Do not link clang_rt.cfi on Android.

[eugenis]

Summary

The OS provides cross-dso CFI support starting with Android O.
Trapping mode does not require any runtime at all, and diagnostic mode
requires just ubsan-standalone.

[pcc]

clang/test/Driver/sanitizer-ld.c

605

Why was this passing before?

[eugenis]

clang/test/Driver/sanitizer-ld.c

605

because android has NeedsSharedRt, and clang driver never adds clang_rt.cfi as a shared library.

[pcc]

LGTM

clang/include/clang/Driver/SanitizerArgs.h

class SanitizerArgs {
   bool LinkCXXRuntimes = false;
   bool NeedPIE = false;
   bool SafeStackRuntime = false;
   bool Stats = false;
   bool TsanMemoryAccess = true;
   bool TsanFuncEntryExit = true;
   bool TsanAtomics = true;
   bool MinimalRuntime = false;
+  // True if cross-dso CFI support if provided by the system (i.e. Android).
+  bool ImplicitCfiRuntime = false;
 
  public:
   /// Parses the sanitizer arguments from an argument list.
   SanitizerArgs(const ToolChain &TC, const llvm::opt::ArgList &Args);
 
   bool needsSharedRt() const { return SharedRuntime; }
 
   bool needsAsanRt() const { return Sanitizers.has(SanitizerKind::Address); }

clang/lib/Driver/SanitizerArgs.cpp

static SanitizerMask parseSanitizeTrapArgs(const Driver &D,
 
   // Apply default trapping behavior.
   TrappingKinds |= TrappingDefault & ~TrapRemove;
 
   return TrappingKinds;
 }
 
 bool SanitizerArgs::needsUbsanRt() const {
-  return ((Sanitizers.Mask & NeedsUbsanRt & ~TrapSanitizers.Mask) ||
-          CoverageFeatures) &&
-         !Sanitizers.has(Address) && !Sanitizers.has(Memory) &&
-         !Sanitizers.has(Thread) && !Sanitizers.has(DataFlow) &&
-         !Sanitizers.has(Leak) && !CfiCrossDso;
+  // All of these include ubsan.
+  if (needsAsanRt() || needsMsanRt() || needsTsanRt() || needsDfsanRt() ||
+      needsLsanRt() || needsCfiDiagRt())
+    return false;
+
+  return (Sanitizers.Mask & NeedsUbsanRt & ~TrapSanitizers.Mask) ||
+         CoverageFeatures;
 }
 
 bool SanitizerArgs::needsCfiRt() const {
-  return !(Sanitizers.Mask & CFI & ~TrapSanitizers.Mask) && CfiCrossDso;
+  return !(Sanitizers.Mask & CFI & ~TrapSanitizers.Mask) && CfiCrossDso &&
+         !ImplicitCfiRuntime;
 }
 
 bool SanitizerArgs::needsCfiDiagRt() const {
-  return (Sanitizers.Mask & CFI & ~TrapSanitizers.Mask) && CfiCrossDso;
+  return (Sanitizers.Mask & CFI & ~TrapSanitizers.Mask) && CfiCrossDso &&
+         !ImplicitCfiRuntime;
 }
 
 bool SanitizerArgs::requiresPIE() const {
   return NeedPIE || (Sanitizers.Mask & RequiresPIE);
 }
 
 bool SanitizerArgs::needsUnwindTables() const {
   return Sanitizers.Mask & NeedsUnwindTables;
if (CoverageFeatures & CoverageStackDepth)
       CoverageFeatures |= CoverageFunc;
   }
 
   SharedRuntime =
       Args.hasFlag(options::OPT_shared_libsan, options::OPT_static_libsan,
                    TC.getTriple().isAndroid() || TC.getTriple().isOSFuchsia() ||
                        TC.getTriple().isOSDarwin());
 
+  ImplicitCfiRuntime = TC.getTriple().isAndroid();
+
   if (AllAddedKinds & Address) {
     NeedPIE |= TC.getTriple().isAndroid() || TC.getTriple().isOSFuchsia();
     if (Arg *A =
             Args.getLastArg(options::OPT_fsanitize_address_field_padding)) {
         StringRef S = A->getValue();
         // Legal values are 0 and 1, 2, but in future we may add more levels.
         if (S.getAsInteger(0, AsanFieldPadding) || AsanFieldPadding < 0 ||
             AsanFieldPadding > 2) {

clang/test/Driver/sanitizer-ld.c

 // RUN:     -fno-sanitize-trap=cfi -fsanitize-recover=cfi \
 // RUN:     -target x86_64-unknown-linux -fuse-ld=ld \
 // RUN:     --sysroot=%S/Inputs/basic_linux_tree \
 // RUN:   | FileCheck --check-prefix=CHECK-CFI-CROSS-DSO-DIAG-LINUX %s
 // CHECK-CFI-CROSS-DSO-DIAG-LINUX: "{{.*}}ld{{(.exe)?}}"
 // CHECK-CFI-CROSS-DSO-DIAG-LINUX: "-whole-archive" "{{[^"]*}}libclang_rt.cfi_diag-x86_64.a" "-no-whole-archive"
 // CHECK-CFI-CROSS-DSO-DIAG-LINUX: -export-dynamic
 
