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      1 //===-- sanitizer_coverage_mapping.cc -------------------------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // Mmap-based implementation of sanitizer coverage.
     11 //
     12 // This is part of the implementation of code coverage that does not require
     13 // __sanitizer_cov_dump() call. Data is stored in 2 files per process.
     14 //
     15 // $pid.sancov.map describes process memory layout in the following text-based
     16 // format:
     17 // <pointer size in bits>  // 1 line, 32 or 64
     18 // <mapping start> <mapping end> <base address> <dso name> // repeated
     19 // ...
     20 // Mapping lines are NOT sorted. This file is updated every time memory layout
     21 // is changed (i.e. in dlopen() and dlclose() interceptors).
     22 //
     23 // $pid.sancov.raw is a binary dump of PC values, sizeof(uptr) each. Again, not
     24 // sorted. This file is extended by 64Kb at a time and mapped into memory. It
     25 // contains one or more 0 words at the end, up to the next 64Kb aligned offset.
     26 //
     27 // To convert these 2 files to the usual .sancov format, run sancov.py rawunpack
     28 // $pid.sancov.raw.
     29 //
     30 //===----------------------------------------------------------------------===//
     31 
     32 #include "sanitizer_allocator_internal.h"
     33 #include "sanitizer_libc.h"
     34 #include "sanitizer_procmaps.h"
     35 
     36 namespace __sanitizer {
     37 
     38 static const uptr kMaxTextSize = 64 * 1024;
     39 
     40 struct CachedMapping {
     41  public:
     42   bool NeedsUpdate(uptr pc) {
     43     int new_pid = internal_getpid();
     44     if (last_pid == new_pid && pc && pc >= last_range_start &&
     45         pc < last_range_end)
     46       return false;
     47     last_pid = new_pid;
     48     return true;
     49   }
     50 
     51   void SetModuleRange(uptr start, uptr end) {
     52     last_range_start = start;
     53     last_range_end = end;
     54   }
     55 
     56  private:
     57   uptr last_range_start, last_range_end;
     58   int last_pid;
     59 };
     60 
     61 static CachedMapping cached_mapping;
     62 static StaticSpinMutex mapping_mu;
     63 
     64 void CovUpdateMapping(const char *coverage_dir, uptr caller_pc) {
     65   if (!common_flags()->coverage_direct) return;
     66 
     67   SpinMutexLock l(&mapping_mu);
     68 
     69   if (!cached_mapping.NeedsUpdate(caller_pc))
     70     return;
     71 
     72   InternalScopedString text(kMaxTextSize);
     73 
     74   {
     75     text.append("%d\n", sizeof(uptr) * 8);
     76     ListOfModules modules;
     77     modules.init();
     78     for (const LoadedModule &module : modules) {
     79       const char *module_name = StripModuleName(module.full_name());
     80       uptr base = module.base_address();
     81       for (const auto &range : module.ranges()) {
     82         if (range.executable) {
     83           uptr start = range.beg;
     84           uptr end = range.end;
     85           text.append("%zx %zx %zx %s\n", start, end, base, module_name);
     86           if (caller_pc && caller_pc >= start && caller_pc < end)
     87             cached_mapping.SetModuleRange(start, end);
     88         }
     89       }
     90     }
     91   }
     92 
     93   error_t err;
     94   InternalScopedString tmp_path(64 + internal_strlen(coverage_dir));
     95   uptr res = internal_snprintf((char *)tmp_path.data(), tmp_path.size(),
     96                                "%s/%zd.sancov.map.tmp", coverage_dir,
     97                                internal_getpid());
     98   CHECK_LE(res, tmp_path.size());
     99   fd_t map_fd = OpenFile(tmp_path.data(), WrOnly, &err);
    100   if (map_fd == kInvalidFd) {
    101     Report("Coverage: failed to open %s for writing: %d\n", tmp_path.data(),
    102            err);
    103     Die();
    104   }
    105 
    106   if (!WriteToFile(map_fd, text.data(), text.length(), nullptr, &err)) {
    107     Printf("sancov.map write failed: %d\n", err);
    108     Die();
    109   }
    110   CloseFile(map_fd);
    111 
    112   InternalScopedString path(64 + internal_strlen(coverage_dir));
    113   res = internal_snprintf((char *)path.data(), path.size(), "%s/%zd.sancov.map",
    114                           coverage_dir, internal_getpid());
    115   CHECK_LE(res, path.size());
    116   if (!RenameFile(tmp_path.data(), path.data(), &err)) {
    117     Printf("sancov.map rename failed: %d\n", err);
    118     Die();
    119   }
    120 }
    121 
    122 } // namespace __sanitizer
    123