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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 lld;
using namespace lld::elf;
ScriptConfiguration *elf::ScriptConfig;
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;
}
template <class ELFT> static bool isDiscarded(InputSectionBase<ELFT> *S) {
return !S || !S->Live;
}
template <class ELFT>
bool LinkerScript<ELFT>::shouldKeep(InputSectionBase<ELFT> *S) {
for (StringRef Pat : Opt.KeptSections)
if (globMatch(Pat, S->getSectionName()))
return true;
return false;
}
static bool match(ArrayRef<StringRef> Patterns, StringRef S) {
for (StringRef Pat : Patterns)
if (globMatch(Pat, S))
return true;
return false;
}
// Create a vector of (<output section name>, <input section description>).
template <class ELFT>
std::vector<std::pair<StringRef, const InputSectionDescription *>>
LinkerScript<ELFT>::getSectionMap() {
std::vector<std::pair<StringRef, const InputSectionDescription *>> Ret;
for (const std::unique_ptr<BaseCommand> &Base1 : Opt.Commands)
if (auto *Cmd1 = dyn_cast<OutputSectionCommand>(Base1.get()))
for (const std::unique_ptr<BaseCommand> &Base2 : Cmd1->Commands)
if (auto *Cmd2 = dyn_cast<InputSectionDescription>(Base2.get()))
Ret.emplace_back(Cmd1->Name, Cmd2);
return Ret;
}
static bool fileMatches(const InputSectionDescription *Desc,
StringRef Filename) {
if (!globMatch(Desc->FilePattern, Filename))
return false;
return Desc->ExcludedFiles.empty() || !match(Desc->ExcludedFiles, Filename);
}
// Returns input sections filtered by given glob patterns.
template <class ELFT>
std::vector<InputSectionBase<ELFT> *>
LinkerScript<ELFT>::getInputSections(const InputSectionDescription *I) {
ArrayRef<StringRef> Patterns = I->SectionPatterns;
std::vector<InputSectionBase<ELFT> *> Ret;
for (const std::unique_ptr<ObjectFile<ELFT>> &F :
Symtab<ELFT>::X->getObjectFiles()) {
if (fileMatches(I, sys::path::filename(F->getName())))
for (InputSectionBase<ELFT> *S : F->getSections())
if (!isDiscarded(S) && !S->OutSec &&
match(Patterns, S->getSectionName()))
Ret.push_back(S);
}
if ((llvm::find(Patterns, "COMMON") != Patterns.end()))
Ret.push_back(CommonInputSection<ELFT>::X);
return Ret;
}
// Add input section to output section. If there is no output section yet,
// then create it and add to output section list.
template <class ELFT>
static void addSection(OutputSectionFactory<ELFT> &Factory,
std::vector<OutputSectionBase<ELFT> *> &Out,
InputSectionBase<ELFT> *C, StringRef Name) {
OutputSectionBase<ELFT> *Sec;
bool IsNew;
std::tie(Sec, IsNew) = Factory.create(C, Name);
if (IsNew)
Out.push_back(Sec);
Sec->addSection(C);
}
template <class ELFT> struct SectionsSorter {
SectionsSorter(SortKind Kind) : Kind(Kind) {}
bool operator()(InputSectionBase<ELFT> *A, InputSectionBase<ELFT> *B) {
int AlignmentCmp = A->Alignment - B->Alignment;
if (Kind == SortKind::Align || (Kind == SortKind::AlignName && AlignmentCmp != 0))
return AlignmentCmp < 0;
int NameCmp = A->getSectionName().compare(B->getSectionName());
if (Kind == SortKind::Name || (Kind == SortKind::NameAlign && NameCmp != 0))
return NameCmp < 0;
if (Kind == SortKind::NameAlign)
return AlignmentCmp < 0;
if (Kind == SortKind::AlignName)
return NameCmp < 0;
llvm_unreachable("unknown section sort kind in predicate");
return false;
}
SortKind Kind;
};
template <class ELFT>
void LinkerScript<ELFT>::createSections(
std::vector<OutputSectionBase<ELFT> *> *Out,
OutputSectionFactory<ELFT> &Factory) {
OutputSections = Out;
for (auto &P : getSectionMap()) {
std::vector<InputSectionBase<ELFT> *> Sections;
StringRef OutputName = P.first;
const InputSectionDescription *I = P.second;
for (InputSectionBase<ELFT> *S : getInputSections(I)) {
if (OutputName == "/DISCARD/") {
S->Live = false;
reportDiscarded(S);
continue;
}
Sections.push_back(S);
}
if (I->Sort != SortKind::None)
std::stable_sort(Sections.begin(), Sections.end(),
SectionsSorter<ELFT>(I->Sort));
for (InputSectionBase<ELFT> *S : Sections)
addSection(Factory, *Out, S, OutputName);
}
// Add all other input sections, which are not listed in script.
