[asan] A clang flag to enable ELF globals-gc

[eugenis]

Summary

This feature is subtly broken when the linker is gold 2.26 or
earlier. See the following bug for details:

https://sourceware.org/bugzilla/show_bug.cgi?id=19002

Since the decision needs to be made at compilation time, we can not
test the linker version. The flag is off by default on ELF targets,
and on otherwise.

[chandlerc]

Generally makes sense. A question about the name. Feel free to land with a name that you and other sanitizer folks are happy with.

include/clang/Driver/Options.td

830

Would the name "-fsanitize-address-globals-dead-stripping" be a bit easier to understand? not sure.

[eugenis]

include/clang/Driver/Options.td

830

It does sound a little bit better.
The current name is copied from the -mllvm flag, which was initially OSX-specific, where "live_support" is part of the section name.

[pcc]

LGTM

Unfortunate, but I guess this is in the same category as things like -fsized-deallocation.

lib/Driver/SanitizerArgs.cpp

568

Maybe include a binutils PR reference so that we can remove this eventually?

729

I think you don't need MakeArgString for string literals.

[eugenis]

I'll fix the other unnecessary MakeArgString calls in a separate commit

[eugenis]

r302591, thanks for the review!

include/clang/Driver/Options.td

def fsanitize_address_field_padding : Joined<["-"], "fsanitize-address-field-padding=">,
                                         HelpText<"Level of field padding for AddressSanitizer">;
 def fsanitize_address_use_after_scope : Flag<["-"], "fsanitize-address-use-after-scope">,
                                         Group<f_clang_Group>,
                                         HelpText<"Enable use-after-scope detection in AddressSanitizer">;
 def fno_sanitize_address_use_after_scope : Flag<["-"], "fno-sanitize-address-use-after-scope">,
                                            Group<f_clang_Group>,
                                            Flags<[CoreOption, DriverOption]>,
                                            HelpText<"Disable use-after-scope detection in AddressSanitizer">;
+def fsanitize_address_globals_dead_stripping : Flag<["-"], "fsanitize-address-globals-dead-stripping">,
+                                        Group<f_clang_Group>,
+                                        HelpText<"Enable linker dead stripping of globals in AddressSanitizer">;
 def fsanitize_recover : Flag<["-"], "fsanitize-recover">, Group<f_clang_Group>;
 def fno_sanitize_recover : Flag<["-"], "fno-sanitize-recover">,
                            Flags<[CoreOption, DriverOption]>,
                            Group<f_clang_Group>;
 def fsanitize_recover_EQ : CommaJoined<["-"], "fsanitize-recover=">,
                            Group<f_clang_Group>,
                            HelpText<"Enable recovery for specified sanitizers">;
 def fno_sanitize_recover_EQ

include/clang/Driver/SanitizerArgs.h

class SanitizerArgs {
   std::vector<std::string> ExtraDeps;
   int CoverageFeatures = 0;
   int MsanTrackOrigins = 0;
   bool MsanUseAfterDtor = false;
   bool CfiCrossDso = false;
   int AsanFieldPadding = 0;
   bool AsanSharedRuntime = false;
   bool AsanUseAfterScope = true;
+  bool AsanGlobalsDeadStripping = false;
   bool LinkCXXRuntimes = false;
   bool NeedPIE = false;
   bool Stats = false;
   bool TsanMemoryAccess = true;
   bool TsanFuncEntryExit = true;
   bool TsanAtomics = true;
 
  public:

include/clang/Frontend/CodeGenOptions.def

 ENUM_CODEGENOPT(StructReturnConvention, StructReturnConventionKind, 2, SRCK_Default)
 
 CODEGENOPT(RelaxAll          , 1, 0) ///< Relax all machine code instructions.
 CODEGENOPT(RelaxedAliasing   , 1, 0) ///< Set when -fno-strict-aliasing is enabled.
 CODEGENOPT(StructPathTBAA    , 1, 0) ///< Whether or not to use struct-path TBAA.
 CODEGENOPT(SaveTempLabels    , 1, 0) ///< Save temporary labels.
 CODEGENOPT(SanitizeAddressUseAfterScope , 1, 0) ///< Enable use-after-scope detection
                                                 ///< in AddressSanitizer
+CODEGENOPT(SanitizeAddressGlobalsDeadStripping, 1, 0) ///< Enable linker dead stripping
+                                                      ///< of globals in AddressSanitizer
 CODEGENOPT(SanitizeMemoryTrackOrigins, 2, 0) ///< Enable tracking origins in
                                              ///< MemorySanitizer
 CODEGENOPT(SanitizeMemoryUseAfterDtor, 1, 0) ///< Enable use-after-delete detection
                                              ///< in MemorySanitizer
 CODEGENOPT(SanitizeCfiCrossDso, 1, 0) ///< Enable cross-dso support in CFI.
 CODEGENOPT(SanitizeCoverageType, 2, 0) ///< Type of sanitizer coverage
                                        ///< instrumentation.
 CODEGENOPT(SanitizeCoverageIndirectCalls, 1, 0) ///< Enable sanitizer coverage

lib/CodeGen/BackendUtil.cpp

static void addSanitizerCoveragePass(const PassManagerBuilder &Builder,
   PM.add(createSanitizerCoverageModulePass(Opts));
 }
 
