linux-kernel - [PATCH 02/24] bpf: Add build_id_parse

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Date:   Mon,  9 Nov 2020 22:53:53 +0100
From:   Jiri Olsa <jolsa@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Song Liu <songliubraving@...com>,
        lkml <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Michael Petlan <mpetlan@...hat.com>,
        Ian Rogers <irogers@...gle.com>,
        Stephane Eranian <eranian@...gle.com>,
        Alexey Budankov <alexey.budankov@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>
Subject: [PATCH 02/24] bpf: Add build_id_parse_size function

It's possible to have other build id types (other than default
SHA1). Currently there's also ld support for MD5 build id.

Adding build_id_parse_size function, that returns also size of
the parsed build id, so we can recognize the build id type.

Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Song Liu <songliubraving@...com>
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 include/linux/buildid.h |  2 ++
 lib/buildid.c           | 31 ++++++++++++++++++++++++-------
 2 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/include/linux/buildid.h b/include/linux/buildid.h
index 3be5b49719f1..edba89834b4c 100644
--- a/include/linux/buildid.h
+++ b/include/linux/buildid.h
@@ -7,5 +7,7 @@
 #define BUILD_ID_SIZE 20
 
 int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id);
+int build_id_parse_size(struct vm_area_struct *vma, unsigned char *build_id,
+			__u32 *size);
 
 #endif
diff --git a/lib/buildid.c b/lib/buildid.c
index e8d5feb7ef20..c52f86110635 100644
--- a/lib/buildid.c
+++ b/lib/buildid.c
@@ -12,6 +12,7 @@
  */
 static inline int parse_build_id(void *page_addr,
 				 unsigned char *build_id,
+				 __u32 *size,
 				 void *note_start,
 				 Elf32_Word note_size)
 {
@@ -38,6 +39,8 @@ static inline int parse_build_id(void *page_addr,
 			       nhdr->n_descsz);
 			memset(build_id + nhdr->n_descsz, 0,
 			       BUILD_ID_SIZE - nhdr->n_descsz);
+			if (size)
+				*size = nhdr->n_descsz;
 			return 0;
 		}
 		new_offs = note_offs + sizeof(Elf32_Nhdr) +
@@ -50,7 +53,8 @@ static inline int parse_build_id(void *page_addr,
 }
 
 /* Parse build ID from 32-bit ELF */
-static int get_build_id_32(void *page_addr, unsigned char *build_id)
+static int get_build_id_32(void *page_addr, unsigned char *build_id,
+			   __u32 *size)
 {
 	Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr;
 	Elf32_Phdr *phdr;
@@ -65,7 +69,7 @@ static int get_build_id_32(void *page_addr, unsigned char *build_id)
 
 	for (i = 0; i < ehdr->e_phnum; ++i) {
 		if (phdr[i].p_type == PT_NOTE &&
-		    !parse_build_id(page_addr, build_id,
+		    !parse_build_id(page_addr, build_id, size,
 				    page_addr + phdr[i].p_offset,
 				    phdr[i].p_filesz))
 			return 0;
@@ -74,7 +78,8 @@ static int get_build_id_32(void *page_addr, unsigned char *build_id)
 }
 
 /* Parse build ID from 64-bit ELF */
-static int get_build_id_64(void *page_addr, unsigned char *build_id)
+static int get_build_id_64(void *page_addr, unsigned char *build_id,
+			   __u32 *size)
 {
 	Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr;
 	Elf64_Phdr *phdr;
@@ -89,7 +94,7 @@ static int get_build_id_64(void *page_addr, unsigned char *build_id)
 
 	for (i = 0; i < ehdr->e_phnum; ++i) {
 		if (phdr[i].p_type == PT_NOTE &&
-		    !parse_build_id(page_addr, build_id,
+		    !parse_build_id(page_addr, build_id, size,
 				    page_addr + phdr[i].p_offset,
 				    phdr[i].p_filesz))
 			return 0;
@@ -98,7 +103,8 @@ static int get_build_id_64(void *page_addr, unsigned char *build_id)
 }
 
 /* Parse build ID of ELF file mapped to vma */
-int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id)
+static int __build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
+			    __u32 *size)
 {
 	Elf32_Ehdr *ehdr;
 	struct page *page;
@@ -126,11 +132,22 @@ int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id)
 		goto out;
 
 	if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
-		ret = get_build_id_32(page_addr, build_id);
+		ret = get_build_id_32(page_addr, build_id, size);
 	else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
-		ret = get_build_id_64(page_addr, build_id);
+		ret = get_build_id_64(page_addr, build_id, size);
 out:
 	kunmap_atomic(page_addr);
 	put_page(page);
 	return ret;
 }
+
+int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id)
+{
+	return __build_id_parse(vma, build_id, NULL);
+}
+
+int build_id_parse_size(struct vm_area_struct *vma, unsigned char *build_id,
+			__u32 *size)
+{
+	return __build_id_parse(vma, build_id, size);
+}
-- 
2.26.2