1 // Copyright 2015 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 // Support for memory sanitizer. See runtime/cgo/mmap.go. 6 7 // +build linux,amd64 8 9 package runtime 10 11 import "unsafe" 12 13 // _cgo_mmap is filled in by runtime/cgo when it is linked into the 14 // program, so it is only non-nil when using cgo. 15 //go:linkname _cgo_mmap _cgo_mmap 16 var _cgo_mmap unsafe.Pointer 17 18 // _cgo_munmap is filled in by runtime/cgo when it is linked into the 19 // program, so it is only non-nil when using cgo. 20 //go:linkname _cgo_munmap _cgo_munmap 21 var _cgo_munmap unsafe.Pointer 22 23 func mmap(addr unsafe.Pointer, n uintptr, prot, flags, fd int32, off uint32) (unsafe.Pointer, int) { 24 if _cgo_mmap != nil { 25 // Make ret a uintptr so that writing to it in the 26 // function literal does not trigger a write barrier. 27 // A write barrier here could break because of the way 28 // that mmap uses the same value both as a pointer and 29 // an errno value. 30 var ret uintptr 31 systemstack(func() { 32 ret = callCgoMmap(addr, n, prot, flags, fd, off) 33 }) 34 if ret < 4096 { 35 return nil, int(ret) 36 } 37 return unsafe.Pointer(ret), 0 38 } 39 return sysMmap(addr, n, prot, flags, fd, off) 40 } 41 42 func munmap(addr unsafe.Pointer, n uintptr) { 43 if _cgo_munmap != nil { 44 systemstack(func() { callCgoMunmap(addr, n) }) 45 return 46 } 47 sysMunmap(addr, n) 48 } 49 50 // sysMmap calls the mmap system call. It is implemented in assembly. 51 func sysMmap(addr unsafe.Pointer, n uintptr, prot, flags, fd int32, off uint32) (p unsafe.Pointer, err int) 52 53 // callCgoMmap calls the mmap function in the runtime/cgo package 54 // using the GCC calling convention. It is implemented in assembly. 55 func callCgoMmap(addr unsafe.Pointer, n uintptr, prot, flags, fd int32, off uint32) uintptr 56 57 // sysMunmap calls the munmap system call. It is implemented in assembly. 58 func sysMunmap(addr unsafe.Pointer, n uintptr) 59 60 // callCgoMunmap calls the munmap function in the runtime/cgo package 61 // using the GCC calling convention. It is implemented in assembly. 62 func callCgoMunmap(addr unsafe.Pointer, n uintptr) 63
