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 // Copyright (c) 2006, Google Inc.

 // All rights reserved.

 //

 // Redistribution and use in source and binary forms, with or without

 // modification, are permitted provided that the following conditions are

 // met:

 //

 //     * Redistributions of source code must retain the above copyright

 // notice, this list of conditions and the following disclaimer.

 //     * Redistributions in binary form must reproduce the above

 // copyright notice, this list of conditions and the following disclaimer

 // in the documentation and/or other materials provided with the

 // distribution.

 //     * Neither the name of Google Inc. nor the names of its

 // contributors may be used to endorse or promote products derived from

 // this software without specific prior written permission.

 //

 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 //

 // file_id.cc: Return a unique identifier for a file

 //

 // See file_id.h for documentation

 //

 #include "common/linux/file_id.h"

 #include <arpa/inet.h>

 #include <assert.h>

 #include <string.h>

 #include <algorithm>

 #include "common/linux/elfutils.h"

 #include "common/linux/linux_libc_support.h"

 #include "common/linux/memory_mapped_file.h"

 #include "third_party/lss/linux_syscall_support.h"

 namespace google_breakpad {

 #ifndef NT_GNU_BUILD_ID

 #define NT_GNU_BUILD_ID 3

 #endif

 FileID::FileID(const char* path) {

   strncpy(path_, path, sizeof(path_));

 }

 // ELF note name and desc are 32-bits word padded.

 #define NOTE_PADDING(a) ((a + 3) & ~3)

 // These functions are also used inside the crashed process, so be safe

 // and use the syscall/libc wrappers instead of direct syscalls or libc.

 template<typename ElfClass>

 static bool ElfClassBuildIDNoteIdentifier(const void *section, int length,

                                           uint8_t identifier[kMDGUIDSize]) {

   typedef typename ElfClass::Nhdr Nhdr;

   const void* section_end = reinterpret_cast<const char*>(section) + length;

   const Nhdr* note_header = reinterpret_cast<const Nhdr*>(section);

   while (reinterpret_cast<const void *>(note_header) < section_end) {

     if (note_header->n_type == NT_GNU_BUILD_ID)

       break;

     note_header = reinterpret_cast<const Nhdr*>(

                   reinterpret_cast<const char*>(note_header) + sizeof(Nhdr) +

                   NOTE_PADDING(note_header->n_namesz) +

                   NOTE_PADDING(note_header->n_descsz));

   }

   if (reinterpret_cast<const void *>(note_header) >= section_end ||

       note_header->n_descsz == 0) {

     return false;

   }

   const char* build_id = reinterpret_cast<const char*>(note_header) +

     sizeof(Nhdr) + NOTE_PADDING(note_header->n_namesz);

   // Copy as many bits of the build ID as will fit

   // into the GUID space.

   my_memset(identifier, 0, kMDGUIDSize);

   memcpy(identifier, build_id,

          std::min(kMDGUIDSize, (size_t)note_header->n_descsz));

   return true;

 }

 // Attempt to locate a .note.gnu.build-id section in an ELF binary

 // and copy as many bytes of it as will fit into |identifier|.

 static bool FindElfBuildIDNote(const void *elf_mapped_base,

                                uint8_t identifier[kMDGUIDSize]) {

   void* note_section;

   int note_size, elfclass;

   if ((!FindElfSegment(elf_mapped_base, PT_NOTE,

                        (const void**)&note_section, &note_size, &elfclass) ||

       note_size == 0)  &&

       (!FindElfSection(elf_mapped_base, ".note.gnu.build-id", SHT_NOTE,

                        (const void**)&note_section, &note_size, &elfclass) ||

       note_size == 0)) {

     return false;

   }

   if (elfclass == ELFCLASS32) {

     return ElfClassBuildIDNoteIdentifier<ElfClass32>(note_section, note_size,

                                                      identifier);

   } else if (elfclass == ELFCLASS64) {

     return ElfClassBuildIDNoteIdentifier<ElfClass64>(note_section, note_size,

                                                      identifier);

   }

   return false;

 }

 // Attempt to locate the .text section of an ELF binary and generate

 // a simple hash by XORing the first page worth of bytes into |identifier|.

 static bool HashElfTextSection(const void *elf_mapped_base,

                                uint8_t identifier[kMDGUIDSize]) {

   void* text_section;

   int text_size;

   if (!FindElfSection(elf_mapped_base, ".text", SHT_PROGBITS,

                       (const void**)&text_section, &text_size, NULL) ||

       text_size == 0) {

     return false;

   }

   my_memset(identifier, 0, kMDGUIDSize);

   const uint8_t* ptr = reinterpret_cast<const uint8_t*>(text_section);

   const uint8_t* ptr_end = ptr + std::min(text_size, 4096);

   while (ptr < ptr_end) {

     for (unsigned i = 0; i < kMDGUIDSize; i++)

       identifier[i] ^= ptr[i];

     ptr += kMDGUIDSize;

   }

   return true;

 }

 // static

 bool FileID::ElfFileIdentifierFromMappedFile(const void* base,

                                              uint8_t identifier[kMDGUIDSize]) {

   // Look for a build id note first.

   if (FindElfBuildIDNote(base, identifier))

     return true;

   // Fall back on hashing the first page of the text section.

   return HashElfTextSection(base, identifier);

 }

 bool FileID::ElfFileIdentifier(uint8_t identifier[kMDGUIDSize]) {

   MemoryMappedFile mapped_file(path_);

   if (!mapped_file.data())  // Should probably check if size >= ElfW(Ehdr)?

     return false;

   return ElfFileIdentifierFromMappedFile(mapped_file.data(), identifier);

 }

 // static

 void FileID::ConvertIdentifierToString(const uint8_t identifier[kMDGUIDSize],

                                        char* buffer, int buffer_length) {

   uint8_t identifier_swapped[kMDGUIDSize];

   // Endian-ness swap to match dump processor expectation.

   memcpy(identifier_swapped, identifier, kMDGUIDSize);

   uint32_t* data1 = reinterpret_cast<uint32_t*>(identifier_swapped);

   *data1 = htonl(*data1);

   uint16_t* data2 = reinterpret_cast<uint16_t*>(identifier_swapped + 4);

   *data2 = htons(*data2);

   uint16_t* data3 = reinterpret_cast<uint16_t*>(identifier_swapped + 6);

   *data3 = htons(*data3);

   int buffer_idx = 0;

   for (unsigned int idx = 0;

        (buffer_idx < buffer_length) && (idx < kMDGUIDSize);

        ++idx) {

     int hi = (identifier_swapped[idx] >> 4) & 0x0F;

     int lo = (identifier_swapped[idx]) & 0x0F;

     if (idx == 4 || idx == 6 || idx == 8 || idx == 10)

       buffer[buffer_idx++] = '-';

     buffer[buffer_idx++] = (hi >= 10) ? 'A' + hi - 10 : '0' + hi;

     buffer[buffer_idx++] = (lo >= 10) ? 'A' + lo - 10 : '0' + lo;

   }

   // NULL terminate

   buffer[(buffer_idx < buffer_length) ? buffer_idx : buffer_idx - 1] = 0;

 }

 }  // namespace google_breakpad