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sold.cc
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sold.cc
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// Copyright (C) 2021 The sold authors
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
#include "sold.h"
#include <algorithm>
#include <list>
#include <queue>
#include <set>
Sold::Sold(const std::string& elf_filename, const std::vector<std::string>& exclude_sos, const std::vector<std::string>& exclude_finis,
const std::vector<std::string> custome_library_path, bool emit_section_header)
: exclude_sos_(exclude_sos),
exclude_finis_(exclude_finis),
custome_library_path_(custome_library_path),
emit_section_header_(emit_section_header) {
main_binary_ = ReadELF(elf_filename);
is_executable_ = main_binary_->FindPhdr(PT_INTERP);
machine_type = main_binary_->ehdr()->e_machine;
memprotect_builder_.SetMachineType(machine_type);
// Register (filename, soname) of main_binary_
if (main_binary_->name() != "" && main_binary_->soname() != "") {
filename_to_soname_[main_binary_->name()] = main_binary_->soname();
soname_to_filename_[main_binary_->soname()] = main_binary_->name();
LOG(INFO) << SOLD_LOG_KEY(main_binary_->name()) << SOLD_LOG_KEY(main_binary_->soname());
} else {
// soname of main_binary_ can be empty when main_binary_ is executable file.
LOG(WARNING) << "Empty filename or soname: " << SOLD_LOG_KEY(main_binary_->name()) << SOLD_LOG_KEY(main_binary_->soname());
}
InitLdLibraryPaths();
ResolveLibraryPaths(main_binary_.get());
version_.SetSonameToFilename(soname_to_filename_);
}
void Sold::Link(const std::string& out_filename) {
DecideMemOffset();
CollectTLS();
CollectArrays();
CollectSymbols();
CopyPublicSymbols();
Relocate();
syms_.Build(strtab_, version_);
syms_.MergePublicSymbols(strtab_, version_);
// BuildEhdr();
if (is_executable_) {
BuildInterp();
}
BuildArrays();
BuildDynamic();
BuildMprotect();
strtab_.Freeze();
BuildLoads();
BuildEHFrameHeader();
shdr_.RegisterShdr(GnuHashOffset(), GnuHashSize(), ShdrBuilder::ShdrType::GnuHash);
shdr_.RegisterShdr(SymtabOffset(), SymtabSize(), ShdrBuilder::ShdrType::Dynsym, sizeof(Elf_Sym));
if (version_.NumVerneed() > 0) {
shdr_.RegisterShdr(VersymOffset(), VersymSize(), ShdrBuilder::ShdrType::GnuVersion, sizeof(Elf_Versym));
shdr_.RegisterShdr(VerneedOffset(), VerneedSize(), ShdrBuilder::ShdrType::GnuVersionR, 0, version_.NumVerneed());
}
shdr_.RegisterShdr(RelOffset(), RelSize(), ShdrBuilder::ShdrType::RelaDyn, sizeof(Elf_Rel));
shdr_.RegisterShdr(InitArrayOffset(), InitArraySize(), ShdrBuilder::ShdrType::InitArray);
shdr_.RegisterShdr(FiniArrayOffset(), FiniArraySize(), ShdrBuilder::ShdrType::FiniArray);
shdr_.RegisterShdr(StrtabOffset(), StrtabSize(), ShdrBuilder::ShdrType::Dynstr);
shdr_.RegisterShdr(DynamicOffset(), DynamicSize(), ShdrBuilder::ShdrType::Dynamic, sizeof(Elf_Dyn));
shdr_.RegisterShdr(ShstrtabOffset(), ShstrtabSize(), ShdrBuilder::ShdrType::Shstrtab);
// TODO(akawashiro) .text and .tls
shdr_.Freeze();
// We must call BuildEhdr at the last because of e_shoff
BuildEhdr();
Emit(out_filename);
CHECK(chmod(out_filename.c_str(), 0755) == 0);
}
void Sold::Emit(const std::string& out_filename) {
FILE* fp = fopen(out_filename.c_str(), "wb");
CHECK(fp);
Write(fp, ehdr_);
EmitPhdrs(fp);
EmitArrays(fp);
EmitGnuHash(fp);
EmitSymtab(fp);
EmitVersym(fp);
EmitVerneed(fp);
EmitRel(fp);
EmitStrtab(fp);
EmitDynamic(fp);
EmitShstrtab(fp);
EmitAlign(fp);
EmitCode(fp);
EmitTLS(fp);
EmitEHFrame(fp);
EmitMemprotect(fp);
if (emit_section_header_) EmitShdr(fp);
fclose(fp);
}
// You must call this function after building all stuffs
// because ShdrOffset() cannot be fixed before it.
void Sold::BuildEhdr() {
ehdr_ = *main_binary_->ehdr();
ehdr_.e_entry += offsets_[main_binary_.get()];
ehdr_.e_shoff = ShdrOffset();
ehdr_.e_shnum = shdr_.CountShdrs();
ehdr_.e_shstrndx = shdr_.Shstrndx();
ehdr_.e_phnum = CountPhdrs();
}
void Sold::BuildLoads() {
uintptr_t file_offset = CodeOffset();
CHECK(file_offset < offsets_[main_binary_.get()]);
for (ELFBinary* bin : link_binaries_) {
uintptr_t offset = offsets_[bin];
for (Elf_Phdr* phdr : bin->loads()) {
Load load;
load.bin = bin;
load.orig = phdr;
load.emit = *phdr;
file_offset += phdr->p_vaddr & 0xfff;
load.emit.p_offset = file_offset;
file_offset = AlignNext(file_offset + phdr->p_filesz);
load.emit.p_vaddr += offset;
load.emit.p_paddr += offset;
// TODO(hamaji): Add PF_W only for GOT.
