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Message-ID: <d4a18b96db831ea31d2f8781b39fa9a3d1ebc749.1746821544.git.jpoimboe@kernel.org>
Date: Fri, 9 May 2025 13:17:02 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org,
Petr Mladek <pmladek@...e.com>,
Miroslav Benes <mbenes@...e.cz>,
Joe Lawrence <joe.lawrence@...hat.com>,
live-patching@...r.kernel.org,
Song Liu <song@...nel.org>,
laokz <laokz@...mail.com>,
Jiri Kosina <jikos@...nel.org>,
Marcos Paulo de Souza <mpdesouza@...e.com>,
Weinan Liu <wnliu@...gle.com>,
Fazla Mehrab <a.mehrab@...edance.com>,
Chen Zhongjin <chenzhongjin@...wei.com>,
Puranjay Mohan <puranjay@...nel.org>
Subject: [PATCH v2 38/62] objtool: Generalize elf_create_section()
In preparation for the objtool klp diff subcommand, broaden the
elf_create_section() interface to give callers more control and reduce
duplication of some subtle setup logic.
While at it, make elf_create_rela_section() public so sections can be
created by the upcoming klp diff code.
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
tools/objtool/elf.c | 118 ++++++++++++++++------------
tools/objtool/include/objtool/elf.h | 7 +-
tools/objtool/orc_gen.c | 6 +-
3 files changed, 77 insertions(+), 54 deletions(-)
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 38bf9ae86c89..c38b109f441f 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -1136,51 +1136,53 @@ static int elf_add_string(struct elf *elf, struct section *strtab, const char *s
}
struct section *elf_create_section(struct elf *elf, const char *name,
- size_t entsize, unsigned int nr)
+ size_t size, size_t entsize,
+ unsigned int type, unsigned int align,
+ unsigned int flags)
{
struct section *sec, *shstrtab;
- size_t size = entsize * nr;
Elf_Scn *s;
- sec = malloc(sizeof(*sec));
- if (!sec) {
- ERROR_GLIBC("malloc");
+ if (name && find_section_by_name(elf, name)) {
+ ERROR("section '%s' already exists", name);
+ return NULL;
+ }
+
+ sec = calloc(1, sizeof(*sec));
+ if (!sec) {
+ ERROR_GLIBC("calloc");
return NULL;
}
- memset(sec, 0, sizeof(*sec));
INIT_LIST_HEAD(&sec->symbol_list);
+ /* don't actually create the section, just the data structures */
+ if (type == SHT_NULL)
+ goto add;
+
s = elf_newscn(elf->elf);
if (!s) {
ERROR_ELF("elf_newscn");
return NULL;
}
- sec->name = strdup(name);
- if (!sec->name) {
- ERROR_GLIBC("strdup");
- return NULL;
- }
-
sec->idx = elf_ndxscn(s);
- sec->data = elf_newdata(s);
- if (!sec->data) {
- ERROR_ELF("elf_newdata");
- return NULL;
- }
-
- sec->data->d_size = size;
- sec->data->d_align = 1;
-
if (size) {
- sec->data->d_buf = malloc(size);
- if (!sec->data->d_buf) {
- ERROR_GLIBC("malloc");
+ sec->data = elf_newdata(s);
+ if (!sec->data) {
+ ERROR_ELF("elf_newdata");
+ return NULL;
+ }
+
+ sec->data->d_size = size;
+ sec->data->d_align = 1;
+
+ sec->data->d_buf = calloc(1, size);
+ if (!sec->data->d_buf) {
+ ERROR_GLIBC("calloc");
return NULL;
}
- memset(sec->data->d_buf, 0, size);
}
if (!gelf_getshdr(s, &sec->sh)) {
@@ -1190,34 +1192,44 @@ struct section *elf_create_section(struct elf *elf, const char *name,
sec->sh.sh_size = size;
sec->sh.sh_entsize = entsize;
- sec->sh.sh_type = SHT_PROGBITS;
- sec->sh.sh_addralign = 1;
- sec->sh.sh_flags = SHF_ALLOC;
+ sec->sh.sh_type = type;
+ sec->sh.sh_addralign = align;
+ sec->sh.sh_flags = 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) {
- ERROR("can't find .shstrtab or .strtab section");
- return NULL;
+ if (name) {
+ sec->name = strdup(name);
+ if (!sec->name) {
+ ERROR("strdup");
