1 //===- tools/lld/lld.cpp - Linker Driver Dispatcher -----------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file contains the main function of the lld executable. The main 10 // function is a thin wrapper which dispatches to the platform specific 11 // driver. 12 // 13 // lld is a single executable that contains four different linkers for ELF, 14 // COFF, WebAssembly and Mach-O. The main function dispatches according to 15 // argv[0] (i.e. command name). The most common name for each target is shown 16 // below: 17 // 18 // - ld.lld: ELF (Unix) 19 // - ld64: Mach-O (macOS) 20 // - lld-link: COFF (Windows) 21 // - ld-wasm: WebAssembly 22 // 23 // lld can be invoked as "lld" along with "-flavor" option. This is for 24 // backward compatibility and not recommended. 25 // 26 //===----------------------------------------------------------------------===// 27 28 #include "lld/Common/Driver.h" 29 #include "lld/Common/Memory.h" 30 #include "llvm/ADT/STLExtras.h" 31 #include "llvm/ADT/SmallVector.h" 32 #include "llvm/ADT/StringSwitch.h" 33 #include "llvm/ADT/Triple.h" 34 #include "llvm/ADT/Twine.h" 35 #include "llvm/Support/CommandLine.h" 36 #include "llvm/Support/Host.h" 37 #include "llvm/Support/InitLLVM.h" 38 #include "llvm/Support/Path.h" 39 #include "llvm/Support/PluginLoader.h" 40 #include <cstdlib> 41 42 using namespace lld; 43 using namespace llvm; 44 using namespace llvm::sys; 45 46 enum Flavor { 47 Invalid, 48 Gnu, // -flavor gnu 49 WinLink, // -flavor link 50 Darwin, // -flavor darwin 51 DarwinNew, // -flavor darwinnew 52 Wasm, // -flavor wasm 53 }; 54 55 LLVM_ATTRIBUTE_NORETURN static void die(const Twine &s) { 56 llvm::errs() << s << "\n"; 57 exit(1); 58 } 59 60 static Flavor getFlavor(StringRef s) { 61 return StringSwitch<Flavor>(s) 62 .CasesLower("ld", "ld.lld", "gnu", Gnu) 63 .CasesLower("wasm", "ld-wasm", Wasm) 64 .CaseLower("link", WinLink) 65 .CasesLower("ld64", "ld64.lld", "darwin", Darwin) 66 .CaseLower("darwinnew", DarwinNew) 67 .Default(Invalid); 68 } 69 70 static cl::TokenizerCallback getDefaultQuotingStyle() { 71 if (Triple(sys::getProcessTriple()).getOS() == Triple::Win32) 72 return cl::TokenizeWindowsCommandLine; 73 return cl::TokenizeGNUCommandLine; 74 } 75 76 static bool isPETargetName(StringRef s) { 77 return s == "i386pe" || s == "i386pep" || s == "thumb2pe" || s == "arm64pe"; 78 } 79 80 static bool isPETarget(std::vector<const char *> &v) { 81 for (auto it = v.begin(); it + 1 != v.end(); ++it) { 82 if (StringRef(*it) != "-m") 83 continue; 84 return isPETargetName(*(it + 1)); 85 } 86 // Expand response files (arguments in the form of @<filename>) 87 // to allow detecting the -m argument from arguments in them. 88 SmallVector<const char *, 256> expandedArgs(v.data(), v.data() + v.size()); 89 cl::ExpandResponseFiles(saver, getDefaultQuotingStyle(), expandedArgs); 90 for (auto it = expandedArgs.begin(); it + 1 != expandedArgs.end(); ++it) { 91 if (StringRef(*it) != "-m") 92 continue; 93 return isPETargetName(*(it + 1)); 94 } 95 return false; 96 } 97 98 static Flavor parseProgname(StringRef progname) { 99 // Use GNU driver for "ld" by default. 100 if (progname == "ld") 101 return Gnu; 102 103 // Progname may be something like "lld-gnu". Parse it. 104 SmallVector<StringRef, 3> v; 105 progname.split(v, "-"); 106 for (StringRef s : v) 107 if (Flavor f = getFlavor(s)) 108 return f; 109 return Invalid; 110 } 111 112 static Flavor parseFlavor(std::vector<const char *> &v) { 113 // Parse -flavor option. 114 if (v.size() > 1 && v[1] == StringRef("-flavor")) { 115 if (v.size() <= 2) 116 die("missing arg value for '-flavor'"); 117 Flavor f = getFlavor(v[2]); 118 if (f == Invalid) 119 die("Unknown flavor: " + StringRef(v[2])); 120 v.erase(v.begin() + 1, v.begin() + 3); 121 return f; 122 } 123 124 // Deduct the flavor from argv[0]. 125 StringRef arg0 = path::filename(v[0]); 126 if (arg0.endswith_lower(".exe")) 127 arg0 = arg0.drop_back(4); 128 return parseProgname(arg0); 129 } 130 131 // If this function returns true, lld calls _exit() so that it quickly 132 // exits without invoking destructors of globally allocated objects. 133 // 134 // We don't want to do that if we are running tests though, because 135 // doing that breaks leak sanitizer. So, lit sets this environment variable, 136 // and we use it to detect whether we are running tests or not. 137 static bool canExitEarly() { return StringRef(getenv("LLD_IN_TEST")) != "1"; } 138 139 /// Universal linker main(). This linker emulates the gnu, darwin, or 140 /// windows linker based on the argv[0] or -flavor option. 141 int main(int argc, const char **argv) { 142 InitLLVM x(argc, argv); 143 144 std::vector<const char *> args(argv, argv + argc); 145 #ifdef __FreeBSD__ 146 return !elf::link(args, canExitEarly(), llvm::outs(), llvm::errs()); 147 #else 148 switch (parseFlavor(args)) { 149 case Gnu: 150 if (isPETarget(args)) 151 return !mingw::link(args, canExitEarly(), llvm::outs(), llvm::errs()); 152 return !elf::link(args, canExitEarly(), llvm::outs(), llvm::errs()); 153 case WinLink: 154 return !coff::link(args, canExitEarly(), llvm::outs(), llvm::errs()); 155 case Darwin: 156 return !mach_o::link(args, canExitEarly(), llvm::outs(), llvm::errs()); 157 case DarwinNew: 158 return !macho::link(args, canExitEarly(), llvm::outs(), llvm::errs()); 159 case Wasm: 160 return !wasm::link(args, canExitEarly(), llvm::outs(), llvm::errs()); 161 default: 162 die("lld is a generic driver.\n" 163 "Invoke ld.lld (Unix), ld64.lld (macOS), lld-link (Windows), wasm-ld" 164 " (WebAssembly) instead"); 165 } 166 #endif 167 } 168