1 //===--- Linux.h - Linux ToolChain Implementations --------------*- C++ -*-===//
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 #include "Linux.h"
10 #include "Arch/ARM.h"
11 #include "Arch/Mips.h"
12 #include "Arch/PPC.h"
13 #include "Arch/RISCV.h"
14 #include "CommonArgs.h"
15 #include "clang/Config/config.h"
16 #include "clang/Driver/Distro.h"
17 #include "clang/Driver/Driver.h"
18 #include "clang/Driver/Options.h"
19 #include "clang/Driver/SanitizerArgs.h"
20 #include "llvm/Option/ArgList.h"
21 #include "llvm/ProfileData/InstrProf.h"
22 #include "llvm/Support/Path.h"
23 #include "llvm/Support/ScopedPrinter.h"
24 #include "llvm/Support/VirtualFileSystem.h"
25 #include <system_error>
26 
27 using namespace clang::driver;
28 using namespace clang::driver::toolchains;
29 using namespace clang;
30 using namespace llvm::opt;
31 
32 using tools::addPathIfExists;
33 
34 /// Get our best guess at the multiarch triple for a target.
35 ///
36 /// Debian-based systems are starting to use a multiarch setup where they use
37 /// a target-triple directory in the library and header search paths.
38 /// Unfortunately, this triple does not align with the vanilla target triple,
39 /// so we provide a rough mapping here.
40 std::string Linux::getMultiarchTriple(const Driver &D,
41                                       const llvm::Triple &TargetTriple,
42                                       StringRef SysRoot) const {
43   llvm::Triple::EnvironmentType TargetEnvironment =
44       TargetTriple.getEnvironment();
45   bool IsAndroid = TargetTriple.isAndroid();
46   bool IsMipsR6 = TargetTriple.getSubArch() == llvm::Triple::MipsSubArch_r6;
47   bool IsMipsN32Abi = TargetTriple.getEnvironment() == llvm::Triple::GNUABIN32;
48 
49   // For most architectures, just use whatever we have rather than trying to be
50   // clever.
51   switch (TargetTriple.getArch()) {
52   default:
53     break;
54 
55   // We use the existence of '/lib/<triple>' as a directory to detect some
56   // common linux triples that don't quite match the Clang triple for both
57   // 32-bit and 64-bit targets. Multiarch fixes its install triples to these
58   // regardless of what the actual target triple is.
59   case llvm::Triple::arm:
60   case llvm::Triple::thumb:
61     if (IsAndroid) {
62       return "arm-linux-androideabi";
63     } else if (TargetEnvironment == llvm::Triple::GNUEABIHF) {
64       if (D.getVFS().exists(SysRoot + "/lib/arm-linux-gnueabihf"))
65         return "arm-linux-gnueabihf";
66     } else {
67       if (D.getVFS().exists(SysRoot + "/lib/arm-linux-gnueabi"))
68         return "arm-linux-gnueabi";
69     }
70     break;
71   case llvm::Triple::armeb:
72   case llvm::Triple::thumbeb:
73     if (TargetEnvironment == llvm::Triple::GNUEABIHF) {
74       if (D.getVFS().exists(SysRoot + "/lib/armeb-linux-gnueabihf"))
75         return "armeb-linux-gnueabihf";
76     } else {
77       if (D.getVFS().exists(SysRoot + "/lib/armeb-linux-gnueabi"))
78         return "armeb-linux-gnueabi";
79     }
80     break;
81   case llvm::Triple::x86:
82     if (IsAndroid)
83       return "i686-linux-android";
84     if (D.getVFS().exists(SysRoot + "/lib/i386-linux-gnu"))
85       return "i386-linux-gnu";
86     break;
87   case llvm::Triple::x86_64:
88     if (IsAndroid)
89       return "x86_64-linux-android";
90     // We don't want this for x32, otherwise it will match x86_64 libs
91     if (TargetEnvironment != llvm::Triple::GNUX32 &&
92         D.getVFS().exists(SysRoot + "/lib/x86_64-linux-gnu"))
93       return "x86_64-linux-gnu";
94     break;
95   case llvm::Triple::aarch64:
96     if (IsAndroid)
97       return "aarch64-linux-android";
98     if (D.getVFS().exists(SysRoot + "/lib/aarch64-linux-gnu"))
99       return "aarch64-linux-gnu";
100     break;
101   case llvm::Triple::aarch64_be:
102     if (D.getVFS().exists(SysRoot + "/lib/aarch64_be-linux-gnu"))
