Implement C11's aligned_alloc(3). ok guenther@

2 files changed, 84 insertions, 5 deletions

diff --git a/lib/libc/stdlib/malloc.3 b/lib/libc/stdlib/malloc.3
index 1f5d9c71044..71c329f9ece 100644
--- a/lib/libc/stdlib/malloc.3
+++ b/lib/libc/stdlib/malloc.3
@@ -30,9 +30,9 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.\"	$OpenBSD: malloc.3,v 1.115 2017/05/15 18:05:34 tb Exp $
+.\"	$OpenBSD: malloc.3,v 1.116 2018/11/05 08:23:40 otto Exp $
 .\"
-.Dd $Mdocdate: May 15 2017 $
+.Dd $Mdocdate: November 5 2018 $
 .Dt MALLOC 3
 .Os
 .Sh NAME
@@ -42,7 +42,8 @@
 .Nm free ,
 .Nm reallocarray ,
 .Nm recallocarray ,
-.Nm freezero
+.Nm freezero ,
+.Nm aligned_alloc
 .Nd memory allocation and deallocation
 .Sh SYNOPSIS
 .In stdlib.h
@@ -60,6 +61,8 @@
 .Fn recallocarray "void *ptr" "size_t oldnmemb" "size_t nmemb" "size_t size"
 .Ft void
 .Fn freezero "void *ptr" "size_t size"
+.Ft void *
+.Fn aligned_alloc "size_t alignment" "size_t size"
 .Vt char *malloc_options ;
 .Sh DESCRIPTION
 The standard functions
@@ -206,7 +209,7 @@ is not
 .Dv NULL ,
 the
 .Fa size
-argument must be equal or smaller than the size of the earlier allocation
+argument must be equal to or smaller than the size of the earlier allocation
 that returned
 .Fa ptr .
 .Fn freezero
@@ -215,6 +218,21 @@ guarantees the memory range starting at
 with length
 .Fa size
 is discarded while deallocating the whole object originally allocated.
+.Pp
+The
+.Fn aligned_alloc
+function allocates
+.Fa size
+bytes of memory such that the allocation's base address is a multiple of
+.Fa alignment .
+The requested
+.Fa alignment
+must be a power of 2.
+If
+.Fa size
+is not a multiple of
+.Fa alignment ,
+behavior is undefined.
 .Sh RETURN VALUES
 Upon successful completion, the allocation functions
 return a pointer to the allocated space; otherwise,
@@ -223,6 +241,17 @@ is returned and
 .Va errno
 is set to
 .Er ENOMEM .
+The function
+.Fn aligned_alloc
+returns
+.Dv NULL
+and sets
+.Va errno
+to
+.Er EINVAL
+if
+.Fa alignment
+is not a power of 2.
 .Pp
 If
 .Fa nmemb
@@ -514,6 +543,10 @@ and
 .Fn free
 functions conform to
 .St -ansiC .
+The
+.Fn aligned_alloc
+function conforms to
+.St -isoC-2011 .
 .Pp
 If
 .Fa nmemb
@@ -588,6 +621,10 @@ The
 .Fn freezero
 function appeared in
 .Ox 6.2 .
+The
+.Fn aligned_alloc
+function appeared in
+.Ox 6.5 .
 .Sh CAVEATS
 When using
 .Fn malloc ,
diff --git a/lib/libc/stdlib/malloc.c b/lib/libc/stdlib/malloc.c
index 81c30812a46..70e7f37dc82 100644
--- a/lib/libc/stdlib/malloc.c
+++ b/lib/libc/stdlib/malloc.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: malloc.c,v 1.249 2018/04/07 09:57:08 otto Exp $	*/
+/*	$OpenBSD: malloc.c,v 1.250 2018/11/05 08:23:40 otto Exp $	*/
 /*
  * Copyright (c) 2008, 2010, 2011, 2016 Otto Moerbeek <otto@drijf.net>
  * Copyright (c) 2012 Matthew Dempsky <matthew@openbsd.org>
@@ -2058,6 +2058,48 @@ err:
 }
 /*DEF_STRONG(posix_memalign);*/
 
+void *
+aligned_alloc(size_t alignment, size_t size)
+{
+	struct dir_info *d;
+	int saved_errno = errno;
+	void *r;
+
+	/* Make sure that alignment is a positive power of 2. */
+	if (((alignment - 1) & alignment) != 0 || alignment == 0) {
+		errno = EINVAL;
+		return NULL;
+	};
+	/* Per spec, size should be a multiple of alignment */
+	if ((size & (alignment - 1)) != 0) {
+		errno = EINVAL;
+		return NULL;
+	}
+
+	d = getpool();
+	if (d == NULL) {
+		_malloc_init(0);
+		d = getpool();
+	}
+	_MALLOC_LOCK(d->mutex);
+	d->func = "aligned_alloc";
+	if (d->active++) {
+		malloc_recurse(d);
+		return NULL;
+	}
+	r = omemalign(d, alignment, size, 0, CALLER);
+	d->active--;
+	_MALLOC_UNLOCK(d->mutex);
+	if (r == NULL) {
+		if (mopts.malloc_xmalloc)
+			wrterror(d, "out of memory");
+		return NULL;
+	}
+	errno = saved_errno;
+	return r;
+}
+/*DEF_STRONG(aligned_alloc);*/
+
 #ifdef MALLOC_STATS
 
 struct malloc_leak {