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clang-p2996/lld/ELF/LinkerScript.cpp
George Rimar 8f66df92ba [ELF] - Linkerscript: fix VA value assigned to sections when using constraints. 
Previously we searched output section by name to assign VA. That did not
work in the case when multiple output sections with different constraints were defined in script.
Testcase shows the possible issue scenario, patch fixes the issue.

Differential revision: https://reviews.llvm.org/D23451

llvm-svn: 278561
2016-08-12 20:38:20 +00:00

1276 lines
36 KiB
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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;
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();
}
template <class ELFT> static void addSynthetic(SymbolAssignment *Cmd) {
Symbol *Sym = Symtab<ELFT>::X->addSynthetic(Cmd->Name, nullptr, 0);
Sym->Visibility = Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT;
Cmd->Sym = Sym->body();
}
// 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;
}
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 (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;
}
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;
}
// You can define new symbols using linker scripts. For example,
// ".text { abc.o(.text); foo = .; def.o(.text); }" defines symbol
// foo just after abc.o's text section contents. This class is to
// handle such symbol definitions.
//
// In order to handle scripts like the above one, we want to
// keep symbol definitions in output sections. Because output sections
// can contain only input sections, we wrap symbol definitions
// with dummy input sections. This class serves that purpose.
template <class ELFT>
class elf::LayoutInputSection : public InputSectionBase<ELFT> {
public:
explicit LayoutInputSection(SymbolAssignment *Cmd);
static bool classof(const InputSectionBase<ELFT> *S);
SymbolAssignment *Cmd;
private:
typename ELFT::Shdr Hdr;
};
template <class ELFT>
static InputSectionBase<ELFT> *
getNonLayoutSection(std::vector<InputSectionBase<ELFT> *> &Vec) {
for (InputSectionBase<ELFT> *S : Vec)
if (!isa<LayoutInputSection<ELFT>>(S))
return S;
return nullptr;
}
template <class T> static T *zero(T *Val) {
memset(Val, 0, sizeof(*Val));
return Val;
}
template <class ELFT>
LayoutInputSection<ELFT>::LayoutInputSection(SymbolAssignment *Cmd)
: InputSectionBase<ELFT>(nullptr, zero(&Hdr),
InputSectionBase<ELFT>::Layout),
Cmd(Cmd) {
this->Live = true;
Hdr.sh_type = SHT_NOBITS;
}
template <class ELFT>
bool LayoutInputSection<ELFT>::classof(const InputSectionBase<ELFT> *S) {
return S->SectionKind == InputSectionBase<ELFT>::Layout;
}
template <class ELFT>
static bool compareName(InputSectionBase<ELFT> *A, InputSectionBase<ELFT> *B) {
return A->getSectionName() < B->getSectionName();
}
template <class ELFT>
static bool compareAlignment(InputSectionBase<ELFT> *A,
InputSectionBase<ELFT> *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;
}
template <class ELFT>
static std::function<bool(InputSectionBase<ELFT> *, InputSectionBase<ELFT> *)>
getComparator(SortKind K) {
if (K == SortByName)
return compareName<ELFT>;
return compareAlignment<ELFT>;
}
template <class ELFT>
void LinkerScript<ELFT>::discard(OutputSectionCommand &Cmd) {
for (const std::unique_ptr<BaseCommand> &Base : Cmd.Commands) {
if (auto *Cmd = dyn_cast<InputSectionDescription>(Base.get())) {
for (InputSectionBase<ELFT> *S : getInputSections(Cmd)) {
S->Live = false;
reportDiscarded(S);
}
}
}
}
static bool checkConstraint(uint64_t Flags, ConstraintKind Kind) {
bool RO = (Kind == ConstraintKind::ReadOnly);
bool RW = (Kind == ConstraintKind::ReadWrite);
bool Writable = Flags & SHF_WRITE;
return !((RO && Writable) || (RW && !Writable));
}
template <class ELFT>
static bool matchConstraints(ArrayRef<InputSectionBase<ELFT> *> Sections,
ConstraintKind Kind) {
if (Kind == ConstraintKind::NoConstraint)
return true;
return llvm::all_of(Sections, [=](InputSectionBase<ELFT> *Sec) {
return checkConstraint(Sec->getSectionHdr()->sh_flags, Kind);
});
}
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) {
if (auto *OutCmd = dyn_cast<SymbolAssignment>(Base.get())) {
if (shouldDefine<ELFT>(OutCmd))
addSynthetic<ELFT>(OutCmd);
Ret.push_back(new (LAlloc.Allocate()) LayoutInputSection<ELFT>(OutCmd));
continue;
}
auto *Cmd = cast<InputSectionDescription>(Base.get());
std::vector<InputSectionBase<ELFT> *> V = getInputSections(Cmd);
if (!matchConstraints<ELFT>(V, OutCmd.Constraint))
continue;
if (Cmd->SortInner)
std::stable_sort(V.begin(), V.end(), getComparator<ELFT>(Cmd->SortInner));
if (Cmd->SortOuter)
std::stable_sort(V.begin(), V.end(), getComparator<ELFT>(Cmd->SortOuter));
Ret.insert(Ret.end(), V.begin(), V.end());
}
return Ret;
}
template <class ELFT>
void LinkerScript<ELFT>::createSections(OutputSectionFactory<ELFT> &Factory) {
for (const std::unique_ptr<BaseCommand> &Base1 : Opt.Commands) {
if (auto *Cmd = dyn_cast<SymbolAssignment>(Base1.get())) {
if (shouldDefine<ELFT>(Cmd))
addRegular<ELFT>(Cmd);
continue;
}
if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base1.get())) {
if (Cmd->Name == "/DISCARD/") {
discard(*Cmd);
continue;
}
std::vector<InputSectionBase<ELFT> *> V = createInputSectionList(*Cmd);
InputSectionBase<ELFT> *Head = getNonLayoutSection<ELFT>(V);
if (!Head)
continue;
OutputSectionBase<ELFT> *OutSec;
bool IsNew;
std::tie(OutSec, IsNew) = Factory.create(Head, Cmd->Name);
if (IsNew)
OutputSections->push_back(OutSec);
for (InputSectionBase<ELFT> *Sec : V)
OutSec->addSection(Sec);
}
}
// Add orphan sections.
