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#if defined(__ELF__) && !defined(OS_FREEBSD)
#include <Common/Elf.h>
#include <Common/Exception.h>
#include <base/unaligned.h>
#include <cstring>
namespace DB
{
namespace ErrorCodes
{
extern const int CANNOT_PARSE_ELF;
}
Elf::Elf(const std::string & path)
: in(path, 0)
{
/// Check if it's an elf.
elf_size = in.buffer().size();
if (elf_size < sizeof(ElfEhdr))
throw Exception(ErrorCodes::CANNOT_PARSE_ELF, "The size of supposedly ELF file '{}' is too small", path);
mapped = in.buffer().begin();
header = reinterpret_cast<const ElfEhdr *>(mapped);
if (memcmp(header->e_ident, "\x7F""ELF", 4) != 0)
throw Exception(ErrorCodes::CANNOT_PARSE_ELF, "The file '{}' is not ELF according to magic", path);
/// Get section header.
ElfOff section_header_offset = header->e_shoff;
uint16_t section_header_num_entries = header->e_shnum;
if (!section_header_offset
|| !section_header_num_entries
|| section_header_offset + section_header_num_entries * sizeof(ElfShdr) > elf_size)
throw Exception(ErrorCodes::CANNOT_PARSE_ELF, "The ELF '{}' is truncated (section header points after end of file)", path);
section_headers = reinterpret_cast<const ElfShdr *>(mapped + section_header_offset);
/// The string table with section names.
auto section_names_strtab = findSection([&](const Section & section, size_t idx)
{
return section.header.sh_type == SHT_STRTAB && header->e_shstrndx == idx;
});
if (!section_names_strtab)
throw Exception(ErrorCodes::CANNOT_PARSE_ELF, "The ELF '{}' doesn't have string table with section names", path);
ElfOff section_names_offset = section_names_strtab->header.sh_offset;
if (section_names_offset >= elf_size)
throw Exception(ErrorCodes::CANNOT_PARSE_ELF, "The ELF '{}' is truncated (section names string table points after end of file)", path);
section_names = reinterpret_cast<const char *>(mapped + section_names_offset);
/// Get program headers
ElfOff program_header_offset = header->e_phoff;
uint16_t program_header_num_entries = header->e_phnum;
if (!program_header_offset
|| !program_header_num_entries
|| program_header_offset + program_header_num_entries * sizeof(ElfPhdr) > elf_size)
throw Exception(ErrorCodes::CANNOT_PARSE_ELF, "The ELF '{}' is truncated (program header points after end of file)", path);
program_headers = reinterpret_cast<const ElfPhdr *>(mapped + program_header_offset);
}
Elf::Section::Section(const ElfShdr & header_, const Elf & elf_)
: header(header_), elf(elf_)
{
}
bool Elf::iterateSections(std::function<bool(const Section & section, size_t idx)> && pred) const
{
for (size_t idx = 0; idx < header->e_shnum; ++idx)
{
Section section(section_headers[idx], *this);
/// Sections spans after end of file.
if (section.header.sh_offset + section.header.sh_size > elf_size)
continue;
if (pred(section, idx))
return true;
}
return false;
}
std::optional<Elf::Section> Elf::findSection(std::function<bool(const Section & section, size_t idx)> && pred) const
{
std::optional<Elf::Section> result;
iterateSections([&](const Section & section, size_t idx)
{
if (pred(section, idx))
{
result.emplace(section);
return true;
}
return false;
});
return result;
}
std::optional<Elf::Section> Elf::findSectionByName(const char * name) const
{
return findSection([&](const Section & section, size_t) { return 0 == strcmp(name, section.name()); });
}
String Elf::getBuildID() const
{
/// Section headers are the first choice for a debuginfo file
if (String build_id; iterateSections([&build_id](const Section & section, size_t)
{
if (section.header.sh_type == SHT_NOTE)
{
build_id = Elf::getBuildID(section.begin(), section.size());
if (!build_id.empty())
{
return true;
}
}
return false;
}))
{
return build_id;
}
/// fallback to PHDR
for (size_t idx = 0; idx < header->e_phnum; ++idx)
{
const ElfPhdr & phdr = program_headers[idx];
if (phdr.p_type == PT_NOTE)
return getBuildID(mapped + phdr.p_offset, phdr.p_filesz);
}
return {};
}
#if defined(OS_SUNOS)
String Elf::getBuildID(const char * nhdr_pos, size_t size)
{
return {};
}
#else
String Elf::getBuildID(const char * nhdr_pos, size_t size)
{
const char * nhdr_end = nhdr_pos + size;
while (nhdr_pos < nhdr_end)
{
ElfNhdr nhdr = unalignedLoad<ElfNhdr>(nhdr_pos);
nhdr_pos += sizeof(ElfNhdr) + nhdr.n_namesz;
if (nhdr.n_type == NT_GNU_BUILD_ID)
{
const char * build_id = nhdr_pos;
return {build_id, nhdr.n_descsz};
}
nhdr_pos += nhdr.n_descsz;
}
return {};
}
#endif // OS_SUNOS
String Elf::getStoredBinaryHash() const
{
if (auto section = findSectionByName(".clickhouse.hash"))
return {section->begin(), section->end()};
else
return {};
}
const char * Elf::Section::name() const
{
if (!elf.section_names)
throw Exception(ErrorCodes::CANNOT_PARSE_ELF, "Section names are not initialized");
/// TODO buffer overflow is possible, we may need to check strlen.
return elf.section_names + header.sh_name;
}
const char * Elf::Section::begin() const
{
return elf.mapped + header.sh_offset;
}
const char * Elf::Section::end() const
{
return begin() + size();
}
size_t Elf::Section::size() const
{
return header.sh_size;
}
}
#endif
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