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llvm-project/lld/ELF/ScriptParser.cpp

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//===- ScriptParser.cpp ---------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains a recursive-descendent parser for linker scripts.
// Parsed results are stored to Config and Script global objects.
//
//===----------------------------------------------------------------------===//
#include "ScriptParser.h"
#include "Config.h"
#include "Driver.h"
#include "InputSection.h"
#include "LinkerScript.h"
#include "OutputSections.h"
#include "ScriptLexer.h"
#include "Symbols.h"
#include "Target.h"
#include "lld/Common/Memory.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/StringSet.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Path.h"
#include <cassert>
#include <limits>
#include <vector>
using namespace llvm;
using namespace llvm::ELF;
using namespace llvm::support::endian;
using namespace lld;
using namespace lld::elf;
static bool isUnderSysroot(StringRef Path);
namespace {
class ScriptParser final : ScriptLexer {
public:
ScriptParser(MemoryBufferRef MB)
: ScriptLexer(MB),
IsUnderSysroot(isUnderSysroot(MB.getBufferIdentifier())) {}
void readLinkerScript();
void readVersionScript();
void readDynamicList();
void readDefsym(StringRef Name);
private:
void addFile(StringRef Path);
void readAsNeeded();
void readEntry();
void readExtern();
void readGroup();
void readInclude();
void readInput();
void readMemory();
void readOutput();
void readOutputArch();
void readOutputFormat();
void readPhdrs();
void readRegionAlias();
void readSearchDir();
void readSections();
void readTarget();
void readVersion();
void readVersionScriptCommand();
SymbolAssignment *readSymbolAssignment(StringRef Name);
ByteCommand *readByteCommand(StringRef Tok);
std::array<uint8_t, 4> readFill();
std::array<uint8_t, 4> parseFill(StringRef Tok);
bool readSectionDirective(OutputSection *Cmd, StringRef Tok1, StringRef Tok2);
void readSectionAddressType(OutputSection *Cmd);
OutputSection *readOverlaySectionDescription();
OutputSection *readOutputSectionDescription(StringRef OutSec);
std::vector<BaseCommand *> readOverlay();
std::vector<StringRef> readOutputSectionPhdrs();
InputSectionDescription *readInputSectionDescription(StringRef Tok);
StringMatcher readFilePatterns();
std::vector<SectionPattern> readInputSectionsList();
InputSectionDescription *readInputSectionRules(StringRef FilePattern);
unsigned readPhdrType();
SortSectionPolicy readSortKind();
SymbolAssignment *readProvideHidden(bool Provide, bool Hidden);
SymbolAssignment *readAssignment(StringRef Tok);
void readSort();
Expr readAssert();
Expr readConstant();
Expr getPageSize();
uint64_t readMemoryAssignment(StringRef, StringRef, StringRef);
std::pair<uint32_t, uint32_t> readMemoryAttributes();
Expr combine(StringRef Op, Expr L, Expr R);
Expr readExpr();
Expr readExpr1(Expr Lhs, int MinPrec);
StringRef readParenLiteral();
Expr readPrimary();
Expr readTernary(Expr Cond);
Expr readParenExpr();
// For parsing version script.
std::vector<SymbolVersion> readVersionExtern();
void readAnonymousDeclaration();
void readVersionDeclaration(StringRef VerStr);
std::pair<std::vector<SymbolVersion>, std::vector<SymbolVersion>>
readSymbols();
// True if a script being read is in a subdirectory specified by -sysroot.
bool IsUnderSysroot;
// A set to detect an INCLUDE() cycle.
StringSet<> Seen;
};
} // namespace
static StringRef unquote(StringRef S) {
if (S.startswith("\""))
return S.substr(1, S.size() - 2);
return S;
}
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;
}
// Some operations only support one non absolute value. Move the
// absolute one to the right hand side for convenience.
static void moveAbsRight(ExprValue &A, ExprValue &B) {
if (A.Sec == nullptr || (A.ForceAbsolute && !B.isAbsolute()))
std::swap(A, B);
if (!B.isAbsolute())
error(A.Loc + ": at least one side of the expression must be absolute");
}
static ExprValue add(ExprValue A, ExprValue B) {
moveAbsRight(A, B);
return {A.Sec, A.ForceAbsolute, A.getSectionOffset() + B.getValue(), A.Loc};
}
static ExprValue sub(ExprValue A, ExprValue B) {
// The distance between two symbols in sections is absolute.
