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There's a problem in liveness, where liveness of any part of an aggregate keeps the whole aggregate alive, but the not-live parts don't get spilled. The GC can observe those live-but-not-spilled slots, which can contain junk. A better fix is to change liveness to work pointer-by-pointer, but that is also a riskier, trickier fix. To avoid this, in the case of (1) an aggregate input parameter (2) containing pointers (3) passed in registers pre-spill the pointers. Updates #40724. Change-Id: I6beb8e0a353b1ae3c68c16072f56698061922c04 Reviewed-on: https://go-review.googlesource.com/c/go/+/307909 Trust: David Chase <drchase@google.com> Run-TryBot: David Chase <drchase@google.com> Reviewed-by: Cherry Zhang <cherryyz@google.com>
54 lines
986 B
Go
54 lines
986 B
Go
// run
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// Copyright 2021 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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// A test for partial liveness / partial spilling / compiler-induced GC failure
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package main
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import "runtime"
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import "unsafe"
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//go:registerparams
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func F(s []int) {
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for i, x := range s {
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G(i, x)
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}
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GC()
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H(&s[0]) // It's possible that this will make the spill redundant, but there's a bug in spill slot allocation.
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G(len(s), cap(s))
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GC()
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}
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//go:noinline
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//go:registerparams
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func G(int, int) {}
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//go:noinline
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//go:registerparams
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func H(*int) {}
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//go:registerparams
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func GC() { runtime.GC(); runtime.GC() }
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func main() {
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s := make([]int, 3)
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escape(s)
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p := int(uintptr(unsafe.Pointer(&s[2])) + 42) // likely point to unallocated memory
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poison([3]int{p, p, p})
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F(s)
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}
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//go:noinline
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//go:registerparams
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func poison([3]int) {}
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//go:noinline
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//go:registerparams
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func escape(s []int) {
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g = s
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}
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var g []int
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