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llvm-project/lld/ELF/LinkerScript.cpp

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//===- LinkerScript.cpp ---------------------------------------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the parser/evaluator of the linker script.
// It parses a linker script and write the result to Config or ScriptConfig
// objects.
//
// If SECTIONS command is used, a ScriptConfig contains an AST
// of the command which will later be consumed by createSections() and
// assignAddresses().
//
//===----------------------------------------------------------------------===//
#include "LinkerScript.h"
#include "Config.h"
#include "Driver.h"
#include "InputSection.h"
#include "OutputSections.h"
#include "ScriptParser.h"
#include "Strings.h"
#include "Symbols.h"
#include "SymbolTable.h"
#include "Target.h"
#include "Writer.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/Support/ELF.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/StringSaver.h"
using namespace llvm;
using namespace llvm::ELF;
using namespace llvm::object;
using namespace llvm::support::endian;
using namespace lld;
using namespace lld::elf;
LinkerScriptBase *elf::ScriptBase;
ScriptConfiguration *elf::ScriptConfig;
template <class ELFT> static void addRegular(SymbolAssignment *Cmd) {
Symbol *Sym = Symtab<ELFT>::X->addRegular(Cmd->Name, STB_GLOBAL, STV_DEFAULT);
Sym->Visibility = Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT;
Cmd->Sym = Sym->body();
// If we have no SECTIONS then we don't have '.' and don't call
// assignAddresses(). We calculate symbol value immediately in this case.
if (!ScriptConfig->HasSections)
cast<DefinedRegular<ELFT>>(Cmd->Sym)->Value = Cmd->Expression(0);
}
template <class ELFT> static void addSynthetic(SymbolAssignment *Cmd) {
Symbol *Sym = Symtab<ELFT>::X->addSynthetic(
Cmd->Name, nullptr, 0, Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT);
Cmd->Sym = Sym->body();
}
template <class ELFT> static void addSymbol(SymbolAssignment *Cmd) {
if (Cmd->IsAbsolute)
addRegular<ELFT>(Cmd);
else
addSynthetic<ELFT>(Cmd);
}
// If a symbol was in PROVIDE(), we need to define it only when
// it is an undefined symbol.
template <class ELFT> static bool shouldDefine(SymbolAssignment *Cmd) {
if (Cmd->Name == ".")
return false;
if (!Cmd->Provide)
return true;
SymbolBody *B = Symtab<ELFT>::X->find(Cmd->Name);
return B && B->isUndefined();
}
bool SymbolAssignment::classof(const BaseCommand *C) {
return C->Kind == AssignmentKind;
}
bool OutputSectionCommand::classof(const BaseCommand *C) {
return C->Kind == OutputSectionKind;
}
bool InputSectionDescription::classof(const BaseCommand *C) {
return C->Kind == InputSectionKind;
}
bool AssertCommand::classof(const BaseCommand *C) {
return C->Kind == AssertKind;
}
bool BytesDataCommand::classof(const BaseCommand *C) {
return C->Kind == BytesDataKind;
}
template <class ELFT> static bool isDiscarded(InputSectionBase<ELFT> *S) {
return !S || !S->Live;
}
template <class ELFT> LinkerScript<ELFT>::LinkerScript() {}
template <class ELFT> LinkerScript<ELFT>::~LinkerScript() {}
template <class ELFT>
bool LinkerScript<ELFT>::shouldKeep(InputSectionBase<ELFT> *S) {
for (InputSectionDescription *ID : Opt.KeptSections) {
StringRef Filename = S->getFile()->getName();
if (!ID->FileRe.match(sys::path::filename(Filename)))
continue;
for (SectionPattern &P : ID->SectionPatterns)
if (P.SectionRe.match(S->Name))
return true;
}
return false;
}
static bool comparePriority(InputSectionData *A, InputSectionData *B) {
return getPriority(A->Name) < getPriority(B->Name);
}
static bool compareName(InputSectionData *A, InputSectionData *B) {
return A->Name < B->Name;
}
static bool compareAlignment(InputSectionData *A, InputSectionData *B) {
// ">" is not a mistake. Larger alignments are placed before smaller
// alignments in order to reduce the amount of padding necessary.
// This is compatible with GNU.
return A->Alignment > B->Alignment;
}
static std::function<bool(InputSectionData *, InputSectionData *)>
getComparator(SortSectionPolicy K) {
switch (K) {
case SortSectionPolicy::Alignment:
return compareAlignment;
case SortSectionPolicy::Name:
return compareName;
case SortSectionPolicy::Priority:
return comparePriority;
default:
llvm_unreachable("unknown sort policy");
}
}
template <class ELFT>
static bool matchConstraints(ArrayRef<InputSectionBase<ELFT> *> Sections,
ConstraintKind Kind) {
if (Kind == ConstraintKind::NoConstraint)
return true;
bool IsRW = llvm::any_of(Sections, [=](InputSectionData *Sec2) {
auto *Sec = static_cast<InputSectionBase<ELFT> *>(Sec2);
return Sec->getSectionHdr()->sh_flags & SHF_WRITE;
});
return (IsRW && Kind == ConstraintKind::ReadWrite) ||
(!IsRW && Kind == ConstraintKind::ReadOnly);
}
static void sortSections(InputSectionData **Begin, InputSectionData **End,
SortSectionPolicy K) {
if (K != SortSectionPolicy::Default && K != SortSectionPolicy::None)
std::stable_sort(Begin, End, getComparator(K));
}
// Compute and remember which sections the InputSectionDescription matches.
template <class ELFT>
void LinkerScript<ELFT>::computeInputSections(InputSectionDescription *I) {
// Collects all sections that satisfy constraints of I
// and attach them to I.
for (SectionPattern &Pat : I->SectionPatterns) {
size_t SizeBefore = I->Sections.size();
for (ObjectFile<ELFT> *F : Symtab<ELFT>::X->getObjectFiles()) {
StringRef Filename = sys::path::filename(F->getName());
if (!I->FileRe.match(Filename) || Pat.ExcludedFileRe.match(Filename))
continue;
for (InputSectionBase<ELFT> *S : F->getSections())
if (!isDiscarded(S) && !S->OutSec && Pat.SectionRe.match(S->Name))
I->Sections.push_back(S);
if (Pat.SectionRe.match("COMMON"))
I->Sections.push_back(CommonInputSection<ELFT>::X);
}
// Sort sections as instructed by SORT-family commands and --sort-section
// option. Because SORT-family commands can be nested at most two depth
// (e.g. SORT_BY_NAME(SORT_BY_ALIGNMENT(.text.*))) and because the command
// line option is respected even if a SORT command is given, the exact
// behavior we have here is a bit complicated. Here are the rules.
//
// 1. If two SORT commands are given, --sort-section is ignored.
// 2. If one SORT command is given, and if it is not SORT_NONE,
// --sort-section is handled as an inner SORT command.
// 3. If one SORT command is given, and if it is SORT_NONE, don't sort.
// 4. If no SORT command is given, sort according to --sort-section.
