objtool: Optimize read_sections()

Perf showed that __hash_init() is a significant portion of
read_sections(), so instead of doing a per section rela_hash, use an
elf-wide rela_hash.

Statistics show us there are about 1.1 million relas, so size it
accordingly.

This reduces the objtool on vmlinux.o runtime to a third, from 15 to 5
seconds.

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/20200324160924.739153726@infradead.org

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 6df1bae..54a6043 100644 (file)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -569,8 +569,8 @@ static int add_jump_destinations(struct objtool_file *file)
                if (insn->ignore || insn->offset == FAKE_JUMP_OFFSET)
                        continue;
 
-               rela = find_rela_by_dest_range(insn->sec, insn->offset,
-                                              insn->len);
+               rela = find_rela_by_dest_range(file->elf, insn->sec,
+                                              insn->offset, insn->len);
                if (!rela) {
                        dest_sec = insn->sec;
                        dest_off = insn->offset + insn->len + insn->immediate;
@@ -666,8 +666,8 @@ static int add_call_destinations(struct objtool_file *file)
                if (insn->type != INSN_CALL)
                        continue;
 
-               rela = find_rela_by_dest_range(insn->sec, insn->offset,
-                                              insn->len);
+               rela = find_rela_by_dest_range(file->elf, insn->sec,
+                                              insn->offset, insn->len);
                if (!rela) {
                        dest_off = insn->offset + insn->len + insn->immediate;
                        insn->call_dest = find_func_by_offset(insn->sec, dest_off);
@@ -796,7 +796,7 @@ static int handle_group_alt(struct objtool_file *file,
                 */
                if ((insn->offset != special_alt->new_off ||
                    (insn->type != INSN_CALL && !is_static_jump(insn))) &&
-                   find_rela_by_dest_range(insn->sec, insn->offset, insn->len)) {
+                   find_rela_by_dest_range(file->elf, insn->sec, insn->offset, insn->len)) {
 
                        WARN_FUNC("unsupported relocation in alternatives section",
                                  insn->sec, insn->offset);
@@ -1066,8 +1066,8 @@ static struct rela *find_jump_table(struct objtool_file *file,
                    break;
 
                /* look for a relocation which references .rodata */
-               text_rela = find_rela_by_dest_range(insn->sec, insn->offset,
-                                                   insn->len);
+               text_rela = find_rela_by_dest_range(file->elf, insn->sec,
+                                                   insn->offset, insn->len);
                if (!text_rela || text_rela->sym->type != STT_SECTION ||
                    !text_rela->sym->sec->rodata)
                        continue;
@@ -1096,7 +1096,7 @@ static struct rela *find_jump_table(struct objtool_file *file,
                 * should reference text in the same function as the original
                 * instruction.
                 */
-               table_rela = find_rela_by_dest(table_sec, table_offset);
+               table_rela = find_rela_by_dest(file->elf, table_sec, table_offset);
                if (!table_rela)
                        continue;
                dest_insn = find_insn(file, table_rela->sym->sec, table_rela->addend);
@@ -1232,7 +1232,7 @@ static int read_unwind_hints(struct objtool_file *file)
        for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
                hint = (struct unwind_hint *)sec->data->d_buf + i;
 
-               rela = find_rela_by_dest(sec, i * sizeof(*hint));
+               rela = find_rela_by_dest(file->elf, sec, i * sizeof(*hint));
                if (!rela) {
                        WARN("can't find rela for unwind_hints[%d]", i);
                        return -1;

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 43abae7..8a0a1bc 100644 (file)
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -212,8 +212,8 @@ struct symbol *find_symbol_by_name(struct elf *elf, const char *name)
        return NULL;
 }
 
-struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,
-                                    unsigned int len)
+struct rela *find_rela_by_dest_range(struct elf *elf, struct section *sec,
+                                    unsigned long offset, unsigned int len)
 {
        struct rela *rela;
        unsigned long o;
@@ -221,17 +221,22 @@ struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,
        if (!sec->rela)
                return NULL;
 
-       for (o = offset; o < offset + len; o++)
-               hash_for_each_possible(sec->rela->rela_hash, rela, hash, o)
-                       if (rela->offset == o)
+       sec = sec->rela;
+
+       for (o = offset; o < offset + len; o++) {
+               hash_for_each_possible(elf->rela_hash, rela, hash,
+                                      sec_offset_hash(sec, o)) {
+                       if (rela->sec == sec && rela->offset == o)
                                return rela;
+               }
+       }
 
        return NULL;
 }
 
-struct rela *find_rela_by_dest(struct section *sec, unsigned long offset)
+struct rela *find_rela_by_dest(struct elf *elf, struct section *sec, unsigned long offset)
 {
-       return find_rela_by_dest_range(sec, offset, 1);
+       return find_rela_by_dest_range(elf, sec, offset, 1);
 }
 
 static int read_sections(struct elf *elf)
@@ -261,7 +266,6 @@ static int read_sections(struct elf *elf)
 
                INIT_LIST_HEAD(&sec->symbol_list);
                INIT_LIST_HEAD(&sec->rela_list);
-               hash_init(sec->rela_hash);
 
                s = elf_getscn(elf->elf, i);
                if (!s) {
@@ -493,7 +497,7 @@ static int read_relas(struct elf *elf)
                        }
 
