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