for (const std::unique_ptr<ObjectFile<ELFT>> &F :
Symtab<ELFT>::X->getObjectFiles())
for (InputSectionBase<ELFT> *S : F->getSections())
if (!isDiscarded(S) && !S->OutSec)
addSection(Factory, *Out, S, getOutputSectionName(S));
// Remove from the output all the sections which did not meet
// the optional constraints.
filter();
}
// Process ONLY_IF_RO and ONLY_IF_RW.
template <class ELFT> void LinkerScript<ELFT>::filter() {
// In this loop, we remove output sections if they don't satisfy
// requested properties.
for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands) {
auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get());
if (!Cmd || Cmd->Name == "/DISCARD/")
continue;
if (Cmd->Constraint == ConstraintKind::NoConstraint)
continue;
auto It = llvm::find_if(*OutputSections, [&](OutputSectionBase<ELFT> *S) {
return S->getName() == Cmd->Name;
});
if (It == OutputSections->end())
continue;
OutputSectionBase<ELFT> *Sec = *It;
bool Writable = (Sec->getFlags() & SHF_WRITE);
bool RO = (Cmd->Constraint == ConstraintKind::ReadOnly);
bool RW = (Cmd->Constraint == ConstraintKind::ReadWrite);
if ((RO && Writable) || (RW && !Writable))
OutputSections->erase(It);
}
}
template <class ELFT> void LinkerScript<ELFT>::assignAddresses() {
ArrayRef<OutputSectionBase<ELFT> *> Sections = *OutputSections;
// 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.
for (OutputSectionBase<ELFT> *Sec : Sections) {
StringRef Name = Sec->getName();
if (getSectionIndex(Name) == INT_MAX)
Opt.Commands.push_back(llvm::make_unique<OutputSectionCommand>(Name));
}
// Assign addresses as instructed by linker script SECTIONS sub-commands.
Dot = Out<ELFT>::ElfHeader->getSize() + Out<ELFT>::ProgramHeaders->getSize();
uintX_t MinVA = std::numeric_limits<uintX_t>::max();
uintX_t ThreadBssOffset = 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;
}
// Find all the sections with required name. There can be more than
// one section with such name, if the alignment, flags or type
// attribute differs.
auto *Cmd = cast<OutputSectionCommand>(Base.get());
for (OutputSectionBase<ELFT> *Sec : Sections) {
if (Sec->getName() != Cmd->Name)
continue;
if (Cmd->AddrExpr)
Dot = Cmd->AddrExpr(Dot);
if (Cmd->AlignExpr)
Sec->updateAlignment(Cmd->AlignExpr(Dot));
if ((Sec->getFlags() & SHF_TLS) && Sec->getType() == SHT_NOBITS) {
uintX_t TVA = Dot + ThreadBssOffset;
TVA = alignTo(TVA, Sec->getAlignment());
Sec->setVA(TVA);
ThreadBssOffset = TVA - Dot + Sec->getSize();
continue;
}
if (Sec->getFlags() & SHF_ALLOC) {
Dot = alignTo(Dot, Sec->getAlignment());
Sec->setVA(Dot);
MinVA = std::min(MinVA, Dot);
Dot += Sec->getSize();
continue;
}
}
}
// ELF and Program headers need to be right before the first section in
// memory. Set their addresses accordingly.
