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) || 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.
  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
  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
  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                &region.start, &region.end, permissions, &region.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