[PATCH 07/22] objtool: Add elf_create_section_pair()

From: Josh Poimboeuf
Date: Tue May 30 2023 - 13:22:12 EST

When creating an annotation section, allocate the reloc section data at
the beginning. This simplifies the data model a bit and also saves
memory due to the removal of malloc() in elf_rebuild_reloc_section().

With allyesconfig + CONFIG_DEBUG_INFO:

- Before: peak heap memory consumption: 53.49G
- After: peak heap memory consumption: 49.02G

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
tools/objtool/arch/powerpc/include/arch/elf.h | 11 +-
tools/objtool/arch/x86/include/arch/elf.h | 11 +-
tools/objtool/check.c | 129 ++++++---------
tools/objtool/elf.c | 151 +++++++++++-------
tools/objtool/include/objtool/elf.h | 33 +++-
tools/objtool/orc_gen.c | 6 +-
6 files changed, 184 insertions(+), 157 deletions(-)

diff --git a/tools/objtool/arch/powerpc/include/arch/elf.h b/tools/objtool/arch/powerpc/include/arch/elf.h
index 73f9ae172fe5..66814fa28024 100644
--- a/tools/objtool/arch/powerpc/include/arch/elf.h
+++ b/tools/objtool/arch/powerpc/include/arch/elf.h
@@ -1,10 +1,13 @@
/* SPDX-License-Identifier: GPL-2.0-or-later */
-
#ifndef _OBJTOOL_ARCH_ELF
#define _OBJTOOL_ARCH_ELF

-#define R_NONE R_PPC_NONE
-#define R_ABS64 R_PPC64_ADDR64
-#define R_ABS32 R_PPC_ADDR32
+#define R_NONE R_PPC_NONE
+#define R_ABS64 R_PPC64_ADDR64
+#define R_ABS32 R_PPC_ADDR32
+#define R_DATA32 R_PPC_REL32
+#define R_DATA64 R_PPC64_REL64
+#define R_TEXT32 R_PPC_REL32
+#define R_TEXT64 R_PPC64_REL32

#endif /* _OBJTOOL_ARCH_ELF */
diff --git a/tools/objtool/arch/x86/include/arch/elf.h b/tools/objtool/arch/x86/include/arch/elf.h
index ac14987cf687..7131f7f51a4e 100644
--- a/tools/objtool/arch/x86/include/arch/elf.h
+++ b/tools/objtool/arch/x86/include/arch/elf.h
@@ -1,8 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
#ifndef _OBJTOOL_ARCH_ELF
#define _OBJTOOL_ARCH_ELF

-#define R_NONE R_X86_64_NONE
-#define R_ABS64 R_X86_64_64
-#define R_ABS32 R_X86_64_32
+#define R_NONE R_X86_64_NONE
+#define R_ABS32 R_X86_64_32
+#define R_ABS64 R_X86_64_64
+#define R_DATA32 R_X86_64_PC32
+#define R_DATA64 R_X86_64_PC32
+#define R_TEXT32 R_X86_64_PC32
+#define R_TEXT64 R_X86_64_PC32

#endif /* _OBJTOOL_ARCH_ELF */
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index b6d0cb24085b..88f54bb1b01c 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -8,7 +8,6 @@
#include <inttypes.h>
#include <sys/mman.h>

-#include <arch/elf.h>
#include <objtool/builtin.h>
#include <objtool/cfi.h>
#include <objtool/arch.h>
@@ -655,8 +654,8 @@ static int add_dead_ends(struct objtool_file *file)

static int create_static_call_sections(struct objtool_file *file)
{
- struct section *sec;
struct static_call_site *site;
+ struct section *sec;
struct instruction *insn;
struct symbol *key_sym;
char *key_name, *tmp;
@@ -676,25 +675,21 @@ static int create_static_call_sections(struct objtool_file *file)
list_for_each_entry(insn, &file->static_call_list, call_node)
idx++;

- sec = elf_create_section(file->elf, ".static_call_sites",
- sizeof(struct static_call_site), idx);
+ sec = elf_create_section_pair(file->elf, ".static_call_sites",
+ sizeof(*site), idx, idx * 2);
if (!sec)
return -1;

- /* Allow modules to set the low bits of static_call_site::key */
+ /* Allow modules to modify the low bits of static_call_site::key */
sec->sh.sh_flags |= SHF_WRITE;

idx = 0;
list_for_each_entry(insn, &file->static_call_list, call_node) {

- site = (struct static_call_site *)sec->data->d_buf + idx;
- memset(site, 0, sizeof(struct static_call_site));
-
/* populate reloc for 'addr' */
- if (elf_add_reloc_to_insn(file->elf, sec,
- idx * sizeof(struct static_call_site),
- R_X86_64_PC32,
- insn->sec, insn->offset))
+ if (!elf_init_reloc_text_sym(file->elf, sec,
+ idx * sizeof(*site), idx * 2,
+ insn->sec, insn->offset))
return -1;