InputSectionData **Begin = I->Sections.data() + SizeBefore;
InputSectionData **End = I->Sections.data() + I->Sections.size();
if (Pat.SortOuter != SortSectionPolicy::None) {
if (Pat.SortInner == SortSectionPolicy::Default)
sortSections(Begin, End, Config->SortSection);
else
sortSections(Begin, End, Pat.SortInner);
sortSections(Begin, End, Pat.SortOuter);
}
}
// We do not add duplicate input sections, so mark them with a dummy output
// section for now.
for (InputSectionData *S : I->Sections) {
auto *S2 = static_cast<InputSectionBase<ELFT> *>(S);
S2->OutSec = (OutputSectionBase<ELFT> *)-1;
}
}
template <class ELFT>
void LinkerScript<ELFT>::discard(ArrayRef<InputSectionBase<ELFT> *> V) {
for (InputSectionBase<ELFT> *S : V) {
S->Live = false;
reportDiscarded(S);
}
}
template <class ELFT>
std::vector<InputSectionBase<ELFT> *>
LinkerScript<ELFT>::createInputSectionList(OutputSectionCommand &OutCmd) {
std::vector<InputSectionBase<ELFT> *> Ret;
for (const std::unique_ptr<BaseCommand> &Base : OutCmd.Commands) {
auto *Cmd = dyn_cast<InputSectionDescription>(Base.get());
if (!Cmd)
continue;
computeInputSections(Cmd);
for (InputSectionData *S : Cmd->Sections)
Ret.push_back(static_cast<InputSectionBase<ELFT> *>(S));
}
return Ret;
}
template <class ELFT>
static SectionKey<ELFT::Is64Bits> createKey(InputSectionBase<ELFT> *C,
StringRef OutsecName) {
// When using linker script the merge rules are different.
// Unfortunately, linker scripts are name based. This means that expressions
// like *(.foo*) can refer to multiple input sections that would normally be
// placed in different output sections. We cannot put them in different
// output sections or we would produce wrong results for
// start = .; *(.foo.*) end = .; *(.bar)
// and a mapping of .foo1 and .bar1 to one section and .foo2 and .bar2 to
// another. The problem is that there is no way to layout those output
// sections such that the .foo sections are the only thing between the
// start and end symbols.
// An extra annoyance is that we cannot simply disable merging of the contents
// of SHF_MERGE sections, but our implementation requires one output section
// per "kind" (string or not, which size/aligment).
// Fortunately, creating symbols in the middle of a merge section is not
// supported by bfd or gold, so we can just create multiple section in that
// case.
const typename ELFT::Shdr *H = C->getSectionHdr();
typedef typename ELFT::uint uintX_t;
uintX_t Flags = H->sh_flags & (SHF_MERGE | SHF_STRINGS);
uintX_t Alignment = 0;
if (isa<MergeInputSection<ELFT>>(C))
Alignment = std::max(H->sh_addralign, H->sh_entsize);
return SectionKey<ELFT::Is64Bits>{OutsecName, /*Type*/ 0, Flags, Alignment};
}
template <class ELFT>
void LinkerScript<ELFT>::addSection(OutputSectionFactory<ELFT> &Factory,
InputSectionBase<ELFT> *Sec,
StringRef Name) {
OutputSectionBase<ELFT> *OutSec;
bool IsNew;
std::tie(OutSec, IsNew) = Factory.create(createKey(Sec, Name), Sec);
if (IsNew)
OutputSections->push_back(OutSec);
OutSec->addSection(Sec);
}
template <class ELFT>
void LinkerScript<ELFT>::processCommands(OutputSectionFactory<ELFT> &Factory) {
for (unsigned I = 0; I < Opt.Commands.size(); ++I) {
auto Iter = Opt.Commands.begin() + I;
const std::unique_ptr<BaseCommand> &Base1 = *Iter;
if (auto *Cmd = dyn_cast<SymbolAssignment>(Base1.get())) {
if (shouldDefine<ELFT>(Cmd))
addRegular<ELFT>(Cmd);
continue;
}
if (auto *Cmd = dyn_cast<AssertCommand>(Base1.get())) {
// If we don't have SECTIONS then output sections have already been
// created by Writer<ELFT>. The LinkerScript<ELFT>::assignAddresses
// will not be called, so ASSERT should be evaluated now.
if (!Opt.HasSections)
Cmd->Expression(0);
continue;
}
if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base1.get())) {
std::vector<InputSectionBase<ELFT> *> V = createInputSectionList(*Cmd);
if (Cmd->Name == "/DISCARD/") {
discard(V);
continue;
}
if (!matchConstraints<ELFT>(V, Cmd->Constraint)) {
for (InputSectionBase<ELFT> *S : V)
S->OutSec = nullptr;
Opt.Commands.erase(Iter);
--I;
continue;
}
for (const std::unique_ptr<BaseCommand> &Base : Cmd->Commands)
if (auto *OutCmd = dyn_cast<SymbolAssignment>(Base.get()))
if (shouldDefine<ELFT>(OutCmd))
addSymbol<ELFT>(OutCmd);
if (V.empty())
continue;
for (InputSectionBase<ELFT> *Sec : V) {
addSection(Factory, Sec, Cmd->Name);
if (uint32_t Subalign = Cmd->SubalignExpr ? Cmd->SubalignExpr(0) : 0)
Sec->Alignment = Subalign;
}
}
}
}
template <class ELFT>
void LinkerScript<ELFT>::createSections(OutputSectionFactory<ELFT> &Factory) {
processCommands(Factory);
// Add orphan sections.
for (ObjectFile<ELFT> *F : Symtab<ELFT>::X->getObjectFiles())
for (InputSectionBase<ELFT> *S : F->getSections())
if (!isDiscarded(S) && !S->OutSec)
addSection(Factory, S, getOutputSectionName(S->Name));
}
// Sets value of a section-defined symbol. Two kinds of
// symbols are processed: synthetic symbols, whose value
// is an offset from beginning of section and regular
// symbols whose value is absolute.
template <class ELFT>
static void assignSectionSymbol(SymbolAssignment *Cmd,
OutputSectionBase<ELFT> *Sec,
typename ELFT::uint Off) {
if (!Cmd->Sym)
return;
if (auto *Body = dyn_cast<DefinedSynthetic<ELFT>>(Cmd->Sym)) {
Body->Section = Sec;
Body->Value = Cmd->Expression(Sec->getVA() + Off) - Sec->getVA();
return;
}
auto *Body = cast<DefinedRegular<ELFT>>(Cmd->Sym);
Body->Value = Cmd->Expression(Sec->getVA() + Off);
}
template <class ELFT> static bool isTbss(OutputSectionBase<ELFT> *Sec) {
return (Sec->getFlags() & SHF_TLS) && Sec->getType() == SHT_NOBITS;
}
template <class ELFT> void LinkerScript<ELFT>::output(InputSection<ELFT> *S) {
if (!AlreadyOutputIS.insert(S).second)
return;
bool IsTbss = isTbss(CurOutSec);
uintX_t Pos = IsTbss ? Dot + ThreadBssOffset : Dot;
Pos = alignTo(Pos, S->Alignment);
S->OutSecOff = Pos - CurOutSec->getVA();
Pos += S->getSize();
// Update output section size after adding each section. This is so that
// SIZEOF works correctly in the case below:
// .foo { *(.aaa) a = SIZEOF(.foo); *(.bbb) }
CurOutSec->setSize(Pos - CurOutSec->getVA());
if (IsTbss)
ThreadBssOffset = Pos - Dot;
else
Dot = Pos;
}
template <class ELFT> void LinkerScript<ELFT>::flush() {
if (!CurOutSec || !AlreadyOutputOS.insert(CurOutSec).second)
return;
if (auto *OutSec = dyn_cast<OutputSection<ELFT>>(CurOutSec)) {
for (InputSection<ELFT> *I : OutSec->Sections)
output(I);
} else {
Dot += CurOutSec->getSize();
}
}
template <class ELFT>
void LinkerScript<ELFT>::switchTo(OutputSectionBase<ELFT> *Sec) {
if (CurOutSec == Sec)
return;
if (AlreadyOutputOS.count(Sec))
return;
flush();
CurOutSec = Sec;
Dot = alignTo(Dot, CurOutSec->getAlignment());
CurOutSec->setVA(isTbss(CurOutSec) ? Dot + ThreadBssOffset : Dot);
// If neither AT nor AT> is specified for an allocatable section, the linker
// will set the LMA such that the difference between VMA and LMA for the
// section is the same as the preceding output section in the same region
// https://sourceware.org/binutils/docs-2.20/ld/Output-Section-LMA.html
CurOutSec->setLMAOffset(LMAOffset);
}
template <class ELFT> void LinkerScript<ELFT>::process(BaseCommand &Base) {
// This handles the assignments to symbol or to a location counter (.)
if (auto *AssignCmd = dyn_cast<SymbolAssignment>(&Base)) {
if (AssignCmd->Name == ".") {
// Update to location counter means update to section size.
