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hanchenye-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(StringRef Pattern, ArrayRef<StringRef> Arr) {
for (StringRef S : Arr)
if (globMatch(S, Pattern))
return true;
return false;
}
template <class ELFT>
std::vector<OutputSectionBase<ELFT> *>
LinkerScript<ELFT>::createSections(OutputSectionFactory<ELFT> &Factory) {
typedef const std::unique_ptr<ObjectFile<ELFT>> ObjectFile;
std::vector<OutputSectionBase<ELFT> *> Result;
// Add input section to output section. If there is no output section yet,
// then create it and add to output section list.
auto AddInputSec = [&](InputSectionBase<ELFT> *C, StringRef Name) {
OutputSectionBase<ELFT> *Sec;
bool IsNew;
std::tie(Sec, IsNew) = Factory.create(C, Name);
if (IsNew)
Result.push_back(Sec);
Sec->addSection(C);
};
// Select input sections matching rule and add them to corresponding
// output section. Section rules are processed in order they're listed
// in script, so correct input section order is maintained by design.
for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands) {
auto *OutCmd = dyn_cast<OutputSectionCommand>(Base.get());
if (!OutCmd)
continue;
for (const std::unique_ptr<BaseCommand> &Cmd : OutCmd->Commands) {
auto *InCmd = dyn_cast<InputSectionDescription>(Cmd.get());
if (!InCmd)
continue;
for (ObjectFile &F : Symtab<ELFT>::X->getObjectFiles()) {
for (InputSectionBase<ELFT> *S : F->getSections()) {
if (isDiscarded(S) || S->OutSec)
continue;
if (match(S->getSectionName(), InCmd->Patterns)) {
if (OutCmd->Name == "/DISCARD/")
S->Live = false;
else
AddInputSec(S, OutCmd->Name);
}
}
}
}
}
// Add all other input sections, which are not listed in script.
for (ObjectFile &F : Symtab<ELFT>::X->getObjectFiles())
for (InputSectionBase<ELFT> *S : F->getSections()) {
if (!isDiscarded(S)) {
if (!S->OutSec)
AddInputSec(S, getOutputSectionName(S));
} else
reportDiscarded(S, F);
}
// Remove from the output all the sections which did not meet
// the optional constraints.
return filter(Result);
}
// Process ONLY_IF_RO and ONLY_IF_RW.
template <class ELFT>
std::vector<OutputSectionBase<ELFT> *>
LinkerScript<ELFT>::filter(std::vector<OutputSectionBase<ELFT> *> &Sections) {
// Sections and OutputSectionCommands are parallel arrays.
// In this loop, we remove output sections if they don't satisfy
// requested properties.
auto It = Sections.begin();
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) {
++It;
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)) {
Sections.erase(It);
continue;
}
++It;
}
return Sections;
}
template <class ELFT>
void LinkerScript<ELFT>::dispatchAssignment(SymbolAssignment *Cmd) {
uint64_t Val = Cmd->Expression(Dot);
if (Cmd->Name == ".") {
Dot = Val;
} else if (!Cmd->Ignore) {
auto *D = cast<DefinedRegular<ELFT>>(Symtab<ELFT>::X->find(Cmd->Name));
D->Value = Val;
}
}
template <class ELFT>
void LinkerScript<ELFT>::assignAddresses(
ArrayRef<OutputSectionBase<ELFT> *> Sections) {
// 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())) {
dispatchAssignment(Cmd);
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 ((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) {
std::vector<PhdrEntry<ELFT>> Ret;
PhdrEntry<ELFT> *TlsPhdr = nullptr;
PhdrEntry<ELFT> *NotePhdr = nullptr;
PhdrEntry<ELFT> *RelroPhdr = nullptr;
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 = toPhdrFlags(Out<ELFT>::Dynamic->getFlags());
Phdr.add(Out<ELFT>::Dynamic);
}
break;
case PT_TLS:
TlsPhdr = &Phdr;
break;
case PT_NOTE:
NotePhdr = &Phdr;
break;
case PT_GNU_RELRO:
RelroPhdr = &Phdr;
break;
case PT_GNU_EH_FRAME:
if (!Out<ELFT>::EhFrame->empty() && Out<ELFT>::EhFrameHdr) {
Phdr.H.p_flags = toPhdrFlags(Out<ELFT>::EhFrameHdr->getFlags());
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;
if (TlsPhdr && (Sec->getFlags() & SHF_TLS))
TlsPhdr->add(Sec);
if (!needsPtLoad<ELFT>(Sec))
continue;
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 |= toPhdrFlags(Sec->getFlags());
}
} else {
// If we have no load segment or flags've changed then we want new load
// segment.