                        list_add_tail(&rela->list, &sec->rela_list);
-                       hash_add(sec->rela_hash, &rela->hash, rela->offset);
+                       hash_add(elf->rela_hash, &rela->hash, rela_hash(rela));
                        nr_rela++;
                }
                max_rela = max(max_rela, nr_rela);
@@ -526,6 +530,7 @@ struct elf *elf_read(const char *name, int flags)
        hash_init(elf->symbol_name_hash);
        hash_init(elf->section_hash);
        hash_init(elf->section_name_hash);
+       hash_init(elf->rela_hash);
        INIT_LIST_HEAD(&elf->sections);
 
        elf->fd = open(name, flags);
@@ -586,7 +591,6 @@ 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);
 
        s = elf_newscn(elf->elf);
        if (!s) {

diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h
index 3088d92..dfd2431 100644 (file)
--- a/tools/objtool/elf.h
+++ b/tools/objtool/elf.h
@@ -33,7 +33,6 @@ struct section {
        struct rb_root symbol_tree;
        struct list_head symbol_list;
        struct list_head rela_list;
-       DECLARE_HASHTABLE(rela_hash, 16);
        struct section *base, *rela;
        struct symbol *sym;
        Elf_Data *data;
@@ -81,8 +80,22 @@ struct elf {
        DECLARE_HASHTABLE(symbol_name_hash, 20);
        DECLARE_HASHTABLE(section_hash, 16);
        DECLARE_HASHTABLE(section_name_hash, 16);
+       DECLARE_HASHTABLE(rela_hash, 20);
 };
 
+static inline u32 sec_offset_hash(struct section *sec, unsigned long offset)
+{
+       u32 ol = offset, oh = offset >> 32, idx = sec->idx;
+
+       __jhash_mix(ol, oh, idx);
+
+       return ol;
+}
+
+static inline u32 rela_hash(struct rela *rela)
+{
+       return sec_offset_hash(rela->sec, rela->offset);
+}
 
 struct elf *elf_read(const char *name, int flags);
 struct section *find_section_by_name(struct elf *elf, const char *name);
@@ -90,9 +103,9 @@ struct symbol *find_func_by_offset(struct section *sec, unsigned long offset);
 struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset);
 struct symbol *find_symbol_by_name(struct elf *elf, const char *name);
 struct symbol *find_symbol_containing(struct section *sec, unsigned long offset);
-struct rela *find_rela_by_dest(struct section *sec, unsigned long offset);
-struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,
-                                    unsigned int len);
+struct rela *find_rela_by_dest(struct elf *elf, struct section *sec, unsigned long offset);
+struct rela *find_rela_by_dest_range(struct elf *elf, struct section *sec,
+                                    unsigned long offset, unsigned int len);
 struct symbol *find_func_containing(struct section *sec, unsigned long offset);
 struct section *elf_create_section(struct elf *elf, const char *name, size_t
                                   entsize, int nr);

diff --git a/tools/objtool/orc_gen.c b/tools/objtool/orc_gen.c
index 27a4112..41e4a27 100644 (file)
--- a/tools/objtool/orc_gen.c
+++ b/tools/objtool/orc_gen.c
@@ -81,7 +81,7 @@ int create_orc(struct objtool_file *file)
        return 0;
 }
 
-static int create_orc_entry(struct section *u_sec, struct section *ip_relasec,
+static int create_orc_entry(struct elf *elf, struct section *u_sec, struct section *ip_relasec,
                                unsigned int idx, struct section *insn_sec,
                                unsigned long insn_off, struct orc_entry *o)
 {
@@ -109,9 +109,10 @@ static int create_orc_entry(struct section *u_sec, struct section *ip_relasec,
        rela->addend = insn_off;
        rela->type = R_X86_64_PC32;
        rela->offset = idx * sizeof(int);
+       rela->sec = ip_relasec;
 
        list_add_tail(&rela->list, &ip_relasec->rela_list);
-       hash_add(ip_relasec->rela_hash, &rela->hash, rela->offset);
+       hash_add(elf->rela_hash, &rela->hash, rela_hash(rela));
 
        return 0;
 }
@@ -182,7 +183,7 @@ int create_orc_sections(struct objtool_file *file)
                        if (!prev_insn || memcmp(&insn->orc, &prev_insn->orc,
                                                 sizeof(struct orc_entry))) {
 
-                               if (create_orc_entry(u_sec, ip_relasec, idx,
+                               if (create_orc_entry(file->elf, u_sec, ip_relasec, idx,
                                                     insn->sec, insn->offset,
                                                     &insn->orc))
                                        return -1;
@@ -194,7 +195,7 @@ int create_orc_sections(struct objtool_file *file)
 
                /* section terminator */
                if (prev_insn) {
-                       if (create_orc_entry(u_sec, ip_relasec, idx,
+                       if (create_orc_entry(file->elf, u_sec, ip_relasec, idx,
                                             prev_insn->sec,
                                             prev_insn->offset + prev_insn->len,
                                             &empty))

diff --git a/tools/objtool/special.c b/tools/objtool/special.c
index fdbaa61..e74e018 100644 (file)
--- a/tools/objtool/special.c
+++ b/tools/objtool/special.c
@@ -118,7 +118,7 @@ static int get_alt_entry(struct elf *elf, struct special_entry *entry,
                }
        }
 
-       orig_rela = find_rela_by_dest(sec, offset + entry->orig);
+       orig_rela = find_rela_by_dest(elf, sec, offset + entry->orig);
        if (!orig_rela) {
                WARN_FUNC("can't find orig rela", sec, offset + entry->orig);
                return -1;
@@ -133,7 +133,7 @@ static int get_alt_entry(struct elf *elf, struct special_entry *entry,
        alt->orig_off = orig_rela->addend;
 
        if (!entry->group || alt->new_len) {
-               new_rela = find_rela_by_dest(sec, offset + entry->new);
+               new_rela = find_rela_by_dest(elf, sec, offset + entry->new);
                if (!new_rela) {
                        WARN_FUNC("can't find new rela",
                                  sec, offset + entry->new);