load.emit.p_flags |= PF_W;
// TODO(hamaji): Check if this is really safe.
if (load.emit.p_align > 0x1000) {
load.emit.p_align = 0x1000;
}
loads_.push_back(load);
}
}
tls_file_offset_ = file_offset;
file_offset = AlignNext(file_offset + TLSFileSize());
ehframe_file_offset_ = file_offset;
file_offset = AlignNext(file_offset + EHFrameSize());
mprotect_file_offset_ = file_offset;
for (const Load& load : loads_) {
LOG(INFO) << "PT_LOAD mapping: name=" << load.bin->name() << " vaddr=" << load.emit.p_vaddr << " memsz=" << load.emit.p_memsz
<< " offset=" << load.emit.p_offset << " filesz=" << load.emit.p_filesz << " orig_vaddr=" << load.orig->p_vaddr
<< " orig_offset=" << load.orig->p_offset;
}
}
void Sold::BuildArrays() {
std::vector<uintptr_t> array = init_array_;
std::copy(fini_array_.begin(), fini_array_.end(), std::back_inserter(array));
// We must emit a relocation because the first element of init_array_ is
// mprotect_offset_.
CHECK_GE(init_array_.size(), 1);
Elf_Rel mprotect_rel;
if (machine_type == EM_X86_64) {
mprotect_rel.r_info = ELF_R_INFO(0, R_X86_64_RELATIVE);
} else if (machine_type == EM_AARCH64) {
mprotect_rel.r_info = ELF_R_INFO(0, R_AARCH64_RELATIVE);
} else {
CHECK(false);
}
mprotect_rel.r_offset = InitArrayOffset();
mprotect_rel.r_addend = array[0];
rels_.emplace_back(mprotect_rel);
}
void Sold::BuildDynamic() {
std::set<ELFBinary*> linked(link_binaries_.begin(), link_binaries_.end());
std::set<std::string> neededs;
for (const auto& p : libraries_) {
ELFBinary* bin = p.second.get();
if (!linked.count(bin)) {
neededs.insert(bin->name());
}
}
for (const std::string& needed : neededs) {
MakeDyn(DT_NEEDED, AddStr(needed));
}
if (!main_binary_->soname().empty()) {
MakeDyn(DT_SONAME, AddStr(main_binary_->soname()));
}
if (!main_binary_->rpath().empty()) {
MakeDyn(DT_RPATH, AddStr(main_binary_->rpath()));
}
if (!main_binary_->runpath().empty()) {
MakeDyn(DT_RUNPATH, AddStr(main_binary_->runpath()));
}
if (uintptr_t ptr = main_binary_->init()) {
MakeDyn(DT_INIT, ptr + offsets_[main_binary_.get()]);
}
if (uintptr_t ptr = main_binary_->fini()) {
MakeDyn(DT_FINI, ptr + offsets_[main_binary_.get()]);
}
MakeDyn(DT_INIT_ARRAY, InitArrayOffset());
MakeDyn(DT_INIT_ARRAYSZ, init_array_.size() * sizeof(uintptr_t));
MakeDyn(DT_FINI_ARRAY, FiniArrayOffset());
MakeDyn(DT_FINI_ARRAYSZ, fini_array_.size() * sizeof(uintptr_t));
MakeDyn(DT_GNU_HASH, GnuHashOffset());
MakeDyn(DT_STRTAB, StrtabOffset());
MakeDyn(DT_STRSZ, strtab_.size());
MakeDyn(DT_SYMTAB, SymtabOffset());
MakeDyn(DT_SYMENT, sizeof(Elf_Sym));
if (version_.NumVerneed() > 0) {
MakeDyn(DT_VERSYM, VersymOffset());
MakeDyn(DT_VERNEEDNUM, version_.NumVerneed());
MakeDyn(DT_VERNEED, VerneedOffset());
}
MakeDyn(DT_RELA, RelOffset());
MakeDyn(DT_RELAENT, sizeof(Elf_Rel));
MakeDyn(DT_RELASZ, rels_.size() * sizeof(Elf_Rel));
MakeDyn(DT_NULL, 0);
}
void Sold::EmitPhdrs(FILE* fp) {
std::vector<Elf_Phdr> phdrs;
CHECK(main_binary_->phdrs().size() > 2);
if (is_executable_) {
phdrs.push_back(main_binary_->GetPhdr(PT_PHDR));
phdrs.push_back(main_binary_->GetPhdr(PT_INTERP));
phdrs[1].p_offset = phdrs[1].p_vaddr = phdrs[1].p_paddr = StrtabOffset() + interp_offset_;
