Commit 042ba73f authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Ingo Molnar
Browse files

objtool: Add several performance improvements 



Use hash tables for instruction and rela lookups (and keep the linked
lists around for sequential access).

Also cache the section struct for the "__func_stack_frame_non_standard"
section.

With this change, "objtool check net/wireless/nl80211.o" goes from:

  real	0m1.168s
  user	0m1.163s
  sys	0m0.005s

to:

  real	0m0.059s
  user	0m0.042s
  sys	0m0.017s

for a 20x speedup.

With the same object, it should be noted that the memory heap usage grew
from 8MB to 62MB.  Reducing the memory usage is on the TODO list.

Reported-by: default avatarIngo Molnar <mingo@kernel.org>
Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Bernd Petrovitsch <bernd@petrovitsch.priv.at>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris J Arges <chris.j.arges@canonical.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Pedro Alves <palves@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Link: http://lkml.kernel.org/r/dd0d8e1449506cfa7701b4e7ba73577077c44253.1457502970.git.jpoimboe@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 1698872b

tools/objtool/builtin-check.c

+12 −6
Original line number Diff line number Diff line
@@ -34,6 +34,8 @@ 
#include "arch.h"

#include "warn.h"



#include <linux/hashtable.h>



#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))



#define STATE_FP_SAVED		0x1
@@ -42,6 +44,7 @@ 


struct instruction {

	struct list_head list;

	struct hlist_node hash;

	struct section *sec;

	unsigned long offset;

	unsigned int len, state;
@@ -61,7 +64,8 @@ struct alternative { 
struct objtool_file {

	struct elf *elf;

	struct list_head insn_list;

	struct section *rodata;

	DECLARE_HASHTABLE(insn_hash, 16);

	struct section *rodata, *whitelist;

};



const char *objname;
@@ -72,7 +76,7 @@ static struct instruction *find_insn(struct objtool_file *file, 
{

	struct instruction *insn;



	list_for_each_entry(insn, &file->insn_list, list)

	hash_for_each_possible(file->insn_hash, insn, hash, offset)

		if (insn->sec == sec && insn->offset == offset)

			return insn;
@@ -111,14 +115,12 @@ static struct instruction *next_insn_same_sec(struct objtool_file *file, 
 */

static bool ignore_func(struct objtool_file *file, struct symbol *func)

{

	struct section *macro_sec;

	struct rela *rela;

	struct instruction *insn;



	/* check for STACK_FRAME_NON_STANDARD */

	macro_sec = find_section_by_name(file->elf, "__func_stack_frame_non_standard");

	if (macro_sec && macro_sec->rela)

		list_for_each_entry(rela, &macro_sec->rela->rela_list, list)

	if (file->whitelist && file->whitelist->rela)

		list_for_each_entry(rela, &file->whitelist->rela->rela_list, list)

			if (rela->sym->sec == func->sec &&

			    rela->addend == func->offset)

				return true;
@@ -276,6 +278,7 @@ static int decode_instructions(struct objtool_file *file) 
				return -1;

			}



			hash_add(file->insn_hash, &insn->hash, insn->offset);

			list_add_tail(&insn->list, &file->insn_list);

		}

	}
@@ -729,6 +732,7 @@ static int decode_sections(struct objtool_file *file) 
{

	int ret;



	file->whitelist = find_section_by_name(file->elf, "__func_stack_frame_non_standard");

	file->rodata = find_section_by_name(file->elf, ".rodata");



	ret = decode_instructions(file);
@@ -1091,6 +1095,7 @@ static void cleanup(struct objtool_file *file) 
			free(alt);

		}

		list_del(&insn->list);

		hash_del(&insn->hash);

		free(insn);

	}

	elf_close(file->elf);
@@ -1125,6 +1130,7 @@ int cmd_check(int argc, const char **argv) 
	}



	INIT_LIST_HEAD(&file.insn_list);

	hash_init(file.insn_hash);



	ret = decode_sections(&file);

	if (ret < 0)

tools/objtool/elf.c

+15 −6
Original line number Diff line number Diff line
@@ -59,7 +59,7 @@ static struct symbol *find_symbol_by_index(struct elf *elf, unsigned int idx) 
	struct symbol *sym;



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

		list_for_each_entry(sym, &sec->symbol_list, list)

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

			if (sym->idx == idx)

				return sym;
@@ -82,12 +82,14 @@ struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset, 
				     unsigned int len)

{

	struct rela *rela;

	unsigned long o;



	if (!sec->rela)

		return NULL;



	list_for_each_entry(rela, &sec->rela->rela_list, list)

		if (rela->offset >= offset && rela->offset < offset + len)

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

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

			if (rela->offset == o)

				return rela;



	return NULL;
@@ -137,6 +139,8 @@ static int read_sections(struct elf *elf) 


		INIT_LIST_HEAD(&sec->symbol_list);

		INIT_LIST_HEAD(&sec->rela_list);

		hash_init(sec->rela_hash);

		hash_init(sec->symbol_hash);



		list_add_tail(&sec->list, &elf->sections);
@@ -261,6 +265,7 @@ static int read_symbols(struct elf *elf) 
			}

		}

		list_add(&sym->list, entry);

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

	}



	return 0;
@@ -298,8 +303,6 @@ static int read_relas(struct elf *elf) 
			}

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



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



			if (!gelf_getrela(sec->elf_data, i, &rela->rela)) {

				perror("gelf_getrela");

				return -1;
@@ -315,6 +318,10 @@ static int read_relas(struct elf *elf) 
				     symndx, sec->name);

				return -1;

			}



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

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



		}

	}
@@ -384,10 +391,12 @@ void elf_close(struct elf *elf) 
	list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {

		list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {

			list_del(&sym->list);

			hash_del(&sym->hash);

			free(sym);

		}

		list_for_each_entry_safe(rela, tmprela, &sec->rela_list, list) {

			list_del(&rela->list);

			hash_del(&rela->hash);

			free(rela);

		}

		list_del(&sec->list);

tools/objtool/elf.h

+8 −2
Original line number Diff line number Diff line
@@ -21,12 +21,15 @@ 
#include <stdio.h>

#include <gelf.h>

#include <linux/list.h>

#include <linux/hashtable.h>



struct section {

	struct list_head list;

	GElf_Shdr sh;

	struct list_head symbol_list;

	DECLARE_HASHTABLE(symbol_hash, 8);

	struct list_head rela_list;

	DECLARE_HASHTABLE(rela_hash, 16);

	struct section *base, *rela;

	struct symbol *sym;

	Elf_Data *elf_data;
@@ -38,10 +41,11 @@ struct section { 


struct symbol {

	struct list_head list;

	struct hlist_node hash;

	GElf_Sym sym;

	struct section *sec;

	char *name;

	int idx;

	unsigned int idx;

	unsigned char bind, type;

	unsigned long offset;

	unsigned int len;
@@ -49,10 +53,11 @@ struct symbol { 


struct rela {

	struct list_head list;

	struct hlist_node hash;

	GElf_Rela rela;

	struct symbol *sym;

	unsigned int type;

	int offset;

	unsigned long offset;

	int addend;

};
@@ -62,6 +67,7 @@ struct elf { 
	int fd;

	char *name;

	struct list_head sections;

	DECLARE_HASHTABLE(rela_hash, 16);

};

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