[ARM] Add clang command line support for -mharden-sls=

[kristof.beyls]

Summary

The command line syntax is identical to the -mharden-sls= command line
syntax for AArch64 targets.

[ostannard]

Why is this restricted to v7-A or later? The DSB and ISB instructions have existed since v6T2 and v6M.

[kristof.beyls]

In D93221#2459903, @ostannard wrote:

Why is this restricted to v7-A or later? The DSB and ISB instructions have existed since v6T2 and v6M.

This mitigation is never needed for M-class cores nor for v6T2.
By restricting it to v7-A it's simpler to explain in the diagnostic for which targets this is supported.
I thought that overall this was a better trade-off.

[ostannard]

Ok, LGTM

clang/include/clang/Basic/DiagnosticDriverKinds.td

def warn_drv_disabling_vptr_no_rtti_default : Warning<
   InGroup<AutoDisableVptrSanitizer>;
 def warn_drv_object_size_disabled_O0 : Warning<
   "the object size sanitizer has no effect at -O0, but is explicitly enabled: %0">,
   InGroup<InvalidCommandLineArgument>, DefaultWarnNoWerror;
 def err_invalid_branch_protection: Error <
   "invalid branch protection option '%0' in '%1'">;
 def err_invalid_sls_hardening : Error<
   "invalid sls hardening option '%0' in '%1'">;
+def err_sls_hardening_arm_not_supported : Error<
+  "-mharden-sls is only supported on armv7-a or later">;
 
 def note_drv_command_failed_diag_msg : Note<
   "diagnostic msg: %0">;
 def note_drv_t_option_is_global : Note<
   "The last /TC or /TP option takes precedence over earlier instances">;
 def note_drv_address_sanitizer_debug_runtime : Note<
   "AddressSanitizer doesn't support linking with debug runtime libraries yet">;
 def note_drv_use_standard : Note<"use '%0'"

clang/lib/Driver/ToolChains/Arch/ARM.h

void getARMArchCPUFromArgs(const llvm::opt::ArgList &Args,
                            llvm::StringRef &Arch, llvm::StringRef &CPU,
                            bool FromAs = false);
 void getARMTargetFeatures(const Driver &D, const llvm::Triple &Triple,
                           const llvm::opt::ArgList &Args,
                           llvm::opt::ArgStringList &CmdArgs,
                           std::vector<llvm::StringRef> &Features, bool ForAS);
 int getARMSubArchVersionNumber(const llvm::Triple &Triple);
 bool isARMMProfile(const llvm::Triple &Triple);
+bool isARMAProfile(const llvm::Triple &Triple);
 
 } // end namespace arm
 } // end namespace tools
 } // end namespace driver
 } // end namespace clang
 
 #endif // LLVM_CLANG_LIB_DRIVER_TOOLCHAINS_ARCH_ARM_H

clang/lib/Driver/ToolChains/Arch/ARM.cpp

 }
 
 // True if M-profile.
 bool arm::isARMMProfile(const llvm::Triple &Triple) {
   llvm::StringRef Arch = Triple.getArchName();
   return llvm::ARM::parseArchProfile(Arch) == llvm::ARM::ProfileKind::M;
 }
 
+// True if A-profile.
+bool arm::isARMAProfile(const llvm::Triple &Triple) {
+  llvm::StringRef Arch = Triple.getArchName();
+  return llvm::ARM::parseArchProfile(Arch) == llvm::ARM::ProfileKind::A;
+}
+
 // Get Arch/CPU from args.
 void arm::getARMArchCPUFromArgs(const ArgList &Args, llvm::StringRef &Arch,
                                 llvm::StringRef &CPU, bool FromAs) {
   if (const Arg *A = Args.getLastArg(clang::driver::options::OPT_mcpu_EQ))
     CPU = A->getValue();
   if (const Arg *A = Args.getLastArg(options::OPT_march_EQ))
     Arch = A->getValue();
   if (!FromAs)
if (Args.hasArg(options::OPT_ffixed_r9))
     Features.push_back("+reserve-r9");
 
   // The kext linker doesn't know how to deal with movw/movt.
   if (KernelOrKext || Args.hasArg(options::OPT_mno_movt))
     Features.push_back("+no-movt");
 
   if (Args.hasArg(options::OPT_mno_neg_immediates))
     Features.push_back("+no-neg-immediates");
+
+  // Enable/disable straight line speculation hardening.
+  if (Arg *A = Args.getLastArg(options::OPT_mharden_sls_EQ)) {
+    StringRef Scope = A->getValue();
+    bool EnableRetBr = false;
+    bool EnableBlr = false;
+    if (Scope != "none" && Scope != "all") {
+      SmallVector<StringRef, 4> Opts;
+      Scope.split(Opts, ",");
+      for (auto Opt : Opts) {
+        Opt = Opt.trim();
+        if (Opt == "retbr") {
+          EnableRetBr = true;
+          continue;
+        }
+        if (Opt == "blr") {
+          EnableBlr = true;
+          continue;
+        }
+        D.Diag(diag::err_invalid_sls_hardening)
+            << Scope << A->getAsString(Args);
+        break;
+      }
+    } else if (Scope == "all") {
+      EnableRetBr = true;
+      EnableBlr = true;
+    }
+
+    if (EnableRetBr || EnableBlr)
+      if (!(isARMAProfile(Triple) && getARMSubArchVersionNumber(Triple) >= 7))
+        D.Diag(diag::err_sls_hardening_arm_not_supported)
+            << Scope << A->getAsString(Args);
+
+    if (EnableRetBr)
+      Features.push_back("+harden-sls-retbr");
+    if (EnableBlr)
+      Features.push_back("+harden-sls-blr");
+  }
+
 }
 