for (const std::unique_ptr<ObjectFile<ELFT>> &F :
Symtab<ELFT>::X->getObjectFiles()) {
for (InputSectionBase<ELFT> *S : F->getSections()) {
if (isDiscarded(S) || S->OutSec)
continue;
OutputSectionBase<ELFT> *OutSec;
bool IsNew;
std::tie(OutSec, IsNew) = Factory.create(S, getOutputSectionName(S));
if (IsNew)
OutputSections->push_back(OutSec);
OutSec->addSection(S);
}
}
}
template <class ELFT> void assignOffsets(OutputSectionBase<ELFT> *Sec) {
auto *OutSec = dyn_cast<OutputSection<ELFT>>(Sec);
if (!OutSec) {
Sec->assignOffsets();
return;
}
typedef typename ELFT::uint uintX_t;
uintX_t Off = 0;
for (InputSection<ELFT> *I : OutSec->Sections) {
if (auto *L = dyn_cast<LayoutInputSection<ELFT>>(I)) {
uintX_t Value = L->Cmd->Expression(Sec->getVA() + Off) - Sec->getVA();
if (L->Cmd->Name == ".") {
Off = Value;
} else {
auto *Sym = cast<DefinedSynthetic<ELFT>>(L->Cmd->Sym);
Sym->Section = OutSec;
Sym->Value = Value;
}
} else {
Off = alignTo(Off, I->Alignment);
I->OutSecOff = Off;
Off += I->getSize();
}
// Update section size inside for-loop, so that SIZEOF
// works correctly in the case below:
// .foo { *(.aaa) a = SIZEOF(.foo); *(.bbb) }
Sec->setSize(Off);
}
}
template <class ELFT>
static OutputSectionBase<ELFT> *
findSection(OutputSectionCommand &Cmd,
ArrayRef<OutputSectionBase<ELFT> *> Sections) {
for (OutputSectionBase<ELFT> *Sec : Sections) {
if (Sec->getName() != Cmd.Name)
continue;
if (checkConstraint(Sec->getFlags(), Cmd.Constraint))
return Sec;
}
return nullptr;
}
template <class ELFT> void LinkerScript<ELFT>::assignAddresses() {
// 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 : *OutputSections) {
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 = getHeaderSize();
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;
}
if (auto *Cmd = dyn_cast<AssertCommand>(Base.get())) {
Cmd->Expression(Dot);
continue;
}
auto *Cmd = cast<OutputSectionCommand>(Base.get());
OutputSectionBase<ELFT> *Sec = findSection<ELFT>(*Cmd, *OutputSections);
if (!Sec)
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);
assignOffsets(Sec);
ThreadBssOffset = TVA - Dot + Sec->getSize();
continue;
}
if (!(Sec->getFlags() & SHF_ALLOC)) {
Sec->assignOffsets();
continue;
}
Dot = alignTo(Dot, Sec->getAlignment());
Sec->setVA(Dot);
assignOffsets(Sec);
MinVA = std::min(MinVA, Dot);
Dot += Sec->getSize();
}
// 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 (Out<ELFT>::DynSymTab) {
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;
}
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;
}
template <class ELFT>
typename ELFT::uint LinkerScript<ELFT>::getHeaderSize() {
return Out<ELFT>::ElfHeader->getSize() + Out<ELFT>::ProgramHeaders->getSize();
}
// 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);
OutputSectionCommand *readOutputSectionDescription(StringRef OutSec);
std::vector<uint8_t> readOutputSectionFiller();
std::vector<StringRef> readOutputSectionPhdrs();
InputSectionDescription *readInputSectionDescription();
std::vector<StringRef> readInputFilePatterns();
InputSectionDescription *readInputSectionRules();
unsigned readPhdrType();
SortKind readSortKind();
SymbolAssignment *readProvide(bool Hidden);
SymbolAssignment *readProvideOrAssignment(StringRef Tok);
Expr readAlign();
void readSort();
Expr readAssert();
Expr readExpr();
Expr readExpr1(Expr Lhs, int MinPrec);
Expr readPrimary();
Expr readTernary(Expr Cond);
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 && !skip(")"))
addFile(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(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();
BaseCommand *Cmd = readProvideOrAssignment(Tok);
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)
.Case("*", 4)
.Case("/", 4)
.Case("+", 3)
.Case("-", 3)
.Case("<", 2)
.Case(">", 2)
.Case(">=", 2)
.Case("<=", 2)
.Case("==", 2)
.Case("!=", 2)
.Case("&", 1)
.Default(-1);
}
std::vector<StringRef> ScriptParser::readInputFilePatterns() {
std::vector<StringRef> V;
while (!Error && !skip(")"))
V.push_back(next());
return V;
}
SortKind ScriptParser::readSortKind() {
if (skip("SORT") || skip("SORT_BY_NAME"))
return SortByName;
if (skip("SORT_BY_ALIGNMENT"))
return SortByAlignment;
return SortNone;
}
InputSectionDescription *ScriptParser::readInputSectionRules() {
auto *Cmd = new InputSectionDescription;
Cmd->FilePattern = next();
expect("(");
// Read EXCLUDE_FILE().
