michael@0: // Copyright (c) 2006, Google Inc.
michael@0: // All rights reserved.
michael@0: //
michael@0: // Redistribution and use in source and binary forms, with or without
michael@0: // modification, are permitted provided that the following conditions are
michael@0: // met:
michael@0: //
michael@0: //     * Redistributions of source code must retain the above copyright
michael@0: // notice, this list of conditions and the following disclaimer.
michael@0: //     * Redistributions in binary form must reproduce the above
michael@0: // copyright notice, this list of conditions and the following disclaimer
michael@0: // in the documentation and/or other materials provided with the
michael@0: // distribution.
michael@0: //     * Neither the name of Google Inc. nor the names of its
michael@0: // contributors may be used to endorse or promote products derived from
michael@0: // this software without specific prior written permission.
michael@0: //
michael@0: // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
michael@0: // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
michael@0: // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
michael@0: // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
michael@0: // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
michael@0: // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
michael@0: // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
michael@0: // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
michael@0: // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
michael@0: // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
michael@0: // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
michael@0: //
michael@0: // file_id.cc: Return a unique identifier for a file
michael@0: //
michael@0: // See file_id.h for documentation
michael@0: //
michael@0: 
michael@0: #include "common/linux/file_id.h"
michael@0: 
michael@0: #include <arpa/inet.h>
michael@0: #include <assert.h>
michael@0: #include <string.h>
michael@0: 
michael@0: #include <algorithm>
michael@0: 
michael@0: #include "common/linux/elfutils.h"
michael@0: #include "common/linux/linux_libc_support.h"
michael@0: #include "common/linux/memory_mapped_file.h"
michael@0: #include "third_party/lss/linux_syscall_support.h"
michael@0: 
michael@0: namespace google_breakpad {
michael@0: 
michael@0: #ifndef NT_GNU_BUILD_ID
michael@0: #define NT_GNU_BUILD_ID 3
michael@0: #endif
michael@0: 
michael@0: FileID::FileID(const char* path) {
michael@0:   strncpy(path_, path, sizeof(path_));
michael@0: }
michael@0: 
michael@0: // ELF note name and desc are 32-bits word padded.
michael@0: #define NOTE_PADDING(a) ((a + 3) & ~3)
michael@0: 
michael@0: // These functions are also used inside the crashed process, so be safe
michael@0: // and use the syscall/libc wrappers instead of direct syscalls or libc.
michael@0: 
michael@0: template<typename ElfClass>
michael@0: static bool ElfClassBuildIDNoteIdentifier(const void *section, int length,
michael@0:                                           uint8_t identifier[kMDGUIDSize]) {
michael@0:   typedef typename ElfClass::Nhdr Nhdr;
michael@0: 
michael@0:   const void* section_end = reinterpret_cast<const char*>(section) + length;
michael@0:   const Nhdr* note_header = reinterpret_cast<const Nhdr*>(section);
michael@0:   while (reinterpret_cast<const void *>(note_header) < section_end) {
michael@0:     if (note_header->n_type == NT_GNU_BUILD_ID)
michael@0:       break;
michael@0:     note_header = reinterpret_cast<const Nhdr*>(
michael@0:                   reinterpret_cast<const char*>(note_header) + sizeof(Nhdr) +
michael@0:                   NOTE_PADDING(note_header->n_namesz) +
michael@0:                   NOTE_PADDING(note_header->n_descsz));
michael@0:   }
michael@0:   if (reinterpret_cast<const void *>(note_header) >= section_end ||
michael@0:       note_header->n_descsz == 0) {
michael@0:     return false;
michael@0:   }
michael@0: 
michael@0:   const char* build_id = reinterpret_cast<const char*>(note_header) +
michael@0:     sizeof(Nhdr) + NOTE_PADDING(note_header->n_namesz);
michael@0:   // Copy as many bits of the build ID as will fit
michael@0:   // into the GUID space.
michael@0:   my_memset(identifier, 0, kMDGUIDSize);
michael@0:   memcpy(identifier, build_id,
michael@0:          std::min(kMDGUIDSize, (size_t)note_header->n_descsz));
michael@0: 
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: // Attempt to locate a .note.gnu.build-id section in an ELF binary
michael@0: // and copy as many bytes of it as will fit into |identifier|.