103       return "aarch64_be-linux-gnu";
104     break;
105 
106   case llvm::Triple::m68k:
107     if (D.getVFS().exists(SysRoot + "/lib/m68k-linux-gnu"))
108       return "m68k-linux-gnu";
109     break;
110 
111   case llvm::Triple::mips: {
112     std::string MT = IsMipsR6 ? "mipsisa32r6-linux-gnu" : "mips-linux-gnu";
113     if (D.getVFS().exists(SysRoot + "/lib/" + MT))
114       return MT;
115     break;
116   }
117   case llvm::Triple::mipsel: {
118     if (IsAndroid)
119       return "mipsel-linux-android";
120     std::string MT = IsMipsR6 ? "mipsisa32r6el-linux-gnu" : "mipsel-linux-gnu";
121     if (D.getVFS().exists(SysRoot + "/lib/" + MT))
122       return MT;
123     break;
124   }
125   case llvm::Triple::mips64: {
126     std::string MT = std::string(IsMipsR6 ? "mipsisa64r6" : "mips64") +
127                      "-linux-" + (IsMipsN32Abi ? "gnuabin32" : "gnuabi64");
128     if (D.getVFS().exists(SysRoot + "/lib/" + MT))
129       return MT;
130     if (D.getVFS().exists(SysRoot + "/lib/mips64-linux-gnu"))
131       return "mips64-linux-gnu";
132     break;
133   }
134   case llvm::Triple::mips64el: {
135     if (IsAndroid)
136       return "mips64el-linux-android";
137     std::string MT = std::string(IsMipsR6 ? "mipsisa64r6el" : "mips64el") +
138                      "-linux-" + (IsMipsN32Abi ? "gnuabin32" : "gnuabi64");
139     if (D.getVFS().exists(SysRoot + "/lib/" + MT))
140       return MT;
141     if (D.getVFS().exists(SysRoot + "/lib/mips64el-linux-gnu"))
142       return "mips64el-linux-gnu";
143     break;
144   }
145   case llvm::Triple::ppc:
146     if (D.getVFS().exists(SysRoot + "/lib/powerpc-linux-gnuspe"))
147       return "powerpc-linux-gnuspe";
148     if (D.getVFS().exists(SysRoot + "/lib/powerpc-linux-gnu"))
149       return "powerpc-linux-gnu";
150     break;
151   case llvm::Triple::ppcle:
152     if (D.getVFS().exists(SysRoot + "/lib/powerpcle-linux-gnu"))
153       return "powerpcle-linux-gnu";
154     break;
155   case llvm::Triple::ppc64:
156     if (D.getVFS().exists(SysRoot + "/lib/powerpc64-linux-gnu"))
157       return "powerpc64-linux-gnu";
158     break;
159   case llvm::Triple::ppc64le:
160     if (D.getVFS().exists(SysRoot + "/lib/powerpc64le-linux-gnu"))
161       return "powerpc64le-linux-gnu";
162     break;
163   case llvm::Triple::sparc:
164     if (D.getVFS().exists(SysRoot + "/lib/sparc-linux-gnu"))
165       return "sparc-linux-gnu";
166     break;
167   case llvm::Triple::sparcv9:
168     if (D.getVFS().exists(SysRoot + "/lib/sparc64-linux-gnu"))
169       return "sparc64-linux-gnu";
170     break;
171   case llvm::Triple::systemz:
172     if (D.getVFS().exists(SysRoot + "/lib/s390x-linux-gnu"))
173       return "s390x-linux-gnu";
174     break;
175   }
176   return TargetTriple.str();
177 }
178 
179 static StringRef getOSLibDir(const llvm::Triple &Triple, const ArgList &Args) {
180   if (Triple.isMIPS()) {
181     if (Triple.isAndroid()) {
182       StringRef CPUName;
183       StringRef ABIName;
184       tools::mips::getMipsCPUAndABI(Args, Triple, CPUName, ABIName);
185       if (CPUName == "mips32r6")
186         return "libr6";
187       if (CPUName == "mips32r2")
188         return "libr2";
189     }
190     // lib32 directory has a special meaning on MIPS targets.
191     // It contains N32 ABI binaries. Use this folder if produce
192     // code for N32 ABI only.
193     if (tools::mips::hasMipsAbiArg(Args, "n32"))
194       return "lib32";
195     return Triple.isArch32Bit() ? "lib" : "lib64";
196   }
197 
198   // It happens that only x86, PPC and SPARC use the 'lib32' variant of
199   // oslibdir, and using that variant while targeting other architectures causes
200   // problems because the libraries are laid out in shared system roots that
201   // can't cope with a 'lib32' library search path being considered. So we only
202   // enable them when we know we may need it.
