- An error in the multithreaded case could print the wrong function name

- Start with a full page of struct region_info's
- Save an mprotect in the init code: allocate 3 pages with none and
make the middle page r/w instead of a r/w allocation and two calls to make the
guard pages none

src/lib/libc/stdlib/malloc.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: malloc.c,v 1.242 2018/01/26 19:14:51 otto Exp $	*/
+/*	$OpenBSD: malloc.c,v 1.243 2018/01/28 13:41:48 otto Exp $	*/
 /*
  * Copyright (c) 2008, 2010, 2011, 2016 Otto Moerbeek <otto@drijf.net>
  * Copyright (c) 2012 Matthew Dempsky <matthew@openbsd.org>
@@ -62,7 +62,7 @@
 #define MALLOC_MAXCHUNK		(1 << MALLOC_MAXSHIFT)
 #define MALLOC_MAXCACHE		256
 #define MALLOC_DELAYED_CHUNK_MASK	15
-#define MALLOC_INITIAL_REGIONS	512
+#define MALLOC_INITIAL_REGIONS	(MALLOC_PAGESIZE / sizeof(struct region_info))
 #define MALLOC_DEFAULT_CACHE	64
 #define MALLOC_CHUNK_LISTS	4
 #define CHUNK_CHECK_LENGTH	32
@@ -93,6 +93,9 @@
 #define MMAP(sz)	mmap(NULL, (sz), PROT_READ | PROT_WRITE, \
     MAP_ANON | MAP_PRIVATE, -1, 0)
 
+#define MMAPNONE(sz)	mmap(NULL, (sz), PROT_NONE, \
+    MAP_ANON | MAP_PRIVATE, -1, 0)
+
 #define MMAPA(a,sz)	mmap((a), (sz), PROT_READ | PROT_WRITE, \
     MAP_ANON | MAP_PRIVATE, -1, 0)
 
@@ -449,7 +452,7 @@ omalloc_init(void)
 static void
 omalloc_poolinit(struct dir_info **dp)
 {
-	void *p;
+	char *p;
 	size_t d_avail, regioninfo_size;
 	struct dir_info *d;
 	int i, j;
@@ -459,13 +462,11 @@ omalloc_poolinit(struct dir_info **dp)
 	 * randomise offset inside the page at which the dir_info
 	 * lies (subject to alignment by 1 << MALLOC_MINSHIFT)
 	 */
-	if ((p = MMAP(DIR_INFO_RSZ + (MALLOC_PAGESIZE * 2))) == MAP_FAILED)
+	if ((p = MMAPNONE(DIR_INFO_RSZ + (MALLOC_PAGESIZE * 2))) == MAP_FAILED)
 		wrterror(NULL, "malloc init mmap failed");
-	mprotect(p, MALLOC_PAGESIZE, PROT_NONE);
-	mprotect((char *)p + MALLOC_PAGESIZE + DIR_INFO_RSZ,
-	    MALLOC_PAGESIZE, PROT_NONE);
+	mprotect(p + MALLOC_PAGESIZE, DIR_INFO_RSZ, PROT_READ | PROT_WRITE);
 	d_avail = (DIR_INFO_RSZ - sizeof(*d)) >> MALLOC_MINSHIFT;
-	d = (struct dir_info *)((char *)p + MALLOC_PAGESIZE +
+	d = (struct dir_info *)(p + MALLOC_PAGESIZE +
 	    (arc4random_uniform(d_avail) << MALLOC_MINSHIFT));
 
 	rbytes_init(d);
@@ -1275,6 +1276,7 @@ ofree(struct dir_info *argpool, void *p, int clear, int check, size_t argsz)
 {
 	struct dir_info *pool;
 	struct region_info *r;
+	char *saved_function;
 	size_t sz;
 	int i;
 
@@ -1291,12 +1293,15 @@ ofree(struct dir_info *argpool, void *p, int clear, int check, size_t argsz)
 				_MALLOC_LOCK(pool->mutex);
 				pool->active++;
 				r = find(pool, p);
-				if (r != NULL)
+				if (r != NULL) {
+					saved_function = pool->func;
+					pool->func = argpool->func;
 					break;
+				}
 			}
 		}
 		if (r == NULL)
-			wrterror(pool, "bogus pointer (double free?) %p", p);
+			wrterror(argpool, "bogus pointer (double free?) %p", p);
 	}
 
 	REALSIZE(sz, r);
@@ -1388,6 +1393,7 @@ ofree(struct dir_info *argpool, void *p, int clear, int check, size_t argsz)
 
 	if (argpool != pool) {
 		pool->active--;
+		pool->func = saved_function;
 		_MALLOC_UNLOCK(pool->mutex);
 		_MALLOC_LOCK(argpool->mutex);
 		argpool->active++;
@@ -1466,6 +1472,7 @@ orealloc(struct dir_info *argpool, void *p, size_t newsz, void *f)
 	struct chunk_info *info;
 	size_t oldsz, goldsz, gnewsz;
 	void *q, *ret;
+	char *saved_function;
 	int i;
 	uint32_t chunknum;
 
@@ -1486,12 +1493,15 @@ orealloc(struct dir_info *argpool, void *p, size_t newsz, void *f)
 				_MALLOC_LOCK(pool->mutex);
 				pool->active++;
 				r = find(pool, p);
-				if (r != NULL)
+				if (r != NULL) {
+					saved_function = pool->func;
+					pool->func = argpool->func;
 					break;
+				}
 			}
 		}
 		if (r == NULL)
-			wrterror(pool, "bogus pointer (double free?) %p", p);
+			wrterror(argpool, "bogus pointer (double free?) %p", p);
 	}
 	if (newsz >= SIZE_MAX - mopts.malloc_guard - MALLOC_PAGESIZE) {
 		errno = ENOMEM;
@@ -1643,6 +1653,7 @@ gotit:
 done:
 	if (argpool != pool) {
 		pool->active--;
+		pool->func = saved_function;
 		_MALLOC_UNLOCK(pool->mutex);
 		_MALLOC_LOCK(argpool->mutex);
 		argpool->active++;