1 /*
2 * Copyright (C) 2013 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 <errno.h>
18 #include <stdint.h>
19 #include <string.h>
20 #include <sys/param.h>
21 #include <sys/ptrace.h>
22 #include <sys/types.h>
23 #include <ucontext.h>
24 #include <unistd.h>
25
26 #include <backtrace/Backtrace.h>
27 #include <backtrace/BacktraceMap.h>
28
29 #include "BacktraceLog.h"
30 #include "BacktracePtrace.h"
31
32 #if !defined(__APPLE__)
PtraceRead(pid_t tid,uint64_t addr,word_t * out_value)33 static bool PtraceRead(pid_t tid, uint64_t addr, word_t* out_value) {
34 // ptrace() returns -1 and sets errno when the operation fails.
35 // To disambiguate -1 from a valid result, we clear errno beforehand.
36 errno = 0;
37 *out_value = ptrace(PTRACE_PEEKTEXT, tid, reinterpret_cast<void*>(addr), nullptr);
38 if (*out_value == static_cast<word_t>(-1) && errno) {
39 return false;
40 }
41 return true;
42 }
43 #endif
44
ReadWord(uint64_t ptr,word_t * out_value)45 bool BacktracePtrace::ReadWord(uint64_t ptr, word_t* out_value) {
46 #if defined(__APPLE__)
47 BACK_LOGW("MacOS does not support reading from another pid.");
48 return false;
49 #else
50 if (!VerifyReadWordArgs(ptr, out_value)) {
51 return false;
52 }
53
54 backtrace_map_t map;
55 FillInMap(ptr, &map);
56 if (!BacktraceMap::IsValid(map) || !(map.flags & PROT_READ)) {
57 return false;
58 }
59
60 return PtraceRead(Tid(), ptr, out_value);
61 #endif
62 }
63
Read(uint64_t addr,uint8_t * buffer,size_t bytes)64 size_t BacktracePtrace::Read(uint64_t addr, uint8_t* buffer, size_t bytes) {
65 #if defined(__APPLE__)
66 BACK_LOGW("MacOS does not support reading from another pid.");
67 return 0;
68 #else
69 backtrace_map_t map;
70 FillInMap(addr, &map);
71 if (!BacktraceMap::IsValid(map) || !(map.flags & PROT_READ)) {
72 return 0;
73 }
74
75 bytes = MIN(map.end - addr, bytes);
76 size_t bytes_read = 0;
77 word_t data_word;
78 size_t align_bytes = addr & (sizeof(word_t) - 1);
79 if (align_bytes != 0) {
80 if (!PtraceRead(Tid(), addr & ~(sizeof(word_t) - 1), &data_word)) {
81 return 0;
82 }
83 size_t copy_bytes = MIN(sizeof(word_t) - align_bytes, bytes);
84 memcpy(buffer, reinterpret_cast<uint8_t*>(&data_word) + align_bytes, copy_bytes);
85 addr += copy_bytes;
86 buffer += copy_bytes;
87 bytes -= copy_bytes;
88 bytes_read += copy_bytes;
89 }
90
91 size_t num_words = bytes / sizeof(word_t);
92 for (size_t i = 0; i < num_words; i++) {
93 if (!PtraceRead(Tid(), addr, &data_word)) {
94 return bytes_read;
95 }
96 memcpy(buffer, &data_word, sizeof(word_t));
97 buffer += sizeof(word_t);
98 addr += sizeof(word_t);
99 bytes_read += sizeof(word_t);
100 }
101
102 size_t left_over = bytes & (sizeof(word_t) - 1);
103 if (left_over) {
104 if (!PtraceRead(Tid(), addr, &data_word)) {
105 return bytes_read;
106 }
107 memcpy(buffer, &data_word, left_over);
108 bytes_read += left_over;
109 }
110 return bytes_read;
111 #endif
112 }
113