203   //
204   // FIXME: This is a bit of a hack. We should really unify this code for
205   // reasoning about oslibdir spellings with the lib dir spellings in the
206   // GCCInstallationDetector, but that is a more significant refactoring.
207   if (Triple.getArch() == llvm::Triple::x86 || Triple.isPPC32() ||
208       Triple.getArch() == llvm::Triple::sparc)
209     return "lib32";
210 
211   if (Triple.getArch() == llvm::Triple::x86_64 &&
212       Triple.getEnvironment() == llvm::Triple::GNUX32)
213     return "libx32";
214 
215   if (Triple.getArch() == llvm::Triple::riscv32)
216     return "lib32";
217 
218   return Triple.isArch32Bit() ? "lib" : "lib64";
219 }
220 
221 Linux::Linux(const Driver &D, const llvm::Triple &Triple, const ArgList &Args)
222     : Generic_ELF(D, Triple, Args) {
223   GCCInstallation.init(Triple, Args);
224   Multilibs = GCCInstallation.getMultilibs();
225   SelectedMultilib = GCCInstallation.getMultilib();
226   llvm::Triple::ArchType Arch = Triple.getArch();
227   std::string SysRoot = computeSysRoot();
228   ToolChain::path_list &PPaths = getProgramPaths();
229 
230   Generic_GCC::PushPPaths(PPaths);
231 
232   Distro Distro(D.getVFS(), Triple);
233 
234   if (Distro.IsAlpineLinux() || Triple.isAndroid()) {
235     ExtraOpts.push_back("-z");
236     ExtraOpts.push_back("now");
237   }
238 
239   if (Distro.IsOpenSUSE() || Distro.IsUbuntu() || Distro.IsAlpineLinux() ||
240       Triple.isAndroid()) {
241     ExtraOpts.push_back("-z");
242     ExtraOpts.push_back("relro");
243   }
244 
245   // Android ARM/AArch64 use max-page-size=4096 to reduce VMA usage. Note, lld
246   // from 11 onwards default max-page-size to 65536 for both ARM and AArch64.
247   if ((Triple.isARM() || Triple.isAArch64()) && Triple.isAndroid()) {
248     ExtraOpts.push_back("-z");
249     ExtraOpts.push_back("max-page-size=4096");
250   }
251 
252   if (GCCInstallation.getParentLibPath().find("opt/rh/devtoolset") !=
253       StringRef::npos)
254     // With devtoolset on RHEL, we want to add a bin directory that is relative
255     // to the detected gcc install, because if we are using devtoolset gcc then
256     // we want to use other tools from devtoolset (e.g. ld) instead of the
257     // standard system tools.
258     PPaths.push_back(Twine(GCCInstallation.getParentLibPath() +
259                      "/../bin").str());
260 
261   if (Arch == llvm::Triple::arm || Arch == llvm::Triple::thumb)
262     ExtraOpts.push_back("-X");
263 
264   const bool IsAndroid = Triple.isAndroid();
265   const bool IsMips = Triple.isMIPS();
266   const bool IsHexagon = Arch == llvm::Triple::hexagon;
267   const bool IsRISCV = Triple.isRISCV();
268 
269   if (IsMips && !SysRoot.empty())
270     ExtraOpts.push_back("--sysroot=" + SysRoot);
271 
272   // Do not use 'gnu' hash style for Mips targets because .gnu.hash
273   // and the MIPS ABI require .dynsym to be sorted in different ways.
274   // .gnu.hash needs symbols to be grouped by hash code whereas the MIPS
275   // ABI requires a mapping between the GOT and the symbol table.
276   // Android loader does not support .gnu.hash until API 23.
277   // Hexagon linker/loader does not support .gnu.hash
278   if (!IsMips && !IsHexagon) {
279     if (Distro.IsRedhat() || Distro.IsOpenSUSE() || Distro.IsAlpineLinux() ||
280         (Distro.IsUbuntu() && Distro >= Distro::UbuntuMaverick) ||
281         (IsAndroid && !Triple.isAndroidVersionLT(23)))
282       ExtraOpts.push_back("--hash-style=gnu");
283 
284     if (Distro.IsDebian() || Distro.IsOpenSUSE() ||
285         Distro == Distro::UbuntuLucid || Distro == Distro::UbuntuJaunty ||
286         Distro == Distro::UbuntuKarmic ||
287         (IsAndroid && Triple.isAndroidVersionLT(23)))
288       ExtraOpts.push_back("--hash-style=both");
289   }
290 
291 #ifdef ENABLE_LINKER_BUILD_ID
292   ExtraOpts.push_back("--build-id");
293 #endif
294 
295   if (IsAndroid || Distro.IsOpenSUSE())
296     ExtraOpts.push_back("--enable-new-dtags");
297 
298   // The selection of paths to try here is designed to match the patterns which
299   // the GCC driver itself uses, as this is part of the GCC-compatible driver.