MinVA = alignDown(MinVA - Out<ELFT>::ElfHeader->getSize() -
Out<ELFT>::ProgramHeaders->getSize(),
Target->PageSize);
Out<ELFT>::ElfHeader->setVA(MinVA);
Out<ELFT>::ProgramHeaders->setVA(Out<ELFT>::ElfHeader->getSize() + MinVA);
}
template <class ELFT>
std::vector<PhdrEntry<ELFT>> LinkerScript<ELFT>::createPhdrs() {
ArrayRef<OutputSectionBase<ELFT> *> Sections = *OutputSections;
std::vector<PhdrEntry<ELFT>> Ret;
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);
switch (Cmd.Type) {
case PT_INTERP:
if (Out<ELFT>::Interp)
Phdr.add(Out<ELFT>::Interp);
break;
case PT_DYNAMIC:
if (isOutputDynamic<ELFT>()) {
Phdr.H.p_flags = Out<ELFT>::Dynamic->getPhdrFlags();
Phdr.add(Out<ELFT>::Dynamic);
}
break;
case PT_GNU_EH_FRAME:
if (!Out<ELFT>::EhFrame->empty() && Out<ELFT>::EhFrameHdr) {
Phdr.H.p_flags = Out<ELFT>::EhFrameHdr->getPhdrFlags();
Phdr.add(Out<ELFT>::EhFrameHdr);
}
break;
}
}
PhdrEntry<ELFT> *Load = nullptr;
uintX_t Flags = PF_R;
for (OutputSectionBase<ELFT> *Sec : Sections) {
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>
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 {};
}
// 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;
}
// A compartor to sort output sections. Returns -1 or 1 if
// A or B are mentioned in linker script. Otherwise, returns 0.
template <class ELFT>
int LinkerScript<ELFT>::compareSections(StringRef A, StringRef B) {
int I = getSectionIndex(A);
int J = getSectionIndex(B);
if (I == INT_MAX && J == INT_MAX)
return 0;
return I < J ? -1 : 1;
}
// Add symbols defined by linker scripts.
template <class ELFT> void LinkerScript<ELFT>::addScriptedSymbols() {
for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands) {
auto *Cmd = dyn_cast<SymbolAssignment>(Base.get());
if (!Cmd || Cmd->Name == ".")
continue;
// If a symbol was in PROVIDE(), define it only when it is an
// undefined symbol.
SymbolBody *B = Symtab<ELFT>::X->find(Cmd->Name);
if (Cmd->Provide && !(B && B->isUndefined()))
continue;
// Define an absolute symbol. The symbol value will be assigned later.
// (At this point, we don't know the final address yet.)
