Enable the SafeStack sanitizer on CloudABI by default.

Over the last month we've been testing SafeStack extensively. As far as
we know, it works perfectly fine. That why I'd like to see us having
this enabled by default for CloudABI.

This change introduces a getDefaultSanitizers() function that toolchains
can use to specify which sanitizers are enabled by default. Once all
flags are processed, only flags that had no -fno-sanitize overrides are
enabled.

Extend the thests for CloudABI to test both the default case and the
case in which we want to explicitly disable SafeStack.

Reviewed by:	eugenis, pcc
Differential Revision:	http://reviews.llvm.org/D18505

llvm-svn: 264787

clang/include/clang/Driver/ToolChain.h

@@ -419,6 +419,9 @@ class ToolChain {
 
   /// \brief Return sanitizers which are available in this toolchain.
   virtual SanitizerMask getSupportedSanitizers() const;
+
+  /// \brief Return sanitizers which are enabled by default.
+  virtual SanitizerMask getDefaultSanitizers() const { return 0; }
 };
 
 } // end namespace driver

clang/lib/Driver/SanitizerArgs.cpp

@@ -268,6 +268,9 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
     }
   }
 
+  // Enable toolchain specific default sanitizers if not explicitly disabled.
+  Kinds |= TC.getDefaultSanitizers() & ~AllRemove;
+
   // We disable the vptr sanitizer if it was enabled by group expansion but RTTI
   // is disabled.
   if ((Kinds & Vptr) &&

clang/lib/Driver/ToolChains.cpp

@@ -2988,6 +2988,10 @@ SanitizerMask CloudABI::getSupportedSanitizers() const {
   return Res;
 }
 
+SanitizerMask CloudABI::getDefaultSanitizers() const {
+  return SanitizerKind::SafeStack;
+}
+
 /// OpenBSD - OpenBSD tool chain which can call as(1) and ld(1) directly.
 
 OpenBSD::OpenBSD(const Driver &D, const llvm::Triple &Triple,

clang/lib/Driver/ToolChains.h

@@ -620,6 +620,7 @@ class LLVM_LIBRARY_VISIBILITY CloudABI : public Generic_ELF {
   bool isPIEDefault() const override { return false; }
 
   SanitizerMask getSupportedSanitizers() const override;
+  SanitizerMask getDefaultSanitizers() const override;
 
 protected:
   Tool *buildLinker() const override;

clang/test/Driver/cloudabi.c

@@ -1,3 +1,8 @@
-// RUN: %clang %s -### -target x86_64-unknown-cloudabi 2>&1 | FileCheck %s
-// CHECK: "-cc1" "-triple" "x86_64-unknown-cloudabi" {{.*}} "-ffunction-sections" "-fdata-sections"
-// CHECK: "-Bstatic" "--eh-frame-hdr" "--gc-sections" "-o" "a.out" "crt0.o" "crtbegin.o" "{{.*}}" "{{.*}}" "-lc" "-lcompiler_rt" "crtend.o"
+// RUN: %clang %s -### -target x86_64-unknown-cloudabi 2>&1 | FileCheck %s -check-prefix=SAFESTACK
+// SAFESTACK: "-cc1" "-triple" "x86_64-unknown-cloudabi" {{.*}} "-ffunction-sections" "-fdata-sections" {{.*}} "-fsanitize=safe-stack"
+// SAFESTACK: "-Bstatic" "--eh-frame-hdr" "--gc-sections" "-o" "a.out" "crt0.o" "crtbegin.o" "{{.*}}" "{{.*}}" "-lc" "-lcompiler_rt" "crtend.o"
+
+// RUN: %clang %s -### -target x86_64-unknown-cloudabi -fno-sanitize=safe-stack 2>&1 | FileCheck %s -check-prefix=NOSAFESTACK
+// NOSAFESTACK: "-cc1" "-triple" "x86_64-unknown-cloudabi" {{.*}} "-ffunction-sections" "-fdata-sections"
+// NOSAFESTACK-NOT: "-fsanitize=safe-stack"
+// NOSAFESTACK: "-Bstatic" "--eh-frame-hdr" "--gc-sections" "-o" "a.out" "crt0.o" "crtbegin.o" "{{.*}}" "{{.*}}" "-lc" "-lcompiler_rt" "crtend.o"

clang/test/Driver/cloudabi.cpp

@@ -1,3 +1,8 @@
-// RUN: %clangxx %s -### -target x86_64-unknown-cloudabi 2>&1 | FileCheck %s
-// CHECK: "-cc1" "-triple" "x86_64-unknown-cloudabi" {{.*}} "-ffunction-sections" "-fdata-sections"
-// CHECK: "-Bstatic" "--eh-frame-hdr" "--gc-sections" "-o" "a.out" "crt0.o" "crtbegin.o" "{{.*}}" "{{.*}}" "-lc++" "-lc++abi" "-lunwind" "-lc" "-lcompiler_rt" "crtend.o"
+// RUN: %clangxx %s -### -target x86_64-unknown-cloudabi 2>&1 | FileCheck %s -check-prefix=SAFESTACK
+// SAFESTACK: "-cc1" "-triple" "x86_64-unknown-cloudabi" {{.*}} "-ffunction-sections" "-fdata-sections" {{.*}} "-fsanitize=safe-stack"
+// SAFESTACK: "-Bstatic" "--eh-frame-hdr" "--gc-sections" "-o" "a.out" "crt0.o" "crtbegin.o" "{{.*}}" "{{.*}}" "-lc++" "-lc++abi" "-lunwind" "-lc" "-lcompiler_rt" "crtend.o"
+
+// RUN: %clangxx %s -### -target x86_64-unknown-cloudabi -fno-sanitize=safe-stack 2>&1 | FileCheck %s -check-prefix=NOSAFESTACk
+// NOSAFESTACK: "-cc1" "-triple" "x86_64-unknown-cloudabi" {{.*}} "-ffunction-sections" "-fdata-sections"
+// NOSAFESTACK-NOT: "-fsanitize=safe-stack"
+// NOSAFESTACk: "-Bstatic" "--eh-frame-hdr" "--gc-sections" "-o" "a.out" "crt0.o" "crtbegin.o" "{{.*}}" "{{.*}}" "-lc++" "-lc++abi" "-lunwind" "-lc" "-lcompiler_rt" "crtend.o"