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 #include <stddef.h> 9 10 #include "base/files/file_util.h" 11 #include "base/files/scoped_file.h" 12 #include "base/strings/string_split.h" 13 #include "build/build_config.h" 14 15 #if defined(OS_LINUX) || defined(OS_ANDROID) 16 #include <inttypes.h> 17 #endif 18 19 #if defined(OS_ANDROID) && !defined(__LP64__) 20 // In 32-bit mode, Bionic's inttypes.h defines PRI/SCNxPTR as an 21 // unsigned long int, which is incompatible with Bionic's stdint.h 22 // defining uintptr_t as an unsigned int: 23 // https://code.google.com/p/android/issues/detail?id=57218 24 #undef SCNxPTR 25 #define SCNxPTR "x" 26 #endif 27 28 namespace base { 29 namespace debug { 30 31 // Scans |proc_maps| starting from |pos| returning true if the gate VMA was 32 // found, otherwise returns false. 33 static bool ContainsGateVMA(std::string* proc_maps, size_t pos) { 34 #if defined(ARCH_CPU_ARM_FAMILY) 35 // The gate VMA on ARM kernels is the interrupt vectors page. 36 return proc_maps->find(" [vectors]\n", pos) != std::string::npos; 37 #elif defined(ARCH_CPU_X86_64) 38 // The gate VMA on x86 64-bit kernels is the virtual system call page. 39 return proc_maps->find(" [vsyscall]\n", pos) != std::string::npos; 40 #else 41 // Otherwise assume there is no gate VMA in which case we shouldn't 42 // get duplicate entires. 43 return false; 44 #endif 45 } 46 47 bool ReadProcMaps(std::string* proc_maps) { 48 // seq_file only writes out a page-sized amount on each call. Refer to header 49 // file for details. 50 const long kReadSize = sysconf(_SC_PAGESIZE); 51 52 base::ScopedFD fd(HANDLE_EINTR(open("/proc/self/maps", O_RDONLY))); 53 if (!fd.is_valid()) { 54 DPLOG(ERROR) << "Couldn't open /proc/self/maps"; 55 return false; 56 } 57 proc_maps->clear(); 58 59 while (true) { 60 // To avoid a copy, resize |proc_maps| so read() can write directly into it. 61 // Compute |buffer| afterwards since resize() may reallocate. 62 size_t pos = proc_maps->size(); 63 proc_maps->resize(pos + kReadSize); 64 void* buffer = &(*proc_maps)[pos]; 65 66 ssize_t bytes_read = HANDLE_EINTR(read(fd.get(), buffer, kReadSize)); 67 if (bytes_read < 0) { 68 DPLOG(ERROR) << "Couldn't read /proc/self/maps"; 69 proc_maps->clear(); 70 return false; 71 } 72 73 // ... and don't forget to trim off excess bytes. 74 proc_maps->resize(pos + bytes_read); 75 76 if (bytes_read == 0) 77 break; 78 79 // The gate VMA is handled as a special case after seq_file has finished 80 // iterating through all entries in the virtual memory table. 81 // 82 // Unfortunately, if additional entries are added at this point in time 83 // seq_file gets confused and the next call to read() will return duplicate 84 // entries including the gate VMA again. 85 // 86 // Avoid this by searching for the gate VMA and breaking early. 87 if (ContainsGateVMA(proc_maps, pos)) 88 break; 89 } 90 91 return true; 92 } 93 94 bool ParseProcMaps(const std::string& input, 95 std::vector<MappedMemoryRegion>* regions_out) { 96 CHECK(regions_out); 97 std::vector<MappedMemoryRegion> regions; 98 99 // This isn't async safe nor terribly efficient, but it doesn't need to be at 100 // this point in time. 101 std::vector<std::string> lines = SplitString( 102 input, "\n", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL); 103 104 for (size_t i = 0; i < lines.size(); ++i) { 105 // Due to splitting on '\n' the last line should be empty. 106 if (i == lines.size() - 1) { 107 if (!lines[i].empty()) { 108 DLOG(WARNING) << "Last line not empty"; 109 return false; 110 } 111 break; 112 } 113 114 MappedMemoryRegion region; 115 const char* line = lines[i].c_str(); 116 char permissions[5] = {'\0'}; // Ensure NUL-terminated string. 117 uint8_t dev_major = 0; 118 uint8_t dev_minor = 0; 119 long inode = 0; 120 int path_index = 0; 121 122 // Sample format from man 5 proc: 123 // 124 // address perms offset dev inode pathname 125 // 08048000-08056000 r-xp 00000000 03:0c 64593 /usr/sbin/gpm 126 // 127 // The final %n term captures the offset in the input string, which is used 128 // to determine the path name. It *does not* increment the return value. 129 // Refer to man 3 sscanf for details. 130 if (sscanf(line, "%" SCNxPTR "-%" SCNxPTR " %4c %llx %hhx:%hhx %ld %n", 131 ®ion.start, ®ion.end, permissions, ®ion.offset, 132 &dev_major, &dev_minor, &inode, &path_index) < 7) { 133 DPLOG(WARNING) << "sscanf failed for line: " << line; 134 return false; 135 } 136 137 region.permissions = 0; 138 139 if (permissions[0] == 'r') 140 region.permissions |= MappedMemoryRegion::READ; 141 else if (permissions[0] != '-') 142 return false; 143 144 if (permissions[1] == 'w') 145 region.permissions |= MappedMemoryRegion::WRITE; 146 else if (permissions[1] != '-') 147 return false; 148 149 if (permissions[2] == 'x') 150 region.permissions |= MappedMemoryRegion::EXECUTE; 151 else if (permissions[2] != '-') 152 return false; 153 154 if (permissions[3] == 'p') 155 region.permissions |= MappedMemoryRegion::PRIVATE; 156 else if (permissions[3] != 's' && permissions[3] != 'S') // Shared memory. 157 return false; 158 159 // Pushing then assigning saves us a string copy. 160 regions.push_back(region); 161 regions.back().path.assign(line + path_index); 162 } 163 164 regions_out->swap(regions); 165 return true; 166 } 167 168 } // namespace debug 169 } // namespace base 170
