AArch64: Implement support for the shadowcallstack attribute.

The implementation of shadow call stack on aarch64 is quite different to
the implementation on x86_64. Instead of reserving a segment register for
the shadow call stack, we reserve the platform register, x18. Any function
that spills lr to sp also spills it to the shadow call stack, a pointer to
which is stored in x18.

Differential Revision: https://reviews.llvm.org/D45239

llvm-svn: 329236

2 files changed, 12 insertions, 1 deletions

diff --git a/clang/lib/Driver/SanitizerArgs.cpp b/clang/lib/Driver/SanitizerArgs.cpp
index 70dbc5fcb29..b2dbcc43a6c 100644
--- a/clang/lib/Driver/SanitizerArgs.cpp
+++ b/clang/lib/Driver/SanitizerArgs.cpp
@@ -18,6 +18,7 @@
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/SpecialCaseList.h"
+#include "llvm/Support/TargetParser.h"
 #include <memory>
 
 using namespace clang;
@@ -375,6 +376,15 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
         << lastArgumentForMask(D, Args, Kinds & NeedsLTO) << "-flto";
   }
 
+  if ((Kinds & ShadowCallStack) &&
+      TC.getTriple().getArch() == llvm::Triple::aarch64 &&
+      !llvm::AArch64::isX18ReservedByDefault(TC.getTriple()) &&
+      !Args.hasArg(options::OPT_ffixed_x18)) {
+    D.Diag(diag::err_drv_argument_only_allowed_with)
+        << lastArgumentForMask(D, Args, Kinds & ShadowCallStack)
+        << "-ffixed-x18";
+  }
+
   // Report error if there are non-trapping sanitizers that require
   // c++abi-specific  parts of UBSan runtime, and they are not provided by the
   // toolchain. We don't have a good way to check the latter, so we just
diff --git a/clang/lib/Driver/ToolChain.cpp b/clang/lib/Driver/ToolChain.cpp
index 23d6503d333..bf97557bd6f 100644
--- a/clang/lib/Driver/ToolChain.cpp
+++ b/clang/lib/Driver/ToolChain.cpp
@@ -814,7 +814,8 @@ SanitizerMask ToolChain::getSupportedSanitizers() const {
       getTriple().getArch() == llvm::Triple::wasm32 ||
       getTriple().getArch() == llvm::Triple::wasm64)
     Res |= CFIICall;
-  if (getTriple().getArch() == llvm::Triple::x86_64)
+  if (getTriple().getArch() == llvm::Triple::x86_64 ||
+      getTriple().getArch() == llvm::Triple::aarch64)
     Res |= ShadowCallStack;
   return Res;
 }