perf tools: Fix endian conversion reading event attr from file header

The perf_event_attr struct has two __u32's at the top and
they need to be swapped individually.

With this change I was able to analyze a perf.data collected in a
32-bit PPC VM on an x86 system. I tested both 32-bit and 64-bit
binaries for the Intel analysis side; both read the PPC perf.data
file correctly.

-v2:
 - changed the existing perf_event__attr_swap() to swap only elements
   of perf_event_attr and exported it for use in swapping the
   attributes in the file header
 - updated swap_ops used for processing events

Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: acme@ghostprotocols.net
Cc: peterz@infradead.org
Cc: paulus@samba.org
Cc: <stable@kernel.org>
Link: http://lkml.kernel.org/r/1310754849-12474-1-git-send-email-dsahern@gmail.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

tools/perf/util/header.c

@@ -877,9 +877,12 @@ int perf_session__read_header(struct perf_session *session, int fd)
 		struct perf_evsel *evsel;
 		off_t tmp;
 
-		if (perf_header__getbuffer64(header, fd, &f_attr, sizeof(f_attr)))
+		if (readn(fd, &f_attr, sizeof(f_attr)) <= 0)
 			goto out_errno;
 
+		if (header->needs_swap)
+			perf_event__attr_swap(&f_attr.attr);
+
 		tmp = lseek(fd, 0, SEEK_CUR);
 		evsel = perf_evsel__new(&f_attr.attr, i);