500 lines
13 KiB
C++
500 lines
13 KiB
C++
//===- LinkerScript.cpp ---------------------------------------------------===//
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//
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// The LLVM Linker
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file contains the parser/evaluator of the linker script.
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// It does not construct an AST but consume linker script directives directly.
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// Results are written to Driver or Config object.
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//
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//===----------------------------------------------------------------------===//
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#include "LinkerScript.h"
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#include "Config.h"
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#include "Driver.h"
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#include "InputSection.h"
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#include "SymbolTable.h"
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#include "llvm/Support/FileSystem.h"
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#include "llvm/Support/MemoryBuffer.h"
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#include "llvm/Support/Path.h"
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#include "llvm/Support/StringSaver.h"
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using namespace llvm;
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using namespace llvm::object;
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using namespace lld;
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using namespace lld::elf;
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LinkerScript *elf::Script;
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template <class ELFT>
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SectionRule *LinkerScript::find(InputSectionBase<ELFT> *S) {
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for (SectionRule &R : Sections)
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if (R.match(S))
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return &R;
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return nullptr;
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}
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template <class ELFT>
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StringRef LinkerScript::getOutputSection(InputSectionBase<ELFT> *S) {
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SectionRule *R = find(S);
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return R ? R->Dest : "";
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}
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template <class ELFT>
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bool LinkerScript::isDiscarded(InputSectionBase<ELFT> *S) {
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return getOutputSection(S) == "/DISCARD/";
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}
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template <class ELFT> bool LinkerScript::shouldKeep(InputSectionBase<ELFT> *S) {
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SectionRule *R = find(S);
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return R && R->Keep;
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}
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ArrayRef<uint8_t> LinkerScript::getFiller(StringRef Name) {
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auto I = Filler.find(Name);
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if (I == Filler.end())
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return {};
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return I->second;
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}
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// A compartor to sort output sections. Returns -1 or 1 if both
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// A and B are mentioned in linker scripts. Otherwise, returns 0
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// to use the default rule which is implemented in Writer.cpp.
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int LinkerScript::compareSections(StringRef A, StringRef B) {
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auto E = SectionOrder.end();
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auto I = std::find(SectionOrder.begin(), E, A);
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auto J = std::find(SectionOrder.begin(), E, B);
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if (I == E || J == E)
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return 0;
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return I < J ? -1 : 1;
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}
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// Returns true if S matches T. S can contain glob meta-characters.
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// The asterisk ('*') matches zero or more characacters, and the question
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// mark ('?') matches one character.
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static bool matchStr(StringRef S, StringRef T) {
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for (;;) {
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if (S.empty())
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return T.empty();
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if (S[0] == '*') {
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S = S.substr(1);
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if (S.empty())
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// Fast path. If a pattern is '*', it matches anything.
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return true;
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for (size_t I = 0, E = T.size(); I < E; ++I)
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if (matchStr(S, T.substr(I)))
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return true;
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return false;
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}
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if (T.empty() || (S[0] != T[0] && S[0] != '?'))
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return false;
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S = S.substr(1);
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T = T.substr(1);
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}
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}
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template <class ELFT> bool SectionRule::match(InputSectionBase<ELFT> *S) {
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return matchStr(SectionPattern, S->getSectionName());
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}
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class elf::ScriptParser {
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typedef void (ScriptParser::*Handler)();
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public:
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ScriptParser(BumpPtrAllocator *A, StringRef S, bool B)
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: Saver(*A), Input(S), Tokens(tokenize(S)), IsUnderSysroot(B) {}
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void run();
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private:
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void setError(const Twine &Msg);
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static std::vector<StringRef> tokenize(StringRef S);
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static StringRef skipSpace(StringRef S);
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bool atEOF();
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StringRef next();
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StringRef peek();
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bool skip(StringRef Tok);
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void expect(StringRef Expect);
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void addFile(StringRef Path);
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void readAsNeeded();
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void readEntry();
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void readExtern();
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void readGroup();
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void readInclude();
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void readNothing() {}
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void readOutput();
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void readOutputArch();
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void readOutputFormat();
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void readSearchDir();
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void readSections();
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void readOutputSectionDescription();
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void readSectionPatterns(StringRef OutSec, bool Keep);
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size_t getPos();
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std::vector<uint8_t> parseHex(StringRef S);
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StringSaver Saver;
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StringRef Input;
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std::vector<StringRef> Tokens;
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const static StringMap<Handler> Cmd;
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size_t Pos = 0;
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bool IsUnderSysroot;
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bool Error = false;
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};
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const StringMap<elf::ScriptParser::Handler> elf::ScriptParser::Cmd = {
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{"ENTRY", &ScriptParser::readEntry},
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{"EXTERN", &ScriptParser::readExtern},
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{"GROUP", &ScriptParser::readGroup},
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{"INCLUDE", &ScriptParser::readInclude},
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{"INPUT", &ScriptParser::readGroup},
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{"OUTPUT", &ScriptParser::readOutput},
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{"OUTPUT_ARCH", &ScriptParser::readOutputArch},
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{"OUTPUT_FORMAT", &ScriptParser::readOutputFormat},
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{"SEARCH_DIR", &ScriptParser::readSearchDir},
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{"SECTIONS", &ScriptParser::readSections},
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{";", &ScriptParser::readNothing}};
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void ScriptParser::run() {
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while (!atEOF()) {
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StringRef Tok = next();
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if (Handler Fn = Cmd.lookup(Tok))
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(this->*Fn)();
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else
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setError("unknown directive: " + Tok);
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}
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}
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// We don't want to record cascading errors. Keep only the first one.
