go outbuf_darwin 源码
golang outbuf_darwin 代码
文件路径：/src/cmd/link/internal/ld/outbuf_darwin.go
// Copyright 2020 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 darwin && go1.12
// +build darwin,go1.12
package ld
import (
"syscall"
"unsafe"
)
// Implemented in the syscall package.
//
//go:linkname fcntl syscall.fcntl
func fcntl(fd int, cmd int, arg int) (int, error)
func (out *OutBuf) fallocate(size uint64) error {
stat, err := out.f.Stat()
if err != nil {
return err
}
// F_PEOFPOSMODE allocates from the end of the file, so we want the size difference.
// Apparently, it uses the end of the allocation, instead of the logical end of the
// the file.
cursize := uint64(stat.Sys().(*syscall.Stat_t).Blocks * 512) // allocated size
if size <= cursize {
return nil
}
store := &syscall.Fstore_t{
Flags: syscall.F_ALLOCATEALL,
Posmode: syscall.F_PEOFPOSMODE,
Offset: 0,
Length: int64(size - cursize),
}
_, err = fcntl(int(out.f.Fd()), syscall.F_PREALLOCATE, int(uintptr(unsafe.Pointer(store))))
return err
}
func (out *OutBuf) purgeSignatureCache() {
// Apparently, the Darwin kernel may cache the code signature at mmap.
// When we mmap the output buffer, it doesn't have a code signature
// (as we haven't generated one). Invalidate the kernel cache now that
// we have generated the signature. See issue #42684.
syscall.Syscall(syscall.SYS_MSYNC, uintptr(unsafe.Pointer(&out.buf[0])), uintptr(len(out.buf)), syscall.MS_INVALIDATE)
// Best effort. Ignore error.
}
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