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Message-ID: <176060834673.709179.11641444836812652627.tip-bot2@tip-bot2>
Date: Thu, 16 Oct 2025 09:52:26 -0000
From: "tip-bot2 for Josh Poimboeuf" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Petr Mladek <pmladek@...e.com>, Joe Lawrence <joe.lawrence@...hat.com>,
Josh Poimboeuf <jpoimboe@...nel.org>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: objtool/core] objtool: Add elf_create_file()
The following commit has been merged into the objtool/core branch of tip:
Commit-ID: 03c19a99ee69f4680d7da11c164ac655b4946b99
Gitweb: https://git.kernel.org/tip/03c19a99ee69f4680d7da11c164ac655b4946b99
Author: Josh Poimboeuf <jpoimboe@...nel.org>
AuthorDate: Wed, 17 Sep 2025 09:03:51 -07:00
Committer: Josh Poimboeuf <jpoimboe@...nel.org>
CommitterDate: Tue, 14 Oct 2025 14:46:49 -07:00
objtool: Add elf_create_file()
Add interface to enable the creation of a new ELF file.
Acked-by: Petr Mladek <pmladek@...e.com>
Tested-by: Joe Lawrence <joe.lawrence@...hat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
tools/objtool/builtin-check.c | 2 +-
tools/objtool/elf.c | 144 ++++++++++++++++++++++++++-
tools/objtool/include/objtool/elf.h | 5 +-
3 files changed, 147 insertions(+), 4 deletions(-)
diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index fc91bc5..9969714 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -329,5 +329,5 @@ int objtool_run(int argc, const char **argv)
if (!opts.dryrun && file->elf->changed && elf_write(file->elf))
return 1;
- return 0;
+ return elf_close(file->elf);
}
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 8d01fc3..6095bab 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -16,6 +16,7 @@
#include <string.h>
#include <unistd.h>
#include <errno.h>
+#include <libgen.h>
#include <linux/interval_tree_generic.h>
#include <objtool/builtin.h>
#include <objtool/elf.h>
@@ -1067,6 +1068,12 @@ struct elf *elf_open_read(const char *name, int flags)
goto err;
}
+ elf->name = strdup(name);
+ if (!elf->name) {
+ ERROR_GLIBC("strdup");
+ return NULL;
+ }
+
if ((flags & O_ACCMODE) == O_RDONLY)
cmd = ELF_C_READ_MMAP;
else if ((flags & O_ACCMODE) == O_RDWR)
@@ -1104,6 +1111,137 @@ err:
return NULL;
}
+struct elf *elf_create_file(GElf_Ehdr *ehdr, const char *name)
+{
+ struct section *null, *symtab, *strtab, *shstrtab;
+ char *dir, *base, *tmp_name;
+ struct symbol *sym;
+ struct elf *elf;
+
+ elf_version(EV_CURRENT);
+
+ elf = calloc(1, sizeof(*elf));
+ if (!elf) {
+ ERROR_GLIBC("calloc");
+ return NULL;
+ }
+
+ INIT_LIST_HEAD(&elf->sections);
+
+ dir = strdup(name);
+ if (!dir) {
+ ERROR_GLIBC("strdup");
+ return NULL;
+ }
+
+ dir = dirname(dir);
+
+ base = strdup(name);
+ if (!base) {
+ ERROR_GLIBC("strdup");
+ return NULL;
+ }
+
+ base = basename(base);
+
+ tmp_name = malloc(256);
+ if (!tmp_name) {
+ ERROR_GLIBC("malloc");
+ return NULL;
+ }
+
+ snprintf(tmp_name, 256, "%s/%s.XXXXXX", dir, base);
+
+ elf->fd = mkstemp(tmp_name);
+ if (elf->fd == -1) {
+ ERROR_GLIBC("can't create tmp file");
+ exit(1);
+ }
+
+ elf->tmp_name = tmp_name;
+
+ elf->name = strdup(name);
+ if (!elf->name) {
+ ERROR_GLIBC("strdup");
+ return NULL;
+ }
+
+ elf->elf = elf_begin(elf->fd, ELF_C_WRITE, NULL);
+ if (!elf->elf) {
+ ERROR_ELF("elf_begin");
+ return NULL;
+ }
+
+ if (!gelf_newehdr(elf->elf, ELFCLASS64)) {
+ ERROR_ELF("gelf_newehdr");
+ return NULL;
