1 // Copyright 2013 The Chromium Authors
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 #include <stddef.h>
9
10 #include "base/files/file_util.h"
11 #include "base/files/scoped_file.h"
12 #include "base/logging.h"
13 #include "base/strings/string_split.h"
14 #include "build/build_config.h"
15
16 #if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_ANDROID)
17 #include <inttypes.h>
18 #endif
19
20 namespace base {
21 namespace debug {
22
23 // Scans |proc_maps| starting from |pos| returning true if the gate VMA was
24 // found, otherwise returns false.
ContainsGateVMA(std::string * proc_maps,size_t pos)25 static bool ContainsGateVMA(std::string* proc_maps, size_t pos) {
26 #if defined(ARCH_CPU_ARM_FAMILY)
27 // The gate VMA on ARM kernels is the interrupt vectors page.
28 return proc_maps->find(" [vectors]\n", pos) != std::string::npos;
29 #elif defined(ARCH_CPU_X86_64)
30 // The gate VMA on x86 64-bit kernels is the virtual system call page.
31 return proc_maps->find(" [vsyscall]\n", pos) != std::string::npos;
32 #else
33 // Otherwise assume there is no gate VMA in which case we shouldn't
34 // get duplicate entires.
35 return false;
36 #endif
37 }
38
ReadProcMaps(std::string * proc_maps)39 bool ReadProcMaps(std::string* proc_maps) {
40 // seq_file only writes out a page-sized amount on each call. Refer to header
41 // file for details.
42 const size_t read_size = static_cast<size_t>(sysconf(_SC_PAGESIZE));
43
44 base::ScopedFD fd(HANDLE_EINTR(open("/proc/self/maps", O_RDONLY)));
45 if (!fd.is_valid()) {
46 DPLOG(ERROR) << "Couldn't open /proc/self/maps";
47 return false;
48 }
49 proc_maps->clear();
50
51 while (true) {
52 // To avoid a copy, resize |proc_maps| so read() can write directly into it.
53 // Compute |buffer| afterwards since resize() may reallocate.
54 size_t pos = proc_maps->size();
55 proc_maps->resize(pos + read_size);
56 void* buffer = &(*proc_maps)[pos];
57
58 ssize_t bytes_read = HANDLE_EINTR(read(fd.get(), buffer, read_size));
59 if (bytes_read < 0) {
60 DPLOG(ERROR) << "Couldn't read /proc/self/maps";
61 proc_maps->clear();
62 return false;
63 }
64
65 // ... and don't forget to trim off excess bytes.
66 proc_maps->resize(pos + static_cast<size_t>(bytes_read));
67
68 if (bytes_read == 0)
69 break;
70
71 // The gate VMA is handled as a special case after seq_file has finished
72 // iterating through all entries in the virtual memory table.
73 //
74 // Unfortunately, if additional entries are added at this point in time
75 // seq_file gets confused and the next call to read() will return duplicate
76 // entries including the gate VMA again.
77 //
78 // Avoid this by searching for the gate VMA and breaking early.
79 if (ContainsGateVMA(proc_maps, pos))
80 break;
81 }
82
83 return true;
84 }
85
ParseProcMaps(const std::string & input,std::vector<MappedMemoryRegion> * regions_out)86 bool ParseProcMaps(const std::string& input,
87 std::vector<MappedMemoryRegion>* regions_out) {
88 CHECK(regions_out);
89 std::vector<MappedMemoryRegion> regions;
90
91 // This isn't async safe nor terribly efficient, but it doesn't need to be at
92 // this point in time.
93 std::vector<std::string> lines = SplitString(
94 input, "\n", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);
95
96 for (size_t i = 0; i < lines.size(); ++i) {
97 // Due to splitting on '\n' the last line should be empty.
98 if (i == lines.size() - 1) {
99 if (!lines[i].empty()) {
100 DLOG(WARNING) << "Last line not empty";
101 return false;
102 }
103 break;
104 }
105
106 MappedMemoryRegion region;
107 const char* line = lines[i].c_str();
108 char permissions[5] = {'\0'}; // Ensure NUL-terminated string.
109 uint8_t dev_major = 0;
110 uint8_t dev_minor = 0;
111 long inode = 0;
112 int path_index = 0;
113
114 // Sample format from man 5 proc:
115 //
116 // address perms offset dev inode pathname
117 // 08048000-08056000 r-xp 00000000 03:0c 64593 /usr/sbin/gpm
118 //
119 // The final %n term captures the offset in the input string, which is used
120 // to determine the path name. It *does not* increment the return value.
121 // Refer to man 3 sscanf for details.
122 if (sscanf(line, "%" SCNxPTR "-%" SCNxPTR " %4c %llx %hhx:%hhx %ld %n",
123 ®ion.start, ®ion.end, permissions, ®ion.offset,
124 &dev_major, &dev_minor, &inode, &path_index) < 7) {
125 DPLOG(WARNING) << "sscanf failed for line: " << line;
126 return false;
127 }
128
129 region.permissions = 0;
130
131 if (permissions[0] == 'r')
132 region.permissions |= MappedMemoryRegion::READ;
133 else if (permissions[0] != '-')
134 return false;
135
136 if (permissions[1] == 'w')
137 region.permissions |= MappedMemoryRegion::WRITE;
138 else if (permissions[1] != '-')
139 return false;
140
141 if (permissions[2] == 'x')
142 region.permissions |= MappedMemoryRegion::EXECUTE;
143 else if (permissions[2] != '-')
144 return false;
145
146 if (permissions[3] == 'p')
147 region.permissions |= MappedMemoryRegion::PRIVATE;
148 else if (permissions[3] != 's' && permissions[3] != 'S') // Shared memory.
149 return false;
150
151 // Pushing then assigning saves us a string copy.
152 regions.push_back(region);
153 regions.back().path.assign(line + path_index);
154 }
155
156 regions_out->swap(regions);
157 return true;
158 }
159
160 } // namespace debug
161 } // namespace base
162