uintX_t NewFlags = toPhdrFlags(Sec->getFlags());
if (Load == nullptr || Flags != NewFlags) {
Load = &*Ret.emplace(Ret.end(), PT_LOAD, NewFlags);
Flags = NewFlags;
}
Load->add(Sec);
}
if (RelroPhdr && isRelroSection(Sec))
RelroPhdr->add(Sec);
if (NotePhdr && Sec->getType() == SHT_NOTE)
NotePhdr->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) {
auto Begin = Opt.Commands.begin();
auto End = Opt.Commands.end();
auto I =
std::find_if(Begin, End, [&](const std::unique_ptr<BaseCommand> &Base) {
if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get()))
if (Cmd->Name == Name)
return true;
return false;
});
return I == End ? INT_MAX : (I - Begin);
}
// 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> 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;
SymbolBody *B = Symtab<ELFT>::X->find(Cmd->Name);
// The semantic of PROVIDE is that of introducing a symbol only if
// it's not defined and there's at least a reference to it.
if ((!B && !Cmd->Provide) || (B && B->isUndefined()))
Symtab<ELFT>::X->addAbsolute(Cmd->Name,
Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT);
else
// Symbol already exists in symbol table. If it is provided
// then we can't override its value.
Cmd->Ignore = Cmd->Provide;
}
}
template <class ELFT> bool LinkerScript<ELFT>::hasPhdrsCommands() {
return !Opt.PhdrsCommands.empty();
}
// 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> Indices;
for (StringRef PhdrName : Cmd->Phdrs) {
auto ItPhdr =
std::find_if(Opt.PhdrsCommands.rbegin(), Opt.PhdrsCommands.rend(),
[&](PhdrsCommand &P) { return P.Name == PhdrName; });
if (ItPhdr == Opt.PhdrsCommands.rend())
error("section header '" + PhdrName + "' is not listed in PHDRS");
else
Indices.push_back(std::distance(ItPhdr, Opt.PhdrsCommands.rend()) - 1);
}
return Indices;
}
return {};
}
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 readKeep(OutputSectionCommand *Cmd);
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<StringRef> readOutputSectionPhdrs();
unsigned readPhdrType();
void readProvide(bool Hidden);
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("(");
next().getAsInteger(0, PhdrCmd.Flags);
expect(")");
} else
setError("unexpected header attribute: " + Tok);
} while (!Error);
}
}
void ScriptParser::readSearchDir() {
expect("(");
Config->SearchPaths.push_back(next());
expect(")");
}
void ScriptParser::readSections() {
Opt.DoLayout = true;
expect("{");
while (!Error && !skip("}")) {
StringRef Tok = next();
if (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::readKeep(OutputSectionCommand *Cmd) {
expect("(");
expect("*");
expect("(");
auto *InCmd = new InputSectionDescription();
Cmd->Commands.emplace_back(InCmd);
while (!Error && !skip(")")) {
Opt.KeptSections.push_back(peek());
InCmd->Patterns.push_back(next());
}
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(":");
// Parse constraints.
if (skip("ONLY_IF_RO"))
Cmd->Constraint = ReadOnly;
if (skip("ONLY_IF_RW"))
Cmd->Constraint = ReadWrite;
expect("{");
while (!Error && !skip("}")) {
StringRef Tok = next();
if (Tok == "*") {
auto *InCmd = new InputSectionDescription();
Cmd->Commands.emplace_back(InCmd);
expect("(");
while (!Error && !skip(")"))
InCmd->Patterns.push_back(next());
} else if (Tok == "KEEP") {
readKeep(Cmd);
} else if (Tok == "PROVIDE") {
readProvide(false);
} else if (Tok == "PROVIDE_HIDDEN") {
readProvide(true);
} else {
setError("unknown command " + Tok);
}
}
Cmd->Phdrs = readOutputSectionPhdrs();
StringRef Tok = peek();
if (Tok.startswith("=")) {
if (!Tok.startswith("=0x")) {
setError("filler should be a hexadecimal value");
return;
}
Tok = Tok.substr(3);
Cmd->Filler = parseHex(Tok);
next();
}
}
void ScriptParser::readProvide(bool Hidden) {
expect("(");
if (SymbolAssignment *Assignment = readAssignment(next())) {
Assignment->Provide = true;
Assignment->Hidden = Hidden;
}
expect(")");
expect(";");
}
SymbolAssignment *ScriptParser::readAssignment(StringRef Name) {
expect("=");
Expr E = readExpr();
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 == ".")
return [](uint64_t Dot) { return Dot; };
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 == "DATA_SEGMENT_ALIGN") {
expect("(");
Expr E = readExpr();
expect(",");
readExpr();
expect(")");
return [=](uint64_t Dot) -> uint64_t {
uint64_t Val = E(Dot);
return alignTo(Dot, Val) + (Dot & (Val - 1));
};
}
if (Tok == "DATA_SEGMENT_END") {
expect("(");
expect(".");
expect(")");
return [](uint64_t Dot) { return Dot; };
}
// Parse a number literal
uint64_t V = 0;
if (Tok.getAsInteger(0, V))
setError("malformed number: " + Tok);
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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