runtime: handle sysReserve failure in mHeap_SysAlloc

sysReserve will return nil on failure - correctly handle this case and return
nil to the caller. Currently, a failure will result in h.arena_end being set
to psize, h.arena_used being set to zero and fun times ensue.

On the openbsd/arm builder this has resulted in:

  runtime: address space conflict: map(0x0) = 0x40946000
  fatal error: runtime: address space conflict

When it should be reporting out of memory instead.

Change-Id: Iba828d5ee48ee1946de75eba409e0cfb04f089d4
Reviewed-on: https://go-review.googlesource.com/15056
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go
index 353f84083fcbf60b2ebf509959d5b887b3202941..f038debdd3d36a77161dbed221212aa8113d0d39 100644 (file)
--- a/src/runtime/malloc.go
+++ b/src/runtime/malloc.go
@@ -398,6 +398,9 @@ func mHeap_SysAlloc(h *mheap, n uintptr) unsafe.Pointer {
                        // is reserved and part is not.
                        var reserved bool
                        p := uintptr(sysReserve((unsafe.Pointer)(h.arena_end), p_size, &reserved))
+                       if p == 0 {
+                               return nil
+                       }
                        if p == h.arena_end {
                                h.arena_end = new_end
                                h.arena_reserved = reserved