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
die(const Twine & s)53 LLVM_ATTRIBUTE_NORETURN static void die(const Twine &s) {
54 llvm::errs() << s << "\n";
55 exit(1);
56 }
57
getFlavor(StringRef s)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
getDefaultQuotingStyle()67 static cl::TokenizerCallback getDefaultQuotingStyle() {
68 if (Triple(sys::getProcessTriple()).getOS() == Triple::Win32)
69 return cl::TokenizeWindowsCommandLine;
70 return cl::TokenizeGNUCommandLine;
71 }
72
isPETargetName(StringRef s)73 static bool isPETargetName(StringRef s) {
74 return s == "i386pe" || s == "i386pep" || s == "thumb2pe" || s == "arm64pe";
75 }
76
isPETarget(std::vector<const char * > & v)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
parseProgname(StringRef progname)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
parseFlavor(std::vector<const char * > & v)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.
canExitEarly()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.
main(int argc,const char ** argv)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