Properly ensure 16-byte alignment on NetBSD.

1 files changed, 14 insertions, 5 deletions

diff --git a/emu/port/alloc.c b/emu/port/alloc.c
index 8b623de0..3cb45552 100644
--- a/emu/port/alloc.c
+++ b/emu/port/alloc.c
@@ -75,11 +75,7 @@ enum {
 
 /* tracing */
 enum {
-#ifdef __NetBSD__
-	Npadlong	= 4,	/* XXX: preserve 16-byte alignment */
-#else
 	Npadlong	= 2,
-#endif
 	MallocOffset = 0,
 	ReallocOffset = 1
 };
@@ -383,9 +379,22 @@ dopoolalloc(Pool *p, ulong asize, ulong pc)
 		unlock(&p->l);
 		return nil;
 	}
+#ifdef __NetBSD__
+	/* Align allocations to 16 bytes */
+	{
+		const size_t off = __builtin_offsetof(struct Bhdr, u.data)
+					+ Npadlong*sizeof(ulong);
+		struct assert_align {
+			unsigned int align_ok : (off % 8 == 0) ? 1 : -1;
+		};
+
+		const ulong align = (off - 1) % 16;
+		t = (Bhdr *)(((ulong)t + align) & ~align);
+	}
+#else
 	/* Double alignment */
 	t = (Bhdr *)(((ulong)t + 7) & ~7);
-
+#endif
 	if(p->chain != nil && (char*)t-(char*)B2LIMIT(p->chain)-ldr == 0){
 		/* can merge chains */
 		if(0)print("merging chains %p and %p in %s\n", p->chain, t, p->name);