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void ScriptParser::setError(const Twine &Msg) {
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if (Error)
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return;
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error("line " + Twine(getPos()) + ": " + Msg);
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Error = true;
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}
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// Split S into linker script tokens.
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std::vector<StringRef> ScriptParser::tokenize(StringRef S) {
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std::vector<StringRef> Ret;
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for (;;) {
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S = skipSpace(S);
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if (S.empty())
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return Ret;
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// Quoted token
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if (S.startswith("\"")) {
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size_t E = S.find("\"", 1);
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if (E == StringRef::npos) {
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error("unclosed quote");
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return {};
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}
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Ret.push_back(S.substr(1, E - 1));
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S = S.substr(E + 1);
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continue;
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}
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// Unquoted token
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size_t Pos = S.find_first_not_of(
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"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
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"0123456789_.$/\\~=+[]*?-:");
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// A character that cannot start a word (which is usually a
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// punctuation) forms a single character token.
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if (Pos == 0)
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Pos = 1;
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Ret.push_back(S.substr(0, Pos));
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S = S.substr(Pos);
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}
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}
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// Skip leading whitespace characters or /**/-style comments.
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StringRef ScriptParser::skipSpace(StringRef S) {
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for (;;) {
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if (S.startswith("/*")) {
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size_t E = S.find("*/", 2);
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if (E == StringRef::npos) {
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error("unclosed comment in a linker script");
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return "";
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}
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S = S.substr(E + 2);
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continue;
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}
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size_t Size = S.size();
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S = S.ltrim();
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if (S.size() == Size)
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return S;
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}
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}
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// An errneous token is handled as if it were the last token before EOF.
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bool ScriptParser::atEOF() { return Error || Tokens.size() == Pos; }
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StringRef ScriptParser::next() {
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if (Error)
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return "";
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if (atEOF()) {
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setError("unexpected EOF");
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return "";
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}
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return Tokens[Pos++];
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}
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StringRef ScriptParser::peek() {
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StringRef Tok = next();
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if (Error)
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return "";
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--Pos;
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return Tok;
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}
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bool ScriptParser::skip(StringRef Tok) {
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if (Error)
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return false;
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if (atEOF()) {
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setError("unexpected EOF");
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return false;
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}
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if (Tok != Tokens[Pos])
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return false;
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++Pos;
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return true;
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}
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void ScriptParser::expect(StringRef Expect) {
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if (Error)
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return;
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StringRef Tok = next();
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if (Tok != Expect)
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setError(Expect + " expected, but got " + Tok);
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}
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void ScriptParser::addFile(StringRef S) {
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if (IsUnderSysroot && S.startswith("/")) {
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SmallString<128> Path;
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(Config->Sysroot + S).toStringRef(Path);
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if (sys::fs::exists(Path)) {
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Driver->addFile(Saver.save(Path.str()));
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return;
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}
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}
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if (sys::path::is_absolute(S)) {
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Driver->addFile(S);
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} else if (S.startswith("=")) {
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if (Config->Sysroot.empty())
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Driver->addFile(S.substr(1));
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else
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Driver->addFile(Saver.save(Config->Sysroot + "/" + S.substr(1)));
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} else if (S.startswith("-l")) {
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Driver->addLibrary(S.substr(2));
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} else if (sys::fs::exists(S)) {
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Driver->addFile(S);
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} else {
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std::string Path = findFromSearchPaths(S);
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if (Path.empty())
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setError("unable to find " + S);
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else
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Driver->addFile(Saver.save(Path));
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}
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}
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void ScriptParser::readAsNeeded() {
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expect("(");
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bool Orig = Config->AsNeeded;
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Config->AsNeeded = true;
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while (!Error) {
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StringRef Tok = next();
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if (Tok == ")")
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break;
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addFile(Tok);
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}
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Config->AsNeeded = Orig;
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}
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void ScriptParser::readEntry() {
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// -e <symbol> takes predecence over ENTRY(<symbol>).
