base/debug/proc_maps_linux.cc

   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                &region.start, &region.end, permissions, &region.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