linux-kernel - [PATCH] perf inject: correct event attribute sizes

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Date:   Tue, 24 Nov 2020 19:58:17 +0000
From:   Al Grant <al.grant@....com>
To:     linux-perf-users@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>
Cc:     Al Grant <al.grant@....com>, Al Grant <al.grant@...s.arm.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] perf inject: correct event attribute sizes

When perf inject reads a perf.data file from an older version of perf,
it writes event attributes into the output with the original size field,
but lays them out as if they had the size currently used. Readers see
a corrupt file. Update the size field to match the layout.

Signed-off-by: Al Grant <al.grant@...s.arm.com>
---
 tools/perf/util/header.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index be850e9f8852..0d95981df8dd 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -3331,6 +3331,14 @@ int perf_session__write_header(struct perf_session *session,
 	attr_offset = lseek(ff.fd, 0, SEEK_CUR);
 
 	evlist__for_each_entry(evlist, evsel) {
+		if (evsel->core.attr.size < sizeof(evsel->core.attr)) {
+			/*
+			 * We are likely in "perf inject" and have read
+			 * from an older file. Update attr size so that
+			 * reader gets the right offset to the ids.
+			 */
+			evsel->core.attr.size = sizeof(evsel->core.attr);
+		}
 		f_attr = (struct perf_file_attr){
 			.attr = evsel->core.attr,
 			.ids  = {
-- 
2.17.1