+ return NULL;
+ }
+
+ /* 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) {
+ ERROR("can't find .shstrtab or .strtab");
+ return NULL;
+ }
+ }
+ sec->sh.sh_name = elf_add_string(elf, shstrtab, sec->name);
+ if (sec->sh.sh_name == -1)
+ return NULL;
+
+ elf_hash_add(section_name, &sec->name_hash, str_hash(sec->name));
}
- sec->sh.sh_name = elf_add_string(elf, shstrtab, sec->name);
- if (sec->sh.sh_name == -1)
- return NULL;
+add:
list_add_tail(&sec->list, &elf->sections);
elf_hash_add(section, &sec->hash, sec->idx);
- elf_hash_add(section_name, &sec->name_hash, str_hash(sec->name));
mark_sec_changed(elf, sec, true);
return sec;
}
-static struct section *elf_create_rela_section(struct elf *elf,
- struct section *sec,
- unsigned int reloc_nr)
+struct section *elf_create_rela_section(struct elf *elf, struct section *sec,
+ unsigned int reloc_nr)
{
struct section *rsec;
char *rsec_name;
@@ -1230,22 +1242,23 @@ static struct section *elf_create_rela_section(struct elf *elf,
strcpy(rsec_name, ".rela");
strcat(rsec_name, sec->name);
- rsec = elf_create_section(elf, rsec_name, elf_rela_size(elf), reloc_nr);
+ rsec = elf_create_section(elf, rsec_name, reloc_nr * elf_rela_size(elf),
+ elf_rela_size(elf), SHT_RELA, elf_addr_size(elf),
+ SHF_INFO_LINK);
free(rsec_name);
if (!rsec)
return NULL;
- rsec->data->d_type = ELF_T_RELA;
- rsec->sh.sh_type = SHT_RELA;
- rsec->sh.sh_addralign = elf_addr_size(elf);
rsec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
rsec->sh.sh_info = sec->idx;
- rsec->sh.sh_flags = SHF_INFO_LINK;
- rsec->relocs = calloc(sec_num_entries(rsec), sizeof(struct reloc));
- if (!rsec->relocs) {
- ERROR_GLIBC("calloc");
- return NULL;
+ if (reloc_nr) {
+ rsec->data->d_type = ELF_T_RELA;
+ rsec->relocs = calloc(sec_num_entries(rsec), sizeof(struct reloc));
+ if (!rsec->relocs) {
+ ERROR_GLIBC("calloc");
+ return NULL;
+ }
}
sec->rsec = rsec;
@@ -1260,7 +1273,8 @@ struct section *elf_create_section_pair(struct elf *elf, const char *name,
{
struct section *sec;
- sec = elf_create_section(elf, name, entsize, nr);
+ sec = elf_create_section(elf, name, nr * entsize, entsize,
+ SHT_PROGBITS, 1, SHF_ALLOC);
if (!sec)
return NULL;
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index ffdf9ec3882e..b366516b119d 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -116,11 +116,16 @@ struct elf {
struct elf *elf_open_read(const char *name, int flags);
struct section *elf_create_section(struct elf *elf, const char *name,
- size_t entsize, unsigned int nr);
+ size_t size, size_t entsize,
+ unsigned int type, unsigned int align,
+ unsigned int flags);
struct section *elf_create_section_pair(struct elf *elf, const char *name,
size_t entsize, unsigned int nr,
unsigned int reloc_nr);
+struct section *elf_create_rela_section(struct elf *elf, struct section *sec,
+ unsigned int reloc_nr);
+
struct symbol *elf_create_symbol(struct elf *elf, const char *name,
struct section *sec, unsigned int bind,
unsigned int type, unsigned long offset,
diff --git a/tools/objtool/orc_gen.c b/tools/objtool/orc_gen.c
index 6eff3d6a125c..9d380abc2ed3 100644
--- a/tools/objtool/orc_gen.c
+++ b/tools/objtool/orc_gen.c
@@ -127,7 +127,11 @@ int orc_create(struct objtool_file *file)
return -1;
}
orc_sec = elf_create_section(file->elf, ".orc_unwind",
- sizeof(struct orc_entry), nr);
+ nr * sizeof(struct orc_entry),
+ sizeof(struct orc_entry),
+ SHT_PROGBITS,
+ 1,
+ SHF_ALLOC);
if (!orc_sec)
return -1;
--
2.49.0
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