[asan] Remove -fsanitize-address-zero-base-shadow command line

flag from clang, and disable zero-base shadow support on all platforms
where it is not the default behavior.

- It is completely unused, as far as we know.
- It is ABI-incompatible with non-zero-base shadow, which means all
objects in a process must be built with the same setting. Failing to
do so results in a segmentation fault at runtime.
- It introduces a backward dependency of compiler-rt on user code,
which is uncommon and complicates testing.

This is the Clang part of a larger change.

llvm-svn: 199372

3 files changed, 4 insertions, 25 deletions

diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index 23d1edf0779..d6d4f47dd68 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -180,12 +180,10 @@ static void addAddressSanitizerPasses(const PassManagerBuilder &Builder,
       LangOpts.Sanitize.InitOrder,
       LangOpts.Sanitize.UseAfterReturn,
       LangOpts.Sanitize.UseAfterScope,
-      CGOpts.SanitizerBlacklistFile,
-      CGOpts.SanitizeAddressZeroBaseShadow));
+      CGOpts.SanitizerBlacklistFile));
   PM.add(createAddressSanitizerModulePass(
       LangOpts.Sanitize.InitOrder,
-      CGOpts.SanitizerBlacklistFile,
-      CGOpts.SanitizeAddressZeroBaseShadow));
+      CGOpts.SanitizerBlacklistFile));
 }
 
 static void addMemorySanitizerPass(const PassManagerBuilder &Builder,
diff --git a/clang/lib/Driver/SanitizerArgs.cpp b/clang/lib/Driver/SanitizerArgs.cpp
index 8e2811453b4..f2ac7b163f9 100644
--- a/clang/lib/Driver/SanitizerArgs.cpp
+++ b/clang/lib/Driver/SanitizerArgs.cpp
@@ -168,22 +168,9 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
       Args.hasFlag(options::OPT_fsanitize_memory_track_origins,
                    options::OPT_fno_sanitize_memory_track_origins,
                    /* Default */false);
-
-  // Parse -f(no-)sanitize-address-zero-base-shadow options.
-  if (NeedsAsan) {
-    bool IsAndroid = (TC.getTriple().getEnvironment() == llvm::Triple::Android);
-    bool ZeroBaseShadowDefault = IsAndroid;
+  if (NeedsAsan)
     AsanZeroBaseShadow =
-        Args.hasFlag(options::OPT_fsanitize_address_zero_base_shadow,
-                     options::OPT_fno_sanitize_address_zero_base_shadow,
-                     ZeroBaseShadowDefault);
-    // Zero-base shadow is a requirement on Android.
-    if (IsAndroid && !AsanZeroBaseShadow) {
-      D.Diag(diag::err_drv_argument_not_allowed_with)
-          << "-fno-sanitize-address-zero-base-shadow"
-          << lastArgumentForKind(D, Args, Address);
-    }
-  }
+        (TC.getTriple().getEnvironment() == llvm::Triple::Android);
 }
 
 void SanitizerArgs::addArgs(const llvm::opt::ArgList &Args,
@@ -206,10 +193,6 @@ void SanitizerArgs::addArgs(const llvm::opt::ArgList &Args,
   if (MsanTrackOrigins)
     CmdArgs.push_back(Args.MakeArgString("-fsanitize-memory-track-origins"));
 
-  if (AsanZeroBaseShadow)
-    CmdArgs.push_back(
-        Args.MakeArgString("-fsanitize-address-zero-base-shadow"));
-
   // Workaround for PR16386.
   if (needsMsanRt())
     CmdArgs.push_back(Args.MakeArgString("-fno-assume-sane-operator-new"));
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index bb20ae7952f..92202b7ee20 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -452,8 +452,6 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
   Opts.SanitizerBlacklistFile = Args.getLastArgValue(OPT_fsanitize_blacklist);
   Opts.SanitizeMemoryTrackOrigins =
     Args.hasArg(OPT_fsanitize_memory_track_origins);
-  Opts.SanitizeAddressZeroBaseShadow =
-    Args.hasArg(OPT_fsanitize_address_zero_base_shadow);
   Opts.SanitizeUndefinedTrapOnError =
     Args.hasArg(OPT_fsanitize_undefined_trap_on_error);
   Opts.SSPBufferSize =