if (!A.isAbsolute() && !B.isAbsolute())
return A.getValue() - B.getValue();
return {A.Sec, false, A.getSectionOffset() - B.getValue(), A.Loc};
}
static ExprValue bitAnd(ExprValue A, ExprValue B) {
moveAbsRight(A, B);
return {A.Sec, A.ForceAbsolute,
(A.getValue() & B.getValue()) - A.getSecAddr(), A.Loc};
}
static ExprValue bitOr(ExprValue A, ExprValue B) {
moveAbsRight(A, B);
return {A.Sec, A.ForceAbsolute,
(A.getValue() | B.getValue()) - A.getSecAddr(), A.Loc};
}
void ScriptParser::readDynamicList() {
Config->HasDynamicList = true;
expect("{");
std::vector<SymbolVersion> Locals;
std::vector<SymbolVersion> Globals;
std::tie(Locals, Globals) = readSymbols();
expect(";");
if (!atEOF()) {
setError("EOF expected, but got " + next());
return;
}
if (!Locals.empty()) {
setError("\"local:\" scope not supported in --dynamic-list");
return;
}
for (SymbolVersion V : Globals)
Config->DynamicList.push_back(V);
}
void ScriptParser::readVersionScript() {
readVersionScriptCommand();
if (!atEOF())
setError("EOF expected, but got " + next());
}
void ScriptParser::readVersionScriptCommand() {
if (consume("{")) {
readAnonymousDeclaration();
return;
}
while (!atEOF() && !errorCount() && 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 == "ENTRY") {
readEntry();
} else if (Tok == "EXTERN") {
readExtern();
} else if (Tok == "GROUP") {
readGroup();
} else if (Tok == "INCLUDE") {
readInclude();
} else if (Tok == "INPUT") {
readInput();
} else if (Tok == "MEMORY") {
readMemory();
} 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 == "REGION_ALIAS") {
readRegionAlias();
} else if (Tok == "SEARCH_DIR") {
readSearchDir();
} else if (Tok == "SECTIONS") {
readSections();
} else if (Tok == "TARGET") {
readTarget();
} else if (Tok == "VERSION") {
readVersion();
} else if (SymbolAssignment *Cmd = readAssignment(Tok)) {
Script->SectionCommands.push_back(Cmd);
} else {
setError("unknown directive: " + Tok);
}
}
}
void ScriptParser::readDefsym(StringRef Name) {
if (errorCount())
return;
Expr E = readExpr();
if (!atEOF())
setError("EOF expected, but got " + next());
SymbolAssignment *Cmd = make<SymbolAssignment>(Name, E, getCurrentLocation());
Script->SectionCommands.push_back(Cmd);
}
void ScriptParser::addFile(StringRef S) {
if (IsUnderSysroot && S.startswith("/")) {
SmallString<128> PathData;
StringRef Path = (Config->Sysroot + S).toStringRef(PathData);
if (sys::fs::exists(Path)) {
Driver->addFile(Saver.save(Path), /*WithLOption=*/false);
return;
}
}
if (S.startswith("/")) {
Driver->addFile(S, /*WithLOption=*/false);
} else if (S.startswith("=")) {
if (Config->Sysroot.empty())
Driver->addFile(S.substr(1), /*WithLOption=*/false);
else
Driver->addFile(Saver.save(Config->Sysroot + "/" + S.substr(1)),
/*WithLOption=*/false);
} else if (S.startswith("-l")) {
Driver->addLibrary(S.substr(2));
} else if (sys::fs::exists(S)) {
Driver->addFile(S, /*WithLOption=*/false);
} else {
if (Optional<std::string> Path = findFromSearchPaths(S))
Driver->addFile(Saver.save(*Path), /*WithLOption=*/true);
else
setError("unable to find " + S);
}
}
void ScriptParser::readAsNeeded() {
expect("(");
bool Orig = Config->AsNeeded;
Config->AsNeeded = true;
while (!errorCount() && !consume(")"))
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 (!errorCount() && !consume(")"))
Config->Undefined.push_back(unquote(next()));
}
void ScriptParser::readGroup() {
bool Orig = InputFile::IsInGroup;
InputFile::IsInGroup = true;
readInput();
InputFile::IsInGroup = Orig;
if (!Orig)
++InputFile::NextGroupId;
}
void ScriptParser::readInclude() {
StringRef Tok = unquote(next());
if (!Seen.insert(Tok).second) {
setError("there is a cycle in linker script INCLUDEs");
return;
}
if (Optional<std::string> Path = searchScript(Tok)) {
if (Optional<MemoryBufferRef> MB = readFile(*Path))
tokenize(*MB);
return;
}
setError("cannot find linker script " + Tok);
}
void ScriptParser::readInput() {
expect("(");
while (!errorCount() && !consume(")")) {
if (consume("AS_NEEDED"))
readAsNeeded();
else
addFile(unquote(next()));
}
}
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() {
// OUTPUT_ARCH is ignored for now.
expect("(");
while (!errorCount() && !consume(")"))
skip();
}
static std::pair<ELFKind, uint16_t> parseBfdName(StringRef S) {
return StringSwitch<std::pair<ELFKind, uint16_t>>(S)
.Case("elf32-i386", {ELF32LEKind, EM_386})
.Case("elf32-iamcu", {ELF32LEKind, EM_IAMCU})
.Case("elf32-littlearm", {ELF32LEKind, EM_ARM})
.Case("elf32-x86-64", {ELF32LEKind, EM_X86_64})
.Case("elf64-aarch64", {ELF64LEKind, EM_AARCH64})
.Case("elf64-littleaarch64", {ELF64LEKind, EM_AARCH64})
.Case("elf32-powerpc", {ELF32BEKind, EM_PPC})
.Case("elf64-powerpc", {ELF64BEKind, EM_PPC64})
.Case("elf64-powerpcle", {ELF64LEKind, EM_PPC64})
.Case("elf64-x86-64", {ELF64LEKind, EM_X86_64})
.Cases("elf32-tradbigmips", "elf32-bigmips", {ELF32BEKind, EM_MIPS})
.Case("elf32-ntradbigmips", {ELF32BEKind, EM_MIPS})
.Case("elf32-tradlittlemips", {ELF32LEKind, EM_MIPS})
.Case("elf32-ntradlittlemips", {ELF32LEKind, EM_MIPS})
.Case("elf64-tradbigmips", {ELF64BEKind, EM_MIPS})
.Case("elf64-tradlittlemips", {ELF64LEKind, EM_MIPS})
.Default({ELFNoneKind, EM_NONE});
}
// Parse OUTPUT_FORMAT(bfdname) or OUTPUT_FORMAT(bfdname, big, little).
