perf inject: Add facility to do in place update

When there is a need to modify only timestamps, it is much simpler and
quicker to do it to the existing file rather than re-write all the
contents.

In preparation for that, add the ability to modify the input file in place.
In practice that just means making the file descriptor and mmaps writable.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: https://lore.kernel.org/r/20210430070309.17624-5-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 22 insertions, 4 deletions

diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
index ddccc0eb7390..6007f1844b01 100644
--- a/tools/perf/builtin-inject.c
+++ b/tools/perf/builtin-inject.c
@@ -43,6 +43,8 @@ struct perf_inject {
 	bool			have_auxtrace;
 	bool			strip;
 	bool			jit_mode;
+	bool			in_place_update;
+	bool			in_place_update_dry_run;
 	const char		*input_name;
 	struct perf_data	output;
 	u64			bytes_written;
@@ -701,7 +703,7 @@ static int __cmd_inject(struct perf_inject *inject)
 	int ret = -EINVAL;
 	struct perf_session *session = inject->session;
 	struct perf_data *data_out = &inject->output;
-	int fd = perf_data__fd(data_out);
+	int fd = inject->in_place_update ? -1 : perf_data__fd(data_out);
 	u64 output_data_offset;
 
 	signal(SIGINT, sig_handler);
@@ -759,14 +761,14 @@ static int __cmd_inject(struct perf_inject *inject)
 	if (!inject->itrace_synth_opts.set)
 		auxtrace_index__free(&session->auxtrace_index);
 
-	if (!data_out->is_pipe)
+	if (!data_out->is_pipe && !inject->in_place_update)
 		lseek(fd, output_data_offset, SEEK_SET);
 
 	ret = perf_session__process_events(session);
 	if (ret)
 		return ret;
 
-	if (!data_out->is_pipe) {
+	if (!data_out->is_pipe && !inject->in_place_update) {
 		if (inject->build_ids)
 			perf_header__set_feat(&session->header,
 					      HEADER_BUILD_ID);
@@ -900,7 +902,23 @@ int cmd_inject(int argc, const char **argv)
 		return -1;
 	}
 
-	if (perf_data__open(&inject.output)) {
+	if (inject.in_place_update) {
+		if (!strcmp(inject.input_name, "-")) {
+			pr_err("Input file name required for in-place updating\n");
+			return -1;
+		}
+		if (strcmp(inject.output.path, "-")) {
+			pr_err("Output file name must not be specified for in-place updating\n");
+			return -1;
+		}
+		if (!data.force && !inject.in_place_update_dry_run) {
+			pr_err("The input file would be updated in place, "
+				"the --force option is required.\n");
+			return -1;
+		}
+		if (!inject.in_place_update_dry_run)
+			data.in_place_update = true;
+	} else if (perf_data__open(&inject.output)) {
 		perror("failed to create output file");
 		return -1;
 	}