Dot = AssignCmd->Expression(Dot);
CurOutSec->setSize(Dot - CurOutSec->getVA());
return;
}
assignSectionSymbol<ELFT>(AssignCmd, CurOutSec, Dot - CurOutSec->getVA());
return;
}
// Handle BYTE(), SHORT(), LONG(), or QUAD().
if (auto *DataCmd = dyn_cast<BytesDataCommand>(&Base)) {
DataCmd->Offset = Dot - CurOutSec->getVA();
Dot += DataCmd->Size;
CurOutSec->setSize(Dot - CurOutSec->getVA());
return;
}
// It handles single input section description command,
// calculates and assigns the offsets for each section and also
// updates the output section size.
auto &ICmd = cast<InputSectionDescription>(Base);
for (InputSectionData *ID : ICmd.Sections) {
auto *IB = static_cast<InputSectionBase<ELFT> *>(ID);
switchTo(IB->OutSec);
if (auto *I = dyn_cast<InputSection<ELFT>>(IB))
output(I);
else
flush();
}
}
template <class ELFT>
static std::vector<OutputSectionBase<ELFT> *>
findSections(StringRef Name,
const std::vector<OutputSectionBase<ELFT> *> &Sections) {
std::vector<OutputSectionBase<ELFT> *> Ret;
for (OutputSectionBase<ELFT> *Sec : Sections)
if (Sec->getName() == Name)
Ret.push_back(Sec);
return Ret;
}
template <class ELFT>
void LinkerScript<ELFT>::assignOffsets(OutputSectionCommand *Cmd) {
if (Cmd->LMAExpr)
LMAOffset = Cmd->LMAExpr(Dot) - Dot;
std::vector<OutputSectionBase<ELFT> *> Sections =
findSections(Cmd->Name, *OutputSections);
if (Sections.empty())
return;
switchTo(Sections[0]);
// Find the last section output location. We will output orphan sections
// there so that end symbols point to the correct location.
auto E = std::find_if(Cmd->Commands.rbegin(), Cmd->Commands.rend(),
[](const std::unique_ptr<BaseCommand> &Cmd) {
return !isa<SymbolAssignment>(*Cmd);
})
.base();
for (auto I = Cmd->Commands.begin(); I != E; ++I)
process(**I);
for (OutputSectionBase<ELFT> *Base : Sections)
switchTo(Base);
flush();
std::for_each(E, Cmd->Commands.end(),
[this](std::unique_ptr<BaseCommand> &B) { process(*B.get()); });
}
template <class ELFT> void LinkerScript<ELFT>::adjustSectionsBeforeSorting() {
// It is common practice to use very generic linker scripts. So for any
// given run some of the output sections in the script will be empty.
// We could create corresponding empty output sections, but that would
// clutter the output.
// We instead remove trivially empty sections. The bfd linker seems even
// more aggressive at removing them.
auto Pos = std::remove_if(
Opt.Commands.begin(), Opt.Commands.end(),
[&](const std::unique_ptr<BaseCommand> &Base) {
auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get());
if (!Cmd)
return false;
std::vector<OutputSectionBase<ELFT> *> Secs =
findSections(Cmd->Name, *OutputSections);
if (!Secs.empty())
return false;
for (const std::unique_ptr<BaseCommand> &I : Cmd->Commands)
if (!isa<InputSectionDescription>(I.get()))
return false;
return true;
});
Opt.Commands.erase(Pos, Opt.Commands.end());
// If the output section contains only symbol assignments, create a
// corresponding output section. The bfd linker seems to only create them if
// '.' is assigned to, but creating these section should not have any bad
// consequeces and gives us a section to put the symbol in.
uintX_t Flags = SHF_ALLOC;
uint32_t Type = 0;
for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands) {
auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get());
if (!Cmd)
continue;
std::vector<OutputSectionBase<ELFT> *> Secs =
findSections(Cmd->Name, *OutputSections);
if (!Secs.empty()) {
Flags = Secs[0]->getFlags();
Type = Secs[0]->getType();
continue;
}
auto *OutSec = new OutputSection<ELFT>(Cmd->Name, Type, Flags);
Out<ELFT>::Pool.emplace_back(OutSec);
OutputSections->push_back(OutSec);
}
}
// When placing orphan sections, we want to place them after symbol assignments
// so that an orphan after
// begin_foo = .;
// foo : { *(foo) }
// end_foo = .;
// doesn't break the intended meaning of the begin/end symbols.
// We don't want to go over sections since Writer<ELFT>::sortSections is the
// one in charge of deciding the order of the sections.
// We don't want to go over alignments, since doing so in
// rx_sec : { *(rx_sec) }
// . = ALIGN(0x1000);
// /* The RW PT_LOAD starts here*/
// rw_sec : { *(rw_sec) }
// would mean that the RW PT_LOAD would become unaligned.
static bool shouldSkip(const BaseCommand &Cmd) {
if (isa<OutputSectionCommand>(Cmd))
return false;
const auto *Assign = dyn_cast<SymbolAssignment>(&Cmd);
if (!Assign)
return true;
return Assign->Name != ".";
}
template <class ELFT>
void LinkerScript<ELFT>::assignAddresses(std::vector<PhdrEntry<ELFT>> &Phdrs) {
// Orphan sections are sections present in the input files which
// are not explicitly placed into the output file by the linker script.
// We place orphan sections at end of file.
// Other linkers places them using some heuristics as described in
// https://sourceware.org/binutils/docs/ld/Orphan-Sections.html#Orphan-Sections.
// The OutputSections are already in the correct order.
// This loops creates or moves commands as needed so that they are in the
// correct order.
int CmdIndex = 0;
for (OutputSectionBase<ELFT> *Sec : *OutputSections) {
StringRef Name = Sec->getName();
// Find the last spot where we can insert a command and still get the
// correct result.
auto CmdIter = Opt.Commands.begin() + CmdIndex;
auto E = Opt.Commands.end();
while (CmdIter != E && shouldSkip(**CmdIter)) {
++CmdIter;
++CmdIndex;
}
auto Pos =
std::find_if(CmdIter, E, [&](const std::unique_ptr<BaseCommand> &Base) {
auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get());
return Cmd && Cmd->Name == Name;
});
if (Pos == E) {
Opt.Commands.insert(CmdIter,
llvm::make_unique<OutputSectionCommand>(Name));
++CmdIndex;
continue;
}
// Continue from where we found it.
CmdIndex = (Pos - Opt.Commands.begin()) + 1;
continue;
}
// Assign addresses as instructed by linker script SECTIONS sub-commands.
