contrib/llvm/tools/lldb/source/Plugins/Process/POSIX/NativeProcessELF.cpp

   1 //===-- NativeProcessELF.cpp ---------------------------------- -*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "NativeProcessELF.h"
  10
  11 #include "lldb/Utility/DataExtractor.h"
  12
  13 namespace lldb_private {
  14
  15 llvm::Optional<uint64_t>
  16 NativeProcessELF::GetAuxValue(enum AuxVector::EntryType type) {
  17   if (m_aux_vector == nullptr) {
  18     auto buffer_or_error = GetAuxvData();
  19     if (!buffer_or_error)
  20       return llvm::None;
  21     DataExtractor auxv_data(buffer_or_error.get()->getBufferStart(),
  22                             buffer_or_error.get()->getBufferSize(),
  23                             GetByteOrder(), GetAddressByteSize());
  24     m_aux_vector = llvm::make_unique<AuxVector>(auxv_data);
  25   }
  26
  27   return m_aux_vector->GetAuxValue(type);
  28 }
  29
  30 lldb::addr_t NativeProcessELF::GetSharedLibraryInfoAddress() {
  31   if (!m_shared_library_info_addr.hasValue()) {
  32     if (GetAddressByteSize() == 8)
  33       m_shared_library_info_addr =
  34           GetELFImageInfoAddress<llvm::ELF::Elf64_Ehdr, llvm::ELF::Elf64_Phdr,
  35                                  llvm::ELF::Elf64_Dyn>();
  36     else
  37       m_shared_library_info_addr =
  38           GetELFImageInfoAddress<llvm::ELF::Elf32_Ehdr, llvm::ELF::Elf32_Phdr,
  39                                  llvm::ELF::Elf32_Dyn>();
  40   }
  41
  42   return m_shared_library_info_addr.getValue();
  43 }
  44
  45 template <typename ELF_EHDR, typename ELF_PHDR, typename ELF_DYN>
  46 lldb::addr_t NativeProcessELF::GetELFImageInfoAddress() {
  47   llvm::Optional<uint64_t> maybe_phdr_addr =
  48       GetAuxValue(AuxVector::AUXV_AT_PHDR);
  49   llvm::Optional<uint64_t> maybe_phdr_entry_size =
  50       GetAuxValue(AuxVector::AUXV_AT_PHENT);
  51   llvm::Optional<uint64_t> maybe_phdr_num_entries =
  52       GetAuxValue(AuxVector::AUXV_AT_PHNUM);
  53   if (!maybe_phdr_addr || !maybe_phdr_entry_size || !maybe_phdr_num_entries)
  54     return LLDB_INVALID_ADDRESS;
  55   lldb::addr_t phdr_addr = *maybe_phdr_addr;
  56   size_t phdr_entry_size = *maybe_phdr_entry_size;
  57   size_t phdr_num_entries = *maybe_phdr_num_entries;
  58
  59   // Find the PT_DYNAMIC segment (.dynamic section) in the program header and
  60   // what the load bias by calculating the difference of the program header
  61   // load address and its virtual address.
  62   lldb::offset_t load_bias;
  63   bool found_load_bias = false;
  64   lldb::addr_t dynamic_section_addr = 0;
  65   uint64_t dynamic_section_size = 0;
  66   bool found_dynamic_section = false;
  67   ELF_PHDR phdr_entry;
  68   for (size_t i = 0; i < phdr_num_entries; i++) {
  69     size_t bytes_read;
  70     auto error = ReadMemory(phdr_addr + i * phdr_entry_size, &phdr_entry,
  71                             sizeof(phdr_entry), bytes_read);
  72     if (!error.Success())
  73       return LLDB_INVALID_ADDRESS;
  74     if (phdr_entry.p_type == llvm::ELF::PT_PHDR) {
  75       load_bias = phdr_addr - phdr_entry.p_vaddr;
  76       found_load_bias = true;
  77     }
  78
  79     if (phdr_entry.p_type == llvm::ELF::PT_DYNAMIC) {
  80       dynamic_section_addr = phdr_entry.p_vaddr;
  81       dynamic_section_size = phdr_entry.p_memsz;
  82       found_dynamic_section = true;
  83     }
  84   }
  85
  86   if (!found_load_bias || !found_dynamic_section)
  87     return LLDB_INVALID_ADDRESS;
  88
  89   // Find the DT_DEBUG entry in the .dynamic section
  90   dynamic_section_addr += load_bias;
  91   ELF_DYN dynamic_entry;
  92   size_t dynamic_num_entries = dynamic_section_size / sizeof(dynamic_entry);
  93   for (size_t i = 0; i < dynamic_num_entries; i++) {
  94     size_t bytes_read;
  95     auto error = ReadMemory(dynamic_section_addr + i * sizeof(dynamic_entry),
  96                             &dynamic_entry, sizeof(dynamic_entry), bytes_read);
  97     if (!error.Success())
  98       return LLDB_INVALID_ADDRESS;
  99     // Return the &DT_DEBUG->d_ptr which points to r_debug which contains the
 100     // link_map.
 101     if (dynamic_entry.d_tag == llvm::ELF::DT_DEBUG) {
 102       return dynamic_section_addr + i * sizeof(dynamic_entry) +
 103              sizeof(dynamic_entry.d_tag);
 104     }
 105   }
 106
 107   return LLDB_INVALID_ADDRESS;
 108 }
 109
 110 } // namespace lldb_private