[Driver][Android] Remove unneeded isNoExecStackDefault

[MaskRay]

Summary

ld.lld used by Android ignores .note.GNU-stack and defaults to noexecstack,
so the -z noexecstack linker option is unneeded.

The --noexecstack assembler option is unneeded because AsmPrinter.cpp
prints .section .note.GNU-stack,"",@progbits (when llvm.init.trampoline is unused),
so the assembler won't synthesize an executable .note.GNU-stack.

[pirama]

Will defer to Dan's review. I think these changes are safe for the Android platform (where we only use lld). The NDK only supports lld but that does not preclude external users from using other linkers.

[danalbert]

Fine by me if this is the default for LLD.

clang/include/clang/Driver/ToolChain.h

public:
   }
 
   /// Test whether this toolchain defaults to PIC.
   virtual bool isPICDefault() const = 0;
 
   /// Test whether this toolchain defaults to PIE.
   virtual bool isPIEDefault(const llvm::opt::ArgList &Args) const = 0;
 
-  /// Test whether this toolchaind defaults to non-executable stacks.
-  virtual bool isNoExecStackDefault() const;
-
   /// Tests whether this toolchain forces its default for PIC, PIE or
   /// non-PIC.  If this returns true, any PIC related flags should be ignored
   /// and instead the results of \c isPICDefault() and \c isPIEDefault(const
   /// llvm::opt::ArgList &Args) are used exclusively.
   virtual bool isPICDefaultForced() const = 0;
 
   /// SupportsProfiling - Does this tool chain support -pg.
   virtual bool SupportsProfiling() const { return true; }

clang/lib/Driver/ToolChain.cpp

return Args.hasFlag(options::OPT_fintegrated_as,
                       options::OPT_fno_integrated_as,
                       IsIntegratedAssemblerDefault());
 }
 
 bool ToolChain::useRelaxRelocations() const {
   return ENABLE_X86_RELAX_RELOCATIONS;
 }
 
-bool ToolChain::isNoExecStackDefault() const {
-    return false;
-}
-
 SanitizerArgs
 ToolChain::getSanitizerArgs(const llvm::opt::ArgList &JobArgs) const {
   SanitizerArgs SanArgs(*this, JobArgs, !SanitizerArgsChecked);
   SanitizerArgsChecked = true;
   return SanArgs;
 }
 
 const XRayArgs& ToolChain::getXRayArgs() const {

clang/lib/Driver/ToolChains/Clang.cpp

static void CollectArgsForIntegratedAssembler(Compilation &C,
   // When passing -I arguments to the assembler we sometimes need to
   // unconditionally take the next argument.  For example, when parsing
   // '-Wa,-I -Wa,foo' we need to accept the -Wa,foo arg after seeing the
   // -Wa,-I arg and when parsing '-Wa,-I,foo' we need to accept the 'foo'
   // arg after parsing the '-I' arg.
   bool TakeNextArg = false;
 
   bool UseRelaxRelocations = C.getDefaultToolChain().useRelaxRelocations();
-  bool UseNoExecStack = C.getDefaultToolChain().isNoExecStackDefault();
+  bool UseNoExecStack = false;
   const char *MipsTargetFeature = nullptr;
   StringRef ImplicitIt;
   for (const Arg *A :
        Args.filtered(options::OPT_Wa_COMMA, options::OPT_Xassembler,
                      options::OPT_mimplicit_it_EQ)) {
     A->claim();
 
     if (A->getOption().getID() == options::OPT_mimplicit_it_EQ) {

clang/lib/Driver/ToolChains/Gnu.cpp

void tools::gnutools::Linker::ConstructJob(Compilation &C, const JobAction &JA,
   if (IsStaticPIE) {
     CmdArgs.push_back("-static");
     CmdArgs.push_back("-pie");
     CmdArgs.push_back("--no-dynamic-linker");
     CmdArgs.push_back("-z");
     CmdArgs.push_back("text");
   }
 
