[PATCH v6 2/3] perf env: Add helper to lazily compute the os_release

[Ian Rogers <irogers@google.com>]

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>
---
 tools/perf/util/data-convert-bt.c |  2 +-
 tools/perf/util/env.c             | 21 +++++++++++++++++++++
 tools/perf/util/env.h             |  1 +
 tools/perf/util/header.c          | 16 +++++++++++-----
 tools/perf/util/symbol.c          |  4 ++--
 5 files changed, 36 insertions(+), 8 deletions(-)

diff --git a/tools/perf/util/data-convert-bt.c b/tools/perf/util/data-convert-bt.c
index 3b8f2df823a9..2c88420fe33e 100644
--- a/tools/perf/util/data-convert-bt.c
+++ b/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");
diff --git a/tools/perf/util/env.c b/tools/perf/util/env.c
index 339d62ca37bb..34b737950f73 100644
--- a/tools/perf/util/env.c
+++ b/tools/perf/util/env.c
@@ -330,6 +330,27 @@ int perf_env__kernel_is_64_bit(struct perf_env *env)
 	return env->kernel_is_64_bit;
 }
 
+const char *perf_env__os_release(struct perf_env *env)
+{
+	struct utsname uts;
+	int ret;
+
+	if (!env)
+		return perf_version_string;
+
+	if (env->os_release)
+		return env->os_release;
+
+	/*
+	 * 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 fails then use the current perf tool version.
+	 */
+	ret = uname(&uts);
+	env->os_release = strdup(ret < 0 ? perf_version_string : uts.release);
+	return env->os_release;
+}
+
 int perf_env__set_cmdline(struct perf_env *env, int argc, const char *argv[])
 {
 	int i;
diff --git a/tools/perf/util/env.h b/tools/perf/util/env.h
index d36a0fb2cd04..56020f4381cd 100644
--- a/tools/perf/util/env.h
+++ b/tools/perf/util/env.h
@@ -175,6 +175,7 @@ void free_cpu_domain_info(struct cpu_domain_map **cd_map, u32 schedstat_version,
 void perf_env__exit(struct perf_env *env);
 
 int perf_env__kernel_is_64_bit(struct perf_env *env);
+const char *perf_env__os_release(struct perf_env *env);
 
 int perf_env__set_cmdline(struct perf_env *env, int argc, const char *argv[]);
 
diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 9bb4a271b4f8..89115134f1d2 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -361,13 +361,19 @@ 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)
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index fcaeeddbbb6b..fd332db56157 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -2209,7 +2209,7 @@ 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) +
@@ -2226,7 +2226,7 @@ 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;
-- 
2.53.0.1213.gd9a14994de-goog