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111d590f86
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>
54 lines
1.1 KiB
Go
54 lines
1.1 KiB
Go
// run
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// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// issue 16515: spilled Duff-adjusted address may be invalid
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package main
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import "runtime"
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type T [62]int // DUFFZERO with non-zero adjustment on AMD64
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var sink interface{}
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//go:noinline
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func zero(x *T) {
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// Two DUFFZEROs on the same address with a function call in between.
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// Duff-adjusted address will be spilled and loaded
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*x = T{} // DUFFZERO
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runtime.GC()
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(*x)[0] = 1
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g() // call a function with large frame, trigger a stack move
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*x = T{} // DUFFZERO again
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}
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//go:noinline
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// a function with large frame
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func g() {
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var x [1000]int
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_ = x
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}
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func main() {
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var s struct { a T; b [8192-62]int } // allocate 64K, hopefully it's in a new span and a few bytes before it is garbage
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sink = &s // force heap allocation
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s.a[0] = 2
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zero(&s.a)
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if s.a[0] != 0 {
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println("s.a[0] =", s.a[0])
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panic("zeroing failed")
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}
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var a T // on stack
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a[0] = 2
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zero(&a)
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if a[0] != 0 {
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println("a[0] =", a[0])
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panic("zeroing failed")
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}
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}
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