if (skip("EXCLUDE_FILE")) {
expect("(");
while (!Error && !skip(")"))
Cmd->ExcludedFiles.push_back(next());
}
// Read SORT().
if (SortKind K1 = readSortKind()) {
Cmd->SortOuter = K1;
expect("(");
if (SortKind K2 = readSortKind()) {
Cmd->SortInner = K2;
expect("(");
Cmd->SectionPatterns = readInputFilePatterns();
expect(")");
} else {
Cmd->SectionPatterns = readInputFilePatterns();
}
expect(")");
return Cmd;
}
Cmd->SectionPatterns = readInputFilePatterns();
return Cmd;
}
InputSectionDescription *ScriptParser::readInputSectionDescription() {
// 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("(");
InputSectionDescription *Cmd = readInputSectionRules();
expect(")");
Opt.KeptSections.insert(Opt.KeptSections.end(),
Cmd->SectionPatterns.begin(),
Cmd->SectionPatterns.end());
return Cmd;
}
return readInputSectionRules();
}
Expr ScriptParser::readAlign() {
expect("(");
Expr E = readExpr();
expect(")");
return E;
}
void ScriptParser::readSort() {
expect("(");
expect("CONSTRUCTORS");
expect(")");
}
Expr ScriptParser::readAssert() {
expect("(");
Expr E = readExpr();
expect(",");
StringRef Msg = next();
expect(")");
return [=](uint64_t Dot) {
uint64_t V = E(Dot);
if (!V)
error(Msg);
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("ALIGN"))
Cmd->AlignExpr = readAlign();
// 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.emplace_back(readInputSectionDescription());
continue;
}
StringRef Tok = next();
if (SymbolAssignment *Assignment = readProvideOrAssignment(Tok))
Cmd->Commands.emplace_back(Assignment);
else if (Tok == "SORT")
readSort();
else
setError("unknown command " + Tok);
}
Cmd->Phdrs = readOutputSectionPhdrs();
Cmd->Filler = readOutputSectionFiller();
return Cmd;
}
std::vector<uint8_t> ScriptParser::readOutputSectionFiller() {
StringRef Tok = peek();
if (!Tok.startswith("="))
return {};
next();
// Read a hexstring of arbitrary length.
if (Tok.startswith("=0x"))
return parseHex(Tok.substr(3));
// Read a decimal or octal value as a big-endian 32 bit value.
// Why do this? I don't know, but that's what gold does.
uint32_t V;
if (Tok.substr(1).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::readProvide(bool Hidden) {
expect("(");
SymbolAssignment *Cmd = readAssignment(next());
Cmd->Provide = true;
Cmd->Hidden = Hidden;
expect(")");
expect(";");
return Cmd;
}
SymbolAssignment *ScriptParser::readProvideOrAssignment(StringRef Tok) {
SymbolAssignment *Cmd = nullptr;
if (peek() == "=" || peek() == "+=") {
Cmd = readAssignment(Tok);
expect(";");
} else if (Tok == "PROVIDE") {
Cmd = readProvide(false);
} else if (Tok == "PROVIDE_HIDDEN") {
Cmd = readProvide(true);
}
return Cmd;
}
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");
}
}
static uint64_t getHeaderSize() {
switch (Config->EKind) {
case ELF32LEKind:
return Script<ELF32LE>::X->getHeaderSize();
case ELF32BEKind:
return Script<ELF32BE>::X->getHeaderSize();
case ELF64LEKind:
return Script<ELF64LE>::X->getHeaderSize();
case ELF64BEKind:
return Script<ELF64BE>::X->getHeaderSize();
default:
llvm_unreachable("unsupported target");
}
}
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); };
return new SymbolAssignment(Name, E);
}
// 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); };
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" || 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 == "ASSERT")
return readAssert();
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); };
}
if (Tok == "SIZEOF_HEADERS")
return [=](uint64_t Dot) { return getHeaderSize(); };
// 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); };
}
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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