Dot = 0;
for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands) {
if (auto *Cmd = dyn_cast<SymbolAssignment>(Base.get())) {
if (Cmd->Name == ".") {
Dot = Cmd->Expression(Dot);
} else if (Cmd->Sym) {
cast<DefinedRegular<ELFT>>(Cmd->Sym)->Value = Cmd->Expression(Dot);
}
continue;
}
if (auto *Cmd = dyn_cast<AssertCommand>(Base.get())) {
Cmd->Expression(Dot);
continue;
}
auto *Cmd = cast<OutputSectionCommand>(Base.get());
if (Cmd->AddrExpr)
Dot = Cmd->AddrExpr(Dot);
assignOffsets(Cmd);
}
uintX_t MinVA = std::numeric_limits<uintX_t>::max();
for (OutputSectionBase<ELFT> *Sec : *OutputSections) {
if (Sec->getFlags() & SHF_ALLOC)
MinVA = std::min(MinVA, Sec->getVA());
else
Sec->setVA(0);
}
uintX_t HeaderSize = getHeaderSize();
auto FirstPTLoad =
std::find_if(Phdrs.begin(), Phdrs.end(), [](const PhdrEntry<ELFT> &E) {
return E.H.p_type == PT_LOAD;
});
if (HeaderSize <= MinVA && FirstPTLoad != Phdrs.end()) {
// ELF and Program headers need to be right before the first section in
// memory. Set their addresses accordingly.
MinVA = alignDown(MinVA - HeaderSize, Target->PageSize);
Out<ELFT>::ElfHeader->setVA(MinVA);
Out<ELFT>::ProgramHeaders->setVA(Out<ELFT>::ElfHeader->getSize() + MinVA);
FirstPTLoad->First = Out<ELFT>::ElfHeader;
if (!FirstPTLoad->Last)
FirstPTLoad->Last = Out<ELFT>::ProgramHeaders;
} else if (!FirstPTLoad->First) {
// Sometimes the very first PT_LOAD segment can be empty.
// This happens if (all conditions met):
// - Linker script is used
// - First section in ELF image is not RO
// - Not enough space for program headers.
// The code below removes empty PT_LOAD segment and updates
// program headers size.
Phdrs.erase(FirstPTLoad);
Out<ELFT>::ProgramHeaders->setSize(sizeof(typename ELFT::Phdr) *
Phdrs.size());
}
}
// Creates program headers as instructed by PHDRS linker script command.
template <class ELFT>
std::vector<PhdrEntry<ELFT>> LinkerScript<ELFT>::createPhdrs() {
std::vector<PhdrEntry<ELFT>> Ret;
// Process PHDRS and FILEHDR keywords because they are not
// real output sections and cannot be added in the following loop.
for (const PhdrsCommand &Cmd : Opt.PhdrsCommands) {
Ret.emplace_back(Cmd.Type, Cmd.Flags == UINT_MAX ? PF_R : Cmd.Flags);
PhdrEntry<ELFT> &Phdr = Ret.back();
if (Cmd.HasFilehdr)
Phdr.add(Out<ELFT>::ElfHeader);
if (Cmd.HasPhdrs)
Phdr.add(Out<ELFT>::ProgramHeaders);
if (Cmd.LMAExpr) {
Phdr.H.p_paddr = Cmd.LMAExpr(0);
Phdr.HasLMA = true;
}
}
// Add output sections to program headers.
PhdrEntry<ELFT> *Load = nullptr;
uintX_t Flags = PF_R;
for (OutputSectionBase<ELFT> *Sec : *OutputSections) {
if (!(Sec->getFlags() & SHF_ALLOC))
break;
std::vector<size_t> PhdrIds = getPhdrIndices(Sec->getName());
if (!PhdrIds.empty()) {
// Assign headers specified by linker script
for (size_t Id : PhdrIds) {
Ret[Id].add(Sec);
if (Opt.PhdrsCommands[Id].Flags == UINT_MAX)
Ret[Id].H.p_flags |= Sec->getPhdrFlags();
}
} else {
// If we have no load segment or flags've changed then we want new load
// segment.
uintX_t NewFlags = Sec->getPhdrFlags();
if (Load == nullptr || Flags != NewFlags) {
Load = &*Ret.emplace(Ret.end(), PT_LOAD, NewFlags);
Flags = NewFlags;
}
Load->add(Sec);
}
}
return Ret;
}
template <class ELFT> bool LinkerScript<ELFT>::ignoreInterpSection() {
// Ignore .interp section in case we have PHDRS specification
// and PT_INTERP isn't listed.
return !Opt.PhdrsCommands.empty() &&
llvm::find_if(Opt.PhdrsCommands, [](const PhdrsCommand &Cmd) {
return Cmd.Type == PT_INTERP;
}) == Opt.PhdrsCommands.end();
}
template <class ELFT>
ArrayRef<uint8_t> LinkerScript<ELFT>::getFiller(StringRef Name) {
for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands)
if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get()))
if (Cmd->Name == Name)
return Cmd->Filler;
return {};
}
template <class ELFT>
static void writeInt(uint8_t *Buf, uint64_t Data, uint64_t Size) {
const endianness E = ELFT::TargetEndianness;
switch (Size) {
case 1:
*Buf = (uint8_t)Data;
break;
case 2:
write16<E>(Buf, Data);
break;
case 4:
write32<E>(Buf, Data);
break;
case 8:
write64<E>(Buf, Data);
break;
default:
llvm_unreachable("unsupported Size argument");
}
}
template <class ELFT>
void LinkerScript<ELFT>::writeDataBytes(StringRef Name, uint8_t *Buf) {
int I = getSectionIndex(Name);
if (I == INT_MAX)
return;
OutputSectionCommand *Cmd =
dyn_cast<OutputSectionCommand>(Opt.Commands[I].get());
for (const std::unique_ptr<BaseCommand> &Base2 : Cmd->Commands)
if (auto *DataCmd = dyn_cast<BytesDataCommand>(Base2.get()))
writeInt<ELFT>(&Buf[DataCmd->Offset], DataCmd->Data, DataCmd->Size);
}
template <class ELFT> bool LinkerScript<ELFT>::hasLMA(StringRef Name) {
for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands)
if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get()))
if (Cmd->LMAExpr && Cmd->Name == Name)
return true;
return false;
}
// Returns the index of the given section name in linker script
// SECTIONS commands. Sections are laid out as the same order as they
// were in the script. If a given name did not appear in the script,
// it returns INT_MAX, so that it will be laid out at end of file.
template <class ELFT> int LinkerScript<ELFT>::getSectionIndex(StringRef Name) {
int I = 0;
for (std::unique_ptr<BaseCommand> &Base : Opt.Commands) {
if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get()))
if (Cmd->Name == Name)
return I;
++I;
}
return INT_MAX;
}
template <class ELFT> bool LinkerScript<ELFT>::hasPhdrsCommands() {
return !Opt.PhdrsCommands.empty();
}
template <class ELFT>
uint64_t LinkerScript<ELFT>::getOutputSectionAddress(StringRef Name) {
for (OutputSectionBase<ELFT> *Sec : *OutputSections)
if (Sec->getName() == Name)
return Sec->getVA();
error("undefined section " + Name);
return 0;
}
template <class ELFT>
uint64_t LinkerScript<ELFT>::getOutputSectionLMA(StringRef Name) {
for (OutputSectionBase<ELFT> *Sec : *OutputSections)
if (Sec->getName() == Name)
return Sec->getLMA();
error("undefined section " + Name);
return 0;
}
template <class ELFT>
uint64_t LinkerScript<ELFT>::getOutputSectionSize(StringRef Name) {
for (OutputSectionBase<ELFT> *Sec : *OutputSections)
if (Sec->getName() == Name)
return Sec->getSize();
error("undefined section " + Name);
return 0;
}
template <class ELFT>
uint64_t LinkerScript<ELFT>::getOutputSectionAlign(StringRef Name) {
for (OutputSectionBase<ELFT> *Sec : *OutputSections)
if (Sec->getName() == Name)
return Sec->getAlignment();
error("undefined section " + Name);
return 0;
}
template <class ELFT> uint64_t LinkerScript<ELFT>::getHeaderSize() {
return elf::getHeaderSize<ELFT>();
}
template <class ELFT> uint64_t LinkerScript<ELFT>::getSymbolValue(StringRef S) {
if (SymbolBody *B = Symtab<ELFT>::X->find(S))
return B->getVA<ELFT>();
error("symbol not found: " + S);
return 0;
}
template <class ELFT> bool LinkerScript<ELFT>::isDefined(StringRef S) {
return Symtab<ELFT>::X->find(S) != nullptr;
}
// Returns indices of ELF headers containing specific section, identified
// by Name. Each index is a zero based number of ELF header listed within
// PHDRS {} script block.