/* find key symbol */
@@ -734,10 +729,10 @@ static int create_static_call_sections(struct objtool_file *file)
free(key_name);

/* populate reloc for 'key' */
- if (elf_add_reloc(file->elf, sec,
- idx * sizeof(struct static_call_site) + 4,
- R_X86_64_PC32, key_sym,
- is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
+ if (!elf_init_reloc_data_sym(file->elf, sec,
+ idx * sizeof(*site) + 4,
+ (idx * 2) + 1, key_sym,
+ is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
return -1;

idx++;
@@ -765,26 +760,18 @@ static int create_retpoline_sites_sections(struct objtool_file *file)
if (!idx)
return 0;

- sec = elf_create_section(file->elf, ".retpoline_sites",
- sizeof(int), idx);
- if (!sec) {
- WARN("elf_create_section: .retpoline_sites");
+ sec = elf_create_section_pair(file->elf, ".retpoline_sites",
+ sizeof(int), idx, idx);
+ if (!sec)
return -1;
- }

idx = 0;
list_for_each_entry(insn, &file->retpoline_call_list, call_node) {

- int *site = (int *)sec->data->d_buf + idx;
- *site = 0;
-
- if (elf_add_reloc_to_insn(file->elf, sec,
- idx * sizeof(int),
- R_X86_64_PC32,
- insn->sec, insn->offset)) {
- WARN("elf_add_reloc_to_insn: .retpoline_sites");
+ if (!elf_init_reloc_text_sym(file->elf, sec,
+ idx * sizeof(int), idx,
+ insn->sec, insn->offset))
return -1;
- }

idx++;
}
@@ -811,26 +798,18 @@ static int create_return_sites_sections(struct objtool_file *file)
if (!idx)
return 0;

- sec = elf_create_section(file->elf, ".return_sites",
- sizeof(int), idx);
- if (!sec) {
- WARN("elf_create_section: .return_sites");
+ sec = elf_create_section_pair(file->elf, ".return_sites",
+ sizeof(int), idx, idx);
+ if (!sec)
return -1;
- }

idx = 0;
list_for_each_entry(insn, &file->return_thunk_list, call_node) {

- int *site = (int *)sec->data->d_buf + idx;
- *site = 0;
-
- if (elf_add_reloc_to_insn(file->elf, sec,
- idx * sizeof(int),
- R_X86_64_PC32,
- insn->sec, insn->offset)) {
- WARN("elf_add_reloc_to_insn: .return_sites");
+ if (!elf_init_reloc_text_sym(file->elf, sec,
+ idx * sizeof(int), idx,
+ insn->sec, insn->offset))
return -1;
- }

idx++;
}
@@ -863,12 +842,10 @@ static int create_ibt_endbr_seal_sections(struct objtool_file *file)
if (!idx)
return 0;

- sec = elf_create_section(file->elf, ".ibt_endbr_seal",
- sizeof(int), idx);
- if (!sec) {
- WARN("elf_create_section: .ibt_endbr_seal");
+ sec = elf_create_section_pair(file->elf, ".ibt_endbr_seal",
+ sizeof(int), idx, idx);
+ if (!sec)
return -1;
- }

idx = 0;
list_for_each_entry(insn, &file->endbr_list, call_node) {
@@ -883,13 +860,10 @@ static int create_ibt_endbr_seal_sections(struct objtool_file *file)
!strcmp(sym->name, "cleanup_module")))
WARN("%s(): not an indirect call target", sym->name);

- if (elf_add_reloc_to_insn(file->elf, sec,
- idx * sizeof(int),
- R_X86_64_PC32,
- insn->sec, insn->offset)) {
- WARN("elf_add_reloc_to_insn: .ibt_endbr_seal");
+ if (!elf_init_reloc_text_sym(file->elf, sec,
+ idx * sizeof(int), idx,
+ insn->sec, insn->offset))
return -1;
- }

idx++;
}
@@ -901,7 +875,6 @@ static int create_cfi_sections(struct objtool_file *file)
{
struct section *sec;
struct symbol *sym;
- unsigned int *loc;
int idx;

sec = find_section_by_name(file->elf, ".cfi_sites");
@@ -922,7 +895,8 @@ static int create_cfi_sections(struct objtool_file *file)
idx++;
}