// Currently we ignore big and little parameters.
void ScriptParser::readOutputFormat() {
expect("(");
StringRef Name = unquote(next());
StringRef S = Name;
if (S.consume_back("-freebsd"))
Config->OSABI = ELFOSABI_FREEBSD;
std::tie(Config->EKind, Config->EMachine) = parseBfdName(S);
if (Config->EMachine == EM_NONE)
setError("unknown output format name: " + Name);
if (S == "elf32-ntradlittlemips" || S == "elf32-ntradbigmips")
Config->MipsN32Abi = true;
if (consume(")"))
return;
expect(",");
skip();
expect(",");
skip();
expect(")");
}
void ScriptParser::readPhdrs() {
expect("{");
while (!errorCount() && !consume("}")) {
PhdrsCommand Cmd;
Cmd.Name = next();
Cmd.Type = readPhdrType();
while (!errorCount() && !consume(";")) {
if (consume("FILEHDR"))
Cmd.HasFilehdr = true;
else if (consume("PHDRS"))
Cmd.HasPhdrs = true;
else if (consume("AT"))
Cmd.LMAExpr = readParenExpr();
else if (consume("FLAGS"))
Cmd.Flags = readParenExpr()().getValue();
else
setError("unexpected header attribute: " + next());
}
Script->PhdrsCommands.push_back(Cmd);
}
}
void ScriptParser::readRegionAlias() {
expect("(");
StringRef Alias = unquote(next());
expect(",");
StringRef Name = next();
expect(")");
if (Script->MemoryRegions.count(Alias))
setError("redefinition of memory region '" + Alias + "'");
if (!Script->MemoryRegions.count(Name))
setError("memory region '" + Name + "' is not defined");
Script->MemoryRegions.insert({Alias, Script->MemoryRegions[Name]});
}
void ScriptParser::readSearchDir() {
expect("(");
StringRef Tok = next();
if (!Config->Nostdlib)
Config->SearchPaths.push_back(unquote(Tok));
expect(")");
}
// This reads an overlay description. Overlays are used to describe output
// sections that use the same virtual memory range and normally would trigger
// linker's sections sanity check failures.
// https://sourceware.org/binutils/docs/ld/Overlay-Description.html#Overlay-Description
std::vector<BaseCommand *> ScriptParser::readOverlay() {
// VA and LMA expressions are optional, though for simplicity of
// implementation we assume they are not. That is what OVERLAY was designed
// for first of all: to allow sections with overlapping VAs at different LMAs.
Expr AddrExpr = readExpr();
expect(":");
expect("AT");
Expr LMAExpr = readParenExpr();
expect("{");
std::vector<BaseCommand *> V;
OutputSection *Prev = nullptr;
while (!errorCount() && !consume("}")) {
// VA is the same for all sections. The LMAs are consecutive in memory
// starting from the base load address specified.
OutputSection *OS = readOverlaySectionDescription();
OS->AddrExpr = AddrExpr;
if (Prev)
OS->LMAExpr = [=] { return Prev->getLMA() + Prev->Size; };
else
OS->LMAExpr = LMAExpr;
V.push_back(OS);
Prev = OS;
}
// According to the specification, at the end of the overlay, the location
// counter should be equal to the overlay base address plus size of the
// largest section seen in the overlay.
// Here we want to create the Dot assignment command to achieve that.
Expr MoveDot = [=] {
uint64_t Max = 0;
for (BaseCommand *Cmd : V)
Max = std::max(Max, cast<OutputSection>(Cmd)->Size);
return AddrExpr().getValue() + Max;
};
V.push_back(make<SymbolAssignment>(".", MoveDot, getCurrentLocation()));
return V;
}
void ScriptParser::readSections() {
Script->HasSectionsCommand = true;
// -no-rosegment is used to avoid placing read only non-executable sections in
// their own segment. We do the same if SECTIONS command is present in linker
// script. See comment for computeFlags().
Config->SingleRoRx = true;
expect("{");
std::vector<BaseCommand *> V;
while (!errorCount() && !consume("}")) {
StringRef Tok = next();
if (Tok == "OVERLAY") {
for (BaseCommand *Cmd : readOverlay())
V.push_back(Cmd);
continue;
} else if (Tok == "INCLUDE") {
readInclude();
continue;
}
if (BaseCommand *Cmd = readAssignment(Tok))
V.push_back(Cmd);
else
V.push_back(readOutputSectionDescription(Tok));
}
if (!atEOF() && consume("INSERT")) {
std::vector<BaseCommand *> *Dest = nullptr;
if (consume("AFTER"))
Dest = &Script->InsertAfterCommands[next()];
else if (consume("BEFORE"))
Dest = &Script->InsertBeforeCommands[next()];
else
setError("expected AFTER/BEFORE, but got '" + next() + "'");
if (Dest)
Dest->insert(Dest->end(), V.begin(), V.end());
return;
}
Script->SectionCommands.insert(Script->SectionCommands.end(), V.begin(),
V.end());
}
void ScriptParser::readTarget() {
// TARGET(foo) is an alias for "--format foo". Unlike GNU linkers,
// we accept only a limited set of BFD names (i.e. "elf" or "binary")
// for --format. We recognize only /^elf/ and "binary" in the linker
// script as well.