+ }
+
+ memcpy(&elf->ehdr, ehdr, sizeof(elf->ehdr));
+
+ if (!gelf_update_ehdr(elf->elf, &elf->ehdr)) {
+ ERROR_ELF("gelf_update_ehdr");
+ return NULL;
+ }
+
+ if (!elf_alloc_hash(section, 1000) ||
+ !elf_alloc_hash(section_name, 1000) ||
+ !elf_alloc_hash(symbol, 10000) ||
+ !elf_alloc_hash(symbol_name, 10000) ||
+ !elf_alloc_hash(reloc, 100000))
+ return NULL;
+
+ null = elf_create_section(elf, NULL, 0, 0, SHT_NULL, 0, 0);
+ shstrtab = elf_create_section(elf, NULL, 0, 0, SHT_STRTAB, 1, 0);
+ strtab = elf_create_section(elf, NULL, 0, 0, SHT_STRTAB, 1, 0);
+
+ if (!null || !shstrtab || !strtab)
+ return NULL;
+
+ null->name = "";
+ shstrtab->name = ".shstrtab";
+ strtab->name = ".strtab";
+
+ null->sh.sh_name = elf_add_string(elf, shstrtab, null->name);
+ shstrtab->sh.sh_name = elf_add_string(elf, shstrtab, shstrtab->name);
+ strtab->sh.sh_name = elf_add_string(elf, shstrtab, strtab->name);
+
+ if (null->sh.sh_name == -1 || shstrtab->sh.sh_name == -1 || strtab->sh.sh_name == -1)
+ return NULL;
+
+ elf_hash_add(section_name, &null->name_hash, str_hash(null->name));
+ elf_hash_add(section_name, &strtab->name_hash, str_hash(strtab->name));
+ elf_hash_add(section_name, &shstrtab->name_hash, str_hash(shstrtab->name));
+
+ if (elf_add_string(elf, strtab, "") == -1)
+ return NULL;
+
+ symtab = elf_create_section(elf, ".symtab", 0x18, 0x18, SHT_SYMTAB, 0x8, 0);
+ if (!symtab)
+ return NULL;
+
+ symtab->sh.sh_link = strtab->idx;
+ symtab->sh.sh_info = 1;
+
+ elf->ehdr.e_shstrndx = shstrtab->idx;
+ if (!gelf_update_ehdr(elf->elf, &elf->ehdr)) {
+ ERROR_ELF("gelf_update_ehdr");
+ return NULL;
+ }
+
+ sym = calloc(1, sizeof(*sym));
+ if (!sym) {
+ ERROR_GLIBC("calloc");
+ return NULL;
+ }
+
+ sym->name = "";
+ sym->sec = null;
+ elf_add_symbol(elf, sym);
+
+ return elf;
+}
+
unsigned int elf_add_string(struct elf *elf, struct section *strtab, const char *str)
{
unsigned int offset;
@@ -1568,7 +1706,7 @@ int elf_write(struct elf *elf)
return 0;
}
-void elf_close(struct elf *elf)
+int elf_close(struct elf *elf)
{
if (elf->elf)
elf_end(elf->elf);
@@ -1576,8 +1714,12 @@ void elf_close(struct elf *elf)
if (elf->fd > 0)
close(elf->fd);
+ if (elf->tmp_name && rename(elf->tmp_name, elf->name))
+ return -1;
+
/*
* NOTE: All remaining allocations are leaked on purpose. Objtool is
* about to exit anyway.
*/
+ return 0;
}
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index 999fd93..9f135c2 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -94,7 +94,7 @@ struct elf {
GElf_Ehdr ehdr;
int fd;
bool changed;
- const char *name;
+ const char *name, *tmp_name;
unsigned int num_files;
struct list_head sections;
unsigned long num_relocs;
@@ -116,6 +116,7 @@ struct elf {
};
struct elf *elf_open_read(const char *name, int flags);
+struct elf *elf_create_file(GElf_Ehdr *ehdr, const char *name);
struct section *elf_create_section(struct elf *elf, const char *name,
size_t size, size_t entsize,
@@ -165,7 +166,7 @@ int elf_write_insn(struct elf *elf, struct section *sec, unsigned long offset,
unsigned int len, const char *insn);
int elf_write(struct elf *elf);
-void elf_close(struct elf *elf);
+int elf_close(struct elf *elf);
struct section *find_section_by_name(const struct elf *elf, const char *name);
struct symbol *find_func_by_offset(struct section *sec, unsigned long offset);
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