perf inject: Lazily allocate guest_event event_buf

The event_buf is 64kb (PERF_SAMPLE_SIZE_MAX) and stack allocated in
struct perf_inject. It is used for guest events that may not exist in
a file. Make the array allocation lazy to cut down on the stack usage.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20230527034324.2597593-5-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
index 2023b7a0daa6246d693c1dd1d68f927d1980f8fe..c8cf2fdd9cff9637ebd97660321e858fa3aeb3e0 100644 (file)
--- a/tools/perf/builtin-inject.c
+++ b/tools/perf/builtin-inject.c
@@ -47,7 +47,7 @@
 struct guest_event {
        struct perf_sample              sample;
        union perf_event                *event;
-       char                            event_buf[PERF_SAMPLE_MAX_SIZE];
+       char                            *event_buf;
 };
 
 struct guest_id {
@@ -1374,11 +1374,19 @@ static void guest_session__convert_time(struct guest_session *gs, u64 guest_time
 
 static int guest_session__fetch(struct guest_session *gs)
 {
-       void *buf = gs->ev.event_buf;
-       struct perf_event_header *hdr = buf;
+       void *buf;
+       struct perf_event_header *hdr;
        size_t hdr_sz = sizeof(*hdr);
        ssize_t ret;
 
+       buf = gs->ev.event_buf;
+       if (!buf) {
+               buf = malloc(PERF_SAMPLE_MAX_SIZE);
+               if (!buf)
+                       return -ENOMEM;
+               gs->ev.event_buf = buf;
+       }
+       hdr = buf;
        ret = readn(gs->tmp_fd, buf, hdr_sz);
        if (ret < 0)
                return ret;
@@ -2401,5 +2409,6 @@ out_close_output:
                perf_data__close(&inject.output);
        free(inject.itrace_synth_opts.vm_tm_corr_args);
        free(inject.event_copy);
+       free(inject.guest_session.ev.event_buf);
        return ret;
 }