Commit 65fb11a7 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

objtool: Optimize find_symbol_by_index() 



The symbol index is object wide, not per section, so it makes no sense
to have the symbol_hash be part of the section object. By moving it to
the elf object we avoid the linear sections iteration.

This reduces the runtime of objtool on vmlinux.o from over 3 hours (I
gave up) to a few minutes. The defconfig vmlinux.o has around 20k
sections.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarMiroslav Benes <mbenes@suse.cz>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20200324160924.261852348@infradead.org
parent 36cc5520

tools/objtool/elf.c

+5 −8
Original line number Original line Diff line number Diff line
@@ -46,11 +46,9 @@ static struct section *find_section_by_index(struct elf *elf, 




static struct symbol *find_symbol_by_index(struct elf *elf, unsigned int idx)

static struct symbol *find_symbol_by_index(struct elf *elf, unsigned int idx)

{

{

	struct section *sec;

	struct symbol *sym;

	struct symbol *sym;





	list_for_each_entry(sec, &elf->sections, list)

	hash_for_each_possible(elf->symbol_hash, sym, hash, idx)

		hash_for_each_possible(sec->symbol_hash, sym, hash, idx)

		if (sym->idx == idx)

		if (sym->idx == idx)

			return sym;

			return sym;
@@ -166,7 +164,6 @@ static int read_sections(struct elf *elf) 
		INIT_LIST_HEAD(&sec->symbol_list);

		INIT_LIST_HEAD(&sec->symbol_list);

		INIT_LIST_HEAD(&sec->rela_list);

		INIT_LIST_HEAD(&sec->rela_list);

		hash_init(sec->rela_hash);

		hash_init(sec->rela_hash);

		hash_init(sec->symbol_hash);





		list_add_tail(&sec->list, &elf->sections);

		list_add_tail(&sec->list, &elf->sections);
@@ -299,7 +296,7 @@ static int read_symbols(struct elf *elf) 
		}

		}

		sym->alias = alias;

		sym->alias = alias;

		list_add(&sym->list, entry);

		list_add(&sym->list, entry);

		hash_add(sym->sec->symbol_hash, &sym->hash, sym->idx);

		hash_add(elf->symbol_hash, &sym->hash, sym->idx);

	}

	}





	/* Create parent/child links for any cold subfunctions */

	/* Create parent/child links for any cold subfunctions */
@@ -425,6 +422,7 @@ struct elf *elf_read(const char *name, int flags) 
	}

	}

	memset(elf, 0, sizeof(*elf));

	memset(elf, 0, sizeof(*elf));





	hash_init(elf->symbol_hash);

	INIT_LIST_HEAD(&elf->sections);

	INIT_LIST_HEAD(&elf->sections);





	elf->fd = open(name, flags);

	elf->fd = open(name, flags);
@@ -486,7 +484,6 @@ struct section *elf_create_section(struct elf *elf, const char *name, 
	INIT_LIST_HEAD(&sec->symbol_list);

	INIT_LIST_HEAD(&sec->symbol_list);

	INIT_LIST_HEAD(&sec->rela_list);

	INIT_LIST_HEAD(&sec->rela_list);

	hash_init(sec->rela_hash);

	hash_init(sec->rela_hash);

	hash_init(sec->symbol_hash);





	list_add_tail(&sec->list, &elf->sections);

	list_add_tail(&sec->list, &elf->sections);

tools/objtool/elf.h

+1 −2
Original line number Original line Diff line number Diff line
@@ -27,7 +27,6 @@ struct section { 
	struct list_head list;

	struct list_head list;

	GElf_Shdr sh;

	GElf_Shdr sh;

	struct list_head symbol_list;

	struct list_head symbol_list;

	DECLARE_HASHTABLE(symbol_hash, 8);

	struct list_head rela_list;

	struct list_head rela_list;

	DECLARE_HASHTABLE(rela_hash, 16);

	DECLARE_HASHTABLE(rela_hash, 16);

	struct section *base, *rela;

	struct section *base, *rela;
@@ -71,7 +70,7 @@ struct elf { 
	int fd;

	int fd;

	char *name;

	char *name;

	struct list_head sections;

	struct list_head sections;

	DECLARE_HASHTABLE(rela_hash, 16);

	DECLARE_HASHTABLE(symbol_hash, 20);

};

};

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