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>

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)

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);

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);
 };