mmap_unix.go (1762B)
1 // Copyright 2011 Evan Shaw. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE-MMAP-GO file. 4 5 //go:build darwin || dragonfly || freebsd || linux || openbsd || (solaris && !illumos) || netbsd 6 // +build darwin dragonfly freebsd linux openbsd solaris,!illumos netbsd 7 8 // Modifications (c) 2017 The Memory Authors. 9 10 package memory // import "modernc.org/memory" 11 12 import ( 13 "os" 14 "syscall" 15 ) 16 17 const pageSizeLog = 20 18 19 var ( 20 osPageMask = osPageSize - 1 21 osPageSize = os.Getpagesize() 22 ) 23 24 func unmap(addr uintptr, size int) error { 25 _, _, errno := syscall.Syscall(syscall.SYS_MUNMAP, addr, uintptr(size), 0) 26 if errno != 0 { 27 return errno 28 } 29 30 return nil 31 } 32 33 // pageSize aligned. 34 func mmap(size int) (uintptr, int, error) { 35 size = roundup(size, osPageSize) 36 // The actual mmap syscall varies by architecture. mmapSyscall provides same 37 // functionality as the unexported funtion syscall.mmap and is declared in 38 // mmap_*_*.go and mmap_fallback.go. To add support for a new architecture, 39 // check function mmap in src/syscall/syscall_*_*.go or 40 // src/syscall/zsyscall_*_*.go in Go's source code. 41 p, err := mmapSyscall(0, uintptr(size+pageSize), syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_PRIVATE|syscall.MAP_ANON, -1, 0) 42 if err != nil { 43 return 0, 0, err 44 } 45 46 n := size + pageSize 47 if p&uintptr(osPageMask) != 0 { 48 panic("internal error") 49 } 50 51 mod := int(p) & pageMask 52 if mod != 0 { 53 m := pageSize - mod 54 if err := unmap(p, m); err != nil { 55 return 0, 0, err 56 } 57 58 n -= m 59 p += uintptr(m) 60 } 61 62 if p&uintptr(pageMask) != 0 { 63 panic("internal error") 64 } 65 66 if n-size != 0 { 67 if err := unmap(p+uintptr(size), n-size); err != nil { 68 return 0, 0, err 69 } 70 } 71 72 return p, size, nil 73 }