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/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);