expect("(");
StringRef Tok = next();
expect(")");
if (Tok.startswith("elf"))
Config->FormatBinary = false;
else if (Tok == "binary")
Config->FormatBinary = true;
else
setError("unknown target: " + Tok);
}
static int precedence(StringRef Op) {
return StringSwitch<int>(Op)
.Cases("*", "/", "%", 8)
.Cases("+", "-", 7)
.Cases("<<", ">>", 6)
.Cases("<", "<=", ">", ">=", "==", "!=", 5)
.Case("&", 4)
.Case("|", 3)
.Case("&&", 2)
.Case("||", 1)
.Default(-1);
}
StringMatcher ScriptParser::readFilePatterns() {
std::vector<StringRef> V;
while (!errorCount() && !consume(")"))
V.push_back(next());
return StringMatcher(V);
}
SortSectionPolicy ScriptParser::readSortKind() {
if (consume("SORT") || consume("SORT_BY_NAME"))
return SortSectionPolicy::Name;
if (consume("SORT_BY_ALIGNMENT"))
return SortSectionPolicy::Alignment;
if (consume("SORT_BY_INIT_PRIORITY"))
return SortSectionPolicy::Priority;
if (consume("SORT_NONE"))
return SortSectionPolicy::None;
return SortSectionPolicy::Default;
}
// Reads SECTIONS command contents in the following form:
//
// <contents> ::= <elem>*
// <elem> ::= <exclude>? <glob-pattern>
// <exclude> ::= "EXCLUDE_FILE" "(" <glob-pattern>+ ")"
//
// For example,
//
// *(.foo EXCLUDE_FILE (a.o) .bar EXCLUDE_FILE (b.o) .baz)
//
// is parsed as ".foo", ".bar" with "a.o", and ".baz" with "b.o".
// The semantics of that is section .foo in any file, section .bar in
// any file but a.o, and section .baz in any file but b.o.
std::vector<SectionPattern> ScriptParser::readInputSectionsList() {
std::vector<SectionPattern> Ret;
while (!errorCount() && peek() != ")") {
StringMatcher ExcludeFilePat;
if (consume("EXCLUDE_FILE")) {
expect("(");
ExcludeFilePat = readFilePatterns();
}
std::vector<StringRef> V;
while (!errorCount() && peek() != ")" && peek() != "EXCLUDE_FILE")
V.push_back(unquote(next()));
if (!V.empty())
Ret.push_back({std::move(ExcludeFilePat), StringMatcher(V)});
else
setError("section pattern is expected");
}
return Ret;
}
// Reads contents of "SECTIONS" directive. That directive contains a
// list of glob patterns for input sections. The grammar is as follows.
//
// <patterns> ::= <section-list>
// | <sort> "(" <section-list> ")"
// | <sort> "(" <sort> "(" <section-list> ")" ")"
//
// <sort> ::= "SORT" | "SORT_BY_NAME" | "SORT_BY_ALIGNMENT"
// | "SORT_BY_INIT_PRIORITY" | "SORT_NONE"
//
// <section-list> is parsed by readInputSectionsList().
InputSectionDescription *
ScriptParser::readInputSectionRules(StringRef FilePattern) {
auto *Cmd = make<InputSectionDescription>(FilePattern);
expect("(");
while (!errorCount() && !consume(")")) {
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(")");
Script->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 [=] {
if (!E().getValue())
error(Msg);
return Script->getDot();
};
}
// 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::array<uint8_t, 4> ScriptParser::readFill() {
expect("(");
std::array<uint8_t, 4> V = parseFill(next());
expect(")");
return V;
}
// Tries to read the special directive for an output section definition which
// can be one of following: "(NOLOAD)", "(COPY)", "(INFO)" or "(OVERLAY)".
// Tok1 and Tok2 are next 2 tokens peeked. See comment for readSectionAddressType below.
bool ScriptParser::readSectionDirective(OutputSection *Cmd, StringRef Tok1, StringRef Tok2) {
if (Tok1 != "(")
return false;
if (Tok2 != "NOLOAD" && Tok2 != "COPY" && Tok2 != "INFO" && Tok2 != "OVERLAY")
return false;
expect("(");
if (consume("NOLOAD")) {
Cmd->Noload = true;
} else {
skip(); // This is "COPY", "INFO" or "OVERLAY".
Cmd->NonAlloc = true;
}
expect(")");
return true;
}
// Reads an expression and/or the special directive for an output
// section definition. Directive is one of following: "(NOLOAD)",
// "(COPY)", "(INFO)" or "(OVERLAY)".
//
// An output section name can be followed by an address expression
// and/or directive. This grammar is not LL(1) because "(" can be
// interpreted as either the beginning of some expression or beginning
// of directive.
//
// https://sourceware.org/binutils/docs/ld/Output-Section-Address.html
// https://sourceware.org/binutils/docs/ld/Output-Section-Type.html
void ScriptParser::readSectionAddressType(OutputSection *Cmd) {
if (readSectionDirective(Cmd, peek(), peek2()))
return;
Cmd->AddrExpr = readExpr();
if (peek() == "(" && !readSectionDirective(Cmd, "(", peek2()))
setError("unknown section directive: " + peek2());
}
static Expr checkAlignment(Expr E, std::string &Loc) {
return [=] {
uint64_t Alignment = std::max((uint64_t)1, E().getValue());
if (!isPowerOf2_64(Alignment)) {
error(Loc + ": alignment must be power of 2");
return (uint64_t)1; // Return a dummy value.