- sec = elf_create_section(file->elf, ".cfi_sites", sizeof(unsigned int), idx);
+ sec = elf_create_section_pair(file->elf, ".cfi_sites",
+ sizeof(unsigned int), idx, idx);
if (!sec)
return -1;

@@ -934,13 +908,9 @@ static int create_cfi_sections(struct objtool_file *file)
if (strncmp(sym->name, "__cfi_", 6))
continue;

- loc = (unsigned int *)sec->data->d_buf + idx;
- memset(loc, 0, sizeof(unsigned int));
-
- if (elf_add_reloc_to_insn(file->elf, sec,
- idx * sizeof(unsigned int),
- R_X86_64_PC32,
- sym->sec, sym->offset))
+ if (!elf_init_reloc_text_sym(file->elf, sec,
+ idx * sizeof(unsigned int), idx,
+ sym->sec, sym->offset))
return -1;

idx++;
@@ -970,7 +940,8 @@ static int create_mcount_loc_sections(struct objtool_file *file)
list_for_each_entry(insn, &file->mcount_loc_list, call_node)
idx++;

- sec = elf_create_section(file->elf, "__mcount_loc", addr_size, idx);
+ sec = elf_create_section_pair(file->elf, "__mcount_loc", addr_size,
+ idx, idx);
if (!sec)
return -1;

@@ -978,17 +949,17 @@ static int create_mcount_loc_sections(struct objtool_file *file)

idx = 0;
list_for_each_entry(insn, &file->mcount_loc_list, call_node) {
- void *loc;

- loc = sec->data->d_buf + idx;
- memset(loc, 0, addr_size);
+ struct reloc *reloc;

- if (elf_add_reloc_to_insn(file->elf, sec, idx,
- addr_size == sizeof(u64) ? R_ABS64 : R_ABS32,
- insn->sec, insn->offset))
+ reloc = elf_init_reloc_text_sym(file->elf, sec, idx * addr_size, idx,
+ insn->sec, insn->offset);
+ if (!reloc)
return -1;

- idx += addr_size;
+ reloc->type = addr_size == 8 ? R_ABS64 : R_ABS32;
+
+ idx++;
}

return 0;
@@ -998,7 +969,6 @@ static int create_direct_call_sections(struct objtool_file *file)
{
struct instruction *insn;
struct section *sec;
- unsigned int *loc;
int idx;

sec = find_section_by_name(file->elf, ".call_sites");
@@ -1015,20 +985,17 @@ static int create_direct_call_sections(struct objtool_file *file)
list_for_each_entry(insn, &file->call_list, call_node)
idx++;

- sec = elf_create_section(file->elf, ".call_sites", sizeof(unsigned int), idx);
+ sec = elf_create_section_pair(file->elf, ".call_sites",
+ sizeof(unsigned int), idx, idx);
if (!sec)
return -1;

idx = 0;
list_for_each_entry(insn, &file->call_list, call_node) {

- loc = (unsigned int *)sec->data->d_buf + idx;
- memset(loc, 0, sizeof(unsigned int));
-
- if (elf_add_reloc_to_insn(file->elf, sec,
- idx * sizeof(unsigned int),
- R_X86_64_PC32,
- insn->sec, insn->offset))
+ if (!elf_init_reloc_text_sym(file->elf, sec,
+ idx * sizeof(unsigned int), idx,
+ insn->sec, insn->offset))
return -1;

idx++;
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 67967c231972..5cbc9d578a45 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -533,41 +533,6 @@ static int read_symbols(struct elf *elf)
return -1;
}

-static struct section *elf_create_rela_section(struct elf *elf,
- struct section *sec);
-
-int elf_add_reloc(struct elf *elf, struct section *sec, unsigned long offset,
- unsigned int type, struct symbol *sym, s64 addend)
-{
- struct reloc *reloc;
-
- if (!sec->rsec && !elf_create_rela_section(elf, sec))
- return -1;
-
- reloc = malloc(sizeof(*reloc));
- if (!reloc) {
- perror("malloc");
- return -1;
- }
- memset(reloc, 0, sizeof(*reloc));
-
- reloc->sec = sec->rsec;
- reloc->offset = offset;
- reloc->type = type;
- reloc->sym = sym;
- reloc->addend = addend;
-
- list_add_tail(&reloc->sym_reloc_entry, &sym->reloc_list);
- list_add_tail(&reloc->list, &sec->rsec->reloc_list);
- elf_hash_add(reloc, &reloc->hash, reloc_hash(reloc));
-
- sec->rsec->sh.sh_size += sec->rsec->sh.sh_entsize;
-
- mark_sec_changed(elf, sec->rsec, true);
-
- return 0;
-}
-
/*
* Ensure that any reloc section containing references to @sym is marked
* changed such that it will get re-generated in elf_rebuild_reloc_sections()
@@ -841,13 +806,57 @@ elf_create_prefix_symbol(struct elf *elf, struct symbol *orig, long size)
return sym;
}

