[PATCH 3/7] buildid: Add API to parse build ID out of buffer

[Stephen Boyd <swboyd@chromium.org>]

Add an API that can parse the build ID in hex string form out of a
buffer to support printing a kernel module's build ID.

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>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
---
 include/linux/buildid.h |  1 +
 lib/buildid.c           | 20 ++++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/include/linux/buildid.h b/include/linux/buildid.h
index dd134a96a87c..f5a5b920d18c 100644
--- a/include/linux/buildid.h
+++ b/include/linux/buildid.h
@@ -10,6 +10,7 @@
 int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
 		   __u32 *size);
 
+int build_id_parse_buf(const void *buf, char *build_id, u32 buf_size);
 const char *vmlinux_build_id(void);
 
 #endif
diff --git a/lib/buildid.c b/lib/buildid.c
index 57daf928b133..4e1d7c51dc5f 100644
--- a/lib/buildid.c
+++ b/lib/buildid.c
@@ -165,6 +165,26 @@ static void build_id2hex(char *dst, const unsigned char *src, __u32 size)
 	dst[2 * size] = '\0';
 }
 
+/**
+ * build_id_parse_buf - Get build ID in hex string format from elf section note
+ * @buf: Elf note section(s) to parse
+ * @build_id: Build ID in hex string format parsed from @buf
+ * @buf_size: Size of @buf in bytes
+ *
+ * Return: 0 on success, -EINVAL otherwise
+ */
+int build_id_parse_buf(const void *buf, char *build_id, u32 buf_size)
+{
+	unsigned char build_id_buf[BUILD_ID_SIZE_MAX];
+	__u32 size;
+	int ret;
+
+	ret = parse_build_id_buf(build_id_buf, &size, buf, buf_size);
+	if (!ret)
+		build_id2hex(build_id, build_id_buf, size);
+
+	return ret;
+}
 /**
  * vmlinux_build_id - Get the running kernel's build-id in hex string format
  *
-- 
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