300   // This was determined by running GCC in a fake filesystem, creating all
301   // possible permutations of these directories, and seeing which ones it added
302   // to the link paths.
303   path_list &Paths = getFilePaths();
304 
305   const std::string OSLibDir = std::string(getOSLibDir(Triple, Args));
306   const std::string MultiarchTriple = getMultiarchTriple(D, Triple, SysRoot);
307 
308   Generic_GCC::AddMultilibPaths(D, SysRoot, OSLibDir, MultiarchTriple, Paths);
309 
310   addPathIfExists(D, SysRoot + "/lib/" + MultiarchTriple, Paths);
311   addPathIfExists(D, SysRoot + "/lib/../" + OSLibDir, Paths);
312 
313   if (IsAndroid) {
314     // Android sysroots contain a library directory for each supported OS
315     // version as well as some unversioned libraries in the usual multiarch
316     // directory.
317     unsigned Major;
318     unsigned Minor;
319     unsigned Micro;
320     Triple.getEnvironmentVersion(Major, Minor, Micro);
321     addPathIfExists(D,
322                     SysRoot + "/usr/lib/" + MultiarchTriple + "/" +
323                         llvm::to_string(Major),
324                     Paths);
325   }
326 
327   addPathIfExists(D, SysRoot + "/usr/lib/" + MultiarchTriple, Paths);
328   // 64-bit OpenEmbedded sysroots may not have a /usr/lib dir. So they cannot
329   // find /usr/lib64 as it is referenced as /usr/lib/../lib64. So we handle
330   // this here.
331   if (Triple.getVendor() == llvm::Triple::OpenEmbedded &&
332       Triple.isArch64Bit())
333     addPathIfExists(D, SysRoot + "/usr/" + OSLibDir, Paths);
334   else
335     addPathIfExists(D, SysRoot + "/usr/lib/../" + OSLibDir, Paths);
336   if (IsRISCV) {
337     StringRef ABIName = tools::riscv::getRISCVABI(Args, Triple);
338     addPathIfExists(D, SysRoot + "/" + OSLibDir + "/" + ABIName, Paths);
339     addPathIfExists(D, SysRoot + "/usr/" + OSLibDir + "/" + ABIName, Paths);
340   }
341 
342   Generic_GCC::AddMultiarchPaths(D, SysRoot, OSLibDir, Paths);
343 
344   // Similar to the logic for GCC above, if we are currently running Clang
345   // inside of the requested system root, add its parent library path to those
346   // searched.
347   // FIXME: It's not clear whether we should use the driver's installed
348   // directory ('Dir' below) or the ResourceDir.
349   if (StringRef(D.Dir).startswith(SysRoot))
350     addPathIfExists(D, D.Dir + "/../lib", Paths);
351 
352   addPathIfExists(D, SysRoot + "/lib", Paths);
353   addPathIfExists(D, SysRoot + "/usr/lib", Paths);
354 }
355 
356 ToolChain::RuntimeLibType Linux::GetDefaultRuntimeLibType() const {
357   if (getTriple().isAndroid())
358     return ToolChain::RLT_CompilerRT;
359   return Generic_ELF::GetDefaultRuntimeLibType();
360 }
361 
362 ToolChain::CXXStdlibType Linux::GetDefaultCXXStdlibType() const {
363   if (getTriple().isAndroid())
364     return ToolChain::CST_Libcxx;
365   return ToolChain::CST_Libstdcxx;
366 }
367 
368 bool Linux::HasNativeLLVMSupport() const { return true; }
369 
370 Tool *Linux::buildLinker() const { return new tools::gnutools::Linker(*this); }
371 
372 Tool *Linux::buildStaticLibTool() const {
373   return new tools::gnutools::StaticLibTool(*this);
374 }
375 
376 Tool *Linux::buildAssembler() const {
377   return new tools::gnutools::Assembler(*this);
378 }
379 
380 std::string Linux::computeSysRoot() const {
381   if (!getDriver().SysRoot.empty())
382     return getDriver().SysRoot;
383 
384   if (getTriple().isAndroid()) {
385     // Android toolchains typically include a sysroot at ../sysroot relative to
386     // the clang binary.
