Commit 8b5fa6bc authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

objtool: Optimize read_sections() 



Perf showed that __hash_init() is a significant portion of
read_sections(), so instead of doing a per section rela_hash, use an
elf-wide rela_hash.

Statistics show us there are about 1.1 million relas, so size it
accordingly.

This reduces the objtool on vmlinux.o runtime to a third, from 15 to 5
seconds.

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/20200324160924.739153726@infradead.org
parent cdb3d057

tools/objtool/check.c

+9 −9
Original line number Diff line number Diff line
@@ -569,8 +569,8 @@ static int add_jump_destinations(struct objtool_file *file) 
		if (insn->ignore || insn->offset == FAKE_JUMP_OFFSET)

			continue;



		rela = find_rela_by_dest_range(insn->sec, insn->offset,

					       insn->len);

		rela = find_rela_by_dest_range(file->elf, insn->sec,

					       insn->offset, insn->len);

		if (!rela) {

			dest_sec = insn->sec;

			dest_off = insn->offset + insn->len + insn->immediate;
@@ -666,8 +666,8 @@ static int add_call_destinations(struct objtool_file *file) 
		if (insn->type != INSN_CALL)

			continue;



		rela = find_rela_by_dest_range(insn->sec, insn->offset,

					       insn->len);

		rela = find_rela_by_dest_range(file->elf, insn->sec,

					       insn->offset, insn->len);

		if (!rela) {

			dest_off = insn->offset + insn->len + insn->immediate;

			insn->call_dest = find_func_by_offset(insn->sec, dest_off);
@@ -796,7 +796,7 @@ static int handle_group_alt(struct objtool_file *file, 
		 */

		if ((insn->offset != special_alt->new_off ||

		    (insn->type != INSN_CALL && !is_static_jump(insn))) &&

		    find_rela_by_dest_range(insn->sec, insn->offset, insn->len)) {

		    find_rela_by_dest_range(file->elf, insn->sec, insn->offset, insn->len)) {



			WARN_FUNC("unsupported relocation in alternatives section",

				  insn->sec, insn->offset);
@@ -1066,8 +1066,8 @@ static struct rela *find_jump_table(struct objtool_file *file, 
		    break;



		/* look for a relocation which references .rodata */

		text_rela = find_rela_by_dest_range(insn->sec, insn->offset,

						    insn->len);

		text_rela = find_rela_by_dest_range(file->elf, insn->sec,

						    insn->offset, insn->len);

		if (!text_rela || text_rela->sym->type != STT_SECTION ||

		    !text_rela->sym->sec->rodata)

			continue;
@@ -1096,7 +1096,7 @@ static struct rela *find_jump_table(struct objtool_file *file, 
		 * should reference text in the same function as the original

		 * instruction.

		 */

		table_rela = find_rela_by_dest(table_sec, table_offset);

		table_rela = find_rela_by_dest(file->elf, table_sec, table_offset);

		if (!table_rela)

			continue;

		dest_insn = find_insn(file, table_rela->sym->sec, table_rela->addend);
@@ -1232,7 +1232,7 @@ static int read_unwind_hints(struct objtool_file *file) 
	for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {

		hint = (struct unwind_hint *)sec->data->d_buf + i;



		rela = find_rela_by_dest(sec, i * sizeof(*hint));

		rela = find_rela_by_dest(file->elf, sec, i * sizeof(*hint));

		if (!rela) {

			WARN("can't find rela for unwind_hints[%d]", i);

			return -1;

tools/objtool/elf.c

+14 −10
Original line number Diff line number Diff line
@@ -212,8 +212,8 @@ struct symbol *find_symbol_by_name(struct elf *elf, const char *name) 
	return NULL;

}



struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,

				     unsigned int len)

struct rela *find_rela_by_dest_range(struct elf *elf, struct section *sec,

				     unsigned long offset, unsigned int len)

{

	struct rela *rela;

	unsigned long o;
@@ -221,17 +221,22 @@ struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset, 
	if (!sec->rela)

		return NULL;



	for (o = offset; o < offset + len; o++)

		hash_for_each_possible(sec->rela->rela_hash, rela, hash, o)

			if (rela->offset == o)

	sec = sec->rela;



	for (o = offset; o < offset + len; o++) {

		hash_for_each_possible(elf->rela_hash, rela, hash,

				       sec_offset_hash(sec, o)) {

			if (rela->sec == sec && rela->offset == o)

				return rela;

		}

	}



	return NULL;

}



struct rela *find_rela_by_dest(struct section *sec, unsigned long offset)

struct rela *find_rela_by_dest(struct elf *elf, struct section *sec, unsigned long offset)

{

	return find_rela_by_dest_range(sec, offset, 1);

	return find_rela_by_dest_range(elf, sec, offset, 1);

}



static int read_sections(struct elf *elf)
@@ -261,7 +266,6 @@ static int read_sections(struct elf *elf) 


		INIT_LIST_HEAD(&sec->symbol_list);

		INIT_LIST_HEAD(&sec->rela_list);

		hash_init(sec->rela_hash);



		s = elf_getscn(elf->elf, i);

		if (!s) {
@@ -493,7 +497,7 @@ static int read_relas(struct elf *elf) 
			}



			list_add_tail(&rela->list, &sec->rela_list);

			hash_add(sec->rela_hash, &rela->hash, rela->offset);

			hash_add(elf->rela_hash, &rela->hash, rela_hash(rela));

			nr_rela++;

