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

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.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@302591 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Driver/Options.td

@@ -827,6 +827,9 @@ def fno_sanitize_address_use_after_scope : Flag<["-"], "fno-sanitize-address-use
                                            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]>,

include/clang/Driver/SanitizerArgs.h

@@ -35,6 +35,7 @@ class SanitizerArgs {
   int AsanFieldPadding = 0;
   bool AsanSharedRuntime = false;
   bool AsanUseAfterScope = true;
+  bool AsanGlobalsDeadStripping = false;
   bool LinkCXXRuntimes = false;
   bool NeedPIE = false;
   bool Stats = false;

include/clang/Frontend/CodeGenOptions.def

@@ -137,6 +137,8 @@ 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

lib/CodeGen/BackendUtil.cpp

@@ -194,6 +194,8 @@ static void addSanitizerCoveragePass(const PassManagerBuilder &Builder,
 // 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:

lib/Driver/SanitizerArgs.cpp

@@ -566,6 +566,13 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
     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;
   }
@@ -717,6 +724,9 @@ void SanitizerArgs::addArgs(const ToolChain &TC, const llvm::opt::ArgList &Args,
   if (AsanUseAfterScope)
     CmdArgs.push_back("-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

lib/Frontend/CompilerInvocation.cpp

@@ -778,6 +778,8 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
     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);

test/CodeGen/asan-globals-gc.cpp

@@ -1,5 +1,16 @@
-// 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;
 

test/Driver/fsanitize.c

@@ -126,6 +126,13 @@
 // 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'