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expect("(");
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StringRef Tok = next();
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if (Config->Entry.empty())
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Config->Entry = Tok;
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expect(")");
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}
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void ScriptParser::readExtern() {
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expect("(");
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while (!Error) {
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StringRef Tok = next();
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if (Tok == ")")
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return;
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Config->Undefined.push_back(Tok);
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}
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}
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void ScriptParser::readGroup() {
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expect("(");
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while (!Error) {
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StringRef Tok = next();
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if (Tok == ")")
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return;
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if (Tok == "AS_NEEDED") {
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readAsNeeded();
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continue;
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}
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addFile(Tok);
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}
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}
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void ScriptParser::readInclude() {
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StringRef Tok = next();
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auto MBOrErr = MemoryBuffer::getFile(Tok);
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if (!MBOrErr) {
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setError("cannot open " + Tok);
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return;
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}
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std::unique_ptr<MemoryBuffer> &MB = *MBOrErr;
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StringRef S = Saver.save(MB->getMemBufferRef().getBuffer());
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std::vector<StringRef> V = tokenize(S);
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Tokens.insert(Tokens.begin() + Pos, V.begin(), V.end());
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}
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void ScriptParser::readOutput() {
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// -o <file> takes predecence over OUTPUT(<file>).
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expect("(");
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StringRef Tok = next();
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if (Config->OutputFile.empty())
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Config->OutputFile = Tok;
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expect(")");
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}
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void ScriptParser::readOutputArch() {
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// Error checking only for now.
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expect("(");
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next();
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expect(")");
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}
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void ScriptParser::readOutputFormat() {
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// Error checking only for now.
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expect("(");
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next();
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StringRef Tok = next();
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if (Tok == ")")
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return;
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if (Tok != ",") {
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setError("unexpected token: " + Tok);
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return;
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}
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next();
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expect(",");
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next();
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expect(")");
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}
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void ScriptParser::readSearchDir() {
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expect("(");
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Config->SearchPaths.push_back(next());
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expect(")");
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}
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void ScriptParser::readSections() {
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expect("{");
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while (!Error && !skip("}"))
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readOutputSectionDescription();
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}
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void ScriptParser::readSectionPatterns(StringRef OutSec, bool Keep) {
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expect("(");
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while (!Error && !skip(")"))
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Script->Sections.emplace_back(OutSec, next(), Keep);
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}
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// Returns the current line number.
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size_t ScriptParser::getPos() {
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if (Pos == 0)
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return 1;
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const char *Begin = Input.data();
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const char *Tok = Tokens[Pos - 1].data();
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return StringRef(Begin, Tok - Begin).count('\n') + 1;
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}
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std::vector<uint8_t> ScriptParser::parseHex(StringRef S) {
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std::vector<uint8_t> Hex;
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while (!S.empty()) {
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StringRef B = S.substr(0, 2);
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S = S.substr(2);
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uint8_t H;
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if (B.getAsInteger(16, H)) {
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setError("not a hexadecimal value: " + B);
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return {};
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}
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Hex.push_back(H);
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}
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return Hex;
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}
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void ScriptParser::readOutputSectionDescription() {
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StringRef OutSec = next();
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Script->SectionOrder.push_back(OutSec);
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expect(":");
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expect("{");
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while (!Error && !skip("}")) {
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StringRef Tok = next();
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if (Tok == "*") {
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readSectionPatterns(OutSec, false);
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} else if (Tok == "KEEP") {
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expect("(");
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next(); // Skip *
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readSectionPatterns(OutSec, true);
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expect(")");
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} else {
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setError("unknown command " + Tok);
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}
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}
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StringRef Tok = peek();
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if (Tok.startswith("=")) {
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if (!Tok.startswith("=0x")) {
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setError("filler should be a hexadecimal value");
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return;
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}
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Tok = Tok.substr(3);
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Script->Filler[OutSec] = parseHex(Tok);
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next();
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}
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}
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static bool isUnderSysroot(StringRef Path) {
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if (Config->Sysroot == "")
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return false;
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for (; !Path.empty(); Path = sys::path::parent_path(Path))
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if (sys::fs::equivalent(Config->Sysroot, Path))
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return true;
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return false;
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}
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// Entry point. The other functions or classes are private to this file.
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void LinkerScript::read(MemoryBufferRef MB) {
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StringRef Path = MB.getBufferIdentifier();
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ScriptParser(&Alloc, MB.getBuffer(), isUnderSysroot(Path)).run();
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}
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template StringRef LinkerScript::getOutputSection(InputSectionBase<ELF32LE> *);
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template StringRef LinkerScript::getOutputSection(InputSectionBase<ELF32BE> *);
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template StringRef LinkerScript::getOutputSection(InputSectionBase<ELF64LE> *);
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template StringRef LinkerScript::getOutputSection(InputSectionBase<ELF64BE> *);
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template bool LinkerScript::isDiscarded(InputSectionBase<ELF32LE> *);
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template bool LinkerScript::isDiscarded(InputSectionBase<ELF32BE> *);
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template bool LinkerScript::isDiscarded(InputSectionBase<ELF64LE> *);
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template bool LinkerScript::isDiscarded(InputSectionBase<ELF64BE> *);
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template bool LinkerScript::shouldKeep(InputSectionBase<ELF32LE> *);
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template bool LinkerScript::shouldKeep(InputSectionBase<ELF32BE> *);
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template bool LinkerScript::shouldKeep(InputSectionBase<ELF64LE> *);
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template bool LinkerScript::shouldKeep(InputSectionBase<ELF64BE> *);
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