linux-kernel - [PATCH v2 09/14] objtool: Extract elf_strtab

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Date:   Thu, 18 Mar 2021 18:11:12 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org, jpoimboe@...hat.com, jgross@...e.com,
        mbenes@...e.com
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org
Subject: [PATCH v2 09/14] objtool: Extract elf_strtab_concat()

Create a common helper to append strings to a strtab.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 tools/objtool/elf.c |   73 +++++++++++++++++++++++++++++-----------------------
 1 file changed, 42 insertions(+), 31 deletions(-)

--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -676,13 +676,51 @@ struct elf *elf_open_read(const char *na
 	return NULL;
 }
 
+static int elf_strtab_concat(struct elf *elf, char *name, const char *strtab_name)
+{
+	struct section *strtab = NULL;
+	Elf_Data *data;
+	Elf_Scn *s;
+	int len;
+
+	if (strtab_name)
+		strtab = find_section_by_name(elf, strtab_name);
+	if (!strtab)
+		strtab = find_section_by_name(elf, ".strtab");
+	if (!strtab) {
+		WARN("can't find %s or .strtab section", strtab_name);
+		return -1;
+	}
+
+	s = elf_getscn(elf->elf, strtab->idx);
+	if (!s) {
+		WARN_ELF("elf_getscn");
+		return -1;
+	}
+
+	data = elf_newdata(s);
+	if (!data) {
+		WARN_ELF("elf_newdata");
+		return -1;
+	}
+
+	data->d_buf = name;
+	data->d_size = strlen(name) + 1;;
+	data->d_align = 1;
+
+	len = strtab->len;
+	strtab->len += data->d_size;
+	strtab->changed = true;
+
+	return len;
+}
+
 struct section *elf_create_section(struct elf *elf, const char *name,
 				   unsigned int sh_flags, size_t entsize, int nr)
 {
-	struct section *sec, *shstrtab;
+	struct section *sec;
 	size_t size = entsize * nr;
 	Elf_Scn *s;
-	Elf_Data *data;
 
 	sec = malloc(sizeof(*sec));
 	if (!sec) {
@@ -739,36 +777,9 @@ struct section *elf_create_section(struc
 	sec->sh.sh_addralign = 1;
 	sec->sh.sh_flags = SHF_ALLOC | sh_flags;
 
-
-	/* Add section name to .shstrtab (or .strtab for Clang) */
-	shstrtab = find_section_by_name(elf, ".shstrtab");
-	if (!shstrtab)
-		shstrtab = find_section_by_name(elf, ".strtab");
-	if (!shstrtab) {
-		WARN("can't find .shstrtab or .strtab section");
-		return NULL;
-	}
-
-	s = elf_getscn(elf->elf, shstrtab->idx);
-	if (!s) {
-		WARN_ELF("elf_getscn");
+	sec->sh.sh_name = elf_strtab_concat(elf, sec->name, ".shstrtab");
+	if (sec->sh.sh_name == -1)
 		return NULL;
-	}
-
-	data = elf_newdata(s);
-	if (!data) {
-		WARN_ELF("elf_newdata");
-		return NULL;
-	}
-
-	data->d_buf = sec->name;
-	data->d_size = strlen(name) + 1;
-	data->d_align = 1;
-
-	sec->sh.sh_name = shstrtab->len;
-
-	shstrtab->len += strlen(name) + 1;
-	shstrtab->changed = true;
 
 	list_add_tail(&sec->list, &elf->sections);
 	elf_hash_add(elf->section_hash, &sec->hash, sec->idx);