Implement malloc_usable_size(); ok millert@ deraadt@ and jmc@ for the man page

1 files changed, 79 insertions, 1 deletions

diff --git a/lib/libc/stdlib/malloc.c b/lib/libc/stdlib/malloc.c
index af9cf39199d..ee4d4c055e9 100644
--- a/lib/libc/stdlib/malloc.c
+++ b/lib/libc/stdlib/malloc.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: malloc.c,v 1.251 2018/11/06 08:01:43 otto Exp $	*/
+/*	$OpenBSD: malloc.c,v 1.252 2018/11/18 16:15:18 otto Exp $	*/
 /*
  * Copyright (c) 2008, 2010, 2011, 2016 Otto Moerbeek <otto@drijf.net>
  * Copyright (c) 2012 Matthew Dempsky <matthew@openbsd.org>
@@ -1466,6 +1466,84 @@ freezero(void *ptr, size_t sz)
 }
 DEF_WEAK(freezero);
 
+static size_t
+osize(struct dir_info *argpool, void *p)
+{
+	struct dir_info *pool;
+	struct region_info *r;
+	char *saved_function;
+	size_t sz;
+	int i;
+
+	pool = argpool;
+	r = find(pool, p);
+	if (r == NULL) {
+		if (mopts.malloc_mt)  {
+			for (i = 0; i < _MALLOC_MUTEXES; i++) {
+				if (i == argpool->mutex)
+					continue;
+				pool->active--;
+				_MALLOC_UNLOCK(pool->mutex);
+				pool = mopts.malloc_pool[i];
+				_MALLOC_LOCK(pool->mutex);
+				pool->active++;
+				r = find(pool, p);
+				if (r != NULL) {
+					saved_function = pool->func;
+					pool->func = argpool->func;
+					break;
+				}
+			}
+		}
+		if (r == NULL)
+			wrterror(argpool, "bogus pointer (double free?) %p", p);
+	}
+
+	REALSIZE(sz, r);
+	if (sz > MALLOC_MAXCHUNK) {
+		if (MALLOC_MOVE_COND(sz))
+			sz = MALLOC_PAGESIZE - ((char *)p - (char *)r->p);
+		else
+			sz = PAGEROUND(sz);
+	}
+	if (argpool != pool) {
+		pool->active--;
+		pool->func = saved_function;
+		_MALLOC_UNLOCK(pool->mutex);
+		_MALLOC_LOCK(argpool->mutex);
+		argpool->active++;
+	}
+	return sz;
+}
+
+size_t
+malloc_usable_size(void *ptr)
+{
+	struct dir_info *d;
+	int saved_errno = errno;
+	size_t sz;
+
+	/* This is legal. */
+	if (ptr == NULL)
+		return 0;
+
+	d = getpool();
+	if (d == NULL)
+		wrterror(d, "malloc_usable_size() called before allocation");
+	_MALLOC_LOCK(d->mutex);
+	d->func = "malloc_usable_size";
+	if (d->active++) {
+		malloc_recurse(d);
+		return 0;
+	}
+	sz = osize(d, ptr);
+	d->active--;
+	_MALLOC_UNLOCK(d->mutex);
+	errno = saved_errno;
+	return sz;
+}
+DEF_WEAK(malloc_usable_size);
+
 static void *
 orealloc(struct dir_info *argpool, void *p, size_t newsz, void *f)
 {