if (magic == __perf_magic2)

		return 0;



	/* check magic number but opposite endianness */

	if (*magic != __perf_magic2_sw)

	/* check magic number with opposite endianness */

	if (magic != __perf_magic2_sw)

		return -1;



	ph->needs_swap = true;
@@ -1850,8 +1916,11 @@ int perf_file_header__read(struct perf_file_header *header, 
	if (ret <= 0)

		return -1;



	if (check_magic_endian(&header->magic, header, ph) < 0)

	if (check_magic_endian(header->magic,

			       header->attr_size, false, ph) < 0) {

		pr_debug("magic/endian check failed\n");

		return -1;

	}



	if (ph->needs_swap) {

		mem_bswap_64(header, offsetof(struct perf_file_header,
@@ -1938,21 +2007,17 @@ static int perf_file_header__read_pipe(struct perf_pipe_file_header *header, 
	if (ret <= 0)

		return -1;



	 if (check_magic_endian(&header->magic, NULL, ph) < 0)

		return -1;



	if (repipe && do_write(STDOUT_FILENO, header, sizeof(*header)) < 0)

	if (check_magic_endian(header->magic, header->size, true, ph) < 0) {

		pr_debug("endian/magic failed\n");

		return -1;

	}



	if (header->size != sizeof(*header)) {

		u64 size = bswap_64(header->size);

	if (ph->needs_swap)

		header->size = bswap_64(header->size);



		if (size != sizeof(*header))

	if (repipe && do_write(STDOUT_FILENO, header, sizeof(*header)) < 0)

		return -1;



		ph->needs_swap = true;

	}



	return 0;

}
@@ -1992,6 +2057,7 @@ static int read_attr(int fd, struct perf_header *ph, 


	/* on file perf_event_attr size */

	sz = attr->size;



	if (ph->needs_swap)

		sz = bswap_32(sz);