perf env: Add helper to lazily compute the os_release

In live mode the os_release isn't being initialized, make a lazy
initialization helper that assumes when the os_release isn't
initialized this is live mode.

Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Honglei Wang <jameshongleiwang@126.com>
Cc: Jan Polensky <japo@linux.ibm.com>
Cc: Sumanth Korikkar <sumanthk@linux.ibm.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/data-convert-bt.c

@@ -1414,7 +1414,7 @@ do {									\
 
 	ADD("host",    env->hostname);
 	ADD("sysname", "Linux");
-	ADD("release", env->os_release);
+	ADD("release", perf_env__os_release(env));
 	ADD("version", env->version);
 	ADD("machine", env->arch);
 	ADD("domain", "kernel");

tools/perf/util/data-convert-json.c

@@ -16,6 +16,7 @@
 #include "linux/err.h"
 #include "util/auxtrace.h"
 #include "util/debug.h"
+#include "util/env.h"
 #include "util/dso.h"
 #include "util/event.h"
 #include "util/evsel.h"
@@ -272,7 +273,7 @@ static void output_headers(struct perf_session *session, struct convert_json *c)
 {
 	struct stat st;
 	const struct perf_header *header = &session->header;
-	const struct perf_env *env = perf_session__env(session);
+	struct perf_env *env = perf_session__env(session);
 	int ret;
 	int fd = perf_data__fd(session->data);
 	int i;
@@ -296,7 +297,8 @@ static void output_headers(struct perf_session *session, struct convert_json *c)
 	output_json_key_format(out, true, 2, "feat-offset", "%" PRIu64, header->feat_offset);
 
 	output_json_key_string(out, true, 2, "hostname", env->hostname);
-	output_json_key_string(out, true, 2, "os-release", env->os_release);
+	output_json_key_string(out, true, 2, "os-release",
+			       perf_env__os_release(env));
 	output_json_key_string(out, true, 2, "arch", env->arch);
 
 	if (env->cpu_desc)

tools/perf/util/env.c

@@ -361,6 +361,44 @@ bool perf_arch_is_big_endian(const char *arch)
 	return false;
 }
 
+const char *perf_env__os_release(struct perf_env *env)
+{
+	struct utsname uts;
+	int ret;
+	const char *release;
+
+	if (!env)
+		return perf_version_string;
+
+	mutex_lock(&env->lock);
+	if (env->os_release) {
+		release = env->os_release;
+		goto out;
+	}
+
+	/*
+	 * If env->arch is set, this is an offline target environment.
+	 * If the os_release is not populated in the file, we do not want
+	 * to poison it with the host's release which would break guest checks.
+	 */
+	if (env->arch) {
+		release = NULL;
+		goto out;
+	}
+
+	/*
+	 * The os_release is being accessed but wasn't initialized from a data
+	 * file, assume this is 'live' mode and use the release from uname. If
+	 * uname or strdup fails then use the current perf tool version.
+	 */
+	ret = uname(&uts);
+	env->os_release = strdup(ret < 0 ? perf_version_string : uts.release);
+	release = env->os_release ?: perf_version_string;
+out:
+	mutex_unlock(&env->lock);
+	return release;
+}
+
 int perf_env__set_cmdline(struct perf_env *env, int argc, const char *argv[])
 {
 	int i;

tools/perf/util/env.h

@@ -176,6 +176,7 @@ void perf_env__exit(struct perf_env *env);
 
 int perf_env__kernel_is_64_bit(struct perf_env *env);
 bool perf_arch_is_big_endian(const char *arch);
+const char *perf_env__os_release(struct perf_env *env);
 
 int perf_env__set_cmdline(struct perf_env *env, int argc, const char *argv[]);
 

tools/perf/util/header.c

@@ -432,13 +432,19 @@ static int write_osrelease(struct feat_fd *ff,
 			   struct evlist *evlist __maybe_unused)
 {
 	struct utsname uts;
-	int ret;
+	const char *release = NULL;
 
-	ret = uname(&uts);
-	if (ret < 0)
-		return -1;
+	if (evlist->session)
+		release = perf_env__os_release(perf_session__env(evlist->session));
 
-	return do_write_string(ff, uts.release);
+	if (!release) {
+		int ret = uname(&uts);
+
+		if (ret < 0)
+			return -1;
+		release = uts.release;
+	}
+	return do_write_string(ff, release);
 }
 
 static int write_arch(struct feat_fd *ff, struct evlist *evlist)

tools/perf/util/symbol.c

@@ -2225,7 +2225,7 @@ static int vmlinux_path__init(struct perf_env *env)
 {
 	struct utsname uts;
 	char bf[PATH_MAX];
-	char *kernel_version;
+	const char *kernel_version;
 	unsigned int i;
 
 	vmlinux_path = malloc(sizeof(char *) * (ARRAY_SIZE(vmlinux_paths) +
@@ -2242,7 +2242,7 @@ static int vmlinux_path__init(struct perf_env *env)
 		return 0;
 
 	if (env) {
-		kernel_version = env->os_release;
+		kernel_version = perf_env__os_release(env);
 	} else {
 		if (uname(&uts) < 0)
 			goto out_fail;