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
 7package unix
 8
 9import "unsafe"
10
11type mremapMmapper struct {
12	mmapper
13	mremap func(oldaddr uintptr, oldlength uintptr, newlength uintptr, flags int, newaddr uintptr) (xaddr uintptr, err error)
14}
15
16var mapper = &mremapMmapper{
17	mmapper: mmapper{
18		active: make(map[*byte][]byte),
19		mmap:   mmap,
20		munmap: munmap,
21	},
22	mremap: mremap,
23}
24
25func (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
50func Mremap(oldData []byte, newLength int, flags int) (data []byte, err error) {
51	return mapper.Mremap(oldData, newLength, flags)
52}
53
54func 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}