387     const StringRef ClangDir = getDriver().getInstalledDir();
388     std::string AndroidSysRootPath = (ClangDir + "/../sysroot").str();
389     if (getVFS().exists(AndroidSysRootPath))
390       return AndroidSysRootPath;
391   }
392 
393   if (!GCCInstallation.isValid() || !getTriple().isMIPS())
394     return std::string();
395 
396   // Standalone MIPS toolchains use different names for sysroot folder
397   // and put it into different places. Here we try to check some known
398   // variants.
399 
400   const StringRef InstallDir = GCCInstallation.getInstallPath();
401   const StringRef TripleStr = GCCInstallation.getTriple().str();
402   const Multilib &Multilib = GCCInstallation.getMultilib();
403 
404   std::string Path =
405       (InstallDir + "/../../../../" + TripleStr + "/libc" + Multilib.osSuffix())
406           .str();
407 
408   if (getVFS().exists(Path))
409     return Path;
410 
411   Path = (InstallDir + "/../../../../sysroot" + Multilib.osSuffix()).str();
412 
413   if (getVFS().exists(Path))
414     return Path;
415 
416   return std::string();
417 }
418 
419 std::string Linux::getDynamicLinker(const ArgList &Args) const {
420   const llvm::Triple::ArchType Arch = getArch();
421   const llvm::Triple &Triple = getTriple();
422 
423   const Distro Distro(getDriver().getVFS(), Triple);
424 
425   if (Triple.isAndroid())
426     return Triple.isArch64Bit() ? "/system/bin/linker64" : "/system/bin/linker";
427 
428   if (Triple.isMusl()) {
429     std::string ArchName;
430     bool IsArm = false;
431 
432     switch (Arch) {
433     case llvm::Triple::arm:
434     case llvm::Triple::thumb:
435       ArchName = "arm";
436       IsArm = true;
437       break;
438     case llvm::Triple::armeb:
439     case llvm::Triple::thumbeb:
440       ArchName = "armeb";
441       IsArm = true;
442       break;
443     default:
444       ArchName = Triple.getArchName().str();
445     }
446     if (IsArm &&
447         (Triple.getEnvironment() == llvm::Triple::MuslEABIHF ||
448          tools::arm::getARMFloatABI(*this, Args) == tools::arm::FloatABI::Hard))
449       ArchName += "hf";
450 
451     return "/lib/ld-musl-" + ArchName + ".so.1";
452   }
453 
454   std::string LibDir;
455   std::string Loader;
456 
457   switch (Arch) {
458   default:
459     llvm_unreachable("unsupported architecture");
460 
461   case llvm::Triple::aarch64:
462     LibDir = "lib";
463     Loader = "ld-linux-aarch64.so.1";
464     break;
465   case llvm::Triple::aarch64_be:
466     LibDir = "lib";
467     Loader = "ld-linux-aarch64_be.so.1";
468     break;
469   case llvm::Triple::arm:
470   case llvm::Triple::thumb:
471   case llvm::Triple::armeb:
472   case llvm::Triple::thumbeb: {
473     const bool HF =
474         Triple.getEnvironment() == llvm::Triple::GNUEABIHF ||
475         tools::arm::getARMFloatABI(*this, Args) == tools::arm::FloatABI::Hard;
476 
477     LibDir = "lib";
478     Loader = HF ? "ld-linux-armhf.so.3" : "ld-linux.so.3";
479     break;
480   }
481   case llvm::Triple::m68k:
482     LibDir = "lib";
483     Loader = "ld.so.1";
484     break;
485   case llvm::Triple::mips:
486   case llvm::Triple::mipsel:
487   case llvm::Triple::mips64:
488   case llvm::Triple::mips64el: {
489     bool IsNaN2008 = tools::mips::isNaN2008(Args, Triple);
490 
491     LibDir = "lib" + tools::mips::getMipsABILibSuffix(Args, Triple);
492 
493     if (tools::mips::isUCLibc(Args))
494       Loader = IsNaN2008 ? "ld-uClibc-mipsn8.so.0" : "ld-uClibc.so.0";
495     else if (!Triple.hasEnvironment() &&
496              Triple.getVendor() == llvm::Triple::VendorType::MipsTechnologies)
497       Loader =
498           Triple.isLittleEndian() ? "ld-musl-mipsel.so.1" : "ld-musl-mips.so.1";
499     else