template <class ELFT>
std::vector<size_t> LinkerScript<ELFT>::getPhdrIndices(StringRef SectionName) {
for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands) {
auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get());
if (!Cmd || Cmd->Name != SectionName)
continue;
std::vector<size_t> Ret;
for (StringRef PhdrName : Cmd->Phdrs)
Ret.push_back(getPhdrIndex(PhdrName));
return Ret;
}
return {};
}
template <class ELFT>
size_t LinkerScript<ELFT>::getPhdrIndex(StringRef PhdrName) {
size_t I = 0;
for (PhdrsCommand &Cmd : Opt.PhdrsCommands) {
if (Cmd.Name == PhdrName)
return I;
++I;
}
error("section header '" + PhdrName + "' is not listed in PHDRS");
return 0;
}
class elf::ScriptParser : public ScriptParserBase {
typedef void (ScriptParser::*Handler)();
public:
ScriptParser(StringRef S, bool B) : ScriptParserBase(S), IsUnderSysroot(B) {}
void readLinkerScript();
void readVersionScript();
private:
void addFile(StringRef Path);
void readAsNeeded();
void readEntry();
void readExtern();
void readGroup();
void readInclude();
void readOutput();
void readOutputArch();
void readOutputFormat();
void readPhdrs();
void readSearchDir();
void readSections();
void readVersion();
void readVersionScriptCommand();
SymbolAssignment *readAssignment(StringRef Name);
BytesDataCommand *readBytesDataCommand(StringRef Tok);
std::vector<uint8_t> readFill();
OutputSectionCommand *readOutputSectionDescription(StringRef OutSec);
std::vector<uint8_t> readOutputSectionFiller(StringRef Tok);
std::vector<StringRef> readOutputSectionPhdrs();
InputSectionDescription *readInputSectionDescription(StringRef Tok);
Regex readFilePatterns();
std::vector<SectionPattern> readInputSectionsList();
InputSectionDescription *readInputSectionRules(StringRef FilePattern);
unsigned readPhdrType();
SortSectionPolicy readSortKind();
SymbolAssignment *readProvideHidden(bool Provide, bool Hidden);
SymbolAssignment *readProvideOrAssignment(StringRef Tok, bool MakeAbsolute);
void readSort();
Expr readAssert();
Expr readExpr();
Expr readExpr1(Expr Lhs, int MinPrec);
StringRef readParenLiteral();
Expr readPrimary();
Expr readTernary(Expr Cond);
Expr readParenExpr();
// For parsing version script.
void readExtern(std::vector<SymbolVersion> *Globals);
void readVersionDeclaration(StringRef VerStr);
void readGlobal(StringRef VerStr);
void readLocal();
ScriptConfiguration &Opt = *ScriptConfig;
StringSaver Saver = {ScriptConfig->Alloc};
bool IsUnderSysroot;
};
void ScriptParser::readVersionScript() {
readVersionScriptCommand();
if (!atEOF())
setError("EOF expected, but got " + next());
}
void ScriptParser::readVersionScriptCommand() {
if (skip("{")) {
readVersionDeclaration("");
return;
}
while (!atEOF() && !Error && peek() != "}") {
StringRef VerStr = next();
if (VerStr == "{") {
setError("anonymous version definition is used in "
"combination with other version definitions");
return;
}
expect("{");
readVersionDeclaration(VerStr);
}
}
void ScriptParser::readVersion() {
expect("{");
readVersionScriptCommand();
expect("}");
}
void ScriptParser::readLinkerScript() {
while (!atEOF()) {
StringRef Tok = next();
if (Tok == ";")
continue;
if (Tok == "ASSERT") {
Opt.Commands.emplace_back(new AssertCommand(readAssert()));
} else if (Tok == "ENTRY") {
readEntry();
} else if (Tok == "EXTERN") {
readExtern();
} else if (Tok == "GROUP" || Tok == "INPUT") {
readGroup();
} else if (Tok == "INCLUDE") {
readInclude();
} else if (Tok == "OUTPUT") {
readOutput();
} else if (Tok == "OUTPUT_ARCH") {
readOutputArch();
} else if (Tok == "OUTPUT_FORMAT") {
readOutputFormat();
} else if (Tok == "PHDRS") {
readPhdrs();
} else if (Tok == "SEARCH_DIR") {
readSearchDir();
} else if (Tok == "SECTIONS") {
readSections();
} else if (Tok == "VERSION") {
readVersion();
} else if (SymbolAssignment *Cmd = readProvideOrAssignment(Tok, true)) {
Opt.Commands.emplace_back(Cmd);
} else {
setError("unknown directive: " + Tok);
}
}
}
void ScriptParser::addFile(StringRef S) {
if (IsUnderSysroot && S.startswith("/")) {
SmallString<128> Path;
(Config->Sysroot + S).toStringRef(Path);
if (sys::fs::exists(Path)) {
Driver->addFile(Saver.save(Path.str()));
return;
}
}
if (sys::path::is_absolute(S)) {
Driver->addFile(S);
} else if (S.startswith("=")) {
if (Config->Sysroot.empty())
Driver->addFile(S.substr(1));
else
Driver->addFile(Saver.save(Config->Sysroot + "/" + S.substr(1)));
} else if (S.startswith("-l")) {
Driver->addLibrary(S.substr(2));
} else if (sys::fs::exists(S)) {
Driver->addFile(S);
} else {
std::string Path = findFromSearchPaths(S);
if (Path.empty())
setError("unable to find " + S);
else
Driver->addFile(Saver.save(Path));
}
}
void ScriptParser::readAsNeeded() {
expect("(");
bool Orig = Config->AsNeeded;
Config->AsNeeded = true;
while (!Error && !skip(")"))
addFile(unquote(next()));
Config->AsNeeded = Orig;
}
void ScriptParser::readEntry() {
// -e <symbol> takes predecence over ENTRY(<symbol>).
expect("(");
StringRef Tok = next();
if (Config->Entry.empty())
Config->Entry = Tok;
expect(")");
}
void ScriptParser::readExtern() {
expect("(");
while (!Error && !skip(")"))
Config->Undefined.push_back(next());
}
void ScriptParser::readGroup() {
expect("(");
while (!Error && !skip(")")) {
StringRef Tok = next();
if (Tok == "AS_NEEDED")
readAsNeeded();
else
addFile(unquote(Tok));
}
}
void ScriptParser::readInclude() {
StringRef Tok = next();
auto MBOrErr = MemoryBuffer::getFile(unquote(Tok));
if (!MBOrErr) {
setError("cannot open " + Tok);
return;
}
std::unique_ptr<MemoryBuffer> &MB = *MBOrErr;
StringRef S = Saver.save(MB->getMemBufferRef().getBuffer());
std::vector<StringRef> V = tokenize(S);
Tokens.insert(Tokens.begin() + Pos, V.begin(), V.end());
}
void ScriptParser::readOutput() {
// -o <file> takes predecence over OUTPUT(<file>).
expect("(");
StringRef Tok = next();
if (Config->OutputFile.empty())
Config->OutputFile = unquote(Tok);
expect(")");
}
void ScriptParser::readOutputArch() {
// Error checking only for now.
