objtool: Add several performance improvements

Use hash tables for instruction and rela lookups (and keep the linked
lists around for sequential access).

Also cache the section struct for the "__func_stack_frame_non_standard"
section.

With this change, "objtool check net/wireless/nl80211.o" goes from:

  real	0m1.168s
  user	0m1.163s
  sys	0m0.005s

to:

  real	0m0.059s
  user	0m0.042s
  sys	0m0.017s

for a 20x speedup.

With the same object, it should be noted that the memory heap usage grew
from 8MB to 62MB.  Reducing the memory usage is on the TODO list.

Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Bernd Petrovitsch <bernd@petrovitsch.priv.at>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris J Arges <chris.j.arges@canonical.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Pedro Alves <palves@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Link: http://lkml.kernel.org/r/dd0d8e1449506cfa7701b4e7ba73577077c44253.1457502970.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

3 files changed, 35 insertions, 14 deletions

diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index cf1e48dbfa97..bfeee227aaab 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -34,6 +34,8 @@
 #include "arch.h"
 #include "warn.h"
 
+#include <linux/hashtable.h>
+
 #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
 
 #define STATE_FP_SAVED          0x1
@@ -42,6 +44,7 @@
 
 struct instruction {
         struct list_head list;
+        struct hlist_node hash;
         struct section *sec;
         unsigned long offset;
         unsigned int len, state;
@@ -61,7 +64,8 @@ struct alternative {
 struct objtool_file {
         struct elf *elf;
         struct list_head insn_list;
-        struct section *rodata;
+        DECLARE_HASHTABLE(insn_hash, 16);
+        struct section *rodata, *whitelist;
 };
 
 const char *objname;
@@ -72,7 +76,7 @@ static struct instruction *find_insn(struct objtool_file *file,
 {
         struct instruction *insn;
 
-        list_for_each_entry(insn, &file->insn_list, list)
+        hash_for_each_possible(file->insn_hash, insn, hash, offset)
                 if (insn->sec == sec && insn->offset == offset)
                         return insn;
 
@@ -111,14 +115,12 @@ static struct instruction *next_insn_same_sec(struct objtool_file *file,
  */
 static bool ignore_func(struct objtool_file *file, struct symbol *func)
 {
-        struct section *macro_sec;
         struct rela *rela;
         struct instruction *insn;
 
         /* check for STACK_FRAME_NON_STANDARD */
-        macro_sec = find_section_by_name(file->elf, "__func_stack_frame_non_standard");
-        if (macro_sec && macro_sec->rela)
-                list_for_each_entry(rela, &macro_sec->rela->rela_list, list)
+        if (file->whitelist && file->whitelist->rela)
+                list_for_each_entry(rela, &file->whitelist->rela->rela_list, list)
                         if (rela->sym->sec == func->sec &&
                             rela->addend == func->offset)
                                 return true;
@@ -276,6 +278,7 @@ static int decode_instructions(struct objtool_file *file)
                                 return -1;
                         }
 
+                        hash_add(file->insn_hash, &insn->hash, insn->offset);
                         list_add_tail(&insn->list, &file->insn_list);
                 }
         }
@@ -729,6 +732,7 @@ static int decode_sections(struct objtool_file *file)
 {
         int ret;
 
+        file->whitelist = find_section_by_name(file->elf, "__func_stack_frame_non_standard");
         file->rodata = find_section_by_name(file->elf, ".rodata");
 
         ret = decode_instructions(file);
@@ -1091,6 +1095,7 @@ static void cleanup(struct objtool_file *file)
                         free(alt);
                 }
                 list_del(&insn->list);
+                hash_del(&insn->hash);
                 free(insn);
         }
         elf_close(file->elf);
@@ -1125,6 +1130,7 @@ int cmd_check(int argc, const char **argv)
         }
 
         INIT_LIST_HEAD(&file.insn_list);
+        hash_init(file.insn_hash);
 
         ret = decode_sections(&file);
         if (ret < 0)
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 7de243f0a7be..e11f6b69cce6 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -59,7 +59,7 @@ static struct symbol *find_symbol_by_index(struct elf *elf, unsigned int idx)
         struct symbol *sym;
 
         list_for_each_entry(sec, &elf->sections, list)
-                list_for_each_entry(sym, &sec->symbol_list, list)
+                hash_for_each_possible(sec->symbol_hash, sym, hash, idx)
                         if (sym->idx == idx)
                                 return sym;
 
@@ -82,13 +82,15 @@ struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,
                                      unsigned int len)
 {
         struct rela *rela;
+        unsigned long o;
 
         if (!sec->rela)
                 return NULL;
 
-        list_for_each_entry(rela, &sec->rela->rela_list, list)
-                if (rela->offset >= offset && rela->offset < offset + len)
-                        return rela;
+        for (o = offset; o < offset + len; o++)
+                hash_for_each_possible(sec->rela->rela_hash, rela, hash, o)
+                        if (rela->offset == o)
+                                return rela;
 
         return NULL;
 }
@@ -137,6 +139,8 @@ 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);
 
@@ -261,6 +265,7 @@ static int read_symbols(struct elf *elf)
                         }
                 }
                 list_add(&sym->list, entry);
+                hash_add(sym->sec->symbol_hash, &sym->hash, sym->idx);
         }
 
         return 0;
@@ -298,8 +303,6 @@ static int read_relas(struct elf *elf)
                         }
                         memset(rela, 0, sizeof(*rela));
 
-                        list_add_tail(&rela->list, &sec->rela_list);
-
                         if (!gelf_getrela(sec->elf_data, i, &rela->rela)) {
                                 perror("gelf_getrela");
                                 return -1;
@@ -315,6 +318,10 @@ static int read_relas(struct elf *elf)
                                      symndx, sec->name);
                                 return -1;
                         }
+
+                        list_add_tail(&rela->list, &sec->rela_list);
+                        hash_add(sec->rela_hash, &rela->hash, rela->offset);
+
                 }
         }
 
@@ -384,10 +391,12 @@ void elf_close(struct elf *elf)
         list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {
                 list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {
                         list_del(&sym->list);
+                        hash_del(&sym->hash);
                         free(sym);
                 }
                 list_for_each_entry_safe(rela, tmprela, &sec->rela_list, list) {
                         list_del(&rela->list);
+                        hash_del(&rela->hash);
                         free(rela);
                 }
                 list_del(&sec->list);
diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h
index 57e4653f8383..7f3e00a2f907 100644
--- a/tools/objtool/elf.h
+++ b/tools/objtool/elf.h
@@ -21,12 +21,15 @@
 #include <stdio.h>
 #include <gelf.h>
 #include <linux/list.h>
+#include <linux/hashtable.h>
 
 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;
         struct symbol *sym;
         Elf_Data *elf_data;
@@ -38,10 +41,11 @@ struct section {
 
 struct symbol {
         struct list_head list;
+        struct hlist_node hash;
         GElf_Sym sym;
         struct section *sec;
         char *name;
-        int idx;
+        unsigned int idx;
         unsigned char bind, type;
         unsigned long offset;
         unsigned int len;
@@ -49,10 +53,11 @@ struct symbol {
 
 struct rela {
         struct list_head list;
+        struct hlist_node hash;
         GElf_Rela rela;
         struct symbol *sym;
         unsigned int type;
-        int offset;
+        unsigned long offset;
         int addend;
 };
 
@@ -62,6 +67,7 @@ struct elf {
         int fd;
         char *name;
         struct list_head sections;
+        DECLARE_HASHTABLE(rela_hash, 16);
 };