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  1. 11 Dec, 2017 3 commits
    • Austin Clements's avatar
      runtime: reset write barrier buffer on all flush paths · 043f112e
      Austin Clements authored 
      Currently, wbBufFlush does nothing if the goroutine is dying on the
assumption that the system is crashing anyway and running the write
barrier may crash it even more. However, it fails to reset the
buffer's "next" pointer. As a result, if there are later write
barriers on the same P, the write barrier will overflow the write
barrier buffer and start corrupting other fields in the P or other
heap objects. Often, this corrupts fields in the next allocated P
since they tend to be together in the heap.

Fix this by always resetting the buffer's "next" pointer, even if
we're not doing anything with the pointers in the buffer.

Updates #22987 and #22988. (May fix; it's hard to say.)

Change-Id: I82c11ea2d399e1658531c3e8065445a66b7282b2
Reviewed-on: https://go-review.googlesource.com/83016
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: default avatarRick Hudson <rlh@golang.org>
Reviewed-by: default avatarMatthew Dempsky <mdempsky@google.com>
      043f112e
    • Austin Clements's avatar
      runtime: mark heapBits.bits nosplit · 3675bff5
      Austin Clements authored 
      heapBits.bits is used during bulkBarrierPreWrite via
heapBits.isPointer, which means it must not be preempted. If it is
preempted, several bad things can happen:

1. This could allow a GC phase change, and the resulting shear between
the barriers and the memory writes could result in a lost pointer.

2. Since bulkBarrierPreWrite uses the P's local write barrier buffer,
if it also migrates to a different P, it could try to append to the
write barrier buffer concurrently with another write barrier. This can
result in the buffer's next pointer skipping over its end pointer,
which results in a buffer overflow that can corrupt arbitrary other
fields in the Ps (or anything in the heap, really, but it'll probably
crash from the corrupted P quickly).

Fix this by marking heapBits.bits go:nosplit. This would be the
perfect use for a recursive no-preempt annotation (#21314).

This doesn't actually affect any binaries because this function was
always inlined anyway. (I discovered it when I was modifying heapBits
and make h.bits() no longer inline, which led to rampant crashes from
problem 2 above.)

Updates #22987 and #22988 (but doesn't fix because it doesn't actually
change the generated code).

Change-Id: I60ebb928b1233b0613361ac3d0558d7b1cb65610
Reviewed-on: https://go-review.googlesource.com/83015
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: default avatarMatthew Dempsky <mdempsky@google.com>
Reviewed-by: default avatarRick Hudson <rlh@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
      3675bff5
    • Brad Fitzpatrick's avatar
      doc: update NetBSD status · 0da486dc
      Brad Fitzpatrick authored 
      Fixes #23073

Change-Id: Ia43b28beeff9e57579caf5dcb76146ee29d5033b
Reviewed-on: https://go-review.googlesource.com/82918Reviewed-by: default avatarIan Lance Taylor <iant@golang.org>
      0da486dc
  3. 10 Dec, 2017 2 commits
  5. 09 Dec, 2017 2 commits
  7. 08 Dec, 2017 17 commits
  9. 07 Dec, 2017 13 commits
  11. 06 Dec, 2017 3 commits
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