		}

		max_rela = max(max_rela, nr_rela);
@@ -526,6 +530,7 @@ struct elf *elf_read(const char *name, int flags) 
	hash_init(elf->symbol_name_hash);

	hash_init(elf->section_hash);

	hash_init(elf->section_name_hash);

	hash_init(elf->rela_hash);

	INIT_LIST_HEAD(&elf->sections);



	elf->fd = open(name, flags);
@@ -586,7 +591,6 @@ struct section *elf_create_section(struct elf *elf, const char *name, 


	INIT_LIST_HEAD(&sec->symbol_list);

	INIT_LIST_HEAD(&sec->rela_list);

	hash_init(sec->rela_hash);



	s = elf_newscn(elf->elf);

	if (!s) {

tools/objtool/elf.h

+17 −4
Original line number Diff line number Diff line
@@ -33,7 +33,6 @@ struct section { 
	struct rb_root symbol_tree;

	struct list_head symbol_list;

	struct list_head rela_list;

	DECLARE_HASHTABLE(rela_hash, 16);

	struct section *base, *rela;

	struct symbol *sym;

	Elf_Data *data;
@@ -81,8 +80,22 @@ struct elf { 
	DECLARE_HASHTABLE(symbol_name_hash, 20);

	DECLARE_HASHTABLE(section_hash, 16);

	DECLARE_HASHTABLE(section_name_hash, 16);

	DECLARE_HASHTABLE(rela_hash, 20);

};



static inline u32 sec_offset_hash(struct section *sec, unsigned long offset)

{

	u32 ol = offset, oh = offset >> 32, idx = sec->idx;



	__jhash_mix(ol, oh, idx);



	return ol;

}



static inline u32 rela_hash(struct rela *rela)

{

	return sec_offset_hash(rela->sec, rela->offset);

}



struct elf *elf_read(const char *name, int flags);

struct section *find_section_by_name(struct elf *elf, const char *name);
@@ -90,9 +103,9 @@ struct symbol *find_func_by_offset(struct section *sec, unsigned long offset); 
struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset);

struct symbol *find_symbol_by_name(struct elf *elf, const char *name);

struct symbol *find_symbol_containing(struct section *sec, unsigned long offset);

struct rela *find_rela_by_dest(struct section *sec, unsigned long offset);

struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,

				     unsigned int len);

struct rela *find_rela_by_dest(struct elf *elf, struct section *sec, unsigned long offset);

struct rela *find_rela_by_dest_range(struct elf *elf, struct section *sec,

				     unsigned long offset, unsigned int len);

struct symbol *find_func_containing(struct section *sec, unsigned long offset);

struct section *elf_create_section(struct elf *elf, const char *name, size_t

				   entsize, int nr);

tools/objtool/orc_gen.c

+5 −4
Original line number Diff line number Diff line
@@ -81,7 +81,7 @@ int create_orc(struct objtool_file *file) 
	return 0;

}



static int create_orc_entry(struct section *u_sec, struct section *ip_relasec,

static int create_orc_entry(struct elf *elf, struct section *u_sec, struct section *ip_relasec,

				unsigned int idx, struct section *insn_sec,

				unsigned long insn_off, struct orc_entry *o)

{
@@ -109,9 +109,10 @@ static int create_orc_entry(struct section *u_sec, struct section *ip_relasec, 
	rela->addend = insn_off;

	rela->type = R_X86_64_PC32;

	rela->offset = idx * sizeof(int);

	rela->sec = ip_relasec;



	list_add_tail(&rela->list, &ip_relasec->rela_list);

	hash_add(ip_relasec->rela_hash, &rela->hash, rela->offset);

	hash_add(elf->rela_hash, &rela->hash, rela_hash(rela));



	return 0;

}
@@ -182,7 +183,7 @@ int create_orc_sections(struct objtool_file *file) 
			if (!prev_insn || memcmp(&insn->orc, &prev_insn->orc,

						 sizeof(struct orc_entry))) {



				if (create_orc_entry(u_sec, ip_relasec, idx,

				if (create_orc_entry(file->elf, u_sec, ip_relasec, idx,

						     insn->sec, insn->offset,

						     &insn->orc))

					return -1;
@@ -194,7 +195,7 @@ int create_orc_sections(struct objtool_file *file) 


		/* section terminator */

		if (prev_insn) {

			if (create_orc_entry(u_sec, ip_relasec, idx,

			if (create_orc_entry(file->elf, u_sec, ip_relasec, idx,

					     prev_insn->sec,

					     prev_insn->offset + prev_insn->len,

					     &empty))

tools/objtool/special.c

+2 −2
Original line number Diff line number Diff line
@@ -118,7 +118,7 @@ static int get_alt_entry(struct elf *elf, struct special_entry *entry, 
		}

	}



	orig_rela = find_rela_by_dest(sec, offset + entry->orig);

	orig_rela = find_rela_by_dest(elf, sec, offset + entry->orig);

	if (!orig_rela) {

		WARN_FUNC("can't find orig rela", sec, offset + entry->orig);

		return -1;
@@ -133,7 +133,7 @@ static int get_alt_entry(struct elf *elf, struct special_entry *entry, 
	alt->orig_off = orig_rela->addend;



	if (!entry->group || alt->new_len) {

		new_rela = find_rela_by_dest(sec, offset + entry->new);

		new_rela = find_rela_by_dest(elf, sec, offset + entry->new);

		if (!new_rela) {

			WARN_FUNC("can't find new rela",

				  sec, offset + entry->new);

CRA Git | Maintained and supported by SUSTech CRA and CCSE