-  if (ToolChain.isNoExecStackDefault()) {
-    CmdArgs.push_back("-z");
-    CmdArgs.push_back("noexecstack");
-  }
-
   if (Args.hasArg(options::OPT_rdynamic))
     CmdArgs.push_back("-export-dynamic");
 
   if (Args.hasArg(options::OPT_s))
     CmdArgs.push_back("-s");
 
   if (Triple.isARM() || Triple.isThumb() || Triple.isAArch64()) {
     bool IsBigEndian = isArmBigEndian(Triple, Args);
if (A->getOption().getID() == options::OPT_gz) {
             Args.MakeArgString("--compress-debug-sections=" + Twine(Value)));
       } else {
         D.Diag(diag::err_drv_unsupported_option_argument)
             << A->getOption().getName() << Value;
       }
     }
   }
 
-  if (getToolChain().isNoExecStackDefault()) {
-      CmdArgs.push_back("--noexecstack");
-  }
-
   switch (getToolChain().getArch()) {
   default:
     break;
   // Add --32/--64 to make sure we get the format we want.
   // This is incomplete
   case llvm::Triple::x86:
     CmdArgs.push_back("--32");
     break;

clang/lib/Driver/ToolChains/Linux.h

void AddHIPIncludeArgs(const llvm::opt::ArgList &DriverArgs,
                          llvm::opt::ArgStringList &CC1Args) const override;
   void AddIAMCUIncludeArgs(const llvm::opt::ArgList &DriverArgs,
                            llvm::opt::ArgStringList &CC1Args) const override;
   RuntimeLibType GetDefaultRuntimeLibType() const override;
   CXXStdlibType GetDefaultCXXStdlibType() const override;
   bool
   IsAArch64OutlineAtomicsDefault(const llvm::opt::ArgList &Args) const override;
   bool isPIEDefault(const llvm::opt::ArgList &Args) const override;
-  bool isNoExecStackDefault() const override;
   bool IsMathErrnoDefault() const override;
   SanitizerMask getSupportedSanitizers() const override;
   void addProfileRTLibs(const llvm::opt::ArgList &Args,
                         llvm::opt::ArgStringList &CmdArgs) const override;
   std::string computeSysRoot() const override;
 
   std::string getDynamicLinker(const llvm::opt::ArgList &Args) const override;
 

clang/lib/Driver/ToolChains/Linux.cpp

bool Linux::IsAArch64OutlineAtomicsDefault(const ArgList &Args) const {
   if (RtLib == ToolChain::RLT_CompilerRT)
     return true;
   assert(RtLib == ToolChain::RLT_Libgcc && "unexpected runtime library type!");
   if (GCCInstallation.getVersion().isOlderThan(9, 3, 1))
     return false;
   return true;
 }
 
-bool Linux::isNoExecStackDefault() const {
-    return getTriple().isAndroid();
-}
-
 bool Linux::IsMathErrnoDefault() const {
   if (getTriple().isAndroid())
     return false;
   return Generic_ELF::IsMathErrnoDefault();
 }
 
 SanitizerMask Linux::getSupportedSanitizers() const {
   const bool IsX86 = getTriple().getArch() == llvm::Triple::x86;

clang/test/Driver/integrated-as.c

 // RUN: %clang -### -c -save-temps -integrated-as %s 2>&1 | FileCheck %s
 
 // CHECK: cc1as
 // CHECK: -mrelax-all
 
 // RUN: %clang -### -fintegrated-as -c -save-temps %s 2>&1 | FileCheck %s -check-prefix FIAS
 
 // FIAS: cc1as
 
 // RUN: %clang -target none -### -fno-integrated-as -S %s 2>&1 \
 // RUN:     | FileCheck %s -check-prefix NOFIAS
 
