[PATCH v3 2/6] perf kvm: Check kvm_need_default_arch_event() early

[Namhyung Kim <namhyung@kernel.org>]

There's a subtle issue with option parsing in perf record.  It calls the
function with PARSE_OPT_STOP_AT_NON_OPTION so that it can pass later
options to the external command it runs.

But perf kvm record passes the default arch events after the argv.  So
if user calls it with command, then it passes the event to the external
command and fails it like below:

  $ sudo perf kvm --host record sleep 1
  sleep: invalid option -- 'e'
  Try 'sleep --help' for more information.
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.046 MB perf.data.kvm (5 samples) ]

We can check if the default options are needed before passing the extra
command line to make sure it's passed to perf record.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 tools/perf/builtin-kvm.c | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
index 2f00cc1fd1c7cdbd..24576e4ebb02cade 100644
--- a/tools/perf/builtin-kvm.c
+++ b/tools/perf/builtin-kvm.c
@@ -1996,13 +1996,14 @@ static int __cmd_record(const char *file_name, int argc, const char **argv)
 {
 	int rec_argc, i = 0, j, ret;
 	const char **rec_argv;
+	int need_arch_event = !!kvm_need_default_arch_event(EM_HOST, argc, argv);
 
 	/*
 	 * Besides the 2 more options "-o" and "filename",
 	 * kvm_add_default_arch_event() may add 2 extra options,
-	 * so allocate 4 more items.
+	 * so allocate more items conditionally.
 	 */
-	rec_argc = argc + 2 + 2;
+	rec_argc = argc + 2 + (2 * need_arch_event);
 	rec_argv = calloc(rec_argc + 1, sizeof(char *));
 	if (!rec_argv)
 		return -ENOMEM;
@@ -2010,22 +2011,22 @@ static int __cmd_record(const char *file_name, int argc, const char **argv)
 	rec_argv[i++] = STRDUP_FAIL_EXIT("record");
 	rec_argv[i++] = STRDUP_FAIL_EXIT("-o");
 	rec_argv[i++] = STRDUP_FAIL_EXIT(file_name);
-	for (j = 1; j < argc; j++, i++)
-		rec_argv[i] = STRDUP_FAIL_EXIT(argv[j]);
-
-	BUG_ON(i + 2 != rec_argc);
-
-	if (kvm_need_default_arch_event(EM_HOST, argc, argv)) {
+	if (need_arch_event) {
 		ret = kvm_add_default_arch_event(EM_HOST, &i, rec_argv);
 		if (ret)
 			goto EXIT;
 	}
 
+	for (j = 1; j < argc; j++, i++)
+		rec_argv[i] = STRDUP_FAIL_EXIT(argv[j]);
+
+	BUG_ON(i != rec_argc);
+
 	ret = cmd_record(i, rec_argv);
 
 EXIT:
-	for (i = 0; i < rec_argc; i++)
-		free((void *)rec_argv[i]);
+	for (j = 0; j < i; j++)
+		free((void *)rec_argv[j]);
 	free(rec_argv);
 	return ret;
 }
-- 
2.55.0.rc0.799.gd6f94ed593-goog