1 /*
2 * Copyright (C) 2017 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "safe_copy.h"
18
19 #include <sys/uio.h>
20 #include <sys/user.h>
21 #include <unistd.h>
22
23 #include <algorithm>
24
25 #include <android-base/macros.h>
26
27 #include "base/bit_utils.h"
28
29 namespace art {
30
SafeCopy(void * dst,const void * src,size_t len)31 ssize_t SafeCopy(void *dst, const void *src, size_t len) {
32 #if defined(__linux__)
33 struct iovec dst_iov = {
34 .iov_base = dst,
35 .iov_len = len,
36 };
37
38 // Split up the remote read across page boundaries.
39 // From the manpage:
40 // A partial read/write may result if one of the remote_iov elements points to an invalid
41 // memory region in the remote process.
42 //
43 // Partial transfers apply at the granularity of iovec elements. These system calls won't
44 // perform a partial transfer that splits a single iovec element.
45 constexpr size_t kMaxIovecs = 64;
46 struct iovec src_iovs[kMaxIovecs];
47 size_t iovecs_used = 0;
48
49 const char* cur = static_cast<const char*>(src);
50 while (len > 0) {
51 if (iovecs_used == kMaxIovecs) {
52 errno = EINVAL;
53 return -1;
54 }
55
56 src_iovs[iovecs_used].iov_base = const_cast<char*>(cur);
57 if (!IsAlignedParam(cur, PAGE_SIZE)) {
58 src_iovs[iovecs_used].iov_len = AlignUp(cur, PAGE_SIZE) - cur;
59 } else {
60 src_iovs[iovecs_used].iov_len = PAGE_SIZE;
61 }
62
63 src_iovs[iovecs_used].iov_len = std::min(src_iovs[iovecs_used].iov_len, len);
64
65 len -= src_iovs[iovecs_used].iov_len;
66 cur += src_iovs[iovecs_used].iov_len;
67 ++iovecs_used;
68 }
69
70 ssize_t rc = process_vm_readv(getpid(), &dst_iov, 1, src_iovs, iovecs_used, 0);
71 if (rc == -1) {
72 return 0;
73 }
74 return rc;
75 #else
76 UNUSED(dst, src, len);
77 return -1;
78 #endif
79 }
80
81 } // namespace art
82