expect("(");
next();
expect(")");
}
void ScriptParser::readOutputFormat() {
// Error checking only for now.
expect("(");
next();
StringRef Tok = next();
if (Tok == ")")
return;
if (Tok != ",") {
setError("unexpected token: " + Tok);
return;
}
next();
expect(",");
next();
expect(")");
}
void ScriptParser::readPhdrs() {
expect("{");
while (!Error && !skip("}")) {
StringRef Tok = next();
Opt.PhdrsCommands.push_back(
{Tok, PT_NULL, false, false, UINT_MAX, nullptr});
PhdrsCommand &PhdrCmd = Opt.PhdrsCommands.back();
PhdrCmd.Type = readPhdrType();
do {
Tok = next();
if (Tok == ";")
break;
if (Tok == "FILEHDR")
PhdrCmd.HasFilehdr = true;
else if (Tok == "PHDRS")
PhdrCmd.HasPhdrs = true;
else if (Tok == "AT")
PhdrCmd.LMAExpr = readParenExpr();
else if (Tok == "FLAGS") {
expect("(");
// Passing 0 for the value of dot is a bit of a hack. It means that
// we accept expressions like ".|1".
PhdrCmd.Flags = readExpr()(0);
expect(")");
} else
setError("unexpected header attribute: " + Tok);
} while (!Error);
}
}
void ScriptParser::readSearchDir() {
expect("(");
StringRef Tok = next();
if (!Config->Nostdlib)
Config->SearchPaths.push_back(unquote(Tok));
expect(")");
}
void ScriptParser::readSections() {
Opt.HasSections = true;
expect("{");
while (!Error && !skip("}")) {
StringRef Tok = next();
BaseCommand *Cmd = readProvideOrAssignment(Tok, true);
if (!Cmd) {
if (Tok == "ASSERT")
Cmd = new AssertCommand(readAssert());
else
Cmd = readOutputSectionDescription(Tok);
}
Opt.Commands.emplace_back(Cmd);
}
}
static int precedence(StringRef Op) {
return StringSwitch<int>(Op)
.Cases("*", "/", 5)
.Cases("+", "-", 4)
.Cases("<<", ">>", 3)
.Cases("<", "<=", ">", ">=", "==", "!=", 2)
.Cases("&", "|", 1)
.Default(-1);
}
Regex ScriptParser::readFilePatterns() {
std::vector<StringRef> V;
while (!Error && !skip(")"))
V.push_back(next());
return compileGlobPatterns(V);
}
SortSectionPolicy ScriptParser::readSortKind() {
if (skip("SORT") || skip("SORT_BY_NAME"))
return SortSectionPolicy::Name;
if (skip("SORT_BY_ALIGNMENT"))
return SortSectionPolicy::Alignment;
if (skip("SORT_BY_INIT_PRIORITY"))
return SortSectionPolicy::Priority;
if (skip("SORT_NONE"))
return SortSectionPolicy::None;
return SortSectionPolicy::Default;
}
// Method reads a list of sequence of excluded files and section globs given in
// a following form: ((EXCLUDE_FILE(file_pattern+))? section_pattern+)+
// Example: *(.foo.1 EXCLUDE_FILE (*a.o) .foo.2 EXCLUDE_FILE (*b.o) .foo.3)
// The semantics of that is next:
// * Include .foo.1 from every file.
// * Include .foo.2 from every file but a.o
// * Include .foo.3 from every file but b.o
std::vector<SectionPattern> ScriptParser::readInputSectionsList() {
std::vector<SectionPattern> Ret;
while (!Error && peek() != ")") {
Regex ExcludeFileRe;
if (skip("EXCLUDE_FILE")) {
expect("(");
ExcludeFileRe = readFilePatterns();
}
std::vector<StringRef> V;
while (!Error && peek() != ")" && peek() != "EXCLUDE_FILE")
V.push_back(next());
if (!V.empty())
Ret.push_back({std::move(ExcludeFileRe), compileGlobPatterns(V)});
else
setError("section pattern is expected");
}
return Ret;
}
// Section pattern grammar can have complex expressions, for example:
// *(SORT(.foo.* EXCLUDE_FILE (*file1.o) .bar.*) .bar.* SORT(.zed.*))
// Generally is a sequence of globs and excludes that may be wrapped in a SORT()
// commands, like: SORT(glob0) glob1 glob2 SORT(glob4)
// This methods handles wrapping sequences of excluded files and section globs
// into SORT() if that needed and reads them all.
InputSectionDescription *
ScriptParser::readInputSectionRules(StringRef FilePattern) {
auto *Cmd = new InputSectionDescription(FilePattern);
expect("(");
while (!HasError && !skip(")")) {
SortSectionPolicy Outer = readSortKind();
SortSectionPolicy Inner = SortSectionPolicy::Default;
std::vector<SectionPattern> V;
if (Outer != SortSectionPolicy::Default) {
expect("(");
Inner = readSortKind();
if (Inner != SortSectionPolicy::Default) {
expect("(");
V = readInputSectionsList();
expect(")");
} else {
V = readInputSectionsList();
}
expect(")");
} else {
V = readInputSectionsList();
}
for (SectionPattern &Pat : V) {
Pat.SortInner = Inner;
Pat.SortOuter = Outer;
}
std::move(V.begin(), V.end(), std::back_inserter(Cmd->SectionPatterns));
}
return Cmd;
}
InputSectionDescription *
ScriptParser::readInputSectionDescription(StringRef Tok) {
// Input section wildcard can be surrounded by KEEP.
// https://sourceware.org/binutils/docs/ld/Input-Section-Keep.html#Input-Section-Keep
if (Tok == "KEEP") {
expect("(");
StringRef FilePattern = next();
InputSectionDescription *Cmd = readInputSectionRules(FilePattern);
expect(")");
Opt.KeptSections.push_back(Cmd);
return Cmd;
}
return readInputSectionRules(Tok);
}
void ScriptParser::readSort() {
expect("(");
expect("CONSTRUCTORS");
expect(")");
}
Expr ScriptParser::readAssert() {
expect("(");
Expr E = readExpr();
expect(",");
StringRef Msg = unquote(next());
expect(")");
return [=](uint64_t Dot) {
uint64_t V = E(Dot);
if (!V)
error(Msg);
return V;
};
}
// Reads a FILL(expr) command. We handle the FILL command as an
// alias for =fillexp section attribute, which is different from
// what GNU linkers do.
// https://sourceware.org/binutils/docs/ld/Output-Section-Data.html
std::vector<uint8_t> ScriptParser::readFill() {
expect("(");
std::vector<uint8_t> V = readOutputSectionFiller(next());
expect(")");
expect(";");
return V;
}
OutputSectionCommand *
ScriptParser::readOutputSectionDescription(StringRef OutSec) {
OutputSectionCommand *Cmd = new OutputSectionCommand(OutSec);
// Read an address expression.