}
return Alignment;
};
}
OutputSection *ScriptParser::readOverlaySectionDescription() {
OutputSection *Cmd =
Script->createOutputSection(next(), getCurrentLocation());
Cmd->InOverlay = true;
expect("{");
while (!errorCount() && !consume("}"))
Cmd->SectionCommands.push_back(readInputSectionRules(next()));
Cmd->Phdrs = readOutputSectionPhdrs();
return Cmd;
}
OutputSection *ScriptParser::readOutputSectionDescription(StringRef OutSec) {
OutputSection *Cmd =
Script->createOutputSection(OutSec, getCurrentLocation());
size_t SymbolsReferenced = Script->ReferencedSymbols.size();
if (peek() != ":")
readSectionAddressType(Cmd);
expect(":");
std::string Location = getCurrentLocation();
if (consume("AT"))
Cmd->LMAExpr = readParenExpr();
if (consume("ALIGN"))
Cmd->AlignExpr = checkAlignment(readParenExpr(), Location);
if (consume("SUBALIGN"))
Cmd->SubalignExpr = checkAlignment(readParenExpr(), Location);
// Parse constraints.
if (consume("ONLY_IF_RO"))
Cmd->Constraint = ConstraintKind::ReadOnly;
if (consume("ONLY_IF_RW"))
Cmd->Constraint = ConstraintKind::ReadWrite;
expect("{");
while (!errorCount() && !consume("}")) {
StringRef Tok = next();
if (Tok == ";") {
// Empty commands are allowed. Do nothing here.
} else if (SymbolAssignment *Assign = readAssignment(Tok)) {
Cmd->SectionCommands.push_back(Assign);
} else if (ByteCommand *Data = readByteCommand(Tok)) {
Cmd->SectionCommands.push_back(Data);
} else if (Tok == "CONSTRUCTORS") {
// CONSTRUCTORS is a keyword to make the linker recognize C++ ctors/dtors
// by name. This is for very old file formats such as ECOFF/XCOFF.
// For ELF, we should ignore.
} else if (Tok == "FILL") {
Cmd->Filler = readFill();
} else if (Tok == "SORT") {
readSort();
} else if (Tok == "INCLUDE") {
readInclude();
} else if (peek() == "(") {
Cmd->SectionCommands.push_back(readInputSectionDescription(Tok));
} else {
// We have a file name and no input sections description. It is not a
// commonly used syntax, but still acceptable. In that case, all sections
// from the file will be included.
auto *ISD = make<InputSectionDescription>(Tok);
ISD->SectionPatterns.push_back({{}, StringMatcher({"*"})});
Cmd->SectionCommands.push_back(ISD);
}
}
if (consume(">"))
Cmd->MemoryRegionName = next();
if (consume("AT")) {
expect(">");
Cmd->LMARegionName = next();
}
if (Cmd->LMAExpr && !Cmd->LMARegionName.empty())
error("section can't have both LMA and a load region");
Cmd->Phdrs = readOutputSectionPhdrs();
if (consume("="))
Cmd->Filler = parseFill(next());
else if (peek().startswith("="))
Cmd->Filler = parseFill(next().drop_front());
// Consume optional comma following output section command.
consume(",");
if (Script->ReferencedSymbols.size() > SymbolsReferenced)
Cmd->ExpressionsUseSymbols = true;
return Cmd;
}
// Parses a given string as a octal/decimal/hexadecimal number and
// returns it as a big-endian number. Used for `=<fillexp>`.
// https://sourceware.org/binutils/docs/ld/Output-Section-Fill.html
//
// When reading a hexstring, ld.bfd handles it as a blob of arbitrary
// size, while ld.gold always handles it as a 32-bit big-endian number.
// We are compatible with ld.gold because it's easier to implement.
std::array<uint8_t, 4> ScriptParser::parseFill(StringRef Tok) {
uint32_t V = 0;
if (!to_integer(Tok, V))
setError("invalid filler expression: " + Tok);
std::array<uint8_t, 4> Buf;
write32be(Buf.data(), V);
return Buf;
}
SymbolAssignment *ScriptParser::readProvideHidden(bool Provide, bool Hidden) {
expect("(");
SymbolAssignment *Cmd = readSymbolAssignment(next());
Cmd->Provide = Provide;
Cmd->Hidden = Hidden;
expect(")");
return Cmd;
}
SymbolAssignment *ScriptParser::readAssignment(StringRef Tok) {
// Assert expression returns Dot, so this is equal to ".=."
if (Tok == "ASSERT")
return make<SymbolAssignment>(".", readAssert(), getCurrentLocation());
size_t OldPos = Pos;
SymbolAssignment *Cmd = nullptr;
if (peek() == "=" || peek() == "+=")
Cmd = readSymbolAssignment(Tok);
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) {
Cmd->CommandString =
Tok.str() + " " +
llvm::join(Tokens.begin() + OldPos, Tokens.begin() + Pos, " ");
expect(";");
}
return Cmd;
}
SymbolAssignment *ScriptParser::readSymbolAssignment(StringRef Name) {
StringRef Op = next();
assert(Op == "=" || Op == "+=");
Expr E = readExpr();
if (Op == "+=") {
std::string Loc = getCurrentLocation();
E = [=] { return add(Script->getSymbolValue(Name, Loc), E()); };
}
return make<SymbolAssignment>(Name, E, getCurrentLocation());
}
// This is an operator-precedence parser to parse a linker
// script expression.
