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cmd/compile: fix possible spill of invalid pointer with DUFFZERO on AMD64

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SSA compiler on AMD64 may spill Duff-adjusted address as scalar. If
the object is on stack and the stack moves, the spilled address become
invalid.

Making the spill pointer-typed does not work. The Duff-adjusted address
points to the memory before the area to be zeroed and may be invalid.
This may cause stack scanning code panic.

Fix it by doing Duff-adjustment in genValue, so the intermediate value
is not seen by the reg allocator, and will not be spilled.

Add a test to cover both cases. As it depends on allocation, it may
be not always triggered.

Fixes #16515.

Change-Id: Ia81d60204782de7405b7046165ad063384ede0db
Reviewed-on: https://go-review.googlesource.com/25309
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
This commit is contained in:
Cherry Zhang 2016-07-28 12:22:49 -04:00
parent be91515907
commit 111d590f86
6 changed files with 103 additions and 59 deletions
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4
src/cmd/compile/internal/ssa/gen/AMD64Ops.go
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@ -425,10 +425,10 @@ func init() {
{name: "MOVQstoreconstidx1", argLength: 3, reg: gpstoreconstidx, asm: "MOVQ", aux: "SymValAndOff", typ: "Mem"}, // store 8 bytes of ... arg1 ...
{name: "MOVQstoreconstidx8", argLength: 3, reg: gpstoreconstidx, asm: "MOVQ", aux: "SymValAndOff", typ: "Mem"}, // store 8 bytes of ... 8*arg1 ...
// arg0 = (duff-adjusted) pointer to start of memory to zero
// arg0 = pointer to start of memory to zero
// arg1 = value to store (will always be zero)
// arg2 = mem
// auxint = offset into duffzero code to start executing
// auxint = # of bytes to zero
// returns mem
{
name: "DUFFZERO",