}
size_t dyn_start = DynamicOffset();
size_t dyn_size = sizeof(Elf_Dyn) * dynamic_.size();
size_t seg_start = AlignNext(dyn_start + dyn_size);
{
Elf_Phdr phdr = main_binary_->GetPhdr(PT_LOAD);
phdr.p_offset = 0;
phdr.p_flags = PF_R | PF_W;
phdr.p_vaddr = 0;
phdr.p_paddr = 0;
phdr.p_filesz = seg_start;
phdr.p_memsz = seg_start;
phdrs.push_back(phdr);
}
{
Elf_Phdr phdr = main_binary_->GetPhdr(PT_DYNAMIC);
phdr.p_offset = dyn_start;
phdr.p_flags = PF_R | PF_W;
phdr.p_vaddr = dyn_start;
phdr.p_paddr = dyn_start;
phdr.p_filesz = dyn_size;
phdr.p_memsz = dyn_size;
phdrs.push_back(phdr);
}
for (const Load& load : loads_) {
phdrs.push_back(load.emit);
}
if (tls_.memsz) {
Elf_Phdr phdr;
phdr.p_offset = tls_file_offset_;
phdr.p_vaddr = tls_offset_;
phdr.p_paddr = tls_offset_;
phdr.p_filesz = tls_.filesz;
phdr.p_memsz = tls_.memsz;
phdr.p_align = 0x1000;
phdr.p_type = PT_TLS;
phdr.p_flags = PF_R;
phdrs.push_back(phdr);
phdr.p_type = PT_LOAD;
phdr.p_flags = PF_R | PF_W;
phdrs.push_back(phdr);
}
{
Elf_Phdr phdr;
phdr.p_offset = ehframe_file_offset_;
phdr.p_vaddr = ehframe_offset_;
phdr.p_paddr = ehframe_offset_;
phdr.p_filesz = ehframe_builder_.Size();
phdr.p_memsz = ehframe_builder_.Size();
phdr.p_align = 0x1000;
phdr.p_type = PT_GNU_EH_FRAME;
phdr.p_flags = PF_R;
phdrs.push_back(phdr);
phdr.p_type = PT_LOAD;
phdr.p_flags = PF_R | PF_W;
phdrs.push_back(phdr);
}
{
Elf_Phdr phdr;
phdr.p_offset = mprotect_file_offset_;
phdr.p_vaddr = mprotect_offset_;
phdr.p_paddr = mprotect_offset_;
phdr.p_filesz = MprotectSize();
phdr.p_memsz = MprotectSize();
phdr.p_align = 0x1000;
phdr.p_type = PT_LOAD;
phdr.p_flags = PF_R | PF_X;
phdrs.push_back(phdr);
}
{
Elf_Phdr phdr;
phdr.p_offset = 0;
phdr.p_vaddr = 0;
phdr.p_paddr = 0;
phdr.p_filesz = 0;
phdr.p_memsz = 0;
phdr.p_align = 0x10; // TODO(akawashiro) Is it appropriate?
phdr.p_type = PT_GNU_STACK;
phdr.p_flags = PF_R | PF_W;
for (ELFBinary* bin : link_binaries_) {
if (bin->gnu_stack() != NULL) {
phdr.p_flags |= bin->gnu_stack()->p_flags;
}
}
phdrs.push_back(phdr);
}
CHECK(phdrs.size() == CountPhdrs());
for (const Elf_Phdr& phdr : phdrs) {
Write(fp, phdr);
}
}
void Sold::EmitGnuHash(FILE* fp) {
CHECK(ftell(fp) == GnuHashOffset());
const Elf_GnuHash& gnu_hash = syms_.gnu_hash();
const std::vector<Syminfo>& exposed_syms = syms_.GetExposedSyms();
Write(fp, gnu_hash.nbuckets);
Write(fp, gnu_hash.symndx);
Write(fp, gnu_hash.maskwords);
Write(fp, gnu_hash.shift2);
Elf_Addr bloom_filter = -1;
Write(fp, bloom_filter);
// If there is no symbols in gnu_hash_, bucket must be 0.
uint32_t bucket = (exposed_syms.size() > gnu_hash.symndx) ? gnu_hash.symndx : 0;
Write(fp, bucket);
for (size_t i = gnu_hash.symndx; i < exposed_syms.size(); ++i) {
uint32_t h = CalcGnuHash(exposed_syms[i].name) & ~1;
if (i == exposed_syms.size() - 1) {
h |= 1;
}
Write(fp, h);
}
}
uintptr_t Sold::TLSMemSize() const {
static uintptr_t s = 0;
if (s != 0) return s;
for (ELFBinary* bin : link_binaries_) {
for (Elf_Phdr* phdr : bin->phdrs()) {
if (phdr->p_type == PT_TLS) {
s += phdr->p_memsz;
}
}
}
return s;
}
// Decide locations for each linked shared objects
// TODO(akawashiro) Is the initial value of offset optimal?