500       Loader = IsNaN2008 ? "ld-linux-mipsn8.so.1" : "ld.so.1";
501 
502     break;
503   }
504   case llvm::Triple::ppc:
505     LibDir = "lib";
506     Loader = "ld.so.1";
507     break;
508   case llvm::Triple::ppcle:
509     LibDir = "lib";
510     Loader = "ld.so.1";
511     break;
512   case llvm::Triple::ppc64:
513     LibDir = "lib64";
514     Loader =
515         (tools::ppc::hasPPCAbiArg(Args, "elfv2")) ? "ld64.so.2" : "ld64.so.1";
516     break;
517   case llvm::Triple::ppc64le:
518     LibDir = "lib64";
519     Loader =
520         (tools::ppc::hasPPCAbiArg(Args, "elfv1")) ? "ld64.so.1" : "ld64.so.2";
521     break;
522   case llvm::Triple::riscv32: {
523     StringRef ABIName = tools::riscv::getRISCVABI(Args, Triple);
524     LibDir = "lib";
525     Loader = ("ld-linux-riscv32-" + ABIName + ".so.1").str();
526     break;
527   }
528   case llvm::Triple::riscv64: {
529     StringRef ABIName = tools::riscv::getRISCVABI(Args, Triple);
530     LibDir = "lib";
531     Loader = ("ld-linux-riscv64-" + ABIName + ".so.1").str();
532     break;
533   }
534   case llvm::Triple::sparc:
535   case llvm::Triple::sparcel:
536     LibDir = "lib";
537     Loader = "ld-linux.so.2";
538     break;
539   case llvm::Triple::sparcv9:
540     LibDir = "lib64";
541     Loader = "ld-linux.so.2";
542     break;
543   case llvm::Triple::systemz:
544     LibDir = "lib";
545     Loader = "ld64.so.1";
546     break;
547   case llvm::Triple::x86:
548     LibDir = "lib";
549     Loader = "ld-linux.so.2";
550     break;
551   case llvm::Triple::x86_64: {
552     bool X32 = Triple.getEnvironment() == llvm::Triple::GNUX32;
553 
554     LibDir = X32 ? "libx32" : "lib64";
555     Loader = X32 ? "ld-linux-x32.so.2" : "ld-linux-x86-64.so.2";
556     break;
557   }
558   case llvm::Triple::ve:
559     return "/opt/nec/ve/lib/ld-linux-ve.so.1";
560   }
561 
562   if (Distro == Distro::Exherbo &&
563       (Triple.getVendor() == llvm::Triple::UnknownVendor ||
564        Triple.getVendor() == llvm::Triple::PC))
565     return "/usr/" + Triple.str() + "/lib/" + Loader;
566   return "/" + LibDir + "/" + Loader;
567 }
568 
569 void Linux::AddClangSystemIncludeArgs(const ArgList &DriverArgs,
570                                       ArgStringList &CC1Args) const {
571   const Driver &D = getDriver();
572   std::string SysRoot = computeSysRoot();
573 
574   if (DriverArgs.hasArg(clang::driver::options::OPT_nostdinc))
575     return;
576 
577   if (!DriverArgs.hasArg(options::OPT_nostdlibinc)) {
578     // LOCAL_INCLUDE_DIR
579     addSystemInclude(DriverArgs, CC1Args, SysRoot + "/usr/local/include");
580     // TOOL_INCLUDE_DIR
581     AddMultilibIncludeArgs(DriverArgs, CC1Args);
582   }
583 
584   // Note: in gcc, GCC_INCLUDE_DIR (private headers) precedes LOCAL_INCLUDE_DIR.
585   SmallString<128> ResourceDirInclude(D.ResourceDir);
586   llvm::sys::path::append(ResourceDirInclude, "include");
587   if (!DriverArgs.hasArg(options::OPT_nobuiltininc) &&
588       (!getTriple().isMusl() || DriverArgs.hasArg(options::OPT_nostdlibinc)))
589     addSystemInclude(DriverArgs, CC1Args, ResourceDirInclude);
590 
591   if (DriverArgs.hasArg(options::OPT_nostdlibinc))
592     return;
593 
594   // Check for configure-time C include directories.
595   StringRef CIncludeDirs(C_INCLUDE_DIRS);
596   if (CIncludeDirs != "") {
597     SmallVector<StringRef, 5> dirs;
598     CIncludeDirs.split(dirs, ":");
599     for (StringRef dir : dirs) {
600       StringRef Prefix =
601           llvm::sys::path::is_absolute(dir) ? "" : StringRef(SysRoot);
602       addExternCSystemInclude(DriverArgs, CC1Args, Prefix + dir);
603     }
604     return;
605   }
606 
607   // On Android and Debian, add /usr/include/$triple if exists.
