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 <cstdlib> 40 41 using namespace lld; 42 using namespace llvm; 43 using namespace llvm::sys; 44 45 enum Flavor { 46 Invalid, 47 Gnu, // -flavor gnu 48 WinLink, // -flavor link 49 Darwin, // -flavor darwin 50 Wasm, // -flavor wasm 51 }; 52 53 LLVM_ATTRIBUTE_NORETURN static void die(const Twine &s) { 54 llvm::errs() << s << "\n"; 55 exit(1); 56 } 57 58 static Flavor getFlavor(StringRef s) { 59 return StringSwitch<Flavor>(s) 60 .CasesLower("ld", "ld.lld", "gnu", Gnu) 61 .CasesLower("wasm", "ld-wasm", Wasm) 62 .CaseLower("link", WinLink) 63 .CasesLower("ld64", "ld64.lld", "darwin", Darwin) 64 .Default(Invalid); 65 } 66 67 static cl::TokenizerCallback getDefaultQuotingStyle() { 68 if (Triple(sys::getProcessTriple()).getOS() == Triple::Win32) 69 return cl::TokenizeWindowsCommandLine; 70 return cl::TokenizeGNUCommandLine; 71 } 72 73 static bool isPETargetName(StringRef s) { 74 return s == "i386pe" || s == "i386pep" || s == "thumb2pe" || s == "arm64pe"; 75 } 76 77 static bool isPETarget(std::vector<const char *> &v) { 78 for (auto it = v.begin(); it + 1 != v.end(); ++it) { 79 if (StringRef(*it) != "-m") 80 continue; 81 return isPETargetName(*(it + 1)); 82 } 83 // Expand response files (arguments in the form of @<filename>) 84 // to allow detecting the -m argument from arguments in them. 85 SmallVector<const char *, 256> expandedArgs(v.data(), v.data() + v.size()); 86 cl::ExpandResponseFiles(saver, getDefaultQuotingStyle(), expandedArgs); 87 for (auto it = expandedArgs.begin(); it + 1 != expandedArgs.end(); ++it) { 88 if (StringRef(*it) != "-m") 89 continue; 90 return isPETargetName(*(it + 1)); 91 } 92 return false; 93 } 94 95 static Flavor parseProgname(StringRef progname) { 96 #if __APPLE__ 97 // Use Darwin driver for "ld" on Darwin. 98 if (progname == "ld") 99 return Darwin; 100 #endif 101 102 #if LLVM_ON_UNIX 103 // Use GNU driver for "ld" on other Unix-like system. 104 if (progname == "ld") 105 return Gnu; 106 #endif 107 108 // Progname may be something like "lld-gnu". Parse it. 109 SmallVector<StringRef, 3> v; 110 progname.split(v, "-"); 111 for (StringRef s : v) 112 if (Flavor f = getFlavor(s)) 113 return f; 114 return Invalid; 115 } 116 117 static Flavor parseFlavor(std::vector<const char *> &v) { 118 // Parse -flavor option. 119 if (v.size() > 1 && v[1] == StringRef("-flavor")) { 120 if (v.size() <= 2) 121 die("missing arg value for '-flavor'"); 122 Flavor f = getFlavor(v[2]); 123 if (f == Invalid) 124 die("Unknown flavor: " + StringRef(v[2])); 125 v.erase(v.begin() + 1, v.begin() + 3); 126 return f; 127 } 128 129 // Deduct the flavor from argv[0]. 130 StringRef arg0 = path::filename(v[0]); 131 if (arg0.endswith_lower(".exe")) 132 arg0 = arg0.drop_back(4); 133 return parseProgname(arg0); 134 } 135 136 // If this function returns true, lld calls _exit() so that it quickly 137 // exits without invoking destructors of globally allocated objects. 138 // 139 // We don't want to do that if we are running tests though, because 140 // doing that breaks leak sanitizer. So, lit sets this environment variable, 141 // and we use it to detect whether we are running tests or not. 142 static bool canExitEarly() { return StringRef(getenv("LLD_IN_TEST")) != "1"; } 143 144 /// Universal linker main(). This linker emulates the gnu, darwin, or 145 /// windows linker based on the argv[0] or -flavor option. 146 int main(int argc, const char **argv) { 147 InitLLVM x(argc, argv); 148 149 std::vector<const char *> args(argv, argv + argc); 150 #ifdef __FreeBSD__ 151 return !elf::link(args, canExitEarly(), llvm::outs(), llvm::errs()); 152 #else 153 switch (parseFlavor(args)) { 154 case Gnu: 155 if (isPETarget(args)) 156 return !mingw::link(args, canExitEarly(), llvm::outs(), llvm::errs()); 157 return !elf::link(args, canExitEarly(), llvm::outs(), llvm::errs()); 158 case WinLink: 159 return !coff::link(args, canExitEarly(), llvm::outs(), llvm::errs()); 160 case Darwin: 161 return !mach_o::link(args, canExitEarly(), llvm::outs(), llvm::errs()); 162 case Wasm: 163 return !wasm::link(args, canExitEarly(), llvm::outs(), llvm::errs()); 164 default: 165 die("lld is a generic driver.\n" 166 "Invoke ld.lld (Unix), ld64.lld (macOS), lld-link (Windows), wasm-ld" 167 " (WebAssembly) instead"); 168 } 169 #endif 170 } 171