-int elf_add_reloc_to_insn(struct elf *elf, struct section *sec,
- unsigned long offset, unsigned int type,
- struct section *insn_sec, unsigned long insn_off)
+static struct reloc *elf_init_reloc(struct elf *elf, struct section *rsec,
+ unsigned int reloc_idx,
+ unsigned long offset, struct symbol *sym,
+ s64 addend, unsigned int type)
+{
+ struct reloc *reloc;
+
+ if (reloc_idx >= rsec->sh.sh_size / elf_rela_size(elf)) {
+ WARN("%s: bad reloc_idx %u for %s with size 0x%lx",
+ __func__, reloc_idx, rsec->name, rsec->sh.sh_size);
+ return NULL;
+ }
+
+ reloc = malloc(sizeof(*reloc));
+ if (!reloc) {
+ perror("malloc");
+ return NULL;
+ }
+ memset(reloc, 0, sizeof(*reloc));
+
+ reloc->idx = reloc_idx;
+ reloc->sec = rsec;
+ reloc->offset = offset;
+ reloc->type = type;
+ reloc->sym = sym;
+ reloc->addend = addend;
+
+ list_add_tail(&reloc->sym_reloc_entry, &sym->reloc_list);
+ list_add_tail(&reloc->list, &rsec->reloc_list);
+ elf_hash_add(reloc, &reloc->hash, reloc_hash(reloc));
+
+ mark_sec_changed(elf, rsec, true);
+
+ return reloc;
+}
+
+struct reloc *elf_init_reloc_text_sym(struct elf *elf, struct section *sec,
+ unsigned long offset,
+ unsigned int reloc_idx,
+ struct section *insn_sec,
+ unsigned long insn_off)
{
struct symbol *sym = insn_sec->sym;
int addend = insn_off;

+ if (!(insn_sec->sh.sh_flags & SHF_EXECINSTR)) {
+ WARN("bad call to %s() for data symbol %s",
+ __func__, sym->name);
+ return NULL;
+ }
+
if (!sym) {
/*
* Due to how weak functions work, we must use section based
@@ -857,12 +866,29 @@ int elf_add_reloc_to_insn(struct elf *elf, struct section *sec,
*/
sym = elf_create_section_symbol(elf, insn_sec);
if (!sym)
- return -1;
+ return NULL;

insn_sec->sym = sym;
}

- return elf_add_reloc(elf, sec, offset, type, sym, addend);
+ return elf_init_reloc(elf, sec->rsec, reloc_idx, offset, sym, addend,
+ elf_text_rela_type(elf));
+}
+
+struct reloc *elf_init_reloc_data_sym(struct elf *elf, struct section *sec,
+ unsigned long offset,
+ unsigned int reloc_idx,
+ struct symbol *sym,
+ s64 addend)
+{
+ if (sym->sec && (sec->sh.sh_flags & SHF_EXECINSTR)) {
+ WARN("bad call to %s() for text symbol %s",
+ __func__, sym->name);
+ return NULL;
+ }
+
+ return elf_init_reloc(elf, sec->rsec, reloc_idx, offset, sym, addend,
+ elf_data_rela_type(elf));
}

static int read_reloc(struct section *rsec, int i, struct reloc *reloc)
@@ -1048,7 +1074,7 @@ static int elf_add_string(struct elf *elf, struct section *strtab, char *str)
}

struct section *elf_create_section(struct elf *elf, const char *name,
- size_t entsize, int nr)
+ size_t entsize, unsigned int nr)
{
struct section *sec, *shstrtab;
size_t size = entsize * nr;
@@ -1129,7 +1155,8 @@ struct section *elf_create_section(struct elf *elf, const char *name,
}

static struct section *elf_create_rela_section(struct elf *elf,
- struct section *sec)
+ struct section *sec,
+ unsigned int reloc_nr)
{
struct section *rsec;
char *rsec_name;
@@ -1142,46 +1169,50 @@ 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), 0);
+ rsec = elf_create_section(elf, rsec_name, elf_rela_size(elf), reloc_nr);
free(rsec_name);
if (!rsec)
return NULL;