Symbol *Sym = Symtab<ELFT>::X->addUndefined(Cmd->Name);
replaceBody<DefinedRegular<ELFT>>(Sym, Cmd->Name, STV_DEFAULT);
Sym->Visibility = Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT;
Cmd->Sym = Sym->body();
}
}
template <class ELFT> bool LinkerScript<ELFT>::hasPhdrsCommands() {
return !Opt.PhdrsCommands.empty();
}
template <class ELFT>
typename ELFT::uint LinkerScript<ELFT>::getOutputSectionSize(StringRef Name) {
for (OutputSectionBase<ELFT> *Sec : *OutputSections)
if (Sec->getName() == Name)
return Sec->getSize();
error("undefined section " + Name);
return 0;
}
// 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 run();
private:
void addFile(StringRef Path);
void readAsNeeded();
void readEntry();
void readExtern();
void readGroup();
void readInclude();
void readNothing() {}
void readOutput();
void readOutputArch();
void readOutputFormat();
void readPhdrs();
void readSearchDir();
void readSections();
SymbolAssignment *readAssignment(StringRef Name);
void readOutputSectionDescription(StringRef OutSec);
std::vector<uint8_t> readOutputSectionFiller();
std::vector<StringRef> readOutputSectionPhdrs();
std::unique_ptr<InputSectionDescription> readInputSectionDescription();
void readInputFilePattern(InputSectionDescription *InCmd, bool Keep);
void readInputSectionRules(InputSectionDescription *InCmd, bool Keep);
unsigned readPhdrType();
void readProvide(bool Hidden);
void readAlign(OutputSectionCommand *Cmd);
void readSort();
Expr readExpr();
Expr readExpr1(Expr Lhs, int MinPrec);
Expr readPrimary();
Expr readTernary(Expr Cond);
Expr combine(StringRef Op, Expr Lhs, Expr Rhs);
const static StringMap<Handler> Cmd;
ScriptConfiguration &Opt = *ScriptConfig;
StringSaver Saver = {ScriptConfig->Alloc};
bool IsUnderSysroot;
};
const StringMap<elf::ScriptParser::Handler> elf::ScriptParser::Cmd = {
{"ENTRY", &ScriptParser::readEntry},
{"EXTERN", &ScriptParser::readExtern},
{"GROUP", &ScriptParser::readGroup},
{"INCLUDE", &ScriptParser::readInclude},
{"INPUT", &ScriptParser::readGroup},
{"OUTPUT", &ScriptParser::readOutput},
{"OUTPUT_ARCH", &ScriptParser::readOutputArch},
{"OUTPUT_FORMAT", &ScriptParser::readOutputFormat},
{"PHDRS", &ScriptParser::readPhdrs},
{"SEARCH_DIR", &ScriptParser::readSearchDir},
{"SECTIONS", &ScriptParser::readSections},
{";", &ScriptParser::readNothing}};
void ScriptParser::run() {
while (!atEOF()) {
StringRef Tok = next();
if (Handler Fn = Cmd.lookup(Tok))
(this->*Fn)();
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) {
StringRef Tok = next();
if (Tok == ")")
break;
addFile(Tok);
}
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) {
StringRef Tok = next();
if (Tok == ")")
return;
Config->Undefined.push_back(Tok);
}
}
void ScriptParser::readGroup() {
expect("(");
while (!Error) {
StringRef Tok = next();
if (Tok == ")")
return;
if (Tok == "AS_NEEDED") {
readAsNeeded();
continue;
}
addFile(Tok);
}
}
void ScriptParser::readInclude() {
StringRef Tok = next();
auto MBOrErr = MemoryBuffer::getFile(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 = 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});
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 == "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("(");
Config->SearchPaths.push_back(next());
expect(")");
}
void ScriptParser::readSections() {
Opt.HasContents = true;
expect("{");
while (!Error && !skip("}")) {
StringRef Tok = next();
if (peek() == "=" || peek() == "+=") {
readAssignment(Tok);
expect(";");
} else if (Tok == "PROVIDE") {
readProvide(false);
} else if (Tok == "PROVIDE_HIDDEN") {
readProvide(true);
} else {
