go cgo_mmap 源码
golang cgo_mmap 代码
文件路径：/src/runtime/cgo_mmap.go
// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Support for memory sanitizer. See runtime/cgo/mmap.go.
//go:build (linux && amd64) || (linux && arm64)
package runtime
import "unsafe"
// _cgo_mmap is filled in by runtime/cgo when it is linked into the
// program, so it is only non-nil when using cgo.
//
//go:linkname _cgo_mmap _cgo_mmap
var _cgo_mmap unsafe.Pointer
// _cgo_munmap is filled in by runtime/cgo when it is linked into the
// program, so it is only non-nil when using cgo.
//
//go:linkname _cgo_munmap _cgo_munmap
var _cgo_munmap unsafe.Pointer
// mmap is used to route the mmap system call through C code when using cgo, to
// support sanitizer interceptors. Don't allow stack splits, since this function
// (used by sysAlloc) is called in a lot of low-level parts of the runtime and
// callers often assume it won't acquire any locks.
//
//go:nosplit
func mmap(addr unsafe.Pointer, n uintptr, prot, flags, fd int32, off uint32) (unsafe.Pointer, int) {
if _cgo_mmap != nil {
// Make ret a uintptr so that writing to it in the
// function literal does not trigger a write barrier.
// A write barrier here could break because of the way
// that mmap uses the same value both as a pointer and
// an errno value.
var ret uintptr
systemstack(func() {
ret = callCgoMmap(addr, n, prot, flags, fd, off)
})
if ret < 4096 {
return nil, int(ret)
}
return unsafe.Pointer(ret), 0
}
return sysMmap(addr, n, prot, flags, fd, off)
}
func munmap(addr unsafe.Pointer, n uintptr) {
if _cgo_munmap != nil {
systemstack(func() { callCgoMunmap(addr, n) })
return
}
sysMunmap(addr, n)
}
// sysMmap calls the mmap system call. It is implemented in assembly.
func sysMmap(addr unsafe.Pointer, n uintptr, prot, flags, fd int32, off uint32) (p unsafe.Pointer, err int)
// callCgoMmap calls the mmap function in the runtime/cgo package
// using the GCC calling convention. It is implemented in assembly.
func callCgoMmap(addr unsafe.Pointer, n uintptr, prot, flags, fd int32, off uint32) uintptr
// sysMunmap calls the munmap system call. It is implemented in assembly.
func sysMunmap(addr unsafe.Pointer, n uintptr)
// callCgoMunmap calls the munmap function in the runtime/cgo package
// using the GCC calling convention. It is implemented in assembly.
func callCgoMunmap(addr unsafe.Pointer, n uintptr)
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