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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;
namespace lld {
namespace elf {
namespace {
class ScriptParser final : ScriptLexer {
public:
ScriptParser(MemoryBufferRef mb) : ScriptLexer(mb) {
// Initialize IsUnderSysroot
if (config->sysroot == "")
return;
StringRef path = mb.getBufferIdentifier();
for (; !path.empty(); path = sys::path::parent_path(path)) {
if (!sys::fs::equivalent(config->sysroot, path))
continue;
isUnderSysroot = true;
return;
}
}
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();
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 = false;
// 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;
}
// 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})
.Case("elf32-littleriscv", {ELF32LEKind, EM_RISCV})
.Case("elf64-littleriscv", {ELF64LEKind, EM_RISCV})
.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())
errorOrWarn(msg);
return script->getDot();
};
}
// 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") {
// 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
expect("(");
cmd->filler = readFill();
expect(")");
} 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 (peek() == "=" || peek().startswith("=")) {
inExpr = true;
consume("=");
cmd->filler = readFill();
inExpr = false;
}
// Consume optional comma following output section command.
consume(",");
if (script->referencedSymbols.size() > symbolsReferenced)
cmd->expressionsUseSymbols = true;
return cmd;
}
// Reads a `=<fillexp>` expression and returns its value as a big-endian number.
// https://sourceware.org/binutils/docs/ld/Output-Section-Fill.html
// We do not support using symbols in such expressions.
//
// 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::readFill() {
uint64_t value = readExpr()().val;
if (value > UINT32_MAX)
setError("filler expression result does not fit 32-bit: 0x" +
Twine::utohexstr(value));
std::array<uint8_t, 4> buf;
write32be(buf.data(), (uint32_t)value);
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 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 (const SymbolVersion &pat : locals)
config->versionDefinitions[VER_NDX_LOCAL].patterns.push_back(pat);
for (const SymbolVersion &pat : globals)
config->versionDefinitions[VER_NDX_GLOBAL].patterns.push_back(pat);
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 (const SymbolVersion &pat : locals)
config->versionDefinitions[VER_NDX_LOCAL].patterns.push_back(pat);
// Create a new version definition and add that to the global symbols.
VersionDefinition ver;
ver.name = verStr;
ver.patterns = globals;
ver.id = config->versionDefinitions.size();
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();
ret.push_back(
{unquote(tok), isCXX, !tok.startswith("\"") && hasWildcard(tok)});
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 readLinkerScript(MemoryBufferRef mb) {
ScriptParser(mb).readLinkerScript();
}
void readVersionScript(MemoryBufferRef mb) {
ScriptParser(mb).readVersionScript();
}
void readDynamicList(MemoryBufferRef mb) { ScriptParser(mb).readDynamicList(); }
void readDefsym(StringRef name, MemoryBufferRef mb) {
ScriptParser(mb).readDefsym(name);
}
} // namespace elf
} // namespace lld
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