hwasan: Instrument globals.

Globals are instrumented by adding a pointer tag to their symbol values
and emitting metadata into a special section that allows the runtime to tag
their memory when the library is loaded.

Due to order of initialization issues explained in more detail in the comments,
shadow initialization cannot happen during regular global initialization.
Instead, the location of the global section is marked using an ELF note,
and we require libc support for calling a function provided by the HWASAN
runtime when libraries are loaded and unloaded.

Based on ideas discussed with @evgeny777 in D56672.

Differential Revision: https://reviews.llvm.org/D65770

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@368102 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Driver/SanitizerArgs.cpp

@@ -1013,6 +1013,11 @@ void SanitizerArgs::addArgs(const ToolChain &TC, const llvm::opt::ArgList &Args,
     CmdArgs.push_back(Args.MakeArgString("hwasan-abi=" + HwasanAbi));
   }
 
+  if (Sanitizers.has(SanitizerKind::HWAddress)) {
+    CmdArgs.push_back("-target-feature");
+    CmdArgs.push_back("+tagged-globals");
+  }
+
   // MSan: Workaround for PR16386.
   // ASan: This is mainly to help LSan with cases such as
   // https://github.com/google/sanitizers/issues/373

test/Driver/fsanitize.c

@@ -843,7 +843,9 @@
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=hwaddress -fsanitize-hwaddress-abi=platform %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-HWASAN-PLATFORM-ABI
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=hwaddress -fsanitize-hwaddress-abi=foo %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-HWASAN-FOO-ABI
 // CHECK-HWASAN-INTERCEPTOR-ABI: "-default-function-attr" "hwasan-abi=interceptor"
+// CHECK-HWASAN-INTERCEPTOR-ABI: "-target-feature" "+tagged-globals"
 // CHECK-HWASAN-PLATFORM-ABI: "-default-function-attr" "hwasan-abi=platform"
+// CHECK-HWASAN-PLATFORM-ABI: "-target-feature" "+tagged-globals"
 // CHECK-HWASAN-FOO-ABI: error: invalid value 'foo' in '-fsanitize-hwaddress-abi=foo'
 
 // RUN: %clang -target x86_64-linux-gnu -fsanitize=address,pointer-compare,pointer-subtract %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-POINTER-ALL