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//===-- NativeProcessELF.cpp ----------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "NativeProcessELF.h"
#include "lldb/Utility/DataExtractor.h"
#include <optional>
namespace lldb_private {
std::optional<uint64_t>
NativeProcessELF::GetAuxValue(enum AuxVector::EntryType type) {
if (m_aux_vector == nullptr) {
auto buffer_or_error = GetAuxvData();
if (!buffer_or_error)
return std::nullopt;
DataExtractor auxv_data(buffer_or_error.get()->getBufferStart(),
buffer_or_error.get()->getBufferSize(),
GetByteOrder(), GetAddressByteSize());
m_aux_vector = std::make_unique<AuxVector>(auxv_data);
}
return m_aux_vector->GetAuxValue(type);
}
lldb::addr_t NativeProcessELF::GetSharedLibraryInfoAddress() {
if (!m_shared_library_info_addr) {
if (GetAddressByteSize() == 8)
m_shared_library_info_addr =
GetELFImageInfoAddress<llvm::ELF::Elf64_Ehdr, llvm::ELF::Elf64_Phdr,
llvm::ELF::Elf64_Dyn>();
else
m_shared_library_info_addr =
GetELFImageInfoAddress<llvm::ELF::Elf32_Ehdr, llvm::ELF::Elf32_Phdr,
llvm::ELF::Elf32_Dyn>();
}
return *m_shared_library_info_addr;
}
template <typename ELF_EHDR, typename ELF_PHDR, typename ELF_DYN>
lldb::addr_t NativeProcessELF::GetELFImageInfoAddress() {
std::optional<uint64_t> maybe_phdr_addr =
GetAuxValue(AuxVector::AUXV_AT_PHDR);
std::optional<uint64_t> maybe_phdr_entry_size =
GetAuxValue(AuxVector::AUXV_AT_PHENT);
std::optional<uint64_t> maybe_phdr_num_entries =
GetAuxValue(AuxVector::AUXV_AT_PHNUM);
if (!maybe_phdr_addr || !maybe_phdr_entry_size || !maybe_phdr_num_entries)
return LLDB_INVALID_ADDRESS;
lldb::addr_t phdr_addr = *maybe_phdr_addr;
size_t phdr_entry_size = *maybe_phdr_entry_size;
size_t phdr_num_entries = *maybe_phdr_num_entries;
// Find the PT_DYNAMIC segment (.dynamic section) in the program header and
// what the load bias by calculating the difference of the program header
// load address and its virtual address.
lldb::offset_t load_bias;
bool found_load_bias = false;
lldb::addr_t dynamic_section_addr = 0;
uint64_t dynamic_section_size = 0;
bool found_dynamic_section = false;
ELF_PHDR phdr_entry;
for (size_t i = 0; i < phdr_num_entries; i++) {
size_t bytes_read;
auto error = ReadMemory(phdr_addr + i * phdr_entry_size, &phdr_entry,
sizeof(phdr_entry), bytes_read);
if (!error.Success())
return LLDB_INVALID_ADDRESS;
if (phdr_entry.p_type == llvm::ELF::PT_PHDR) {
load_bias = phdr_addr - phdr_entry.p_vaddr;
found_load_bias = true;
}
if (phdr_entry.p_type == llvm::ELF::PT_DYNAMIC) {
dynamic_section_addr = phdr_entry.p_vaddr;
dynamic_section_size = phdr_entry.p_memsz;
found_dynamic_section = true;
}
}
if (!found_load_bias || !found_dynamic_section)
return LLDB_INVALID_ADDRESS;
// Find the DT_DEBUG entry in the .dynamic section
dynamic_section_addr += load_bias;
ELF_DYN dynamic_entry;
size_t dynamic_num_entries = dynamic_section_size / sizeof(dynamic_entry);
for (size_t i = 0; i < dynamic_num_entries; i++) {
size_t bytes_read;
auto error = ReadMemory(dynamic_section_addr + i * sizeof(dynamic_entry),
&dynamic_entry, sizeof(dynamic_entry), bytes_read);
if (!error.Success())
return LLDB_INVALID_ADDRESS;
// Return the &DT_DEBUG->d_ptr which points to r_debug which contains the
// link_map.
if (dynamic_entry.d_tag == llvm::ELF::DT_DEBUG) {
return dynamic_section_addr + i * sizeof(dynamic_entry) +
sizeof(dynamic_entry.d_tag);
}
}
return LLDB_INVALID_ADDRESS;
}
template lldb::addr_t NativeProcessELF::GetELFImageInfoAddress<
llvm::ELF::Elf32_Ehdr, llvm::ELF::Elf32_Phdr, llvm::ELF::Elf32_Dyn>();
template lldb::addr_t NativeProcessELF::GetELFImageInfoAddress<
llvm::ELF::Elf64_Ehdr, llvm::ELF::Elf64_Phdr, llvm::ELF::Elf64_Dyn>();
template <typename T>
llvm::Expected<SVR4LibraryInfo>
NativeProcessELF::ReadSVR4LibraryInfo(lldb::addr_t link_map_addr) {
ELFLinkMap<T> link_map;
size_t bytes_read;
auto error =
ReadMemory(link_map_addr, &link_map, sizeof(link_map), bytes_read);
if (!error.Success())
return error.ToError();
char name_buffer[PATH_MAX];
llvm::Expected<llvm::StringRef> string_or_error = ReadCStringFromMemory(
link_map.l_name, &name_buffer[0], sizeof(name_buffer), bytes_read);
if (!string_or_error)
return string_or_error.takeError();
SVR4LibraryInfo info;
info.name = string_or_error->str();
info.link_map = link_map_addr;
info.base_addr = link_map.l_addr;
info.ld_addr = link_map.l_ld;
info.next = link_map.l_next;
return info;
}
llvm::Expected<std::vector<SVR4LibraryInfo>>
NativeProcessELF::GetLoadedSVR4Libraries() {
// Address of DT_DEBUG.d_ptr which points to r_debug
lldb::addr_t info_address = GetSharedLibraryInfoAddress();
if (info_address == LLDB_INVALID_ADDRESS)
return llvm::createStringError(llvm::inconvertibleErrorCode(),
"Invalid shared library info address");
// Address of r_debug
lldb::addr_t address = 0;
size_t bytes_read;
auto status =
ReadMemory(info_address, &address, GetAddressByteSize(), bytes_read);
if (!status.Success())
return status.ToError();
if (address == 0)
return llvm::createStringError(llvm::inconvertibleErrorCode(),
"Invalid r_debug address");
// Read r_debug.r_map
lldb::addr_t link_map = 0;
status = ReadMemory(address + GetAddressByteSize(), &link_map,
GetAddressByteSize(), bytes_read);
if (!status.Success())
return status.ToError();
if (link_map == 0)
return llvm::createStringError(llvm::inconvertibleErrorCode(),
"Invalid link_map address");
std::vector<SVR4LibraryInfo> library_list;
while (link_map) {
llvm::Expected<SVR4LibraryInfo> info =
GetAddressByteSize() == 8 ? ReadSVR4LibraryInfo<uint64_t>(link_map)
: ReadSVR4LibraryInfo<uint32_t>(link_map);
if (!info)
return info.takeError();
if (!info->name.empty() && info->base_addr != 0)
library_list.push_back(*info);
link_map = info->next;
}
return library_list;
}
void NativeProcessELF::NotifyDidExec() {
NativeProcessProtocol::NotifyDidExec();
m_shared_library_info_addr.reset();
}
} // namespace lldb_private
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