void Sold::DecideMemOffset() {
uintptr_t offset = 0x10000000;
for (ELFBinary* bin : link_binaries_) {
const Range range = bin->GetRange() + offset;
CHECK(range.start == offset) << "sold cannot handle other than shared objects.";
offsets_.emplace(bin, range.start);
LOG(INFO) << "Assigned: " << bin->soname() << " " << HexString(range.start, 8) << "-" << HexString(range.end, 8);
offset = range.end;
}
tls_offset_ = offset;
offset = AlignNext(offset + TLSMemSize());
ehframe_offset_ = offset;
offset = AlignNext(offset + EHFrameSize());
mprotect_offset_ = offset;
offset = AlignNext(offset + MprotectSize());
}
void Sold::CollectTLS() {
uintptr_t bss_offset = 0;
for (ELFBinary* bin : link_binaries_) {
for (Elf_Phdr* phdr : bin->phdrs()) {
if (phdr->p_type == PT_TLS) {
uint8_t* start = reinterpret_cast<uint8_t*>(bin->GetPtr(phdr->p_vaddr));
size_t size = phdr->p_filesz;
uintptr_t file_offset = tls_.filesz;
CHECK(tls_.bin_to_index.emplace(bin, tls_.data.size()).second);
tls_.data.push_back({bin, start, size, file_offset, bss_offset});
tls_.memsz += phdr->p_memsz;
tls_.filesz += size;
bss_offset += phdr->p_memsz - size;
}
}
}
SOLD_CHECK_EQ(tls_.memsz, TLSMemSize());
for (TLS::Data& d : tls_.data) {
d.bss_offset += tls_.filesz;
LOG(INFO) << "TLS of " << d.bin->name() << ": file=" << HexString(d.file_offset) << " + " << HexString(d.size)
<< " mem=" << HexString(d.bss_offset);
}
LOG(INFO) << "TLS: filesz=" << HexString(tls_.filesz) << " memsz=" << HexString(tls_.memsz) << " cnt=" << HexString(tls_.data.size());
}
// Collect .init_array and .fini_array
void Sold::CollectArrays() {
init_array_.emplace_back(mprotect_offset_);
for (auto iter = link_binaries_.rbegin(); iter != link_binaries_.rend(); ++iter) {
ELFBinary* bin = *iter;
uintptr_t offset = offsets_[bin];
bin_to_init_array_offset_[bin] = InitArrayOffset() + sizeof(uintptr_t) * init_array_.size();
for (uintptr_t ptr : bin->init_array()) {
init_array_.emplace_back(ptr + offset);
}
}
for (ELFBinary* bin : link_binaries_) {
uintptr_t offset = offsets_[bin];
if (std::any_of(exclude_finis_.cbegin(), exclude_finis_.cend(), [bin](const auto s) { return HasPrefix(bin->soname(), s); }))
continue;
bin_to_fini_array_offset_[bin] = FiniArrayOffset() + sizeof(uintptr_t) * fini_array_.size();
for (uintptr_t ptr : bin->fini_array()) {
fini_array_.emplace_back(ptr + offset);
}
}
LOG(INFO) << "Array numbers: init_array=" << init_array_.size() << " fini_array=" << fini_array_.size();
}
uintptr_t Sold::RemapTLS(const char* msg, ELFBinary* bin, uintptr_t off) {
const Elf_Phdr* tls = bin->tls();
CHECK(tls);
CHECK(!tls_.data.empty());
auto found = tls_.bin_to_index.find(bin);
CHECK(found != tls_.bin_to_index.end());
const TLS::Data& entry = tls_.data[found->second];
if (off < tls->p_filesz) {
LOG(INFO) << "TLS data " << msg << " in " << bin->name() << " remapped " << HexString(off) << " => "
<< HexString(off + entry.file_offset);
off += entry.file_offset;
} else {
LOG(INFO) << "TLS bss " << msg << " in " << bin->name() << " remapped " << HexString(off) << " => "
<< HexString(off + entry.bss_offset);
off += entry.bss_offset;
}
return off;
}
// Push symbols of bin to symtab.
// When the same symbol is already in symtab, LoadDynSymtab selects a more
// concretely defined one.
void Sold::LoadDynSymtab(ELFBinary* bin, std::vector<Syminfo>& symtab) {
bin->ReadDynSymtab(filename_to_soname_);
uintptr_t offset = offsets_[bin];
for (const auto& p : bin->GetSymbolMap()) {
const std::string& name = p.name;
Elf_Sym* sym = p.sym;
if (IsTLS(*sym) && sym->st_shndx != SHN_UNDEF) {
sym->st_value = RemapTLS("symbol", bin, sym->st_value);
} else if (sym->st_value) {
sym->st_value += offset;
}
LOG(INFO) << "Symbol " << name << "@" << bin->name() << " " << sym->st_value;
Syminfo* found = NULL;
for (int i = 0; i < symtab.size(); i++) {
if (symtab[i].name == p.name && symtab[i].soname == p.soname && symtab[i].version == p.version) {
found = &symtab[i];
break;
}
}
if (found == NULL) {
symtab.push_back(p);
} else {
Elf_Sym* sym2 = found->sym;
int prio = IsDefined(*sym) ? 2 : ELF_ST_BIND(sym->st_info) == STB_WEAK;
int prio2 = IsDefined(*sym2) ? 2 : ELF_ST_BIND(sym2->st_info) == STB_WEAK;
if (prio > prio2) {
found->sym = sym;
}
if (prio == 2 && prio2 == 2) {
LOG(INFO) << "Symbol " << SOLD_LOG_KEY(p.name) << SOLD_LOG_KEY(p.soname) << SOLD_LOG_KEY(p.version)
<< " is defined in two shared objects.";
}
}
}
}
// Push all global symbols of main_binary_ into public_syms_.
// Push all TLS symbols into public_syms_.
