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objtool: Optimize find_symbol_*() and read_symbols()

Browse Source 
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: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20200324160924.499016559@infradead.org
This commit is contained in:
Peter Zijlstra 2020-03-12 09:34:42 +01:00
parent ae358196fa
commit 2a362ecc3e
3 changed files with 144 additions and 58 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
tools/objtool/Build
View File

@ -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)

194
tools/objtool/elf.c
View File

@ -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;
@ -63,22 +147,56 @@ 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_containing(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_SECTION)
return s;
}
return NULL;
}
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;
}
@ -96,18 +214,6 @@ struct symbol *find_symbol_by_name(struct elf *elf, const char *name)
return NULL;
}
struct symbol *find_symbol_containing(struct section *sec, unsigned long offset)
{
struct symbol *sym;
list_for_each_entry(sym, &sec->symbol_list, list)
if (sym->type != STT_SECTION &&
offset >= sym->offset && offset < sym->offset + sym->len)
return sym;
return NULL;
}
struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,
unsigned int len)
{
@ -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 */
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;
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_add(&sym->list, entry);
hash_add(elf->symbol_hash, &sym->hash, sym->idx);
}

3
tools/objtool/elf.h
View File

@ -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;