[PATCH v2 02/12] buildid: Add method to get running kernel's build ID

[Stephen Boyd]

Add vmlinux_build_id() so that callers 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.

Cc: Jiri Olsa <jolsa at kernel.org>
Cc: Alexei Starovoitov <ast at kernel.org>
Cc: Jessica Yu <jeyu at kernel.org>
Cc: Evan Green <evgreen at chromium.org>
Cc: Hsin-Yi Wang <hsinyi at chromium.org>
Cc: Dave Young <dyoung at redhat.com>
Cc: Baoquan He <bhe at redhat.com>
Cc: Vivek Goyal <vgoyal at redhat.com>
Cc: <kexec at lists.infradead.org>
Signed-off-by: Stephen Boyd <swboyd at chromium.org>
---
 include/linux/buildid.h |  2 ++
 lib/buildid.c           | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/include/linux/buildid.h b/include/linux/buildid.h
index ebce93f26d06..2ff6b1b7cc9b 100644
--- a/include/linux/buildid.h
+++ b/include/linux/buildid.h
@@ -10,4 +10,6 @@ int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
 		   __u32 *size);
 int build_id_parse_buf(const void *buf, unsigned char *build_id, u32 buf_size);
 
+const unsigned char *vmlinux_build_id(void);
+
 #endif
diff --git a/lib/buildid.c b/lib/buildid.c
index 010ab0674cb9..fa1b6466b4b8 100644
--- a/lib/buildid.c
+++ b/lib/buildid.c
@@ -4,6 +4,7 @@
 #include <linux/elf.h>
 #include <linux/kernel.h>
 #include <linux/pagemap.h>
+#include <linux/string.h>
 
 #define BUILD_ID 3
 
@@ -171,3 +172,21 @@ int build_id_parse_buf(const void *buf, unsigned char *build_id, u32 buf_size)
 {
 	return parse_build_id_buf(build_id, NULL, buf, buf_size);
 }
+
+/**
+ * vmlinux_build_id - Get the running kernel's build ID
+ *
+ * Return: Running kernel's build ID
+ */
+const unsigned char *vmlinux_build_id(void)
+{
+	extern const void __start_notes __weak;
+	extern const void __stop_notes __weak;
+	unsigned int size = &__stop_notes - &__start_notes;
+	static unsigned char vmlinux_build_id[BUILD_ID_SIZE_MAX];
+
+	if (!memchr_inv(vmlinux_build_id, 0, BUILD_ID_SIZE_MAX))
+		build_id_parse_buf(&__start_notes, vmlinux_build_id, size);
+
+	return vmlinux_build_id;
+}
-- 
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