// TODO(akawashiro) Does public_syms_ overlap with exposed_syms_?
void Sold::CopyPublicSymbols() {
for (const auto& p : main_binary_->GetSymbolMap()) {
const Elf_Sym* sym = p.sym;
// TODO(akawashiro) Do we need this IsDefined check?
if ((ELF_ST_BIND(sym->st_info) == STB_GLOBAL || ELF_ST_BIND(sym->st_info) == STB_WEAK) && IsDefined(*sym)) {
LOG(INFO) << "Copy public symbol " << SOLD_LOG_KEY(p);
syms_.AddPublicSymbol(p);
} else {
LOG(INFO) << "Don't copy public symbol " << SOLD_LOG_KEY(p);
}
}
for (ELFBinary* bin : link_binaries_) {
if (bin == main_binary_.get()) continue;
for (const auto& p : bin->GetSymbolMap()) {
const Elf_Sym* sym = p.sym;
if (IsTLS(*sym)) {
LOG(INFO) << "Copy TLS symbol " << p.name;
syms_.AddPublicSymbol(p);
}
}
}
}
// Make new relocation table.
// RelocateSymbol_x86_64 rewrites r_offset of each relocation entries
// because we decided locations of shared objects in DecideMemOffset.
void Sold::RelocateSymbol_x86_64(ELFBinary* bin, const Elf_Rel* rel, uintptr_t offset) {
const Elf_Sym* sym = &bin->symtab()[ELF_R_SYM(rel->r_info)];
std::string soname, version_name;
std::tie(soname, version_name) = bin->GetVersion(ELF_R_SYM(rel->r_info), filename_to_soname_);
int type = ELF_R_TYPE(rel->r_info);
const uintptr_t addend = rel->r_addend;
std::vector<Elf_Rel> newrels;
if (bin->IsVaddrInTLSData(rel->r_offset)) {
Elf_Rel newrel = *rel;
const Elf_Phdr* tls = bin->tls();
CHECK(tls);
uintptr_t off = newrel.r_offset - tls->p_vaddr;
off = RemapTLS("reloc", bin, off);
newrel.r_offset = off + tls_offset_;
newrels.emplace_back(newrel);
} else {
Elf_Rel newrel = *rel;
newrel.r_offset += offset;
newrels.emplace_back(newrel);
}
if (bin->IsAddrInInitarray(rel->r_offset)) {
Elf_Rel newrel = *rel;
CHECK(bin_to_init_array_offset_.find(bin) != bin_to_init_array_offset_.end()) << SOLD_LOG_KEY(bin->filename());
newrel.r_offset -= bin->init_array_addr();
newrel.r_offset += bin_to_init_array_offset_[bin];
LOG(INFO) << SOLD_LOG_BITS(bin->init_array_addr()) << SOLD_LOG_BITS(bin_to_init_array_offset_[bin])
<< SOLD_LOG_BITS(newrel.r_offset) << SOLD_LOG_BITS(newrel.r_addend) << SOLD_LOG_BITS(offset);
newrels.emplace_back(newrel);
} else if (bin->IsAddrInFiniarray(rel->r_offset)) {
Elf_Rel newrel = *rel;
CHECK(bin_to_fini_array_offset_.find(bin) != bin_to_fini_array_offset_.end()) << SOLD_LOG_KEY(bin->filename());
newrel.r_offset -= bin->fini_array_addr();
newrel.r_offset += bin_to_fini_array_offset_[bin];
LOG(INFO) << SOLD_LOG_BITS(bin->fini_array_addr()) << SOLD_LOG_BITS(bin_to_fini_array_offset_[bin])
<< SOLD_LOG_BITS(newrel.r_offset) << SOLD_LOG_BITS(newrel.r_addend) << SOLD_LOG_BITS(offset);
newrels.emplace_back(newrel);
}
LOG(INFO) << "Relocate " << bin->Str(sym->st_name) << " at " << rel->r_offset;
for (auto newrel : newrels) {
// Even if we found a defined symbol in src_syms_, we cannot
// erase the relocation entry. The address needs to be fixed at
// runtime by ASLR function so we set RELATIVE to these resolved symbols.
switch (type) {
case R_X86_64_RELATIVE: {
if (IsDefined(*sym)) {
LOG(WARNING)
<< "The symbol associated with R_X86_64_RELATIVE is defined. Because this relocation type doesn't need any "
"symbol, something wrong may have happened.";
}
newrel.r_addend += offset;
break;
}
case R_X86_64_GLOB_DAT:
case R_X86_64_JUMP_SLOT: {
uintptr_t val_or_index;
if (syms_.Resolve(bin->Str(sym->st_name), soname, version_name, val_or_index)) {
newrel.r_info = ELF_R_INFO(0, R_X86_64_RELATIVE);
newrel.r_addend = val_or_index;
} else {
newrel.r_info = ELF_R_INFO(val_or_index, type);
}
break;
}
case R_X86_64_64: {
uintptr_t val_or_index;
if (syms_.Resolve(bin->Str(sym->st_name), soname, version_name, val_or_index)) {
newrel.r_info = ELF_R_INFO(0, R_X86_64_RELATIVE);
newrel.r_addend += val_or_index;
} else {
newrel.r_info = ELF_R_INFO(val_or_index, type);
}
break;
}
// TODO(akawashiro) Handle TLS variables in executables.
case R_X86_64_DTPMOD64: {
// TODO(akawashiro) Refactor out for Arch64
const std::string name = bin->Str(sym->st_name);
uintptr_t index = syms_.ResolveCopy(name, soname, version_name);
newrel.r_info = ELF_R_INFO(index, type);
if (bin->tls() == NULL) {
LOG(INFO) << SOLD_LOG_64BITS(bin->tls()) << " is null. This relocation is TLS generic dynamic model.";
break;
}
uint64_t* mod_on_got =
reinterpret_cast<uint64_t*>(bin->head_mut() + bin->OffsetFromAddr(rel->r_offset));
uint64_t* offset_on_got = mod_on_got + 1;
const bool is_bss = bin->IsOffsetInTLSBSS(*offset_on_got);
// We assume dl_tls_index exists in GOT. This struct is used as
// the argument of __tls_get_addr.
