[patch 33/54] buildid: stash away kernels build ID on init

[Andrew Morton <akpm@linux-foundation.org>]

From: Stephen Boyd <swboyd@chromium.org>
Subject: buildid: stash away kernels build ID on init

Parse the kernel's build ID at initialization so that other code can print
a hex format string representation of the running kernel's build ID.  This
will be used in the kdump and dump_stack code so that developers can
easily locate the vmlinux debug symbols for a crash/stacktrace.

[swboyd@chromium.org: fix implicit declaration of init_vmlinux_build_id()]
  Link: https://lkml.kernel.org/r/CAE-0n51UjTbay8N9FXAyE7_aR2+ePrQnKSRJ0gbmRsXtcLBVaw@mail.gmail.com
Link: https://lkml.kernel.org/r/20210511003845.2429846-4-swboyd@chromium.org
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Evan Green <evgreen@chromium.org>
Cc: Hsin-Yi Wang <hsinyi@chromium.org>
Cc: Dave Young <dyoung@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/buildid.h |    3 +++
 init/main.c             |    2 ++
 lib/buildid.c           |   15 +++++++++++++++
 3 files changed, 20 insertions(+)

--- a/include/linux/buildid.h~buildid-stash-away-kernels-build-id-on-init
+++ a/include/linux/buildid.h
@@ -10,4 +10,7 @@ int build_id_parse(struct vm_area_struct
 		   __u32 *size);
 int build_id_parse_buf(const void *buf, unsigned char *build_id, u32 buf_size);
 
+extern unsigned char vmlinux_build_id[BUILD_ID_SIZE_MAX];
+void init_vmlinux_build_id(void);
+
 #endif
--- a/init/main.c~buildid-stash-away-kernels-build-id-on-init
+++ a/init/main.c
@@ -45,6 +45,7 @@
 #include <linux/srcu.h>
 #include <linux/moduleparam.h>
 #include <linux/kallsyms.h>
+#include <linux/buildid.h>
 #include <linux/writeback.h>
 #include <linux/cpu.h>
 #include <linux/cpuset.h>
@@ -913,6 +914,7 @@ asmlinkage __visible void __init __no_sa
 	set_task_stack_end_magic(&init_task);
 	smp_setup_processor_id();
 	debug_objects_early_init();
+	init_vmlinux_build_id();
 
 	cgroup_init_early();
 
--- a/lib/buildid.c~buildid-stash-away-kernels-build-id-on-init
+++ a/lib/buildid.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 
 #include <linux/buildid.h>
+#include <linux/cache.h>
 #include <linux/elf.h>
 #include <linux/kernel.h>
 #include <linux/pagemap.h>
@@ -172,3 +173,17 @@ int build_id_parse_buf(const void *buf,
 {
 	return parse_build_id_buf(build_id, NULL, buf, buf_size);
 }
+
+unsigned char vmlinux_build_id[BUILD_ID_SIZE_MAX] __ro_after_init;
+
+/**
+ * init_vmlinux_build_id - Compute and stash the running kernel's build ID
+ */
+void __init init_vmlinux_build_id(void)
+{
+	extern const void __start_notes __weak;
+	extern const void __stop_notes __weak;
+	unsigned int size = &__stop_notes - &__start_notes;
+
+	build_id_parse_buf(&__start_notes, vmlinux_build_id, size);
+}
_