Expr ScriptParser::readExpr() {
// Our lexer is context-aware. Set the in-expression bit so that
// they apply different tokenization rules.
bool Orig = InExpr;
InExpr = true;
Expr E = readExpr1(readPrimary(), 0);
InExpr = Orig;
return E;
}
Expr ScriptParser::combine(StringRef Op, Expr L, Expr R) {
if (Op == "+")
return [=] { return add(L(), R()); };
if (Op == "-")
return [=] { return sub(L(), R()); };
if (Op == "*")
return [=] { return L().getValue() * R().getValue(); };
if (Op == "/") {
std::string Loc = getCurrentLocation();
return [=]() -> uint64_t {
if (uint64_t RV = R().getValue())
return L().getValue() / RV;
error(Loc + ": division by zero");
return 0;
};
}
if (Op == "%") {
std::string Loc = getCurrentLocation();
return [=]() -> uint64_t {
if (uint64_t RV = R().getValue())
return L().getValue() % RV;
error(Loc + ": modulo by zero");
return 0;
};
}
if (Op == "<<")
return [=] { return L().getValue() << R().getValue(); };
if (Op == ">>")
return [=] { return L().getValue() >> R().getValue(); };
if (Op == "<")
return [=] { return L().getValue() < R().getValue(); };
if (Op == ">")
return [=] { return L().getValue() > R().getValue(); };
if (Op == ">=")
return [=] { return L().getValue() >= R().getValue(); };
if (Op == "<=")
return [=] { return L().getValue() <= R().getValue(); };
if (Op == "==")
return [=] { return L().getValue() == R().getValue(); };
if (Op == "!=")
return [=] { return L().getValue() != R().getValue(); };
if (Op == "||")
return [=] { return L().getValue() || R().getValue(); };
if (Op == "&&")
return [=] { return L().getValue() && R().getValue(); };
if (Op == "&")
return [=] { return bitAnd(L(), R()); };
if (Op == "|")
return [=] { return bitOr(L(), R()); };
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() && !errorCount()) {
// Read an operator and an expression.
if (consume("?"))
return readTernary(Lhs);
StringRef Op1 = peek();
if (precedence(Op1) < MinPrec)
break;
skip();
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;
}
Expr ScriptParser::getPageSize() {
std::string Location = getCurrentLocation();
return [=]() -> uint64_t {
if (Target)
return Config->CommonPageSize;
error(Location + ": unable to calculate page size");
return 4096; // Return a dummy value.
};
}
Expr ScriptParser::readConstant() {
StringRef S = readParenLiteral();
if (S == "COMMONPAGESIZE")
return getPageSize();
if (S == "MAXPAGESIZE")
return [] { return Config->MaxPageSize; };
setError("unknown constant: " + S);
return [] { return 0; };
}
// Parses Tok as an integer. It recognizes hexadecimal (prefixed with
// "0x" or suffixed with "H") and decimal numbers. Decimal numbers may
// have "K" (Ki) or "M" (Mi) suffixes.
static Optional<uint64_t> parseInt(StringRef Tok) {
// Hexadecimal
uint64_t Val;
if (Tok.startswith_lower("0x")) {
if (!to_integer(Tok.substr(2), Val, 16))
return None;
return Val;
}
if (Tok.endswith_lower("H")) {
if (!to_integer(Tok.drop_back(), Val, 16))
return None;
return Val;
}
// Decimal
if (Tok.endswith_lower("K")) {
if (!to_integer(Tok.drop_back(), Val, 10))
return None;
return Val * 1024;
}
if (Tok.endswith_lower("M")) {
if (!to_integer(Tok.drop_back(), Val, 10))
return None;
return Val * 1024 * 1024;
}
if (!to_integer(Tok, Val, 10))
return None;
return Val;
}
ByteCommand *ScriptParser::readByteCommand(StringRef Tok) {
int Size = StringSwitch<int>(Tok)
.Case("BYTE", 1)
.Case("SHORT", 2)
.Case("LONG", 4)
.Case("QUAD", 8)
.Default(-1);
if (Size == -1)
return nullptr;
size_t OldPos = Pos;
Expr E = readParenExpr();
std::string CommandString =
Tok.str() + " " +
llvm::join(Tokens.begin() + OldPos, Tokens.begin() + Pos, " ");
return make<ByteCommand>(E, Size, CommandString);
}
StringRef ScriptParser::readParenLiteral() {
expect("(");
bool Orig = InExpr;
InExpr = false;
StringRef Tok = next();
InExpr = Orig;
expect(")");
return Tok;
}
static void checkIfExists(OutputSection *Cmd, StringRef Location) {
if (Cmd->Location.empty() && Script->ErrorOnMissingSection)
error(Location + ": undefined section " + Cmd->Name);
}
Expr ScriptParser::readPrimary() {
if (peek() == "(")
return readParenExpr();
if (consume("~")) {
Expr E = readPrimary();
return [=] { return ~E().getValue(); };
}
if (consume("!")) {
Expr E = readPrimary();
return [=] { return !E().getValue(); };
}
if (consume("-")) {
Expr E = readPrimary();
return [=] { return -E().getValue(); };
}
StringRef Tok = next();
std::string Location = getCurrentLocation();
// Built-in functions are parsed here.