//
// typedef struct dl_tls_index
// {
// uint64_t ti_module; <--- mod_on_got
// uint64_t ti_offset; <--- offset_on_got
// } tls_index;
//
// In TLS generic dynamic model, both ti_module and ti_offset are
// rewritten by R_X86_64_DTPMOD64 and R_X86_64_DTPOFF64,
// respectively.
//
// In TLS local dynamic model, the only ti_module is rewrite by
// R_X86_64_DTPMOD64 and ti_offset is fixed in the link process. We
// must rewrite the fixed ti_offset because we remap the TLS
// template.
std::vector<int> rewrite_rel_types; // Type of relocations which rewrite ti_module.
for (size_t i = 0; i < bin->num_rels(); ++i) {
if (rel->r_offset + sizeof(uint64_t) <= bin->rel()[i].r_offset &&
bin->rel()[i].r_offset < rel->r_offset + sizeof(uint64_t) + sizeof(uint64_t)) {
rewrite_rel_types.emplace_back(ELF_R_TYPE(bin->rel()[i].r_info));
}
}
CHECK(rewrite_rel_types.size() == 0 || (rewrite_rel_types.size() == 1 && rewrite_rel_types[0] == R_X86_64_DTPOFF64))
<< SOLD_LOG_KEY(rewrite_rel_types.size()) << SOLD_LOG_KEY(ShowRelocationType(rewrite_rel_types[0]));
if (rewrite_rel_types.size() == 1) {
LOG(INFO) << "R_X86_64_DTPOFF64 exists next to R_X86_64_DTPMOD64. This relocation is TLS generic dynamic model.";
break;
}
LOG(INFO) << "R_X86_64_DTPMOD64 relocation in TLS local dynamic model. " << SOLD_LOG_KEY(*rel) << SOLD_LOG_KEY(newrel)
<< SOLD_LOG_64BITS(bin->OffsetFromAddr(rel->r_offset)) << SOLD_LOG_64BITS(*mod_on_got)
<< SOLD_LOG_64BITS(*offset_on_got) << SOLD_LOG_64BITS(bin->tls()->p_filesz) << SOLD_LOG_KEY(is_bss)
<< SOLD_LOG_64BITS(tls_.data[tls_.bin_to_index[bin]].file_offset)
<< SOLD_LOG_64BITS(tls_.data[tls_.bin_to_index[bin]].bss_offset);
// We cannot determine whether the associated symbol is a dummy or
// not just using its index. In addition to the traditional dummy
// symbol at index 0, I found some compilers emit a dummy symbol at
// index 1 of SECTION type.
CHECK_EQ(name, "") << "The symbol associated with R_X86_64_DTPMOD64 in TLS local dynamic model should be the dummy."
<< SOLD_LOG_KEY(bin->filename());
if (is_bss) {
// TLS variables without initial values are remapped from
// [bin->tls()->p_filesz, bin->tls()->p_memsz) to
// [tls_.data[tls_.bin_to_index[bin]].bss_offset,
// tls_.data[tls_.bin_to_index[bin]].bss_offset + bin->tls()->p_memsz - bin->tls()->p_filesz)
*offset_on_got += tls_.data[tls_.bin_to_index[bin]].bss_offset - bin->tls()->p_filesz;
} else {
// TLS variables with initial values are remapped from
// [0, bin->tls()->p_filesz) to
// [tls_.data[tls_.bin_to_index[bin]].file_offset,
// tls_.data[tls_.bin_to_index[bin]].file_offset + bin->tls()->p_filesz)
*offset_on_got += tls_.data[tls_.bin_to_index[bin]].file_offset;
}
break;
}
case R_X86_64_DTPOFF64:
case R_X86_64_TPOFF64: {
const std::string name = bin->Str(sym->st_name);
uintptr_t index = syms_.ResolveCopy(name, soname, version_name);
newrel.r_info = ELF_R_INFO(index, type);
LOG(INFO) << ShowRelocationType(type) << " relocation: " << SOLD_LOG_KEY(*rel) << SOLD_LOG_KEY(newrel)
<< SOLD_LOG_64BITS(bin->OffsetFromAddr(rel->r_offset));
break;
}
case R_X86_64_COPY: {
const std::string name = bin->Str(sym->st_name);
uintptr_t index = syms_.ResolveCopy(name, soname, version_name);
newrel.r_info = ELF_R_INFO(index, type);
break;
}
default:
LOG(FATAL) << "Unknown relocation type: " << ShowRelocationType(type);
CHECK(false);
}
rels_.push_back(newrel);
}
}
// Make new relocation table.