// https://sourceware.org/binutils/docs/ld/Output-Section-Address.html#Output-Section-Address
if (peek() != ":")
Cmd->AddrExpr = readExpr();
expect(":");
if (skip("AT"))
Cmd->LMAExpr = readParenExpr();
if (skip("ALIGN"))
Cmd->AlignExpr = readParenExpr();
if (skip("SUBALIGN"))
Cmd->SubalignExpr = readParenExpr();
// Parse constraints.
if (skip("ONLY_IF_RO"))
Cmd->Constraint = ConstraintKind::ReadOnly;
if (skip("ONLY_IF_RW"))
Cmd->Constraint = ConstraintKind::ReadWrite;
expect("{");
while (!Error && !skip("}")) {
StringRef Tok = next();
if (SymbolAssignment *Assignment = readProvideOrAssignment(Tok, false))
Cmd->Commands.emplace_back(Assignment);
else if (BytesDataCommand *Data = readBytesDataCommand(Tok))
Cmd->Commands.emplace_back(Data);
else if (Tok == "FILL")
Cmd->Filler = readFill();
else if (Tok == "SORT")
readSort();
else if (peek() == "(")
Cmd->Commands.emplace_back(readInputSectionDescription(Tok));
else
setError("unknown command " + Tok);
}
Cmd->Phdrs = readOutputSectionPhdrs();
if (skip("="))
Cmd->Filler = readOutputSectionFiller(next());
else if (peek().startswith("="))
Cmd->Filler = readOutputSectionFiller(next().drop_front());
return Cmd;
}
// Read "=<number>" where <number> is an octal/decimal/hexadecimal number.
// https://sourceware.org/binutils/docs/ld/Output-Section-Fill.html
//
// ld.gold is not fully compatible with ld.bfd. ld.bfd handles
// hexstrings as blobs of arbitrary sizes, while ld.gold handles them
// as 32-bit big-endian values. We will do the same as ld.gold does
// because it's simpler than what ld.bfd does.
std::vector<uint8_t> ScriptParser::readOutputSectionFiller(StringRef Tok) {
uint32_t V;
if (Tok.getAsInteger(0, V)) {
setError("invalid filler expression: " + Tok);
return {};
}
return {uint8_t(V >> 24), uint8_t(V >> 16), uint8_t(V >> 8), uint8_t(V)};
}
SymbolAssignment *ScriptParser::readProvideHidden(bool Provide, bool Hidden) {
expect("(");
SymbolAssignment *Cmd = readAssignment(next());
Cmd->Provide = Provide;
Cmd->Hidden = Hidden;
expect(")");
expect(";");
return Cmd;
}
SymbolAssignment *ScriptParser::readProvideOrAssignment(StringRef Tok,
bool MakeAbsolute) {
SymbolAssignment *Cmd = nullptr;
if (peek() == "=" || peek() == "+=") {
Cmd = readAssignment(Tok);
expect(";");
} else if (Tok == "PROVIDE") {
Cmd = readProvideHidden(true, false);
} else if (Tok == "HIDDEN") {
Cmd = readProvideHidden(false, true);
} else if (Tok == "PROVIDE_HIDDEN") {
Cmd = readProvideHidden(true, true);
}
if (Cmd && MakeAbsolute)
Cmd->IsAbsolute = true;
return Cmd;
}
static uint64_t getSymbolValue(StringRef S, uint64_t Dot) {
if (S == ".")
return Dot;
return ScriptBase->getSymbolValue(S);
}
SymbolAssignment *ScriptParser::readAssignment(StringRef Name) {
StringRef Op = next();
bool IsAbsolute = false;
Expr E;
assert(Op == "=" || Op == "+=");
if (skip("ABSOLUTE")) {
E = readParenExpr();
IsAbsolute = true;
} else {
E = readExpr();
}
if (Op == "+=")
E = [=](uint64_t Dot) { return getSymbolValue(Name, Dot) + E(Dot); };
return new SymbolAssignment(Name, E, IsAbsolute);
}
// This is an operator-precedence parser to parse a linker
// script expression.
Expr ScriptParser::readExpr() { return readExpr1(readPrimary(), 0); }
static Expr combine(StringRef Op, Expr L, Expr R) {
if (Op == "*")
return [=](uint64_t Dot) { return L(Dot) * R(Dot); };
if (Op == "/") {
return [=](uint64_t Dot) -> uint64_t {
uint64_t RHS = R(Dot);
if (RHS == 0) {
error("division by zero");
return 0;
}
return L(Dot) / RHS;
};
}
if (Op == "+")
return [=](uint64_t Dot) { return L(Dot) + R(Dot); };
if (Op == "-")
return [=](uint64_t Dot) { return L(Dot) - R(Dot); };
if (Op == "<<")
return [=](uint64_t Dot) { return L(Dot) << R(Dot); };
if (Op == ">>")
return [=](uint64_t Dot) { return L(Dot) >> R(Dot); };
if (Op == "<")
return [=](uint64_t Dot) { return L(Dot) < R(Dot); };
if (Op == ">")
return [=](uint64_t Dot) { return L(Dot) > R(Dot); };
if (Op == ">=")
return [=](uint64_t Dot) { return L(Dot) >= R(Dot); };
if (Op == "<=")
return [=](uint64_t Dot) { return L(Dot) <= R(Dot); };
if (Op == "==")
return [=](uint64_t Dot) { return L(Dot) == R(Dot); };
if (Op == "!=")
return [=](uint64_t Dot) { return L(Dot) != R(Dot); };
if (Op == "&")
return [=](uint64_t Dot) { return L(Dot) & R(Dot); };
if (Op == "|")
return [=](uint64_t Dot) { return L(Dot) | R(Dot); };
llvm_unreachable("invalid operator");
}
// This is a part of the operator-precedence parser. This function
// assumes that the remaining token stream starts with an operator.
Expr ScriptParser::readExpr1(Expr Lhs, int MinPrec) {
while (!atEOF() && !Error) {
// Read an operator and an expression.
StringRef Op1 = peek();
if (Op1 == "?")
return readTernary(Lhs);
if (precedence(Op1) < MinPrec)
break;
next();
Expr Rhs = readPrimary();
// Evaluate the remaining part of the expression first if the
// next operator has greater precedence than the previous one.
// For example, if we have read "+" and "3", and if the next
// operator is "*", then we'll evaluate 3 * ... part first.
while (!atEOF()) {
StringRef Op2 = peek();
if (precedence(Op2) <= precedence(Op1))
break;
Rhs = readExpr1(Rhs, precedence(Op2));
}
Lhs = combine(Op1, Lhs, Rhs);
}
return Lhs;
}
uint64_t static getConstant(StringRef S) {
if (S == "COMMONPAGESIZE")
return Target->PageSize;
if (S == "MAXPAGESIZE")
return Config->MaxPageSize;
error("unknown constant: " + S);
return 0;
}
// Parses Tok as an integer. Returns true if successful.
// It recognizes hexadecimal (prefixed with "0x" or suffixed with "H")
// and decimal numbers. Decimal numbers may have "K" (kilo) or
// "M" (mega) prefixes.
static bool readInteger(StringRef Tok, uint64_t &Result) {
if (Tok.startswith("-")) {
if (!readInteger(Tok.substr(1), Result))
return false;
Result = -Result;
return true;
}
if (Tok.startswith_lower("0x"))
return !Tok.substr(2).getAsInteger(16, Result);
if (Tok.endswith_lower("H"))
return !Tok.drop_back().getAsInteger(16, Result);
int Suffix = 1;
if (Tok.endswith_lower("K")) {
Suffix = 1024;
Tok = Tok.drop_back();
} else if (Tok.endswith_lower("M")) {
Suffix = 1024 * 1024;
Tok = Tok.drop_back();
}
if (Tok.getAsInteger(10, Result))
return false;
Result *= Suffix;
return true;
}
BytesDataCommand *ScriptParser::readBytesDataCommand(StringRef Tok) {
int Size = StringSwitch<unsigned>(Tok)
.Case("BYTE", 1)
.Case("SHORT", 2)
.Case("LONG", 4)
.Case("QUAD", 8)
.Default(-1);
if (Size == -1)
return nullptr;
expect("(");
uint64_t Val = 0;
StringRef S = next();
if (!readInteger(S, Val))
setError("unexpected value: " + S);
expect(")");
return new BytesDataCommand(Val, Size);
}
StringRef ScriptParser::readParenLiteral() {
expect("(");
StringRef Tok = next();
expect(")");
return Tok;
}
Expr ScriptParser::readPrimary() {
if (peek() == "(")
return readParenExpr();
StringRef Tok = next();
if (Tok == "~") {
Expr E = readPrimary();
return [=](uint64_t Dot) { return ~E(Dot); };
}
if (Tok == "-") {
Expr E = readPrimary();
return [=](uint64_t Dot) { return -E(Dot); };
}
// Built-in functions are parsed here.
