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 #include "thread_utils.h"
32
33 #if !defined(__APPLE__)
PtraceRead(pid_t tid,uintptr_t addr,word_t * out_value)34 static bool PtraceRead(pid_t tid, uintptr_t addr, word_t* out_value) {
35 // ptrace() returns -1 and sets errno when the operation fails.
36 // To disambiguate -1 from a valid result, we clear errno beforehand.
37 errno = 0;
38 *out_value = ptrace(PTRACE_PEEKTEXT, tid, reinterpret_cast<void*>(addr), nullptr);
39 if (*out_value == static_cast<word_t>(-1) && errno) {
40 return false;
41 }
42 return true;
43 }
44 #endif
45
ReadWord(uintptr_t ptr,word_t * out_value)46 bool BacktracePtrace::ReadWord(uintptr_t ptr, word_t* out_value) {
47 #if defined(__APPLE__)
48 BACK_LOGW("MacOS does not support reading from another pid.");
49 return false;
50 #else
51 if (!VerifyReadWordArgs(ptr, out_value)) {
52 return false;
53 }
54
55 backtrace_map_t map;
56 FillInMap(ptr, &map);
57 if (!BacktraceMap::IsValid(map) || !(map.flags & PROT_READ)) {
58 return false;
59 }
60
61 return PtraceRead(Tid(), ptr, out_value);
62 #endif
63 }
64
Read(uintptr_t addr,uint8_t * buffer,size_t bytes)65 size_t BacktracePtrace::Read(uintptr_t addr, uint8_t* buffer, size_t bytes) {
66 #if defined(__APPLE__)
67 BACK_LOGW("MacOS does not support reading from another pid.");
68 return 0;
69 #else
70 backtrace_map_t map;
71 FillInMap(addr, &map);
72 if (!BacktraceMap::IsValid(map) || !(map.flags & PROT_READ)) {
73 return 0;
74 }
75
76 bytes = MIN(map.end - addr, bytes);
77 size_t bytes_read = 0;
78 word_t data_word;
79 size_t align_bytes = addr & (sizeof(word_t) - 1);
80 if (align_bytes != 0) {
81 if (!PtraceRead(Tid(), addr & ~(sizeof(word_t) - 1), &data_word)) {
82 return 0;
83 }
84 size_t copy_bytes = MIN(sizeof(word_t) - align_bytes, bytes);
85 memcpy(buffer, reinterpret_cast<uint8_t*>(&data_word) + align_bytes, copy_bytes);
86 addr += copy_bytes;
87 buffer += copy_bytes;
88 bytes -= copy_bytes;
89 bytes_read += copy_bytes;
90 }
91
92 size_t num_words = bytes / sizeof(word_t);
93 for (size_t i = 0; i < num_words; i++) {
94 if (!PtraceRead(Tid(), addr, &data_word)) {
95 return bytes_read;
96 }
97 memcpy(buffer, &data_word, sizeof(word_t));
98 buffer += sizeof(word_t);
99 addr += sizeof(word_t);
100 bytes_read += sizeof(word_t);
101 }
102
103 size_t left_over = bytes & (sizeof(word_t) - 1);
104 if (left_over) {
105 if (!PtraceRead(Tid(), addr, &data_word)) {
106 return bytes_read;
107 }
108 memcpy(buffer, &data_word, left_over);
109 bytes_read += left_over;
110 }
111 return bytes_read;
112 #endif
113 }
114