[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.

llvm-svn: 302591

3 files changed, 14 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index 0d96f2efa60..51c21c9f25d 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/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:
diff --git a/clang/lib/Driver/SanitizerArgs.cpp b/clang/lib/Driver/SanitizerArgs.cpp
index b6fc9e9ba4f..9ab2e176845 100644
--- a/clang/lib/Driver/SanitizerArgs.cpp
+++ b/clang/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
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 96854b8fbc1..51147b6f949 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/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);