// RelocateSymbol_aarch64 rewrites r_offset of each relocation entries
// because we decided locations of shared objects in DecideMemOffset.
void Sold::RelocateSymbol_aarch64(ELFBinary* bin, const Elf_Rel* rel, uintptr_t offset) {
const Elf_Sym* sym = &bin->symtab()[ELF_R_SYM(rel->r_info)];
std::string soname, version_name;
std::tie(soname, version_name) = bin->GetVersion(ELF_R_SYM(rel->r_info), filename_to_soname_);
int type = ELF_R_TYPE(rel->r_info);
const uintptr_t addend = rel->r_addend;
std::vector<Elf_Rel> newrels;
if (bin->IsVaddrInTLSData(rel->r_offset)) {
Elf_Rel newrel = *rel;
const Elf_Phdr* tls = bin->tls();
CHECK(tls);
uintptr_t off = newrel.r_offset - tls->p_vaddr;
off = RemapTLS("reloc", bin, off);
newrel.r_offset = off + tls_offset_;
newrels.emplace_back(newrel);
} else {
Elf_Rel newrel = *rel;
newrel.r_offset += offset;
newrels.emplace_back(newrel);
}
if (bin->IsAddrInInitarray(rel->r_offset)) {
Elf_Rel newrel = *rel;
CHECK(bin_to_init_array_offset_.find(bin) != bin_to_init_array_offset_.end()) << SOLD_LOG_KEY(bin->filename());
newrel.r_offset -= bin->init_array_addr();
newrel.r_offset += bin_to_init_array_offset_[bin];
LOG(INFO) << SOLD_LOG_BITS(bin->init_array_addr()) << SOLD_LOG_BITS(bin_to_init_array_offset_[bin])
<< SOLD_LOG_BITS(newrel.r_offset) << SOLD_LOG_BITS(newrel.r_addend) << SOLD_LOG_BITS(offset);
newrels.emplace_back(newrel);
} else if (bin->IsAddrInFiniarray(rel->r_offset)) {
Elf_Rel newrel = *rel;
CHECK(bin_to_fini_array_offset_.find(bin) != bin_to_fini_array_offset_.end()) << SOLD_LOG_KEY(bin->filename());
newrel.r_offset -= bin->fini_array_addr();
newrel.r_offset += bin_to_fini_array_offset_[bin];
LOG(INFO) << SOLD_LOG_BITS(bin->fini_array_addr()) << SOLD_LOG_BITS(bin_to_fini_array_offset_[bin])
<< SOLD_LOG_BITS(newrel.r_offset) << SOLD_LOG_BITS(newrel.r_addend) << SOLD_LOG_BITS(offset);
newrels.emplace_back(newrel);
}
LOG(INFO) << "Relocate " << bin->Str(sym->st_name) << " at " << rel->r_offset;
for (auto newrel : newrels) {
// Even if we found a defined symbol in src_syms_, we cannot
// erase the relocation entry. The address needs to be fixed at
// runtime by ASLR function so we set RELATIVE to these resolved symbols.
switch (type) {
case R_AARCH64_RELATIVE: {
if (IsDefined(*sym)) {
LOG(WARNING)
<< "The symbol associated with R_AARCH64_RELATIVE is defined. Because this relocation type doesn't need any "
"symbol, something wrong may have happened.";
}
newrel.r_addend += offset;
break;
}
case R_AARCH64_GLOB_DAT:
case R_AARCH64_JUMP_SLOT: {
uintptr_t val_or_index;
if (syms_.Resolve(bin->Str(sym->st_name), soname, version_name, val_or_index)) {
newrel.r_info = ELF_R_INFO(0, R_AARCH64_RELATIVE);
newrel.r_addend = val_or_index;
} else {
newrel.r_info = ELF_R_INFO(val_or_index, type);
}
break;
}
case R_AARCH64_ABS64: {
uintptr_t val_or_index;
if (syms_.Resolve(bin->Str(sym->st_name), soname, version_name, val_or_index)) {
newrel.r_info = ELF_R_INFO(0, R_AARCH64_RELATIVE);
newrel.r_addend += val_or_index;
} else {
newrel.r_info = ELF_R_INFO(val_or_index, type);
}
break;
}
case R_AARCH64_TLSDESC: {
const std::string name = bin->Str(sym->st_name);
if (name == "") {
LOG(INFO) << SOLD_LOG_KEY(name) << "R_AARCH64_TLSDESC in local dynamic";
uintptr_t index = syms_.ResolveCopy(name, soname, version_name);
newrel.r_info = ELF_R_INFO(index, type);
const bool is_bss = bin->IsOffsetInTLSBSS(newrel.r_addend);
if (is_bss) {
LOG(INFO) << "R_AARCH64_TLSDESC" << SOLD_LOG_BITS(newrel.r_addend)
<< SOLD_LOG_BITS(tls_.data[tls_.bin_to_index[bin]].bss_offset - bin->tls()->p_filesz);
newrel.r_addend += tls_.data[tls_.bin_to_index[bin]].bss_offset - bin->tls()->p_filesz;
} else {
LOG(INFO) << "R_AARCH64_TLSDESC" << SOLD_LOG_BITS(newrel.r_addend)
<< SOLD_LOG_BITS(tls_.data[tls_.bin_to_index[bin]].file_offset);
newrel.r_addend += tls_.data[tls_.bin_to_index[bin]].file_offset;
}
break;
} else {
LOG(INFO) << SOLD_LOG_KEY(name) << "R_AARCH64_TLSDESC in generic dynamic";
uintptr_t index = syms_.ResolveCopy(name, soname, version_name);
newrel.r_info = ELF_R_INFO(index, type);
break;
}
}
case R_AARCH64_COPY: {
const std::string name = bin->Str(sym->st_name);
