runtime: Don't ask mmap for wrapping memory.

From-SVN: r180732

diff --git a/libgo/runtime/malloc.goc b/libgo/runtime/malloc.goc
index f8d4327d69066457ee1a0c94d2762acad1cc4279..66f5bda66c0b3c9ef2fbbd10f8fb512e1a450afe 100644 (file)
--- a/libgo/runtime/malloc.goc
+++ b/libgo/runtime/malloc.goc
@@ -358,6 +358,8 @@ runtime_mallocinit(void)
                // away from the running binary image and then round up
                // to a MB boundary.
                want = (byte*)(((uintptr)end + (1<<18) + (1<<20) - 1)&~((1<<20)-1));
+               if(0xffffffff - (uintptr)want <= bitmap_size + arena_size)
+                 want = 0;
                p = runtime_SysReserve(want, bitmap_size + arena_size);
                if(p == nil)
                        runtime_throw("runtime: cannot reserve arena virtual address space");