Commit 2a362ecc authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

objtool: Optimize find_symbol_*() and read_symbols() 



All of:

  read_symbols(), find_symbol_by_offset(), find_symbol_containing(),
  find_containing_func()

do a linear search of the symbols. Add an RB tree to make it go
faster.

This about halves objtool runtime on vmlinux.o, from 34s to 18s.

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/20200324160924.499016559@infradead.org
parent ae358196

tools/objtool/Build

+5 −0
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ objtool-y += objtool.o 
objtool-y += libstring.o

objtool-y += libctype.o

objtool-y += str_error_r.o

objtool-y += librbtree.o



CFLAGS += -I$(srctree)/tools/lib
@@ -25,3 +26,7 @@ $(OUTPUT)libctype.o: ../lib/ctype.c FORCE 
$(OUTPUT)str_error_r.o: ../lib/str_error_r.c FORCE

	$(call rule_mkdir)

	$(call if_changed_dep,cc_o_c)



$(OUTPUT)librbtree.o: ../lib/rbtree.c FORCE

	$(call rule_mkdir)

	$(call if_changed_dep,cc_o_c)

tools/objtool/elf.c

+136 −58
Original line number Diff line number Diff line
@@ -27,6 +27,90 @@ static inline u32 str_hash(const char *str) 
	return jhash(str, strlen(str), 0);

}



static void rb_add(struct rb_root *tree, struct rb_node *node,

		   int (*cmp)(struct rb_node *, const struct rb_node *))

{

	struct rb_node **link = &tree->rb_node;

	struct rb_node *parent = NULL;



	while (*link) {

		parent = *link;

		if (cmp(node, parent) < 0)

			link = &parent->rb_left;

		else

			link = &parent->rb_right;

	}



	rb_link_node(node, parent, link);

	rb_insert_color(node, tree);

}



static struct rb_node *rb_find_first(struct rb_root *tree, const void *key,

			       int (*cmp)(const void *key, const struct rb_node *))

{

	struct rb_node *node = tree->rb_node;

	struct rb_node *match = NULL;



	while (node) {

		int c = cmp(key, node);

		if (c <= 0) {

			if (!c)

				match = node;

			node = node->rb_left;

		} else if (c > 0) {

			node = node->rb_right;

		}

	}



	return match;

}



static struct rb_node *rb_next_match(struct rb_node *node, const void *key,

				    int (*cmp)(const void *key, const struct rb_node *))

{

	node = rb_next(node);

	if (node && cmp(key, node))

		node = NULL;

	return node;

}



#define rb_for_each(tree, node, key, cmp) \

	for ((node) = rb_find_first((tree), (key), (cmp)); \

	     (node); (node) = rb_next_match((node), (key), (cmp)))



static int symbol_to_offset(struct rb_node *a, const struct rb_node *b)

{

	struct symbol *sa = rb_entry(a, struct symbol, node);

	struct symbol *sb = rb_entry(b, struct symbol, node);



	if (sa->offset < sb->offset)

		return -1;

	if (sa->offset > sb->offset)

		return 1;



	if (sa->len < sb->len)

		return -1;

	if (sa->len > sb->len)

		return 1;



	sa->alias = sb;



	return 0;

}



static int symbol_by_offset(const void *key, const struct rb_node *node)

{

	const struct symbol *s = rb_entry(node, struct symbol, node);

	const unsigned long *o = key;



	if (*o < s->offset)

		return -1;

	if (*o > s->offset + s->len)

		return 1;



	return 0;

}



struct section *find_section_by_name(struct elf *elf, const char *name)

{

	struct section *sec;
@@ -63,46 +147,68 @@ static struct symbol *find_symbol_by_index(struct elf *elf, unsigned int idx) 


struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset)

{

	struct symbol *sym;

	struct rb_node *node;



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

		if (sym->type != STT_SECTION && sym->offset == offset)

			return sym;

	rb_for_each(&sec->symbol_tree, node, &offset, symbol_by_offset) {

		struct symbol *s = rb_entry(node, struct symbol, node);



		if (s->offset == offset && s->type != STT_SECTION)

			return s;

	}



	return NULL;

}



struct symbol *find_func_by_offset(struct section *sec, unsigned long offset)

{

	struct symbol *sym;

	struct rb_node *node;