readOutputSectionDescription(Tok);
}
}
}
static int precedence(StringRef Op) {
return StringSwitch<int>(Op)
.Case("*", 4)
.Case("/", 4)
.Case("+", 3)
.Case("-", 3)
.Case("<", 2)
.Case(">", 2)
.Case(">=", 2)
.Case("<=", 2)
.Case("==", 2)
.Case("!=", 2)
.Case("&", 1)
.Default(-1);
}
void ScriptParser::readInputFilePattern(InputSectionDescription *InCmd,
bool Keep) {
while (!Error && !skip(")")) {
if (Keep)
Opt.KeptSections.push_back(peek());
InCmd->SectionPatterns.push_back(next());
}
}
void ScriptParser::readInputSectionRules(InputSectionDescription *InCmd,
bool Keep) {
InCmd->FilePattern = next();
expect("(");
if (skip("EXCLUDE_FILE")) {
expect("(");
while (!Error && !skip(")"))
InCmd->ExcludedFiles.push_back(next());
}
if (skip("SORT") || skip("SORT_BY_NAME")) {
expect("(");
if (skip("SORT_BY_ALIGNMENT")) {
InCmd->Sort = SortKind::NameAlign;
expect("(");
readInputFilePattern(InCmd, Keep);
expect(")");
} else {
InCmd->Sort = SortKind::Name;
readInputFilePattern(InCmd, Keep);
}
expect(")");
return;
}
if (skip("SORT_BY_ALIGNMENT")) {
expect("(");
if (skip("SORT") || skip("SORT_BY_NAME")) {
InCmd->Sort = SortKind::AlignName;
expect("(");
readInputFilePattern(InCmd, Keep);
expect(")");
} else {
InCmd->Sort = SortKind::Align;
readInputFilePattern(InCmd, Keep);
}
expect(")");
return;
}
readInputFilePattern(InCmd, Keep);
}
std::unique_ptr<InputSectionDescription>
ScriptParser::readInputSectionDescription() {
auto InCmd = llvm::make_unique<InputSectionDescription>();
// Input section wildcard can be surrounded by KEEP.
// https://sourceware.org/binutils/docs/ld/Input-Section-Keep.html#Input-Section-Keep
if (skip("KEEP")) {
expect("(");
readInputSectionRules(InCmd.get(), true);
expect(")");
} else {
readInputSectionRules(InCmd.get(), false);
}
return InCmd;
}
void ScriptParser::readAlign(OutputSectionCommand *Cmd) {
expect("(");
Cmd->AlignExpr = readExpr();
expect(")");
}
void ScriptParser::readSort() {
expect("(");
expect("CONSTRUCTORS");
expect(")");
}
void ScriptParser::readOutputSectionDescription(StringRef OutSec) {
OutputSectionCommand *Cmd = new OutputSectionCommand(OutSec);
Opt.Commands.emplace_back(Cmd);
// 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("ALIGN"))
readAlign(Cmd);
// Parse constraints.
if (skip("ONLY_IF_RO"))
Cmd->Constraint = ConstraintKind::ReadOnly;
if (skip("ONLY_IF_RW"))
Cmd->Constraint = ConstraintKind::ReadWrite;
expect("{");
while (!Error && !skip("}")) {
if (peek().startswith("*") || peek() == "KEEP") {
Cmd->Commands.push_back(readInputSectionDescription());
continue;
}
StringRef Tok = next();
if (Tok == "PROVIDE") {
readProvide(false);
} else if (Tok == "PROVIDE_HIDDEN") {
readProvide(true);
} else if (Tok == "SORT") {
readSort();
} else {
setError("unknown command " + Tok);
}
}
Cmd->Phdrs = readOutputSectionPhdrs();
Cmd->Filler = readOutputSectionFiller();
}
std::vector<uint8_t> ScriptParser::readOutputSectionFiller() {
StringRef Tok = peek();
if (!Tok.startswith("="))
return {};
next();
if (Tok.startswith("=0x"))
return parseHex(Tok.substr(3));
// This must be a decimal.
unsigned int Value;
if (Tok.substr(1).getAsInteger(10, Value)) {
setError("filler should be a decimal/hexadecimal value");
return {};
}
if (Value > 255)
setError("only single bytes decimal are supported for the filler now");
return {static_cast<unsigned char>(Value)};
}
void ScriptParser::readProvide(bool Hidden) {
expect("(");
SymbolAssignment *Cmd = readAssignment(next());
Cmd->Provide = true;
Cmd->Hidden = Hidden;
expect(")");
expect(";");
}
static uint64_t getSymbolValue(StringRef S, uint64_t Dot) {
if (S == ".")
