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Message-ID: <c42e73faa0cbc4ea17efff201994305e2d6b3770.1746821544.git.jpoimboe@kernel.org>
Date: Fri, 9 May 2025 13:17:01 -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 37/62] objtool: Generalize elf_create_symbol()
In preparation for the objtool klp diff subcommand, broaden the
elf_create_symbol() interface to give callers more control and reduce
duplication of some subtle setup logic.
While at it, make elf_create_symbol() and elf_create_section_symbol()
public so sections can be created by the upcoming klp diff code.
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
tools/objtool/elf.c | 111 +++++++++++++++-------------
tools/objtool/include/objtool/elf.h | 11 ++-
2 files changed, 69 insertions(+), 53 deletions(-)
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 859d677e172c..38bf9ae86c89 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -761,24 +761,60 @@ static int elf_update_symbol(struct elf *elf, struct section *symtab,
return 0;
}
-static struct symbol *
-__elf_create_symbol(struct elf *elf, struct symbol *sym)
+static int elf_add_string(struct elf *elf, struct section *strtab, const char *str);
+
+struct symbol *elf_create_symbol(struct elf *elf, const char *name,
+ struct section *sec, unsigned int bind,
+ unsigned int type, unsigned long offset,
+ size_t size)
{
struct section *symtab, *symtab_shndx;
Elf32_Word first_non_local, new_idx;
- struct symbol *old;
+ struct symbol *old, *sym;
+
+ sym = calloc(1, sizeof(*sym));
+ if (!sym) {
+ ERROR_GLIBC("calloc");
+ return NULL;
+ }
+
+ sym->name = strdup(name);
+ if (!sym->name) {
+ ERROR_GLIBC("strdup");
+ return NULL;
+ }
+
+ if (type != STT_SECTION) {
+ sym->sym.st_name = elf_add_string(elf, NULL, sym->name);
+ if (sym->sym.st_name == -1)
+ return NULL;
+ }
+
+ if (sec) {
+ sym->sec = sec;
+ } else {
+ sym->sec = find_section_by_index(elf, 0);
+ if (!sym->sec) {
+ ERROR("no NULL section");
+ return NULL;
+ }
+ }
+
+ sym->sym.st_info = GELF_ST_INFO(bind, type);
+ sym->sym.st_value = offset;
+ sym->sym.st_size = size;
symtab = find_section_by_name(elf, ".symtab");
- if (symtab) {
- symtab_shndx = find_section_by_name(elf, ".symtab_shndx");
- } else {
+ if (!symtab) {
ERROR("no .symtab");
return NULL;
}
+ symtab_shndx = find_section_by_name(elf, ".symtab_shndx");
+
new_idx = sec_num_entries(symtab);
- if (GELF_ST_BIND(sym->sym.st_info) != STB_LOCAL)
+ if (bind != STB_LOCAL)
goto non_local;
/*
@@ -816,10 +852,8 @@ __elf_create_symbol(struct elf *elf, struct symbol *sym)
non_local:
sym->idx = new_idx;
- if (elf_update_symbol(elf, symtab, symtab_shndx, sym)) {
- ERROR("elf_update_symbol");
+ if (sym->idx && elf_update_symbol(elf, symtab, symtab_shndx, sym))
return NULL;
- }
symtab->sh.sh_size += symtab->sh.sh_entsize;
mark_sec_changed(elf, symtab, true);
@@ -829,64 +863,39 @@ __elf_create_symbol(struct elf *elf, struct symbol *sym)
mark_sec_changed(elf, symtab_shndx, true);
}
+ elf_add_symbol(elf, sym);
+
return sym;
}
-static struct symbol *
-elf_create_section_symbol(struct elf *elf, struct section *sec)
+struct symbol *elf_create_section_symbol(struct elf *elf, struct section *sec)
{
struct symbol *sym = calloc(1, sizeof(*sym));