 // Check if ASan should use GC-friendly instrumentation for globals.
 // First of all, there is no point if -fdata-sections is off (expect for MachO,
 // where this is not a factor). Also, on ELF this feature requires an assembler
 // extension that only works with -integrated-as at the moment.
 static bool asanUseGlobalsGC(const Triple &T, const CodeGenOptions &CGOpts) {
+  if (!CGOpts.SanitizeAddressGlobalsDeadStripping)
+    return false;
   switch (T.getObjectFormat()) {
   case Triple::MachO:
   case Triple::COFF:
     return true;
   case Triple::ELF:
     return CGOpts.DataSections && !CGOpts.DisableIntegratedAS;
   default:
     return false;

lib/Driver/SanitizerArgs.cpp

if (Arg *WindowsDebugRTArg =
             << WindowsDebugRTArg->getAsString(Args)
             << lastArgumentForMask(D, Args, Address);
         D.Diag(clang::diag::note_drv_address_sanitizer_debug_runtime);
       }
     }
 
     AsanUseAfterScope = Args.hasFlag(
         options::OPT_fsanitize_address_use_after_scope,
         options::OPT_fno_sanitize_address_use_after_scope, AsanUseAfterScope);
+
+    // As a workaround for a bug in gold 2.26 and earlier, dead stripping of
+    // globals in ASan is disabled by default on ELF targets.
+    // See https://sourceware.org/bugzilla/show_bug.cgi?id=19002
+    AsanGlobalsDeadStripping =
+        !TC.getTriple().isOSBinFormatELF() ||
+        Args.hasArg(options::OPT_fsanitize_address_globals_dead_stripping);
   } else {
     AsanUseAfterScope = false;
   }
 
   // Parse -link-cxx-sanitizer flag.
   LinkCXXRuntimes =
       Args.hasArg(options::OPT_fsanitize_link_cxx_runtime) || D.CCCIsCXX();
 
void SanitizerArgs::addArgs(const ToolChain &TC, const llvm::opt::ArgList &Args,
 
   if (AsanFieldPadding)
     CmdArgs.push_back(Args.MakeArgString("-fsanitize-address-field-padding=" +
                                          llvm::utostr(AsanFieldPadding)));
 
   if (AsanUseAfterScope)
     CmdArgs.push_back(Args.MakeArgString("-fsanitize-address-use-after-scope"));
 
+  if (AsanGlobalsDeadStripping)
+    CmdArgs.push_back("-fsanitize-address-globals-dead-stripping");
+
   // MSan: Workaround for PR16386.
   // ASan: This is mainly to help LSan with cases such as
   // https://code.google.com/p/address-sanitizer/issues/detail?id=373
   // We can't make this conditional on -fsanitize=leak, as that flag shouldn't
   // affect compilation.
   if (Sanitizers.has(Memory) || Sanitizers.has(Address))
     CmdArgs.push_back(Args.MakeArgString("-fno-assume-sane-operator-new"));
 

lib/Frontend/CompilerInvocation.cpp

Opts.SanitizeMemoryUseAfterDtor =
       Args.hasArg(OPT_fsanitize_memory_use_after_dtor);
   Opts.SanitizeCfiCrossDso = Args.hasArg(OPT_fsanitize_cfi_cross_dso);
   Opts.SanitizeStats = Args.hasArg(OPT_fsanitize_stats);
   if (Arg *A = Args.getLastArg(OPT_fsanitize_address_use_after_scope,
                                OPT_fno_sanitize_address_use_after_scope)) {
     Opts.SanitizeAddressUseAfterScope =
         A->getOption().getID() == OPT_fsanitize_address_use_after_scope;
   }
+  Opts.SanitizeAddressGlobalsDeadStripping =
+      Args.hasArg(OPT_fsanitize_address_globals_dead_stripping);
   Opts.SSPBufferSize =
       getLastArgIntValue(Args, OPT_stack_protector_buffer_size, 8, Diags);
   Opts.StackRealignment = Args.hasArg(OPT_mstackrealign);
   if (Arg *A = Args.getLastArg(OPT_mstack_alignment)) {
     StringRef Val = A->getValue();
     unsigned StackAlignment = Opts.StackAlignment;
     Val.getAsInteger(10, StackAlignment);
     Opts.StackAlignment = StackAlignment;

