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Currently mmap returns an unsafe.Pointer that encodes OS errors as values less than 4096. In practice this is okay, but it borders on being really unsafe: for example, the value has to be checked immediately after return and if stack copying were ever to observe such a value, it would panic. It's also not remotely idiomatic. Fix this by making mmap return a separate pointer value and error, like a normal Go function. Updates #22218. Change-Id: Iefd965095ffc82cc91118872753a5d39d785c3a6 Reviewed-on: https://go-review.googlesource.com/71270 Run-TryBot: Austin Clements <austin@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
63 lines
2.1 KiB
Go
63 lines
2.1 KiB
Go
// Copyright 2015 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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// Support for memory sanitizer. See runtime/cgo/mmap.go.
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// +build linux,amd64
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package runtime
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import "unsafe"
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// _cgo_mmap is filled in by runtime/cgo when it is linked into the
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// program, so it is only non-nil when using cgo.
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//go:linkname _cgo_mmap _cgo_mmap
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var _cgo_mmap unsafe.Pointer
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// _cgo_munmap is filled in by runtime/cgo when it is linked into the
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// program, so it is only non-nil when using cgo.
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//go:linkname _cgo_munmap _cgo_munmap
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var _cgo_munmap unsafe.Pointer
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func mmap(addr unsafe.Pointer, n uintptr, prot, flags, fd int32, off uint32) (unsafe.Pointer, int) {
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if _cgo_mmap != nil {
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// Make ret a uintptr so that writing to it in the
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// function literal does not trigger a write barrier.
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// A write barrier here could break because of the way
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// that mmap uses the same value both as a pointer and
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// an errno value.
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var ret uintptr
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systemstack(func() {
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ret = callCgoMmap(addr, n, prot, flags, fd, off)
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})
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if ret < 4096 {
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return nil, int(ret)
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}
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return unsafe.Pointer(ret), 0
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}
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return sysMmap(addr, n, prot, flags, fd, off)
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}
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func munmap(addr unsafe.Pointer, n uintptr) {
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if _cgo_munmap != nil {
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systemstack(func() { callCgoMunmap(addr, n) })
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return
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}
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sysMunmap(addr, n)
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}
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// sysMmap calls the mmap system call. It is implemented in assembly.
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func sysMmap(addr unsafe.Pointer, n uintptr, prot, flags, fd int32, off uint32) (p unsafe.Pointer, err int)
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// callCgoMmap calls the mmap function in the runtime/cgo package
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// using the GCC calling convention. It is implemented in assembly.
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func callCgoMmap(addr unsafe.Pointer, n uintptr, prot, flags, fd int32, off uint32) uintptr
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// sysMunmap calls the munmap system call. It is implemented in assembly.
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func sysMunmap(addr unsafe.Pointer, n uintptr)
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// callCgoMunmap calls the munmap function in the runtime/cgo package
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// using the GCC calling convention. It is implemented in assembly.
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func callCgoMunmap(addr unsafe.Pointer, n uintptr)
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