return Dot;
switch (Config->EKind) {
case ELF32LEKind:
if (SymbolBody *B = Symtab<ELF32LE>::X->find(S))
return B->getVA<ELF32LE>();
break;
case ELF32BEKind:
if (SymbolBody *B = Symtab<ELF32BE>::X->find(S))
return B->getVA<ELF32BE>();
break;
case ELF64LEKind:
if (SymbolBody *B = Symtab<ELF64LE>::X->find(S))
return B->getVA<ELF64LE>();
break;
case ELF64BEKind:
if (SymbolBody *B = Symtab<ELF64BE>::X->find(S))
return B->getVA<ELF64BE>();
break;
default:
llvm_unreachable("unsupported target");
}
error("symbol not found: " + S);
return 0;
}
static uint64_t getSectionSize(StringRef Name) {
switch (Config->EKind) {
case ELF32LEKind:
return Script<ELF32LE>::X->getOutputSectionSize(Name);
case ELF32BEKind:
return Script<ELF32BE>::X->getOutputSectionSize(Name);
case ELF64LEKind:
return Script<ELF64LE>::X->getOutputSectionSize(Name);
case ELF64BEKind:
return Script<ELF64BE>::X->getOutputSectionSize(Name);
default:
llvm_unreachable("unsupported target");
}
return 0;
}
SymbolAssignment *ScriptParser::readAssignment(StringRef Name) {
StringRef Op = next();
assert(Op == "=" || Op == "+=");
Expr E = readExpr();
if (Op == "+=")
E = [=](uint64_t Dot) { return getSymbolValue(Name, Dot) + E(Dot); };
auto *Cmd = new SymbolAssignment(Name, E);
Opt.Commands.emplace_back(Cmd);
return Cmd;
}
// This is an operator-precedence parser to parse a linker
// script expression.
Expr ScriptParser::readExpr() { return readExpr1(readPrimary(), 0); }
// 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" || S == "MAXPAGESIZE")
return Target->PageSize;
error("unknown constant: " + S);
return 0;
}
Expr ScriptParser::readPrimary() {
StringRef Tok = next();
if (Tok == "(") {
Expr E = readExpr();
expect(")");
return E;
}
// Built-in functions are parsed here.
// https://sourceware.org/binutils/docs/ld/Builtin-Functions.html.
if (Tok == "ALIGN") {
expect("(");
Expr E = readExpr();
expect(")");
return [=](uint64_t Dot) { return alignTo(Dot, E(Dot)); };
}
if (Tok == "CONSTANT") {
expect("(");
StringRef Tok = next();
expect(")");
return [=](uint64_t Dot) { return getConstant(Tok); };
}
if (Tok == "SEGMENT_START") {
expect("(");
next();
expect(",");
uint64_t Val;
next().getAsInteger(0, Val);
expect(")");
return [=](uint64_t Dot) { return Val; };
}
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("(");
next();
expect(",");
readExpr();
expect(")");
return [](uint64_t Dot) { return alignTo(Dot, Target->PageSize); };
}
if (Tok == "SIZEOF") {
expect("(");
StringRef Name = next();
expect(")");
return [=](uint64_t Dot) { return getSectionSize(Name); };
}
// Parse a symbol name or a number literal.
uint64_t V = 0;
if (Tok.getAsInteger(0, V)) {
if (Tok != "." && !isValidCIdentifier(Tok))
setError("malformed number: " + Tok);
return [=](uint64_t Dot) { return getSymbolValue(Tok, Dot); };
}
return [=](uint64_t Dot) { return V; };
}
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::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); };
llvm_unreachable("invalid operator");
}
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;
}
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;
}
// Entry point.
void elf::readLinkerScript(MemoryBufferRef MB) {
StringRef Path = MB.getBufferIdentifier();
ScriptParser(MB.getBuffer(), isUnderSysroot(Path)).run();
}
template class elf::LinkerScript<ELF32LE>;
template class elf::LinkerScript<ELF32BE>;
template class elf::LinkerScript<ELF64LE>;
template class elf::LinkerScript<ELF64BE>;
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