test/CodeGen/asan-globals-gc.cpp

-// RUN: %clang_cc1 -fsanitize=address -emit-llvm -o - -triple x86_64-windows-msvc %s | FileCheck %s --check-prefix=WITH-GC
-// RUN: %clang_cc1 -fsanitize=address -emit-llvm -o - -triple x86_64-windows-msvc -fdata-sections %s | FileCheck %s --check-prefix=WITH-GC
+// RUN: %clang_cc1 -fsanitize=address -fsanitize-address-globals-dead-stripping -emit-llvm -o - -triple x86_64-linux %s | FileCheck %s --check-prefix=WITHOUT-GC
+// RUN: %clang_cc1 -fsanitize=address -fsanitize-address-globals-dead-stripping -fdata-sections -emit-llvm -o - -triple x86_64-linux %s | FileCheck %s --check-prefix=WITH-GC
+// RUN: %clang_cc1 -fsanitize=address -fsanitize-address-globals-dead-stripping -fno-integrated-as -fdata-sections -emit-llvm -o - -triple x86_64-linux %s | FileCheck %s --check-prefix=WITHOUT-GC
+// RUN: %clang_cc1 -fsanitize=address -fsanitize-address-globals-dead-stripping -fno-integrated-as -emit-llvm -o - -triple x86_64-linux %s | FileCheck %s --check-prefix=WITHOUT-GC
+// RUN: %clang_cc1 -fsanitize=address -fdata-sections -emit-llvm -o - -triple x86_64-linux %s | FileCheck %s --check-prefix=WITHOUT-GC
+
+// RUN: %clang_cc1 -fsanitize=address -fsanitize-address-globals-dead-stripping -fno-data-sections -emit-llvm -o - -triple x86_64-windows-msvc %s | FileCheck %s --check-prefix=WITH-GC
+// RUN: %clang_cc1 -fsanitize=address -fsanitize-address-globals-dead-stripping -fdata-sections -emit-llvm -o - -triple x86_64-windows-msvc %s | FileCheck %s --check-prefix=WITH-GC
+// RUN: %clang_cc1 -fsanitize=address -fdata-sections -emit-llvm -o - -triple x86_64-windows-msvc %s | FileCheck %s --check-prefix=WITHOUT-GC
+
+// RUN: %clang_cc1 -fsanitize=address -fsanitize-address-globals-dead-stripping -fno-data-sections -emit-llvm -o - -triple x86_64-apple-macosx11 %s | FileCheck %s --check-prefix=WITH-GC
+// RUN: %clang_cc1 -fsanitize=address -fsanitize-address-globals-dead-stripping -fdata-sections -emit-llvm -o - -triple x86_64-apple-macosx11 %s | FileCheck %s --check-prefix=WITH-GC
+// RUN: %clang_cc1 -fsanitize=address -fdata-sections -emit-llvm -o - -triple x86_64-apple-macosx11 %s | FileCheck %s --check-prefix=WITHOUT-GC
 
 int global;
 
 // WITH-GC-NOT: call void @__asan_register_globals
 // WITHOUT-GC: call void @__asan_register_globals

test/Driver/fsanitize.c

 // CHECK-USE-AFTER-SCOPE-BOTH: -cc1{{.*}}-fsanitize-address-use-after-scope
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=address -fsanitize-address-use-after-scope -fno-sanitize-address-use-after-scope %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-USE-AFTER-SCOPE-BOTH-OFF
 // CHECK-USE-AFTER-SCOPE-BOTH-OFF-NOT: -cc1{{.*}}address-use-after-scope
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=address %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ASAN-WITHOUT-USE-AFTER-SCOPE
 // CHECK-ASAN-WITHOUT-USE-AFTER-SCOPE: -cc1{{.*}}address-use-after-scope
 
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=address -fsanitize-address-globals-dead-stripping %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ASAN-GLOBALS
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=address %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-NO-ASAN-GLOBALS
+// RUN: %clang_cl -target x86_64-windows-msvc -fsanitize=address -fsanitize-address-globals-dead-stripping -### -- %s 2>&1 | FileCheck %s --check-prefix=CHECK-ASAN-GLOBALS
+// RUN: %clang_cl -target x86_64-windows-msvc -fsanitize=address -### -- %s 2>&1 | FileCheck %s --check-prefix=CHECK-ASAN-GLOBALS
+// CHECK-ASAN-GLOBALS: -cc1{{.*}}-fsanitize-address-globals-dead-stripping
+// CHECK-NO-ASAN-GLOBALS-NOT: -cc1{{.*}}-fsanitize-address-globals-dead-stripping
+
 // RUN: %clang -target x86_64-linux-gnu -fsanitize-memory-track-origins -pie %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ONLY-TRACK-ORIGINS
 // CHECK-ONLY-TRACK-ORIGINS: warning: argument unused during compilation: '-fsanitize-memory-track-origins'
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=memory -fno-sanitize=memory -fsanitize-memory-track-origins -pie %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-TRACK-ORIGINS-DISABLED-MSAN
 // CHECK-TRACK-ORIGINS-DISABLED-MSAN-NOT: warning: argument unused
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=address %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-NO-EXTRA-TRACK-ORIGINS
 // CHECK-NO-EXTRA-TRACK-ORIGINS-NOT: "-fsanitize-memory-track-origins"