// https://sourceware.org/binutils/docs/ld/Builtin-Functions.html.
if (Tok == "ABSOLUTE") {
Expr Inner = readParenExpr();
return [=] {
ExprValue I = Inner();
I.ForceAbsolute = true;
return I;
};
}
if (Tok == "ADDR") {
StringRef Name = readParenLiteral();
OutputSection *Sec = Script->getOrCreateOutputSection(Name);
Sec->UsedInExpression = true;
return [=]() -> ExprValue {
checkIfExists(Sec, Location);
return {Sec, false, 0, Location};
};
}
if (Tok == "ALIGN") {
expect("(");
Expr E = readExpr();
if (consume(")")) {
E = checkAlignment(E, Location);
return [=] { return alignTo(Script->getDot(), E().getValue()); };
}
expect(",");
Expr E2 = checkAlignment(readExpr(), Location);
expect(")");
return [=] {
ExprValue V = E();
V.Alignment = E2().getValue();
return V;
};
}
if (Tok == "ALIGNOF") {
StringRef Name = readParenLiteral();
OutputSection *Cmd = Script->getOrCreateOutputSection(Name);
return [=] {
checkIfExists(Cmd, Location);
return Cmd->Alignment;
};
}
if (Tok == "ASSERT")
return readAssert();
if (Tok == "CONSTANT")
return readConstant();
if (Tok == "DATA_SEGMENT_ALIGN") {
expect("(");
Expr E = readExpr();
expect(",");
readExpr();
expect(")");
return [=] {
return alignTo(Script->getDot(), std::max((uint64_t)1, E().getValue()));
};
}
if (Tok == "DATA_SEGMENT_END") {
expect("(");
expect(".");
expect(")");
return [] { return Script->getDot(); };
}
if (Tok == "DATA_SEGMENT_RELRO_END") {
// 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.
expect("(");
readExpr();
expect(",");
readExpr();
expect(")");
Expr E = getPageSize();
return [=] { return alignTo(Script->getDot(), E().getValue()); };
}
if (Tok == "DEFINED") {
StringRef Name = readParenLiteral();
return [=] { return Symtab->find(Name) ? 1 : 0; };
}
if (Tok == "LENGTH") {
StringRef Name = readParenLiteral();
if (Script->MemoryRegions.count(Name) == 0) {
setError("memory region not defined: " + Name);
return [] { return 0; };
}
return [=] { return Script->MemoryRegions[Name]->Length; };
}
if (Tok == "LOADADDR") {
StringRef Name = readParenLiteral();
OutputSection *Cmd = Script->getOrCreateOutputSection(Name);
Cmd->UsedInExpression = true;
return [=] {
checkIfExists(Cmd, Location);
return Cmd->getLMA();
};
}
if (Tok == "MAX" || Tok == "MIN") {
expect("(");
Expr A = readExpr();
expect(",");
Expr B = readExpr();
expect(")");
if (Tok == "MIN")
return [=] { return std::min(A().getValue(), B().getValue()); };
return [=] { return std::max(A().getValue(), B().getValue()); };
}
if (Tok == "ORIGIN") {
StringRef Name = readParenLiteral();
if (Script->MemoryRegions.count(Name) == 0) {
setError("memory region not defined: " + Name);
return [] { return 0; };
}
return [=] { return Script->MemoryRegions[Name]->Origin; };
}
if (Tok == "SEGMENT_START") {
expect("(");
skip();
expect(",");
Expr E = readExpr();
expect(")");
return [=] { return E(); };
}
if (Tok == "SIZEOF") {
StringRef Name = readParenLiteral();
OutputSection *Cmd = Script->getOrCreateOutputSection(Name);
// Linker script does not create an output section if its content is empty.
// We want to allow SIZEOF(.foo) where .foo is a section which happened to
// be empty.
return [=] { return Cmd->Size; };
}
if (Tok == "SIZEOF_HEADERS")
return [=] { return elf::getHeaderSize(); };
// Tok is the dot.
if (Tok == ".")
return [=] { return Script->getSymbolValue(Tok, Location); };
// Tok is a literal number.
if (Optional<uint64_t> Val = parseInt(Tok))
return [=] { return *Val; };
// Tok is a symbol name.
if (!isValidCIdentifier(Tok))
setError("malformed number: " + Tok);
Script->ReferencedSymbols.push_back(Tok);
return [=] { return Script->getSymbolValue(Tok, Location); };
}
Expr ScriptParser::readTernary(Expr Cond) {
Expr L = readExpr();
expect(":");
Expr R = readExpr();
return [=] { return Cond().getValue() ? L() : R(); };
}
Expr ScriptParser::readParenExpr() {
expect("(");
Expr E = readExpr();
expect(")");
return E;
}
std::vector<StringRef> ScriptParser::readOutputSectionPhdrs() {
std::vector<StringRef> Phdrs;
while (!errorCount() && peek().startswith(":")) {
StringRef Tok = next();
Phdrs.push_back((Tok.size() == 1) ? next() : Tok.substr(1));
}
return Phdrs;
}
// Read a program header type name. The next token must be a
// name of a program header type or a constant (e.g. "0x3").
unsigned ScriptParser::readPhdrType() {
StringRef Tok = next();
if (Optional<uint64_t> Val = parseInt(Tok))
return *Val;
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)
.Case("PT_OPENBSD_RANDOMIZE", PT_OPENBSD_RANDOMIZE)
.Case("PT_OPENBSD_WXNEEDED", PT_OPENBSD_WXNEEDED)
.Case("PT_OPENBSD_BOOTDATA", PT_OPENBSD_BOOTDATA)
.Default(-1);
if (Ret == (unsigned)-1) {
setError("invalid program header type: " + Tok);
return PT_NULL;
}
return Ret;
}
// Reads an anonymous version declaration.
void ScriptParser::readAnonymousDeclaration() {
std::vector<SymbolVersion> Locals;
std::vector<SymbolVersion> Globals;
std::tie(Locals, Globals) = readSymbols();
for (SymbolVersion V : Locals) {
if (V.Name == "*")
Config->DefaultSymbolVersion = VER_NDX_LOCAL;
else
Config->VersionScriptLocals.push_back(V);
}
for (SymbolVersion V : Globals)
Config->VersionScriptGlobals.push_back(V);
expect(";");
}
// Reads a non-anonymous version definition,
// e.g. "VerStr { global: foo; bar; local: *; };".
void ScriptParser::readVersionDeclaration(StringRef VerStr) {
// Read a symbol list.
std::vector<SymbolVersion> Locals;
std::vector<SymbolVersion> Globals;
std::tie(Locals, Globals) = readSymbols();
for (SymbolVersion V : Locals) {
if (V.Name == "*")
Config->DefaultSymbolVersion = VER_NDX_LOCAL;
else
Config->VersionScriptLocals.push_back(V);
}
// Create a new version definition and add that to the global symbols.
