// Copyright 2011 Evan Shaw. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE-MMAP-GO file. // Modifications (c) 2022 The Memory Authors. package memory // import "modernc.org/memory" import ( "os" "syscall" _ "unsafe" ) const ( pageSizeLog = 20 // $ find /usr/include -name syscall.h // /usr/include/sys/syscall.h // $ grep -ni munmap /usr/include/sys/syscall.h // 293:#define SYS_munmap 117 // $ grep -ni mmap /usr/include/sys/syscall.h // 291:#define SYS_mmap 115 // 303:#define SYS_mmapobj 127 // 442:#define SYS_mmap64 214 // $ // $ uname -a // SunOS omnios64 5.11 omnios-r151044-d3b715b9d1 i86pc i386 i86pc // $ sys_MUNMAP = 117 sys_MMAP = 214 ) var ( osPageMask = osPageSize - 1 osPageSize = os.Getpagesize() ) //go:linkname mmapSyscall syscall.mmap func mmapSyscall(addr uintptr, length uintptr, prot int, flags int, fd int, offset int64) (xaddr uintptr, err error) func unmap(addr uintptr, size int) error { _, _, errno := syscall.Syscall(sys_MUNMAP, addr, uintptr(size), 0) if errno != 0 { return errno } return nil } // pageSize aligned. func mmap(size int) (uintptr, int, error) { size = roundup(size, osPageSize) // The actual mmap syscall varies by architecture. mmapSyscall provides same // functionality as the unexported funtion syscall.mmap and is declared in // mmap_*_*.go and mmap_fallback.go. To add support for a new architecture, // check function mmap in src/syscall/syscall_*_*.go or // src/syscall/zsyscall_*_*.go in Go's source code. p, err := mmapSyscall(0, uintptr(size+pageSize), syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_PRIVATE|syscall.MAP_ANON, -1, 0) if err != nil { return 0, 0, err } n := size + pageSize if p&uintptr(osPageMask) != 0 { panic("internal error") } mod := int(p) & pageMask if mod != 0 { m := pageSize - mod if err := unmap(p, m); err != nil { return 0, 0, err } n -= m p += uintptr(m) } if p&uintptr(pageMask) != 0 { panic("internal error") } if n-size != 0 { if err := unmap(p+uintptr(size), n-size); err != nil { return 0, 0, err } } return p, size, nil }