michael@0: static bool FindElfBuildIDNote(const void *elf_mapped_base,
michael@0:                                uint8_t identifier[kMDGUIDSize]) {
michael@0:   void* note_section;
michael@0:   int note_size, elfclass;
michael@0:   if ((!FindElfSegment(elf_mapped_base, PT_NOTE,
michael@0:                        (const void**)&note_section, &note_size, &elfclass) ||
michael@0:       note_size == 0)  &&
michael@0:       (!FindElfSection(elf_mapped_base, ".note.gnu.build-id", SHT_NOTE,
michael@0:                        (const void**)&note_section, &note_size, &elfclass) ||
michael@0:       note_size == 0)) {
michael@0:     return false;
michael@0:   }
michael@0: 
michael@0:   if (elfclass == ELFCLASS32) {
michael@0:     return ElfClassBuildIDNoteIdentifier<ElfClass32>(note_section, note_size,
michael@0:                                                      identifier);
michael@0:   } else if (elfclass == ELFCLASS64) {
michael@0:     return ElfClassBuildIDNoteIdentifier<ElfClass64>(note_section, note_size,
michael@0:                                                      identifier);
michael@0:   }
michael@0: 
michael@0:   return false;
michael@0: }
michael@0: 
michael@0: // Attempt to locate the .text section of an ELF binary and generate
michael@0: // a simple hash by XORing the first page worth of bytes into |identifier|.
michael@0: static bool HashElfTextSection(const void *elf_mapped_base,
michael@0:                                uint8_t identifier[kMDGUIDSize]) {
michael@0:   void* text_section;
michael@0:   int text_size;
michael@0:   if (!FindElfSection(elf_mapped_base, ".text", SHT_PROGBITS,
michael@0:                       (const void**)&text_section, &text_size, NULL) ||
michael@0:       text_size == 0) {
michael@0:     return false;
michael@0:   }
michael@0: 
michael@0:   my_memset(identifier, 0, kMDGUIDSize);
michael@0:   const uint8_t* ptr = reinterpret_cast<const uint8_t*>(text_section);
michael@0:   const uint8_t* ptr_end = ptr + std::min(text_size, 4096);
michael@0:   while (ptr < ptr_end) {
michael@0:     for (unsigned i = 0; i < kMDGUIDSize; i++)
michael@0:       identifier[i] ^= ptr[i];
michael@0:     ptr += kMDGUIDSize;
michael@0:   }
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: // static
michael@0: bool FileID::ElfFileIdentifierFromMappedFile(const void* base,
michael@0:                                              uint8_t identifier[kMDGUIDSize]) {
michael@0:   // Look for a build id note first.
michael@0:   if (FindElfBuildIDNote(base, identifier))
michael@0:     return true;
michael@0: 
michael@0:   // Fall back on hashing the first page of the text section.
michael@0:   return HashElfTextSection(base, identifier);
michael@0: }
michael@0: 
michael@0: bool FileID::ElfFileIdentifier(uint8_t identifier[kMDGUIDSize]) {
michael@0:   MemoryMappedFile mapped_file(path_);
michael@0:   if (!mapped_file.data())  // Should probably check if size >= ElfW(Ehdr)?
michael@0:     return false;
michael@0: 
michael@0:   return ElfFileIdentifierFromMappedFile(mapped_file.data(), identifier);
michael@0: }
michael@0: 
michael@0: // static
michael@0: void FileID::ConvertIdentifierToString(const uint8_t identifier[kMDGUIDSize],
michael@0:                                        char* buffer, int buffer_length) {
michael@0:   uint8_t identifier_swapped[kMDGUIDSize];
michael@0: 
michael@0:   // Endian-ness swap to match dump processor expectation.
michael@0:   memcpy(identifier_swapped, identifier, kMDGUIDSize);
michael@0:   uint32_t* data1 = reinterpret_cast<uint32_t*>(identifier_swapped);
michael@0:   *data1 = htonl(*data1);
michael@0:   uint16_t* data2 = reinterpret_cast<uint16_t*>(identifier_swapped + 4);
michael@0:   *data2 = htons(*data2);
michael@0:   uint16_t* data3 = reinterpret_cast<uint16_t*>(identifier_swapped + 6);
michael@0:   *data3 = htons(*data3);
michael@0: 
michael@0:   int buffer_idx = 0;
michael@0:   for (unsigned int idx = 0;
michael@0:        (buffer_idx < buffer_length) && (idx < kMDGUIDSize);
michael@0:        ++idx) {
michael@0:     int hi = (identifier_swapped[idx] >> 4) & 0x0F;
michael@0:     int lo = (identifier_swapped[idx]) & 0x0F;
michael@0: 
michael@0:     if (idx == 4 || idx == 6 || idx == 8 || idx == 10)
michael@0:       buffer[buffer_idx++] = '-';
michael@0: 
michael@0:     buffer[buffer_idx++] = (hi >= 10) ? 'A' + hi - 10 : '0' + hi;
michael@0:     buffer[buffer_idx++] = (lo >= 10) ? 'A' + lo - 10 : '0' + lo;
michael@0:   }
michael@0: 
michael@0:   // NULL terminate
michael@0:   buffer[(buffer_idx < buffer_length) ? buffer_idx : buffer_idx - 1] = 0;
michael@0: }
michael@0: 
michael@0: }  // namespace google_breakpad