perf inject: Fix output from a file to a pipe

When the input is a regular file but the output is a pipe, it should
write a pipe header.  But just repiping would write a portion of the
existing header which is different in 'size' value.  So we need to
prevent it and write a new pipe header along with other information
like event attributes and features.

This can handle something like this:

  # perf record -a -B sleep 1

  # perf inject -b -i perf.data | perf report -i -

Factor out perf_event__synthesize_for_pipe() to be shared between perf
record and inject.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20210719223153.1618812-5-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 26 insertions, 2 deletions

diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
index f9af24350f61..6ad191e731fc 100644
--- a/tools/perf/builtin-inject.c
+++ b/tools/perf/builtin-inject.c
@@ -919,6 +919,7 @@ int cmd_inject(int argc, const char **argv)
 		.use_stdio = true,
 	};
 	int ret;
+	bool repipe = true;
 
 	struct option options[] = {
 		OPT_BOOLEAN('b', "build-ids", &inject.build_ids,
@@ -993,10 +994,18 @@ int cmd_inject(int argc, const char **argv)
 	}
 
 	data.path = inject.input_name;
-	if (!strcmp(inject.input_name, "-") || inject.output.is_pipe)
+	if (!strcmp(inject.input_name, "-") || inject.output.is_pipe) {
 		inject.is_pipe = true;
+		/*
+		 * Do not repipe header when input is a regular file
+		 * since either it can rewrite the header at the end
+		 * or write a new pipe header.
+		 */
+		if (strcmp(inject.input_name, "-"))
+			repipe = false;
+	}
 
-	inject.session = __perf_session__new(&data, inject.is_pipe,
+	inject.session = __perf_session__new(&data, repipe,
 					     perf_data__fd(&inject.output),
 					     &inject.tool);
 	if (IS_ERR(inject.session)) {
@@ -1007,6 +1016,21 @@ int cmd_inject(int argc, const char **argv)
 	if (zstd_init(&(inject.session->zstd_data), 0) < 0)
 		pr_warning("Decompression initialization failed.\n");
 
+	if (!data.is_pipe && inject.output.is_pipe) {
+		ret = perf_header__write_pipe(perf_data__fd(&inject.output));
+		if (ret < 0) {
+			pr_err("Couldn't write a new pipe header.\n");
+			goto out_delete;
+		}
+
+		ret = perf_event__synthesize_for_pipe(&inject.tool,
+						      inject.session,
+						      &inject.output,
+						      perf_event__repipe);
+		if (ret < 0)
+			goto out_delete;
+	}
+
 	if (inject.build_ids && !inject.build_id_all) {
 		/*
 		 * to make sure the mmap records are ordered correctly