- if (!sym) {
- ERROR_GLIBC("malloc");
+ sym = elf_create_symbol(elf, sec->name, sec, STB_LOCAL, STT_SECTION, 0, 0);
+ if (!sym)
return NULL;
- }
- sym->name = sec->name;
- sym->sec = sec;
-
- // st_name 0
- sym->sym.st_info = GELF_ST_INFO(STB_LOCAL, STT_SECTION);
- // st_other 0
- // st_value 0
- // st_size 0
-
- sym = __elf_create_symbol(elf, sym);
- if (sym)
- elf_add_symbol(elf, sym);
+ sec->sym = sym;
return sym;
}
-static int elf_add_string(struct elf *elf, struct section *strtab, const char *str);
-
struct symbol *
-elf_create_prefix_symbol(struct elf *elf, struct symbol *orig, long size)
+elf_create_prefix_symbol(struct elf *elf, struct symbol *orig, size_t size)
{
- struct symbol *sym = calloc(1, sizeof(*sym));
size_t namelen = strlen(orig->name) + sizeof("__pfx_");
- char *name = malloc(namelen);
-
- if (!sym || !name) {
- ERROR_GLIBC("malloc");
- return NULL;
- }
+ char name[SYM_NAME_LEN];
+ unsigned long offset;
snprintf(name, namelen, "__pfx_%s", orig->name);
- sym->name = name;
- sym->sec = orig->sec;
+ offset = orig->sym.st_value - size;
- sym->sym.st_name = elf_add_string(elf, NULL, name);
- sym->sym.st_info = orig->sym.st_info;
- sym->sym.st_value = orig->sym.st_value - size;
- sym->sym.st_size = size;
-
- sym = __elf_create_symbol(elf, sym);
- if (sym)
- elf_add_symbol(elf, sym);
-
- return sym;
+ return elf_create_symbol(elf, name, orig->sec,
+ GELF_ST_BIND(orig->sym.st_info),
+ GELF_ST_TYPE(orig->sym.st_info),
+ offset, size);
}
static struct reloc *elf_init_reloc(struct elf *elf, struct section *rsec,
@@ -932,7 +941,7 @@ struct reloc *elf_init_reloc_text_sym(struct elf *elf, struct section *sec,
unsigned long insn_off)
{
struct symbol *sym = insn_sec->sym;
- int addend = insn_off;
+ s64 addend = insn_off;
if (!is_text_sec(insn_sec)) {
ERROR("bad call to %s() for data symbol %s", __func__, sym->name);
@@ -949,8 +958,6 @@ struct reloc *elf_init_reloc_text_sym(struct elf *elf, struct section *sec,
sym = elf_create_section_symbol(elf, insn_sec);
if (!sym)
return NULL;
-
- insn_sec->sym = sym;
}
return elf_init_reloc(elf, sec->rsec, reloc_idx, offset, sym, addend,
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index 74c7b84b5310..ffdf9ec3882e 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -15,6 +15,8 @@
#include <linux/jhash.h>
#include <arch/elf.h>
+#define SYM_NAME_LEN 512
+
#ifdef LIBELF_USE_DEPRECATED
# define elf_getshdrnum elf_getshnum
# define elf_getshdrstrndx elf_getshstrndx
@@ -119,7 +121,14 @@ struct section *elf_create_section_pair(struct elf *elf, const char *name,
size_t entsize, unsigned int nr,
unsigned int reloc_nr);
-struct symbol *elf_create_prefix_symbol(struct elf *elf, struct symbol *orig, long size);
+struct symbol *elf_create_symbol(struct elf *elf, const char *name,
+ struct section *sec, unsigned int bind,
+ unsigned int type, unsigned long offset,
+ size_t size);
+struct symbol *elf_create_section_symbol(struct elf *elf, struct section *sec);
+struct symbol *elf_create_prefix_symbol(struct elf *elf, struct symbol *orig,
+ size_t size);
+
struct reloc *elf_init_reloc_text_sym(struct elf *elf, struct section *sec,
unsigned long offset,
--
2.49.0
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