+// Cross-DSO CFI on Android does not link runtime libraries.
+// RUN: %clang -fsanitize=cfi -fsanitize-cfi-cross-dso %s -### -o %t.o 2>&1 \
+// RUN:     -target aarch64-linux-android -fuse-ld=ld \
+// RUN:     --sysroot=%S/Inputs/basic_android_tree \
+// RUN:   | FileCheck --check-prefix=CHECK-CFI-CROSS-DSO-ANDROID %s
+// CHECK-CFI-CROSS-DSO-ANDROID: "{{.*}}ld{{(.exe)?}}"
+// CHECK-CFI-CROSS-DSO-ANDROID-NOT: libclang_rt.
+
+// Cross-DSO CFI with diagnostics on Android links just the UBSAN runtime.
+// RUN: %clang -fsanitize=cfi -fsanitize-cfi-cross-dso %s -### -o %t.o 2>&1 \
+// RUN:     -fno-sanitize-trap=cfi -fsanitize-recover=cfi \
+// RUN:     -target aarch64-linux-android -fuse-ld=ld \
+// RUN:     --sysroot=%S/Inputs/basic_android_tree \
+// RUN:   | FileCheck --check-prefix=CHECK-CFI-CROSS-DSO-DIAG-ANDROID %s
+// CHECK-CFI-CROSS-DSO-DIAG-ANDROID: "{{.*}}ld{{(.exe)?}}"
+// CHECK-CFI-CROSS-DSO-DIAG-ANDROID: "{{[^"]*}}libclang_rt.ubsan_standalone-aarch64-android.so"
+// CHECK-CFI-CROSS-DSO-DIAG-ANDROID: "-export-dynamic-symbol=__cfi_check"
+
 // RUN: %clangxx -fsanitize=address %s -### -o %t.o 2>&1 \
 // RUN:     -mmacosx-version-min=10.6 \
 // RUN:     -target x86_64-apple-darwin13.4.0 -fuse-ld=ld -stdlib=platform \
 // RUN:     --sysroot=%S/Inputs/basic_linux_tree \
 // RUN:   | FileCheck --check-prefix=CHECK-ASAN-DARWIN106-CXX %s
 // CHECK-ASAN-DARWIN106-CXX: "{{.*}}ld{{(.exe)?}}"
 // CHECK-ASAN-DARWIN106-CXX: libclang_rt.asan_osx_dynamic.dylib
 // CHECK-ASAN-DARWIN106-CXX-NOT: -lc++abi

 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
 // RUN:     -target aarch64-linux-android -fuse-ld=ld -fsanitize=safe-stack \
 // RUN:     --sysroot=%S/Inputs/basic_android_tree \
 // RUN:   | FileCheck --check-prefix=CHECK-SAFESTACK-ANDROID-AARCH64 %s
 //
 // CHECK-SAFESTACK-ANDROID-AARCH64: "{{(.*[^-.0-9A-Z_a-z])?}}ld{{(.exe)?}}"
 // CHECK-SAFESTACK-ANDROID-AARCH64-NOT: libclang_rt.safestack
 
-// RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
-// RUN:     -target arm-linux-androideabi -fuse-ld=ld -fsanitize=cfi \
-// RUN:     --sysroot=%S/Inputs/basic_android_tree \
-// RUN:   | FileCheck --check-prefix=CHECK-CFI-ANDROID %s
-//
-// CHECK-CFI-ANDROID: "{{(.*[^-.0-9A-Z_a-z])?}}ld{{(.exe)?}}"
-// CHECK-CFI-ANDROID-NOT: libclang_rt.cfi
-// CHECK-CFI-ANDROID-NOT: __cfi_check
-
-// RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
-// RUN:     -target arm-linux-androideabi -fuse-ld=ld -fsanitize=cfi \
-// RUN:     -fsanitize-cfi-cross-dso \
-// RUN:     --sysroot=%S/Inputs/basic_android_tree \
-// RUN:   | FileCheck --check-prefix=CHECK-CROSSDSO-CFI-ANDROID %s
-//
-// CHECK-CROSSDSO-CFI-ANDROID: "{{(.*[^-.0-9A-Z_a-z])?}}ld{{(.exe)?}}"
-// CHECK-CROSSDSO-CFI-ANDROID-NOT: libclang_rt.cfi
-// CHECK-CROSSDSO-CFI-ANDROID: -export-dynamic-symbol=__cfi_check
-// CHECK-CROSSDSO-CFI-ANDROID-NOT: libclang_rt.cfi
-
 // RUN: %clang -fsanitize=undefined %s -### -o %t.o 2>&1 \
 // RUN:     -target x86_64-scei-ps4 -fuse-ld=ld \
 // RUN:     -shared \
 // RUN:   | FileCheck --check-prefix=CHECK-UBSAN-PS4 %s
 // CHECK-UBSAN-PS4: "{{.*}}ld{{(.gold)?(.exe)?}}"
 // CHECK-UBSAN-PS4: -lSceDbgUBSanitizer_stub_weak
 
 // RUN: %clang -fsanitize=address %s -### -o %t.o 2>&1 \