 // NOFIAS-NOT: cc1as
 // NOFIAS: -cc1
 // NOFIAS: "-fno-verbose-asm"
 // NOFIAS: -no-integrated-as
-
-// RUN: %clang -target arm-linux-androideabi -### \
-// RUN:   -integrated-as -c %s 2>&1 \
-// RUN:   | FileCheck -check-prefix=CHECK-ARM-ANDROID %s
-// CHECK-ARM-ANDROID: "-mnoexecstack"

clang/test/Driver/linux-as.c

 // RUN: %clang -target arm-linux -mfloat-abi=hard -### \
 // RUN:   -no-integrated-as -c %s 2>&1 \
 // RUN:   | FileCheck -check-prefix=CHECK-ARM-MFLOAT-ABI %s
 // CHECK-ARM-MFLOAT-ABI: as{{(.exe)?}}" "-EL" "-mfloat-abi=hard"
 //
 // RUN: %clang -target arm-linux-androideabi -### \
 // RUN:   -no-integrated-as -c %s 2>&1 \
 // RUN:   | FileCheck -check-prefix=CHECK-ARM-ANDROID %s
-// CHECK-ARM-ANDROID: as{{(.exe)?}}" "--noexecstack" "-EL" "-mfloat-abi=soft"
+// CHECK-ARM-ANDROID: as{{(.exe)?}}" "-EL" "-mfloat-abi=soft"
 //
 // RUN: %clang -target arm-linux-androideabi -march=armv7-a -### \
 // RUN:   -no-integrated-as -c %s 2>&1 \
 // RUN:   | FileCheck -check-prefix=CHECK-ARM-ANDROID-SOFTFP %s
-// CHECK-ARM-ANDROID-SOFTFP: as{{(.exe)?}}" "--noexecstack" "-EL" "-mfloat-abi=softfp" "-march=armv7-a"
+// CHECK-ARM-ANDROID-SOFTFP: as{{(.exe)?}}" "-EL" "-mfloat-abi=softfp" "-march=armv7-a"
 //
 // RUN: %clang -target arm-linux-eabi -mhard-float -### \
 // RUN:   -no-integrated-as -c %s 2>&1 \
 // RUN:   | FileCheck -check-prefix=CHECK-ARM-HARDFP %s
 // CHECK-ARM-HARDFP: as{{(.exe)?}}" "-EL" "-mfloat-abi=hard"
 //
 // RUN: %clang -target aarch64-linux-gnu -mcpu=cortex-a53 -### \
 // RUN:   -no-integrated-as -c %s 2>&1 \

clang/test/Driver/linux-ld.c

 // RUN: %clang %s -### -o %t.o 2>&1 \
 // RUN:     --target=armv7-linux-android23 \
 // RUN:   | FileCheck --check-prefix=CHECK-ANDROID-HASH-STYLE-M %s
 // CHECK-ANDROID-HASH-STYLE-M: "{{.*}}ld{{(.exe)?}}"
 // CHECK-ANDROID-HASH-STYLE-M: "--hash-style=gnu"
 
 // RUN: %clang %s -### -o %t.o 2>&1 \
 // RUN:     --target=armv7-linux-android21 \
-// RUN:   | FileCheck --check-prefix=CHECK-ANDROID-NOEXECSTACK %s
-// CHECK-ANDROID-NOEXECSTACK: "{{.*}}ld{{(.exe)?}}"
-// CHECK-ANDROID-NOEXECSTACK: "-z" "noexecstack"
-// CHECK-ANDROID-NOEXECSTACK-NOT: "-z" "execstack"
-// CHECK-ANDROID-NOEXECSTACK-NOT: "-z,execstack"
-// CHECK-ANDROID-NOEXECSTACK-NOT: "-zexecstack"
-
-// RUN: %clang %s -### -o %t.o 2>&1 \
-// RUN:     --target=armv7-linux-android21 \
 // RUN:   | FileCheck --check-prefix=CHECK-ANDROID-WARN-SHARED-TEXTREL %s
 // CHECK-ANDROID-WARN-SHARED-TEXTREL: "{{.*}}ld{{(.exe)?}}"
 // CHECK-ANDROID-WARN-SHARED-TEXTREL: "--warn-shared-textrel"
 
 // RUN: %clang %s -### -o %t.o 2>&1 --target=mips64-linux-gnuabin32 \
 // RUN:   | FileCheck --check-prefix=CHECK-MIPS64EL-GNUABIN32 %s
 // CHECK-MIPS64EL-GNUABIN32: "{{.*}}ld{{(.exe)?}}"
 // CHECK-MIPS64EL-GNUABIN32: "-m" "elf32btsmipn32"