VersionDefinition Ver;
Ver.Name = VerStr;
Ver.Globals = Globals;
// User-defined version number starts from 2 because 0 and 1 are
// reserved for VER_NDX_LOCAL and VER_NDX_GLOBAL, respectively.
Ver.Id = Config->VersionDefinitions.size() + 2;
Config->VersionDefinitions.push_back(Ver);
// 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 hint; the runtime doesn't care about it
// at all. In LLD, we simply ignore it.
if (peek() != ";")
skip();
expect(";");
}
static bool hasWildcard(StringRef S) {
return S.find_first_of("?*[") != StringRef::npos;
}
// Reads a list of symbols, e.g. "{ global: foo; bar; local: *; };".
std::pair<std::vector<SymbolVersion>, std::vector<SymbolVersion>>
ScriptParser::readSymbols() {
std::vector<SymbolVersion> Locals;
std::vector<SymbolVersion> Globals;
std::vector<SymbolVersion> *V = &Globals;
while (!errorCount()) {
if (consume("}"))
break;
if (consumeLabel("local")) {
V = &Locals;
continue;
}
if (consumeLabel("global")) {
V = &Globals;
continue;
}
if (consume("extern")) {
std::vector<SymbolVersion> Ext = readVersionExtern();
V->insert(V->end(), Ext.begin(), Ext.end());
} else {
StringRef Tok = next();
V->push_back({unquote(Tok), false, hasWildcard(Tok)});
}
expect(";");
}
return {Locals, Globals};
}
// Reads an "extern C++" directive, e.g.,
// "extern "C++" { ns::*; "f(int, double)"; };"
//
// The last semicolon is optional. E.g. this is OK:
// "extern "C++" { ns::*; "f(int, double)" };"
std::vector<SymbolVersion> ScriptParser::readVersionExtern() {
StringRef Tok = next();
bool IsCXX = Tok == "\"C++\"";
if (!IsCXX && Tok != "\"C\"")
setError("Unknown language");
expect("{");
std::vector<SymbolVersion> Ret;
while (!errorCount() && peek() != "}") {
StringRef Tok = next();
bool HasWildcard = !Tok.startswith("\"") && hasWildcard(Tok);
Ret.push_back({unquote(Tok), IsCXX, HasWildcard});
if (consume("}"))
return Ret;
expect(";");
}
expect("}");
return Ret;
}
uint64_t ScriptParser::readMemoryAssignment(StringRef S1, StringRef S2,
StringRef S3) {
if (!consume(S1) && !consume(S2) && !consume(S3)) {
setError("expected one of: " + S1 + ", " + S2 + ", or " + S3);
return 0;
}
expect("=");
return readExpr()().getValue();
}
// Parse the MEMORY command as specified in:
// https://sourceware.org/binutils/docs/ld/MEMORY.html
//
// MEMORY { name [(attr)] : ORIGIN = origin, LENGTH = len ... }
void ScriptParser::readMemory() {
expect("{");
while (!errorCount() && !consume("}")) {
StringRef Tok = next();
if (Tok == "INCLUDE") {
readInclude();
continue;
}
uint32_t Flags = 0;
uint32_t NegFlags = 0;
if (consume("(")) {
std::tie(Flags, NegFlags) = readMemoryAttributes();
expect(")");
}
expect(":");
uint64_t Origin = readMemoryAssignment("ORIGIN", "org", "o");
expect(",");
uint64_t Length = readMemoryAssignment("LENGTH", "len", "l");
// Add the memory region to the region map.
MemoryRegion *MR = make<MemoryRegion>(Tok, Origin, Length, Flags, NegFlags);
if (!Script->MemoryRegions.insert({Tok, MR}).second)
setError("region '" + Tok + "' already defined");
}
}
// This function parses the attributes used to match against section
// flags when placing output sections in a memory region. These flags
// are only used when an explicit memory region name is not used.
std::pair<uint32_t, uint32_t> ScriptParser::readMemoryAttributes() {
uint32_t Flags = 0;
uint32_t NegFlags = 0;
bool Invert = false;
for (char C : next().lower()) {
uint32_t Flag = 0;
if (C == '!')
Invert = !Invert;
else if (C == 'w')
Flag = SHF_WRITE;
else if (C == 'x')
Flag = SHF_EXECINSTR;
else if (C == 'a')
Flag = SHF_ALLOC;
else if (C != 'r')
setError("invalid memory region attribute");
if (Invert)
NegFlags |= Flag;
else
Flags |= Flag;
}
return {Flags, NegFlags};
}
void elf::readLinkerScript(MemoryBufferRef MB) {
ScriptParser(MB).readLinkerScript();
}
void elf::readVersionScript(MemoryBufferRef MB) {
ScriptParser(MB).readVersionScript();
}
void elf::readDynamicList(MemoryBufferRef MB) {
ScriptParser(MB).readDynamicList();
}
void elf::readDefsym(StringRef Name, MemoryBufferRef MB) {
ScriptParser(MB).readDefsym(Name);
}
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