608   std::string MultiarchIncludeDir = getMultiarchTriple(D, getTriple(), SysRoot);
609   if (!MultiarchIncludeDir.empty() &&
610       D.getVFS().exists(SysRoot + "/usr/include/" + MultiarchIncludeDir))
611     addExternCSystemInclude(DriverArgs, CC1Args, SysRoot + "/usr/include/" + MultiarchIncludeDir);
612 
613   if (getTriple().getOS() == llvm::Triple::RTEMS)
614     return;
615 
616   // Add an include of '/include' directly. This isn't provided by default by
617   // system GCCs, but is often used with cross-compiling GCCs, and harmless to
618   // add even when Clang is acting as-if it were a system compiler.
619   addExternCSystemInclude(DriverArgs, CC1Args, SysRoot + "/include");
620 
621   addExternCSystemInclude(DriverArgs, CC1Args, SysRoot + "/usr/include");
622 
623   if (!DriverArgs.hasArg(options::OPT_nobuiltininc) && getTriple().isMusl())
624     addSystemInclude(DriverArgs, CC1Args, ResourceDirInclude);
625 }
626 
627 void Linux::addLibStdCxxIncludePaths(const llvm::opt::ArgList &DriverArgs,
628                                      llvm::opt::ArgStringList &CC1Args) const {
629   // Try generic GCC detection first.
630   if (Generic_GCC::addGCCLibStdCxxIncludePaths(DriverArgs, CC1Args))
631     return;
632 
633   // We need a detected GCC installation on Linux to provide libstdc++'s
634   // headers in odd Linuxish places.
635   if (!GCCInstallation.isValid())
636     return;
637 
638   StringRef LibDir = GCCInstallation.getParentLibPath();
639   StringRef TripleStr = GCCInstallation.getTriple().str();
640   const Multilib &Multilib = GCCInstallation.getMultilib();
641   const GCCVersion &Version = GCCInstallation.getVersion();
642 
643   const std::string LibStdCXXIncludePathCandidates[] = {
644       // Android standalone toolchain has C++ headers in yet another place.
645       LibDir.str() + "/../" + TripleStr.str() + "/include/c++/" + Version.Text,
646       // Freescale SDK C++ headers are directly in <sysroot>/usr/include/c++,
647       // without a subdirectory corresponding to the gcc version.
648       LibDir.str() + "/../include/c++",
649       // Cray's gcc installation puts headers under "g++" without a
650       // version suffix.
651       LibDir.str() + "/../include/g++",
652   };
653 
654   for (const auto &IncludePath : LibStdCXXIncludePathCandidates) {
655     if (addLibStdCXXIncludePaths(IncludePath, TripleStr,
656                                  Multilib.includeSuffix(), DriverArgs, CC1Args))
657       break;
658   }
659 }
660 
661 void Linux::AddCudaIncludeArgs(const ArgList &DriverArgs,
662                                ArgStringList &CC1Args) const {
663   CudaInstallation.AddCudaIncludeArgs(DriverArgs, CC1Args);
664 }
665 
666 void Linux::AddHIPIncludeArgs(const ArgList &DriverArgs,
667                               ArgStringList &CC1Args) const {
668   RocmInstallation.AddHIPIncludeArgs(DriverArgs, CC1Args);
669 }
670 
671 void Linux::AddIAMCUIncludeArgs(const ArgList &DriverArgs,
672                                 ArgStringList &CC1Args) const {
673   if (GCCInstallation.isValid()) {
674     CC1Args.push_back("-isystem");
675     CC1Args.push_back(DriverArgs.MakeArgString(
676         GCCInstallation.getParentLibPath() + "/../" +
677         GCCInstallation.getTriple().str() + "/include"));
678   }
679 }
680 
681 bool Linux::isPIEDefault() const {
682   return (getTriple().isAndroid() && !getTriple().isAndroidVersionLT(16)) ||
683           getTriple().isMusl() || getSanitizerArgs().requiresPIE();
684 }
685 
686 bool Linux::IsAArch64OutlineAtomicsDefault(const ArgList &Args) const {
687   // Outline atomics for AArch64 are supported by compiler-rt
688   // and libgcc since 9.3.1
689   assert(getTriple().isAArch64() && "expected AArch64 target!");
690   ToolChain::RuntimeLibType RtLib = GetRuntimeLibType(Args);
691   if (RtLib == ToolChain::RLT_CompilerRT)
692     return true;
693   assert(RtLib == ToolChain::RLT_Libgcc && "unexpected runtime library type!");
