objtool: Optimize find_symbol_by_index()

The symbol index is object wide, not per section, so it makes no sense
to have the symbol_hash be part of the section object. By moving it to
the elf object we avoid the linear sections iteration.

This reduces the runtime of objtool on vmlinux.o from over 3 hours (I
gave up) to a few minutes. The defconfig vmlinux.o has around 20k
sections.

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/20200324160924.261852348@infradead.org

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index cc4601c..b188b3e 100644 (file)
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -46,13 +46,11 @@ static struct section *find_section_by_index(struct elf *elf,
 
 static struct symbol *find_symbol_by_index(struct elf *elf, unsigned int idx)
 {
-       struct section *sec;
        struct symbol *sym;
 
-       list_for_each_entry(sec, &elf->sections, list)
-               hash_for_each_possible(sec->symbol_hash, sym, hash, idx)
-                       if (sym->idx == idx)
-                               return sym;
+       hash_for_each_possible(elf->symbol_hash, sym, hash, idx)
+               if (sym->idx == idx)
+                       return sym;
 
        return NULL;
 }
@@ -166,7 +164,6 @@ static int read_sections(struct elf *elf)
                INIT_LIST_HEAD(&sec->symbol_list);
                INIT_LIST_HEAD(&sec->rela_list);
                hash_init(sec->rela_hash);
-               hash_init(sec->symbol_hash);
 
                list_add_tail(&sec->list, &elf->sections);
 
@@ -299,7 +296,7 @@ static int read_symbols(struct elf *elf)
                }
                sym->alias = alias;
                list_add(&sym->list, entry);
-               hash_add(sym->sec->symbol_hash, &sym->hash, sym->idx);
+               hash_add(elf->symbol_hash, &sym->hash, sym->idx);
        }
 
        /* Create parent/child links for any cold subfunctions */
@@ -425,6 +422,7 @@ struct elf *elf_read(const char *name, int flags)
        }
        memset(elf, 0, sizeof(*elf));
 
+       hash_init(elf->symbol_hash);
        INIT_LIST_HEAD(&elf->sections);
 
        elf->fd = open(name, flags);
@@ -486,7 +484,6 @@ 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);
-       hash_init(sec->symbol_hash);
 
        list_add_tail(&sec->list, &elf->sections);
 

diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h
index a196325..1222980 100644 (file)
--- a/tools/objtool/elf.h
+++ b/tools/objtool/elf.h
@@ -27,7 +27,6 @@ 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;
@@ -71,7 +70,7 @@ struct elf {
        int fd;
        char *name;
        struct list_head sections;
-       DECLARE_HASHTABLE(rela_hash, 16);
+       DECLARE_HASHTABLE(symbol_hash, 20);
 };