Source file src/pkg/cmd/link/internal/ld/outbuf_mmap.go

     1	// Copyright 2019 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	// +build darwin dragonfly freebsd linux openbsd
     6	
     7	package ld
     8	
     9	import (
    10		"syscall"
    11		"unsafe"
    12	)
    13	
    14	func (out *OutBuf) Mmap(filesize uint64) error {
    15		err := out.f.Truncate(int64(filesize))
    16		if err != nil {
    17			Exitf("resize output file failed: %v", err)
    18		}
    19		out.buf, err = syscall.Mmap(int(out.f.Fd()), 0, int(filesize), syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_SHARED|syscall.MAP_FILE)
    20		return err
    21	}
    22	
    23	func (out *OutBuf) Munmap() {
    24		err := out.Msync()
    25		if err != nil {
    26			Exitf("msync output file failed: %v", err)
    27		}
    28		syscall.Munmap(out.buf)
    29		out.buf = nil
    30		_, err = out.f.Seek(out.off, 0)
    31		if err != nil {
    32			Exitf("seek output file failed: %v", err)
    33		}
    34	}
    35	
    36	func (out *OutBuf) Msync() error {
    37		// TODO: netbsd supports mmap and msync, but the syscall package doesn't define MSYNC.
    38		// It is excluded from the build tag for now.
    39		_, _, errno := syscall.Syscall(syscall.SYS_MSYNC, uintptr(unsafe.Pointer(&out.buf[0])), uintptr(len(out.buf)), syscall.MS_SYNC)
    40		if errno != 0 {
    41			return errno
    42		}
    43		return nil
    44	}
    45	

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