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

		if (sym->type == STT_FUNC && sym->offset == offset)

			return sym;

	rb_for_each(&sec->symbol_tree, node, &offset, symbol_by_offset) {

		struct symbol *s = rb_entry(node, struct symbol, node);



		if (s->offset == offset && s->type == STT_FUNC)

			return s;

	}



	return NULL;

}



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

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

{

	struct section *sec;

	struct symbol *sym;

	struct rb_node *node;



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

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

			if (!strcmp(sym->name, name))

				return sym;

	rb_for_each(&sec->symbol_tree, node, &offset, symbol_by_offset) {

		struct symbol *s = rb_entry(node, struct symbol, node);



		if (s->type != STT_SECTION)

			return s;

	}



	return NULL;

}



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

struct symbol *find_containing_func(struct section *sec, unsigned long offset)

{

	struct rb_node *node;



	rb_for_each(&sec->symbol_tree, node, &offset, symbol_by_offset) {

		struct symbol *s = rb_entry(node, struct symbol, node);



		if (s->type == STT_FUNC)

			return s;

	}



	return NULL;

}



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

{

	struct section *sec;

	struct symbol *sym;



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

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

		if (sym->type != STT_SECTION &&

		    offset >= sym->offset && offset < sym->offset + sym->len)

			if (!strcmp(sym->name, name))

				return sym;



	return NULL;
@@ -130,18 +236,6 @@ struct rela *find_rela_by_dest(struct section *sec, unsigned long offset) 
	return find_rela_by_dest_range(sec, offset, 1);

}



struct symbol *find_containing_func(struct section *sec, unsigned long offset)

{

	struct symbol *func;



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

		if (func->type == STT_FUNC && offset >= func->offset &&

		    offset < func->offset + func->len)

			return func;



	return NULL;

}



static int read_sections(struct elf *elf)

{

	Elf_Scn *s = NULL;
@@ -225,8 +319,9 @@ static int read_sections(struct elf *elf) 
static int read_symbols(struct elf *elf)

{

	struct section *symtab, *sec;

	struct symbol *sym, *pfunc, *alias;

	struct list_head *entry, *tmp;

	struct symbol *sym, *pfunc;

	struct list_head *entry;

	struct rb_node *pnode;

	int symbols_nr, i;

	char *coldstr;
@@ -245,7 +340,7 @@ static int read_symbols(struct elf *elf) 
			return -1;

		}

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

		alias = sym;

		sym->alias = sym;



		sym->idx = i;
@@ -283,29 +378,12 @@ static int read_symbols(struct elf *elf) 
		sym->offset = sym->sym.st_value;

		sym->len = sym->sym.st_size;



		/* sorted insert into a per-section list */

		rb_add(&sym->sec->symbol_tree, &sym->node, symbol_to_offset);

		pnode = rb_prev(&sym->node);

		if (pnode)

			entry = &rb_entry(pnode, struct symbol, node)->list;

		else

			entry = &sym->sec->symbol_list;

		list_for_each_prev(tmp, &sym->sec->symbol_list) {

			struct symbol *s;



			s = list_entry(tmp, struct symbol, list);



			if (sym->offset > s->offset) {

				entry = tmp;

				break;

			}



			if (sym->offset == s->offset) {

				if (sym->len && sym->len == s->len && alias == sym)

					alias = s;



				if (sym->len >= s->len) {

					entry = tmp;

					break;

				}

			}

		}

		sym->alias = alias;

		list_add(&sym->list, entry);

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

	}

tools/objtool/elf.h

+3 −0
Original line number Diff line number Diff line
@@ -10,6 +10,7 @@ 
#include <gelf.h>

#include <linux/list.h>

#include <linux/hashtable.h>

#include <linux/rbtree.h>

#include <linux/jhash.h>



#ifdef LIBELF_USE_DEPRECATED
@@ -29,6 +30,7 @@ struct section { 
	struct hlist_node hash;

	struct hlist_node name_hash;

	GElf_Shdr sh;

	struct rb_root symbol_tree;

	struct list_head symbol_list;

	struct list_head rela_list;

	DECLARE_HASHTABLE(rela_hash, 16);
@@ -43,6 +45,7 @@ struct section { 


struct symbol {

	struct list_head list;

	struct rb_node node;

	struct hlist_node hash;

	GElf_Sym sym;

	struct section *sec;

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