objtool: Add elf_create_section_pair()

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

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Josh Poimboeuf <[e-mail]>

tools/objtool/arch/powerpc/include/arch/elf.h

···
 /* 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 */

tools/objtool/arch/x86/include/arch/elf.h

···
+/* 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 */

tools/objtool/check.c

···
 #include <inttypes.h>
 #include <sys/mman.h>
 
-#include <arch/elf.h>
 #include <objtool/builtin.h>
 #include <objtool/cfi.h>
 #include <objtool/arch.h>
···
 
 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;
···
 	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 */
···
 		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++;
···
 	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++;
 	}
···
 	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++;
 	}
···
 	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) {
···
 		     !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++;
 	}
···
 {
 	struct section *sec;
 	struct symbol *sym;
-	unsigned int *loc;
 	int idx;
 
 	sec = find_section_by_name(file->elf, ".cfi_sites");
···
 		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;
 
···
 		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++;
···
 	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;
 
···
 
 	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;
···
 {
 	struct instruction *insn;
 	struct section *sec;
-	unsigned int *loc;
 	int idx;
 
 	sec = find_section_by_name(file->elf, ".call_sites");
···
 	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++;

tools/objtool/elf.c

···
 	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()
···
 	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) {
 		/*
···
 		 */
 		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)
···
 }
 
 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;
···
 }
 
 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;
···
 	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 {

tools/objtool/include/objtool/elf.h

···
 };
 
 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,
···
 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)

tools/objtool/orc_gen.c

···
 	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;
···
 	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;