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Commit b7de5f54 authored by Christopher Ferris's avatar Christopher Ferris
Browse files

Demand read load bias for a map. 

Add a static GetLoadBias method to the Elf object that only reads just
enough to get the load bias.

Add a method to MapInfo that gets the load bias. First attempt to get
it if the elf object already exists. If no elf object was created, use
the new static method to get the load bias.

In BacktraceMap, add a custom iterator so that when code dereferences
a map element, that's when the load bias will be retrieved if it hasn't
already been set.

Bug: 69871050

Test: New unit tests, verify tombstones have non-zero load bias values for
Test: libraries with a non-zero load bias.
Change-Id: I125f4abc827589957fce2f0df24b0f25d037d732
parent ebca57ad

debuggerd/libdebuggerd/tombstone.cpp

+15 −14
Original line number Diff line number Diff line
@@ -417,7 +417,7 @@ static void dump_all_maps(Backtrace* backtrace, BacktraceMap* map, log_t* log, p 
       "memory map (%zu entr%s):",

       map->size(), map->size() == 1 ? "y" : "ies");

  if (print_fault_address_marker) {

    if (map->begin() != map->end() && addr < map->begin()->start) {

    if (map->begin() != map->end() && addr < (*map->begin())->start) {

      _LOG(log, logtype::MAPS, "\n--->Fault address falls at %s before any mapped regions\n",

           get_addr_string(addr).c_str());

      print_fault_address_marker = false;
@@ -429,49 +429,50 @@ static void dump_all_maps(Backtrace* backtrace, BacktraceMap* map, log_t* log, p 
  }



  std::string line;

  for (BacktraceMap::const_iterator it = map->begin(); it != map->end(); ++it) {

  for (auto it = map->begin(); it != map->end(); ++it) {

    const backtrace_map_t* entry = *it;

    line = "    ";

    if (print_fault_address_marker) {

      if (addr < it->start) {

      if (addr < entry->start) {

        _LOG(log, logtype::MAPS, "--->Fault address falls at %s between mapped regions\n",

             get_addr_string(addr).c_str());

        print_fault_address_marker = false;

      } else if (addr >= it->start && addr < it->end) {

      } else if (addr >= entry->start && addr < entry->end) {

        line = "--->";

        print_fault_address_marker = false;

      }

    }

    line += get_addr_string(it->start) + '-' + get_addr_string(it->end - 1) + ' ';

    if (it->flags & PROT_READ) {

    line += get_addr_string(entry->start) + '-' + get_addr_string(entry->end - 1) + ' ';

    if (entry->flags & PROT_READ) {

      line += 'r';

    } else {

      line += '-';

    }

    if (it->flags & PROT_WRITE) {

    if (entry->flags & PROT_WRITE) {

      line += 'w';

    } else {

      line += '-';

    }

    if (it->flags & PROT_EXEC) {

    if (entry->flags & PROT_EXEC) {

      line += 'x';

    } else {

      line += '-';

    }

    line += StringPrintf("  %8" PRIxPTR "  %8" PRIxPTR, it->offset, it->end - it->start);

    line += StringPrintf("  %8" PRIxPTR "  %8" PRIxPTR, entry->offset, entry->end - entry->start);

    bool space_needed = true;

    if (it->name.length() > 0) {

    if (entry->name.length() > 0) {

      space_needed = false;

      line += "  " + it->name;

      line += "  " + entry->name;

      std::string build_id;

      if ((it->flags & PROT_READ) && elf_get_build_id(backtrace, it->start, &build_id)) {

      if ((entry->flags & PROT_READ) && elf_get_build_id(backtrace, entry->start, &build_id)) {

        line += " (BuildId: " + build_id + ")";

      }

    }

    if (it->load_bias != 0) {

    if (entry->load_bias != 0) {

      if (space_needed) {

        line += ' ';

      }

      line += StringPrintf(" (load bias 0x%" PRIxPTR ")", it->load_bias);

      line += StringPrintf(" (load bias 0x%" PRIxPTR ")", entry->load_bias);

    }

    _LOG(log, logtype::MAPS, "%s\n", line.c_str());

  }

libbacktrace/BacktraceMap.cpp

+4 −3
Original line number Diff line number Diff line
@@ -40,9 +40,10 @@ BacktraceMap::~BacktraceMap() { 


void BacktraceMap::FillIn(uintptr_t addr, backtrace_map_t* map) {

  ScopedBacktraceMapIteratorLock lock(this);

  for (BacktraceMap::const_iterator it = begin(); it != end(); ++it) {

    if (addr >= it->start && addr < it->end) {

      *map = *it;

  for (auto it = begin(); it != end(); ++it) {

    const backtrace_map_t* entry = *it;

    if (addr >= entry->start && addr < entry->end) {

      *map = *entry;

      return;

    }

  }

libbacktrace/UnwindStackMap.cpp

+13 −2
Original line number Diff line number Diff line
@@ -71,8 +71,19 @@ void UnwindStackMap::FillIn(uintptr_t addr, backtrace_map_t* map) { 
  if (map_info == nullptr) {

    return;

  }

  unwindstack::Elf* elf = map_info->GetElf(process_memory_, true);

  map->load_bias = elf->GetLoadBias();

  map->load_bias = map_info->GetLoadBias(process_memory_);

}



uint64_t UnwindStackMap::GetLoadBias(size_t index) {

  if (index >= stack_maps_->Total()) {

    return 0;

  }



  unwindstack::MapInfo* map_info = stack_maps_->Get(index);

  if (map_info == nullptr) {

    return 0;

  }

  return map_info->GetLoadBias(process_memory_);

}



std::string UnwindStackMap::GetFunctionName(uintptr_t pc, uintptr_t* offset) {

libbacktrace/UnwindStackMap.h

+2 −0
Original line number Diff line number Diff line
@@ -42,6 +42,8 @@ class UnwindStackMap : public BacktraceMap { 
  const std::shared_ptr<unwindstack::Memory>& process_memory() { return process_memory_; }



 protected:

  uint64_t GetLoadBias(size_t index) override;



  std::unique_ptr<unwindstack::Maps> stack_maps_;

  std::shared_ptr<unwindstack::Memory> process_memory_;

};

libbacktrace/backtrace_offline_test.cpp

+6 −4
Original line number Diff line number Diff line
@@ -171,10 +171,12 @@ TEST(libbacktrace, DISABLED_generate_offline_testdata) { 
  testdata += android::base::StringPrintf("pid: %d tid: %d\n", getpid(), arg.tid);

  // 2. Dump maps

  for (auto it = map->begin(); it != map->end(); ++it) {

    testdata += android::base::StringPrintf(

        "map: start: %" PRIxPTR " end: %" PRIxPTR " offset: %" PRIxPTR " load_bias: %" PRIxPTR

        " flags: %d name: %s\n",

        it->start, it->end, it->offset, it->load_bias, it->flags, it->name.c_str());

    const backtrace_map_t* entry = *it;

    testdata +=

        android::base::StringPrintf("map: start: %" PRIxPTR " end: %" PRIxPTR " offset: %" PRIxPTR

                                    " load_bias: %" PRIxPTR " flags: %d name: %s\n",

                                    entry->start, entry->end, entry->offset, entry->load_bias,

                                    entry->flags, entry->name.c_str());

  }

  // 3. Dump registers

  testdata += android::base::StringPrintf("registers: %zu ", sizeof(arg.unw_context));