1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "base/debug/proc_maps_linux.h"
6
7 #include <fcntl.h>
8
9 #if defined(OS_LINUX) || defined(OS_ANDROID)
10 #include <inttypes.h>
11 #endif
12
13 #include "base/files/file_util.h"
14 #include "base/files/scoped_file.h"
15 #include "base/strings/string_split.h"
16
17 #if defined(OS_ANDROID) && !defined(__LP64__)
18 // In 32-bit mode, Bionic's inttypes.h defines PRI/SCNxPTR as an
19 // unsigned long int, which is incompatible with Bionic's stdint.h
20 // defining uintptr_t as an unsigned int:
21 // https://code.google.com/p/android/issues/detail?id=57218
22 #undef SCNxPTR
23 #define SCNxPTR "x"
24 #endif
25
26 namespace base {
27 namespace debug {
28
29 // Scans |proc_maps| starting from |pos| returning true if the gate VMA was
30 // found, otherwise returns false.
ContainsGateVMA(std::string * proc_maps,size_t pos)31 static bool ContainsGateVMA(std::string* proc_maps, size_t pos) {
32 #if defined(ARCH_CPU_ARM_FAMILY)
33 // The gate VMA on ARM kernels is the interrupt vectors page.
34 return proc_maps->find(" [vectors]\n", pos) != std::string::npos;
35 #elif defined(ARCH_CPU_X86_64)
36 // The gate VMA on x86 64-bit kernels is the virtual system call page.
37 return proc_maps->find(" [vsyscall]\n", pos) != std::string::npos;
38 #else
39 // Otherwise assume there is no gate VMA in which case we shouldn't
40 // get duplicate entires.
41 return false;
42 #endif
43 }
44
ReadProcMaps(std::string * proc_maps)45 bool ReadProcMaps(std::string* proc_maps) {
46 // seq_file only writes out a page-sized amount on each call. Refer to header
47 // file for details.
48 const long kReadSize = sysconf(_SC_PAGESIZE);
49
50 base::ScopedFD fd(HANDLE_EINTR(open("/proc/self/maps", O_RDONLY)));
51 if (!fd.is_valid()) {
52 DPLOG(ERROR) << "Couldn't open /proc/self/maps";
53 return false;
54 }
55 proc_maps->clear();
56
57 while (true) {
58 // To avoid a copy, resize |proc_maps| so read() can write directly into it.
59 // Compute |buffer| afterwards since resize() may reallocate.
60 size_t pos = proc_maps->size();
61 proc_maps->resize(pos + kReadSize);
62 void* buffer = &(*proc_maps)[pos];
63
64 ssize_t bytes_read = HANDLE_EINTR(read(fd.get(), buffer, kReadSize));
65 if (bytes_read < 0) {
66 DPLOG(ERROR) << "Couldn't read /proc/self/maps";
67 proc_maps->clear();
68 return false;
69 }
70
71 // ... and don't forget to trim off excess bytes.
72 proc_maps->resize(pos + bytes_read);
73
74 if (bytes_read == 0)
75 break;
76
77 // The gate VMA is handled as a special case after seq_file has finished
78 // iterating through all entries in the virtual memory table.
79 //
80 // Unfortunately, if additional entries are added at this point in time
81 // seq_file gets confused and the next call to read() will return duplicate
82 // entries including the gate VMA again.
83 //
84 // Avoid this by searching for the gate VMA and breaking early.
85 if (ContainsGateVMA(proc_maps, pos))
86 break;
87 }
88
89 return true;
90 }
91
ParseProcMaps(const std::string & input,std::vector<MappedMemoryRegion> * regions_out)92 bool ParseProcMaps(const std::string& input,
93 std::vector<MappedMemoryRegion>* regions_out) {
94 CHECK(regions_out);
95 std::vector<MappedMemoryRegion> regions;
96
97 // This isn't async safe nor terribly efficient, but it doesn't need to be at
98 // this point in time.
99 std::vector<std::string> lines;
100 SplitString(input, '\n', &lines);
101
102 for (size_t i = 0; i < lines.size(); ++i) {
103 // Due to splitting on '\n' the last line should be empty.
104 if (i == lines.size() - 1) {
105 if (!lines[i].empty()) {
106 DLOG(WARNING) << "Last line not empty";
107 return false;
108 }
109 break;
110 }
111
112 MappedMemoryRegion region;
113 const char* line = lines[i].c_str();
114 char permissions[5] = {'\0'}; // Ensure NUL-terminated string.
115 uint8 dev_major = 0;
116 uint8 dev_minor = 0;
117 long inode = 0;
118 int path_index = 0;
119
120 // Sample format from man 5 proc:
121 //
122 // address perms offset dev inode pathname
123 // 08048000-08056000 r-xp 00000000 03:0c 64593 /usr/sbin/gpm
124 //
125 // The final %n term captures the offset in the input string, which is used
126 // to determine the path name. It *does not* increment the return value.
127 // Refer to man 3 sscanf for details.
128 if (sscanf(line, "%" SCNxPTR "-%" SCNxPTR " %4c %llx %hhx:%hhx %ld %n",
129 ®ion.start, ®ion.end, permissions, ®ion.offset,
130 &dev_major, &dev_minor, &inode, &path_index) < 7) {
131 DPLOG(WARNING) << "sscanf failed for line: " << line;
132 return false;
133 }
134
135 region.permissions = 0;
136
137 if (permissions[0] == 'r')
138 region.permissions |= MappedMemoryRegion::READ;
139 else if (permissions[0] != '-')
140 return false;
141
142 if (permissions[1] == 'w')
143 region.permissions |= MappedMemoryRegion::WRITE;
144 else if (permissions[1] != '-')
145 return false;
146
147 if (permissions[2] == 'x')
148 region.permissions |= MappedMemoryRegion::EXECUTE;
149 else if (permissions[2] != '-')
150 return false;
151
152 if (permissions[3] == 'p')
153 region.permissions |= MappedMemoryRegion::PRIVATE;
154 else if (permissions[3] != 's' && permissions[3] != 'S') // Shared memory.
155 return false;
156
157 // Pushing then assigning saves us a string copy.
158 regions.push_back(region);
159 regions.back().path.assign(line + path_index);
160 }
161
162 regions_out->swap(regions);
163 return true;
164 }
165
166 } // namespace debug
167 } // namespace base
168