694   if (GCCInstallation.getVersion().isOlderThan(9, 3, 1))
695     return false;
696   return true;
697 }
698 
699 bool Linux::isNoExecStackDefault() const {
700     return getTriple().isAndroid();
701 }
702 
703 bool Linux::IsMathErrnoDefault() const {
704   if (getTriple().isAndroid())
705     return false;
706   return Generic_ELF::IsMathErrnoDefault();
707 }
708 
709 SanitizerMask Linux::getSupportedSanitizers() const {
710   const bool IsX86 = getTriple().getArch() == llvm::Triple::x86;
711   const bool IsX86_64 = getTriple().getArch() == llvm::Triple::x86_64;
712   const bool IsMIPS = getTriple().isMIPS32();
713   const bool IsMIPS64 = getTriple().isMIPS64();
714   const bool IsPowerPC64 = getTriple().getArch() == llvm::Triple::ppc64 ||
715                            getTriple().getArch() == llvm::Triple::ppc64le;
716   const bool IsAArch64 = getTriple().getArch() == llvm::Triple::aarch64 ||
717                          getTriple().getArch() == llvm::Triple::aarch64_be;
718   const bool IsArmArch = getTriple().getArch() == llvm::Triple::arm ||
719                          getTriple().getArch() == llvm::Triple::thumb ||
720                          getTriple().getArch() == llvm::Triple::armeb ||
721                          getTriple().getArch() == llvm::Triple::thumbeb;
722   const bool IsRISCV64 = getTriple().getArch() == llvm::Triple::riscv64;
723   const bool IsSystemZ = getTriple().getArch() == llvm::Triple::systemz;
724   SanitizerMask Res = ToolChain::getSupportedSanitizers();
725   Res |= SanitizerKind::Address;
726   Res |= SanitizerKind::PointerCompare;
727   Res |= SanitizerKind::PointerSubtract;
728   Res |= SanitizerKind::Fuzzer;
729   Res |= SanitizerKind::FuzzerNoLink;
730   Res |= SanitizerKind::KernelAddress;
731   Res |= SanitizerKind::Memory;
732   Res |= SanitizerKind::Vptr;
733   Res |= SanitizerKind::SafeStack;
734   if (IsX86_64 || IsMIPS64 || IsAArch64)
735     Res |= SanitizerKind::DataFlow;
736   if (IsX86_64 || IsMIPS64 || IsAArch64 || IsX86 || IsArmArch || IsPowerPC64 ||
737       IsRISCV64 || IsSystemZ)
738     Res |= SanitizerKind::Leak;
739   if (IsX86_64 || IsMIPS64 || IsAArch64 || IsPowerPC64)
740     Res |= SanitizerKind::Thread;
741   if (IsX86_64)
742     Res |= SanitizerKind::KernelMemory;
743   if (IsX86 || IsX86_64)
744     Res |= SanitizerKind::Function;
745   if (IsX86_64 || IsMIPS64 || IsAArch64 || IsX86 || IsMIPS || IsArmArch ||
746       IsPowerPC64)
747     Res |= SanitizerKind::Scudo;
748   if (IsX86_64 || IsAArch64) {
749     Res |= SanitizerKind::HWAddress;
750     Res |= SanitizerKind::KernelHWAddress;
751   }
752   return Res;
753 }
754 
755 void Linux::addProfileRTLibs(const llvm::opt::ArgList &Args,
756                              llvm::opt::ArgStringList &CmdArgs) const {
757   // Add linker option -u__llvm_profile_runtime to cause runtime
758   // initialization module to be linked in.
759   if (needsProfileRT(Args))
760     CmdArgs.push_back(Args.MakeArgString(
761         Twine("-u", llvm::getInstrProfRuntimeHookVarName())));
762   ToolChain::addProfileRTLibs(Args, CmdArgs);
763 }
764 
765 llvm::DenormalMode
766 Linux::getDefaultDenormalModeForType(const llvm::opt::ArgList &DriverArgs,
767                                      const JobAction &JA,
768                                      const llvm::fltSemantics *FPType) const {
769   switch (getTriple().getArch()) {
770   case llvm::Triple::x86:
771   case llvm::Triple::x86_64: {
772     std::string Unused;
773     // DAZ and FTZ are turned on in crtfastmath.o
774     if (!DriverArgs.hasArg(options::OPT_nostdlib, options::OPT_nostartfiles) &&
775         isFastMathRuntimeAvailable(DriverArgs, Unused))
776       return llvm::DenormalMode::getPreserveSign();
777     return llvm::DenormalMode::getIEEE();
778   }
779   default:
780     return llvm::DenormalMode::getIEEE();
781   }
782 }
783 
784 void Linux::addExtraOpts(llvm::opt::ArgStringList &CmdArgs) const {
785   for (const auto &Opt : ExtraOpts)
786     CmdArgs.push_back(Opt.c_str());
787 }
788