Current File : //usr/local/go119/src/cmd/link/internal/ld/outbuf_mmap.go
// Copyright 2019 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd
// +build aix darwin dragonfly freebsd linux netbsd openbsd
package ld
import (
"syscall"
)
// Mmap maps the output file with the given size. It unmaps the old mapping
// if it is already mapped. It also flushes any in-heap data to the new
// mapping.
func (out *OutBuf) Mmap(filesize uint64) (err error) {
oldlen := len(out.buf)
if oldlen != 0 {
out.munmap()
}
for {
if err = out.fallocate(filesize); err != syscall.EINTR {
break
}
}
if err != nil {
// Some file systems do not support fallocate. We ignore that error as linking
// can still take place, but you might SIGBUS when you write to the mmapped
// area.
if err != syscall.ENOTSUP && err != syscall.EPERM && err != errNoFallocate {
return err
}
}
err = out.f.Truncate(int64(filesize))
if err != nil {
Exitf("resize output file failed: %v", err)
}
out.buf, err = syscall.Mmap(int(out.f.Fd()), 0, int(filesize), syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_SHARED|syscall.MAP_FILE)
if err != nil {
return err
}
// copy heap to new mapping
if uint64(oldlen+len(out.heap)) > filesize {
panic("mmap size too small")
}
copy(out.buf[oldlen:], out.heap)
out.heap = out.heap[:0]
return nil
}
func (out *OutBuf) munmap() {
if out.buf == nil {
return
}
syscall.Munmap(out.buf)
out.buf = nil
}
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