// https://sourceware.org/binutils/docs/ld/Builtin-Functions.html.
if (Tok == "ADDR") {
StringRef Name = readParenLiteral();
return
[=](uint64_t Dot) { return ScriptBase->getOutputSectionAddress(Name); };
}
if (Tok == "LOADADDR") {
StringRef Name = readParenLiteral();
return [=](uint64_t Dot) { return ScriptBase->getOutputSectionLMA(Name); };
}
if (Tok == "ASSERT")
return readAssert();
if (Tok == "ALIGN") {
Expr E = readParenExpr();
return [=](uint64_t Dot) { return alignTo(Dot, E(Dot)); };
}
if (Tok == "CONSTANT") {
StringRef Name = readParenLiteral();
return [=](uint64_t Dot) { return getConstant(Name); };
}
if (Tok == "DEFINED") {
expect("(");
StringRef Tok = next();
expect(")");
return [=](uint64_t Dot) { return ScriptBase->isDefined(Tok) ? 1 : 0; };
}
if (Tok == "SEGMENT_START") {
expect("(");
next();
expect(",");
Expr E = readExpr();
expect(")");
return [=](uint64_t Dot) { return E(Dot); };
}
if (Tok == "DATA_SEGMENT_ALIGN") {
expect("(");
Expr E = readExpr();
expect(",");
readExpr();
expect(")");
return [=](uint64_t Dot) { return alignTo(Dot, E(Dot)); };
}
if (Tok == "DATA_SEGMENT_END") {
expect("(");
expect(".");
expect(")");
return [](uint64_t Dot) { return Dot; };
}
// GNU linkers implements more complicated logic to handle
// DATA_SEGMENT_RELRO_END. We instead ignore the arguments and just align to
// the next page boundary for simplicity.
if (Tok == "DATA_SEGMENT_RELRO_END") {
expect("(");
readExpr();
expect(",");
readExpr();
expect(")");
return [](uint64_t Dot) { return alignTo(Dot, Target->PageSize); };
}
if (Tok == "SIZEOF") {
StringRef Name = readParenLiteral();
return [=](uint64_t Dot) { return ScriptBase->getOutputSectionSize(Name); };
}
if (Tok == "ALIGNOF") {
StringRef Name = readParenLiteral();
return
[=](uint64_t Dot) { return ScriptBase->getOutputSectionAlign(Name); };
}
if (Tok == "SIZEOF_HEADERS")
return [=](uint64_t Dot) { return ScriptBase->getHeaderSize(); };
// Tok is a literal number.
uint64_t V;
if (readInteger(Tok, V))
return [=](uint64_t Dot) { return V; };
// Tok is a symbol name.
if (Tok != "." && !isValidCIdentifier(Tok))
setError("malformed number: " + Tok);
return [=](uint64_t Dot) { return getSymbolValue(Tok, Dot); };
}
Expr ScriptParser::readTernary(Expr Cond) {
next();
Expr L = readExpr();
expect(":");
Expr R = readExpr();
return [=](uint64_t Dot) { return Cond(Dot) ? L(Dot) : R(Dot); };
}
Expr ScriptParser::readParenExpr() {
expect("(");
Expr E = readExpr();
expect(")");
return E;
}
std::vector<StringRef> ScriptParser::readOutputSectionPhdrs() {
std::vector<StringRef> Phdrs;
while (!Error && peek().startswith(":")) {
StringRef Tok = next();
Tok = (Tok.size() == 1) ? next() : Tok.substr(1);
if (Tok.empty()) {
setError("section header name is empty");
break;
}
Phdrs.push_back(Tok);
}
return Phdrs;
}
unsigned ScriptParser::readPhdrType() {
StringRef Tok = next();
unsigned Ret = StringSwitch<unsigned>(Tok)
.Case("PT_NULL", PT_NULL)
.Case("PT_LOAD", PT_LOAD)
.Case("PT_DYNAMIC", PT_DYNAMIC)
.Case("PT_INTERP", PT_INTERP)
.Case("PT_NOTE", PT_NOTE)
.Case("PT_SHLIB", PT_SHLIB)
.Case("PT_PHDR", PT_PHDR)
.Case("PT_TLS", PT_TLS)
.Case("PT_GNU_EH_FRAME", PT_GNU_EH_FRAME)
.Case("PT_GNU_STACK", PT_GNU_STACK)
.Case("PT_GNU_RELRO", PT_GNU_RELRO)
.Default(-1);
if (Ret == (unsigned)-1) {
setError("invalid program header type: " + Tok);
return PT_NULL;
}
return Ret;
}
void ScriptParser::readVersionDeclaration(StringRef VerStr) {
// Identifiers start at 2 because 0 and 1 are reserved
// for VER_NDX_LOCAL and VER_NDX_GLOBAL constants.
size_t VersionId = Config->VersionDefinitions.size() + 2;
Config->VersionDefinitions.push_back({VerStr, VersionId});
if (skip("global:") || peek() != "local:")
readGlobal(VerStr);
if (skip("local:"))
readLocal();
expect("}");
// Each version may have a parent version. For example, "Ver2" defined as
// "Ver2 { global: foo; local: *; } Ver1;" has "Ver1" as a parent. This
// version hierarchy is, probably against your instinct, purely for human; the
// runtime doesn't care about them at all. In LLD, we simply skip the token.
if (!VerStr.empty() && peek() != ";")
next();
expect(";");
}
void ScriptParser::readLocal() {
Config->DefaultSymbolVersion = VER_NDX_LOCAL;
expect("*");
expect(";");
}
void ScriptParser::readExtern(std::vector<SymbolVersion> *Globals) {
expect("\"C++\"");
expect("{");
for (;;) {
if (peek() == "}" || Error)
break;
bool HasWildcard = !peek().startswith("\"") && hasWildcard(peek());
Globals->push_back({unquote(next()), true, HasWildcard});
expect(";");
}
expect("}");
expect(";");
}
void ScriptParser::readGlobal(StringRef VerStr) {
std::vector<SymbolVersion> *Globals;
if (VerStr.empty())
Globals = &Config->VersionScriptGlobals;
else
Globals = &Config->VersionDefinitions.back().Globals;
for (;;) {
if (skip("extern"))
readExtern(Globals);
StringRef Cur = peek();
if (Cur == "}" || Cur == "local:" || Error)
return;
next();
Globals->push_back({unquote(Cur), false, hasWildcard(Cur)});
expect(";");
}
}
static bool isUnderSysroot(StringRef Path) {
if (Config->Sysroot == "")
return false;
for (; !Path.empty(); Path = sys::path::parent_path(Path))
if (sys::fs::equivalent(Config->Sysroot, Path))
return true;
return false;
}
void elf::readLinkerScript(MemoryBufferRef MB) {
StringRef Path = MB.getBufferIdentifier();
ScriptParser(MB.getBuffer(), isUnderSysroot(Path)).readLinkerScript();
}
void elf::readVersionScript(MemoryBufferRef MB) {
ScriptParser(MB.getBuffer(), false).readVersionScript();
}
template class elf::LinkerScript<ELF32LE>;
template class elf::LinkerScript<ELF32BE>;
template class elf::LinkerScript<ELF64LE>;
template class elf::LinkerScript<ELF64BE>;
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