[PATCH v1 01/11] perf tools: Add HEADER_BOOT_ID feature

[Namhyung Kim <namhyung@kernel.org>]

Save /proc/sys/kernel/random/boot_id in the perf.data header and
struct perf_env so post-processing tools can identify if it's the
same kernel boot on which the data was recorded.

Assisted-by: LLM
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 .../Documentation/perf.data-file-format.txt   |  5 +++
 tools/perf/builtin-inject.c                   |  1 +
 tools/perf/util/env.c                         | 44 +++++++++++++++++++
 tools/perf/util/env.h                         |  2 +
 tools/perf/util/header.c                      | 28 ++++++++++++
 tools/perf/util/header.h                      |  1 +
 6 files changed, 81 insertions(+)

diff --git a/tools/perf/Documentation/perf.data-file-format.txt b/tools/perf/Documentation/perf.data-file-format.txt
index 1f8e7d8e9ae21d73..359d6ef0c80aac26 100644
--- a/tools/perf/Documentation/perf.data-file-format.txt
+++ b/tools/perf/Documentation/perf.data-file-format.txt
@@ -491,6 +491,11 @@ struct memory_range {
 	u8 remote_region_id;
 }; [nr_memory_ranges]
 
+	HEADER_BOOT_ID = 36,
+
+	A perf_header_string with the kernel boot ID read from
+	/proc/sys/kernel/random/boot_id.
+
 	other bits are reserved and should be ignored for now
 	HEADER_FEAT_BITS	= 256,
 
diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
index ce7562fc788c246e..ddb21d888e00d143 100644
--- a/tools/perf/builtin-inject.c
+++ b/tools/perf/builtin-inject.c
@@ -2307,6 +2307,7 @@ static bool keep_feat(struct perf_inject *inject, int feat)
 	case HEADER_CPU_DOMAIN_INFO:
 	case HEADER_CLN_SIZE:
 	case HEADER_MEMORY_RANGES:
+	case HEADER_BOOT_ID:
 		return true;
 	/* Information that can be updated */
 	case HEADER_BUILD_ID:
diff --git a/tools/perf/util/env.c b/tools/perf/util/env.c
index 50993b0dedc577c7..8ca0b677f3172b5f 100644
--- a/tools/perf/util/env.c
+++ b/tools/perf/util/env.c
@@ -12,6 +12,7 @@
 #include <linux/string.h>
 #include <linux/zalloc.h>
 #include "cgroup.h"
+#include <api/fs/fs.h>
 #include <errno.h>
 #include <sys/utsname.h>
 #include <stdlib.h>
@@ -258,6 +259,7 @@ void perf_env__exit(struct perf_env *env)
 	zfree(&env->os_release);
 	zfree(&env->version);
 	zfree(&env->arch);
+	zfree(&env->boot_id);
 	zfree(&env->cpu_desc);
 	zfree(&env->cpuid);
 	zfree(&env->cmdline);
@@ -400,6 +402,48 @@ const char *perf_env__os_release(struct perf_env *env)
 	return release;
 }
 
+static char *read_host_boot_id(void)
+{
+	char *buf = NULL;
+	size_t sz;
+
+	if (procfs__read_str("sys/kernel/random/boot_id", &buf, &sz) < 0)
+		return NULL;
+
+	strim(buf);
+	return buf;
+}
+
+const char *perf_env__boot_id(struct perf_env *env)
+{
+	const char *boot_id;
+
+	if (!env)
+		return NULL;
+
+	mutex_lock(&env->lock);
+	if (env->boot_id) {
+		boot_id = env->boot_id;
+		goto out;
+	}
+
+	/*
+	 * If env->arch or env->hostname is set, this is an offline target
+	 * environment. If the boot_id is not populated in the file, do not
+	 * fall back to the host's boot_id.
+	 */
+	if (env->arch || env->hostname) {
+		boot_id = NULL;
+		goto out;
+	}
+
+	env->boot_id = read_host_boot_id();
+	boot_id = env->boot_id;
+out:
+	mutex_unlock(&env->lock);
+	return boot_id;
+}
+
 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 23d35425efe38b24..772d11eed1bc2a7c 100644
--- a/tools/perf/util/env.h
+++ b/tools/perf/util/env.h
@@ -81,6 +81,7 @@ struct perf_env {
 	char			*os_release;
 	char			*version;
 	char			*arch;
+	char			*boot_id;
 	/* e_machine expanded from 16 to 32-bits for alignment. */
 	u32			e_machine;
 	u32			e_flags;
@@ -187,6 +188,7 @@ 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);
+const char *perf_env__boot_id(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 9eec6deee190ff21..3e0b6fce55973dd1 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -494,6 +494,27 @@ static int write_version(struct feat_fd *ff,
 	return do_write_string(ff, perf_version_string);
 }
 
+static int write_boot_id(struct feat_fd *ff, struct evlist *evlist)
+{
+	const char *boot_id = NULL;
+	char *buf = NULL;
+	size_t sz;
+	int ret;
+
+	if (evlist__session(evlist))
+		boot_id = perf_env__boot_id(perf_session__env(evlist__session(evlist)));
+
+	if (!boot_id) {
+		if (procfs__read_str("sys/kernel/random/boot_id", &buf, &sz) < 0)
+			return -1;
+		boot_id = strim(buf);
+	}
+
+	ret = do_write_string(ff, boot_id);
+	free(buf);
+	return ret;
+}
+
 static int __write_cpudesc(struct feat_fd *ff, const char *cpuinfo_proc)
 {
 	FILE *file;
@@ -2079,6 +2100,11 @@ static void print_version(struct feat_fd *ff, FILE *fp)
 	fprintf(fp, "# perf version : %s\n", ff->ph->env.version);
 }
 
+static void print_boot_id(struct feat_fd *ff, FILE *fp)
+{
+	fprintf(fp, "# boot id : %s\n", ff->ph->env.boot_id);
+}
+
 static void print_cmdline(struct feat_fd *ff, FILE *fp)
 {
 	int nr, i;
@@ -3022,6 +3048,7 @@ FEAT_PROCESS_STR_FUN(osrelease, os_release);
 FEAT_PROCESS_STR_FUN(version, version);
 FEAT_PROCESS_STR_FUN(cpudesc, cpu_desc);
 FEAT_PROCESS_STR_FUN(cpuid, cpuid);
+FEAT_PROCESS_STR_FUN(boot_id, boot_id);
 
 static int process_arch(struct feat_fd *ff, void *data __maybe_unused)
 {
@@ -4496,6 +4523,7 @@ const struct perf_header_feature_ops feat_ops[HEADER_LAST_FEATURE] = {
 	FEAT_OPR(E_MACHINE,	e_machine,	false),
 	FEAT_OPR(CLN_SIZE,	cln_size,	false),
 	FEAT_OPR(MEMORY_RANGES,	memory_ranges,	false),
+	FEAT_OPR(BOOT_ID,	boot_id,	false),
 };
 
 struct header_print_data {
diff --git a/tools/perf/util/header.h b/tools/perf/util/header.h
index 765037762758ca11..5bbf16342b4d26d8 100644
--- a/tools/perf/util/header.h
+++ b/tools/perf/util/header.h
@@ -57,6 +57,7 @@ enum {
 	HEADER_E_MACHINE,
 	HEADER_CLN_SIZE,
 	HEADER_MEMORY_RANGES,
+	HEADER_BOOT_ID,
 	HEADER_LAST_FEATURE,
 	HEADER_FEAT_BITS	= 256,
 };
-- 
2.56.0.257.gf7497c7d27-goog