mremap.go raw

   1  // Copyright 2023 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  //go:build linux || netbsd
   6  
   7  package unix
   8  
   9  import "unsafe"
  10  
  11  type mremapMmapper struct {
  12  	mmapper
  13  	mremap func(oldaddr uintptr, oldlength uintptr, newlength uintptr, flags int, newaddr uintptr) (xaddr uintptr, err error)
  14  }
  15  
  16  var mapper = &mremapMmapper{
  17  	mmapper: mmapper{
  18  		active: make(map[*byte][]byte),
  19  		mmap:   mmap,
  20  		munmap: munmap,
  21  	},
  22  	mremap: mremap,
  23  }
  24  
  25  func (m *mremapMmapper) Mremap(oldData []byte, newLength int, flags int) (data []byte, err error) {
  26  	if newLength <= 0 || len(oldData) == 0 || len(oldData) != cap(oldData) || flags&mremapFixed != 0 {
  27  		return nil, EINVAL
  28  	}
  29  
  30  	pOld := &oldData[cap(oldData)-1]
  31  	m.Lock()
  32  	defer m.Unlock()
  33  	bOld := m.active[pOld]
  34  	if bOld == nil || &bOld[0] != &oldData[0] {
  35  		return nil, EINVAL
  36  	}
  37  	newAddr, errno := m.mremap(uintptr(unsafe.Pointer(&bOld[0])), uintptr(len(bOld)), uintptr(newLength), flags, 0)
  38  	if errno != nil {
  39  		return nil, errno
  40  	}
  41  	bNew := unsafe.Slice((*byte)(unsafe.Pointer(newAddr)), newLength)
  42  	pNew := &bNew[cap(bNew)-1]
  43  	if flags&mremapDontunmap == 0 {
  44  		delete(m.active, pOld)
  45  	}
  46  	m.active[pNew] = bNew
  47  	return bNew, nil
  48  }
  49  
  50  func Mremap(oldData []byte, newLength int, flags int) (data []byte, err error) {
  51  	return mapper.Mremap(oldData, newLength, flags)
  52  }
  53  
  54  func MremapPtr(oldAddr unsafe.Pointer, oldSize uintptr, newAddr unsafe.Pointer, newSize uintptr, flags int) (ret unsafe.Pointer, err error) {
  55  	xaddr, err := mapper.mremap(uintptr(oldAddr), oldSize, newSize, flags, uintptr(newAddr))
  56  	return unsafe.Pointer(xaddr), err
  57  }
  58