- sec->rsec = rsec;
- rsec->base = sec;
-
+ 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;

+ sec->rsec = rsec;
+ rsec->base = sec;
+
return rsec;
}

+struct section *elf_create_section_pair(struct elf *elf, const char *name,
+ size_t entsize, unsigned int nr,
+ unsigned int reloc_nr)
+{
+ struct section *sec;
+
+ sec = elf_create_section(elf, name, entsize, nr);
+ if (!sec)
+ return NULL;
+
+ if (!elf_create_rela_section(elf, sec, reloc_nr))
+ return NULL;
+
+ return sec;
+}
+
static int elf_rebuild_reloc_section(struct elf *elf, struct section *rsec)
{
- bool rela = rsec->sh.sh_type == SHT_RELA;
struct reloc *reloc;
int idx = 0, ret;
- void *buf;
-
- /* Allocate a buffer for relocations */
- buf = malloc(rsec->sh.sh_size);
- if (!buf) {
- perror("malloc");
- return -1;
- }
-
- rsec->data->d_buf = buf;
- rsec->data->d_size = rsec->sh.sh_size;
- rsec->data->d_type = rela ? ELF_T_RELA : ELF_T_REL;

idx = 0;
list_for_each_entry(reloc, &rsec->reloc_list, list) {
reloc->rel.r_offset = reloc->offset;
reloc->rel.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
- if (rela) {
+ if (rsec->sh.sh_type == SHT_RELA) {
reloc->rela.r_addend = reloc->addend;
ret = gelf_update_rela(rsec->data, idx, &reloc->rela);
} else {
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index 56b66ff91943..74f63934afd3 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -111,15 +111,26 @@ 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, int nr);
+
+struct section *elf_create_section(struct elf *elf, const char *name,
+ size_t entsize, unsigned int nr);
+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);

-int elf_add_reloc(struct elf *elf, struct section *sec, unsigned long offset,
- unsigned int type, struct symbol *sym, s64 addend);
-int elf_add_reloc_to_insn(struct elf *elf, struct section *sec,
- unsigned long offset, unsigned int type,
- struct section *insn_sec, unsigned long insn_off);
+struct reloc *elf_init_reloc_text_sym(struct elf *elf, struct section *sec,
+ unsigned long offset,
+ unsigned int reloc_idx,
+ struct section *insn_sec,
+ unsigned long insn_off);
+
+struct reloc *elf_init_reloc_data_sym(struct elf *elf, struct section *sec,
+ unsigned long offset,
+ unsigned int reloc_idx,
+ struct symbol *sym,
+ s64 addend);

int elf_write_insn(struct elf *elf, struct section *sec,
unsigned long offset, unsigned int len,
@@ -159,6 +170,16 @@ static inline size_t elf_rela_size(struct elf *elf)
return elf_addr_size(elf) == 4 ? sizeof(Elf32_Rela) : sizeof(Elf64_Rela);
}

+static inline unsigned int elf_data_rela_type(struct elf *elf)
+{
+ return elf_addr_size(elf) == 4 ? R_DATA32 : R_DATA64;
+}
+
+static inline unsigned int elf_text_rela_type(struct elf *elf)
+{
+ return elf_addr_size(elf) == 4 ? R_TEXT32 : R_TEXT64;
+}
+
static inline bool is_reloc_sec(struct section *sec)
{
return sec->sh.sh_type == SHT_RELA || sec->sh.sh_type == SHT_REL;
diff --git a/tools/objtool/orc_gen.c b/tools/objtool/orc_gen.c
index d5f750be7d7d..bae343908867 100644
--- a/tools/objtool/orc_gen.c
+++ b/tools/objtool/orc_gen.c
@@ -118,8 +118,8 @@ static int write_orc_entry(struct elf *elf, struct section *orc_sec,
orc->bp_offset = bswap_if_needed(elf, orc->bp_offset);

/* populate reloc for ip */
- if (elf_add_reloc_to_insn(elf, ip_sec, idx * sizeof(int), R_X86_64_PC32,
- insn_sec, insn_off))
+ if (!elf_init_reloc_text_sym(elf, ip_sec, idx * sizeof(int), idx,
+ insn_sec, insn_off))
return -1;

return 0;
@@ -242,7 +242,7 @@ int orc_create(struct objtool_file *file)
if (!orc_sec)
return -1;

- sec = elf_create_section(file->elf, ".orc_unwind_ip", sizeof(int), nr);
+ sec = elf_create_section_pair(file->elf, ".orc_unwind_ip", sizeof(int), nr, nr);
if (!sec)
return -1;

--
2.40.1