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: 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

diff --git a/tools/objtool/Build b/tools/objtool/Build
index 8dc4f08..66f44f5 100644 (file)
--- a/tools/objtool/Build
+++ b/tools/objtool/Build
@@ -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)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 20fe40d..3a8b426 100644 (file)
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -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;
@@ -63,47 +147,69 @@ 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(sym, &sec->symbol_list, list)
-               if (sym->type != STT_SECTION &&
-                   offset >= sym->offset && offset < sym->offset + sym->len)
-                       return sym;
+       list_for_each_entry(sec, &elf->sections, list)
+               list_for_each_entry(sym, &sec->symbol_list, list)
+                       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 */
-               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);
        }

diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h
index ac7c46f..e4a8d68 100644 (file)
--- a/tools/objtool/elf.h
+++ b/tools/objtool/elf.h
@@ -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;