uintptr_t index = syms_.ResolveCopy(name, soname, version_name);
newrel.r_info = ELF_R_INFO(index, type);
break;
}
default:
LOG(FATAL) << "Unknown relocation type: " << ShowRelocationType(type);
CHECK(false);
}
rels_.push_back(newrel);
}
}
std::string Sold::ResolveRunPathVariables(const ELFBinary* binary, const std::string& runpath) {
std::string out = runpath;
auto replace = [](std::string& s, const std::string& f, const std::string& t) {
size_t found = s.find(f);
while (found != std::string::npos) {
s.replace(found, f.size(), t);
found = s.find(f);
}
};
std::string origin = binary->filename();
origin = dirname(&origin[0]);
replace(out, "$ORIGIN", origin);
replace(out, "${ORIGIN}", origin);
if (out.find('$') != std::string::npos) {
LOG(INFO) << "Unsupported runpath: " << runpath;
abort();
}
return out;
}
std::vector<std::string> Sold::GetLibraryPaths(const ELFBinary* binary) {
std::vector<std::string> library_paths;
const std::string& runpath = binary->runpath();
const std::string& rpath = binary->rpath();
if (custome_library_path_.empty()) {
if (runpath.empty() && !rpath.empty()) {
for (const std::string& path : SplitString(rpath, ":")) {
library_paths.push_back(ResolveRunPathVariables(binary, path));
}
}
}
for (const std::string& path : ld_library_paths_) {
library_paths.push_back(path);
}
if (!runpath.empty()) {
for (const std::string& path : SplitString(runpath, ":")) {
library_paths.push_back(ResolveRunPathVariables(binary, path));
}
}
if (custome_library_path_.empty()) {
std::vector<std::string> ldsoconfs = ldsoconf::read_ldsoconf();
library_paths.insert(library_paths.end(), ldsoconfs.begin(), ldsoconfs.end());
library_paths.push_back("/lib");
library_paths.push_back("/usr/lib");
library_paths.push_back("/usr/lib64");
}
library_paths.insert(library_paths.end(), custome_library_path_.begin(), custome_library_path_.end());
return library_paths;
}
// This implementation is compatible with _dl_sort_maps in glibc/elf/dl-sort-maps.c.
std::vector<ELFBinary*> TopologicalSort(std::vector<std::pair<std::string, ELFBinary*>> link_binaries_buf) {
if (link_binaries_buf.size() < 1) {
return {};
}
// The third element of tuple is `seen' variable in glibc/elf/dl-sort-maps.c
std::list<std::tuple<std::string, ELFBinary*, int>> buf;
for (const auto& p : link_binaries_buf) buf.emplace_back(p.first, p.second, 0);
auto i_it = buf.begin();
int n_rest = buf.size();
while (1) {
std::get<2>(*i_it)++;
auto k_it = buf.end();
k_it--;
while (i_it != k_it) {
const auto& neededs = std::get<1>(*k_it)->neededs();
if (std::find(neededs.begin(), neededs.end(), std::get<0>(*i_it)) != neededs.end()) {
buf.insert(buf.end(), *i_it);
i_it = buf.erase(i_it);
if (std::get<2>(*i_it) > n_rest) break;
goto next;
}
--k_it;
}
if (i_it == buf.end() || ++i_it == buf.end()) break;
for (auto it = i_it; it != buf.end(); it++) std::get<2>(*it) = 0;
next:;
}
std::vector<ELFBinary*> ret;
for (const auto& t : buf) ret.emplace_back(std::get<1>(t));
return ret;
}
void Sold::ResolveLibraryPaths(ELFBinary* root_binary) {
// We should search for shared objects in BFS order.
std::queue<const ELFBinary*> bfs_queue;
std::vector<std::pair<std::string, ELFBinary*>> link_binaries_buf;
bfs_queue.push(root_binary);
link_binaries_buf.emplace_back("", root_binary);
while (!bfs_queue.empty()) {
const ELFBinary* binary = bfs_queue.front();
bfs_queue.pop();
std::vector<std::string> library_paths = GetLibraryPaths(binary);
for (const std::string& needed : binary->neededs()) {
auto found = libraries_.find(needed);
if (found != libraries_.end()) {
continue;
}
std::unique_ptr<ELFBinary> library;
for (const std::string& path : library_paths) {
const std::string& filename = path + '/' + needed;
if (Exists(filename)) {
library = ReadELF(filename);
if (library) break;
}
}
if (!library) {
LOG(FATAL) << "Library " << needed << " not found";
abort();
}
// Register (filename, soname)
if (library->name() != "" && library->soname() != "") {
filename_to_soname_[library->name()] = library->soname();
soname_to_filename_[library->soname()] = library->name();
LOG(INFO) << SOLD_LOG_KEY(library->name()) << SOLD_LOG_KEY(library->soname());
} else {