Source file src/runtime/cgo_mmap.go
Documentation: runtime
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 //go:build (linux && amd64) || (linux && arm64) 8 // +build linux,amd64 linux,arm64 9 10 package runtime 11 12 import "unsafe" 13 14 // _cgo_mmap is filled in by runtime/cgo when it is linked into the 15 // program, so it is only non-nil when using cgo. 16 //go:linkname _cgo_mmap _cgo_mmap 17 var _cgo_mmap unsafe.Pointer 18 19 // _cgo_munmap is filled in by runtime/cgo when it is linked into the 20 // program, so it is only non-nil when using cgo. 21 //go:linkname _cgo_munmap _cgo_munmap 22 var _cgo_munmap unsafe.Pointer 23 24 // mmap is used to route the mmap system call through C code when using cgo, to 25 // support sanitizer interceptors. Don't allow stack splits, since this function 26 // (used by sysAlloc) is called in a lot of low-level parts of the runtime and 27 // callers often assume it won't acquire any locks. 28 //go:nosplit 29 func mmap(addr unsafe.Pointer, n uintptr, prot, flags, fd int32, off uint32) (unsafe.Pointer, int) { 30 if _cgo_mmap != nil { 31 // Make ret a uintptr so that writing to it in the 32 // function literal does not trigger a write barrier. 33 // A write barrier here could break because of the way 34 // that mmap uses the same value both as a pointer and 35 // an errno value. 36 var ret uintptr 37 systemstack(func() { 38 ret = callCgoMmap(addr, n, prot, flags, fd, off) 39 }) 40 if ret < 4096 { 41 return nil, int(ret) 42 } 43 return unsafe.Pointer(ret), 0 44 } 45 return sysMmap(addr, n, prot, flags, fd, off) 46 } 47 48 func munmap(addr unsafe.Pointer, n uintptr) { 49 if _cgo_munmap != nil { 50 systemstack(func() { callCgoMunmap(addr, n) }) 51 return 52 } 53 sysMunmap(addr, n) 54 } 55 56 // sysMmap calls the mmap system call. It is implemented in assembly. 57 func sysMmap(addr unsafe.Pointer, n uintptr, prot, flags, fd int32, off uint32) (p unsafe.Pointer, err int) 58 59 // callCgoMmap calls the mmap function in the runtime/cgo package 60 // using the GCC calling convention. It is implemented in assembly. 61 func callCgoMmap(addr unsafe.Pointer, n uintptr, prot, flags, fd int32, off uint32) uintptr 62 63 // sysMunmap calls the munmap system call. It is implemented in assembly. 64 func sysMunmap(addr unsafe.Pointer, n uintptr) 65 66 // callCgoMunmap calls the munmap function in the runtime/cgo package 67 // using the GCC calling convention. It is implemented in assembly. 68 func callCgoMunmap(addr unsafe.Pointer, n uintptr) 69