 const std::string arm::getARMArch(StringRef Arch, const llvm::Triple &Triple) {
   std::string MArch;
   if (!Arch.empty())
     MArch = std::string(Arch);
   else
     MArch = std::string(Triple.getArchName());

clang/test/Driver/aarch64-sls-hardening-options.c

-// Check the -mharden-sls= option, which has a required argument to select
-// scope.
-// RUN: %clang -target aarch64--none-eabi -c %s -### 2>&1 | \
-// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-OFF
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=none 2>&1 | \
-// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-OFF
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=retbr 2>&1 | \
-// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-OFF
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=blr 2>&1 | \
-// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-ON
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=blr -mharden-sls=none 2>&1 | \
-// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-OFF
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=blr -mharden-sls=retbr 2>&1 | \
-// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-OFF
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=retbr,blr 2>&1 | \
-// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-ON
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=all 2>&1 | \
-// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-ON
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=retbr,blr,retbr 2>&1 | \
-// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-ON
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=retbr,blr,r 2>&1 | \
-// RUN: FileCheck %s --check-prefix=BAD-SLS-SPEC
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=none,blr 2>&1 | \
-// RUN: FileCheck %s --check-prefix=BAD-SLS-SPEC
-
-// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=all,-blr 2>&1 | \
-// RUN: FileCheck %s --check-prefix=BAD-SLS-SPEC
-
-// RETBR-OFF-NOT: "harden-sls-retbr"
-// RETBR-ON:  "+harden-sls-retbr"
-
-// BLR-OFF-NOT: "harden-sls-blr"
-// BLR-ON:  "+harden-sls-blr"
-
-// BAD-SLS-SPEC: invalid sls hardening option '{{[^']+}}' in '-mharden-sls=

clang/test/Driver/sls-hardening-options.c

+// Check the -mharden-sls= option, which has a required argument to select
+// scope.
+// RUN: %clang -target aarch64--none-eabi -c %s -### 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-OFF
+// RUN: %clang -target armv7a--none-eabi -c %s -### 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-OFF
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=none 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-OFF
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=none 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-OFF
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=retbr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-OFF
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=retbr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-OFF
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=blr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-ON
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=blr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-ON
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=blr -mharden-sls=none 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-OFF
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=blr -mharden-sls=none 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-OFF --check-prefix=BLR-OFF
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=blr -mharden-sls=retbr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-OFF
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=blr -mharden-sls=retbr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-OFF
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=retbr,blr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-ON
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=retbr,blr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-ON
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=all 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-ON
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=all 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-ON
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=retbr,blr,retbr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-ON
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=retbr,blr,retbr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=RETBR-ON --check-prefix=BLR-ON
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=retbr,blr,r 2>&1 | \
+// RUN: FileCheck %s --check-prefix=BAD-SLS-SPEC
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=retbr,blr,r 2>&1 | \
+// RUN: FileCheck %s --check-prefix=BAD-SLS-SPEC
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=none,blr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=BAD-SLS-SPEC
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=none,blr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=BAD-SLS-SPEC
+
+// RUN: %clang -target aarch64--none-eabi -c %s -### -mharden-sls=all,-blr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=BAD-SLS-SPEC
+// RUN: %clang -target armv7a--none-eabi -c %s -### -mharden-sls=all,-blr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=BAD-SLS-SPEC
+
+// RETBR-OFF-NOT: "harden-sls-retbr"
+// RETBR-ON:  "+harden-sls-retbr"
+
+// BLR-OFF-NOT: "harden-sls-blr"
+// BLR-ON:  "+harden-sls-blr"
+
+// BAD-SLS-SPEC: invalid sls hardening option '{{[^']+}}' in '-mharden-sls=
+
+// RUN: %clang -target armv6a--none-eabi -c %s -### -mharden-sls=all 2>&1 | \
+// RUN: FileCheck %s --check-prefix=SLS-NOT-SUPPORTED
+
+// RUN: %clang -target armv6a--none-eabi -c %s -### -mharden-sls=retbr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=SLS-NOT-SUPPORTED
+
+// RUN: %clang -target armv6a--none-eabi -c %s -### -mharden-sls=blr 2>&1 | \
+// RUN: FileCheck %s --check-prefix=SLS-NOT-SUPPORTED
+
+// RUN: %clang -target armv7r--none-eabi -c %s -### -mharden-sls=all 2>&1 | \
+// RUN: FileCheck %s --check-prefix=SLS-NOT-SUPPORTED
+
+// RUN: %clang -target armv7m--none-eabi -c %s -### -mharden-sls=all 2>&1 | \
+// RUN: FileCheck %s --check-prefix=SLS-NOT-SUPPORTED
+
+// RUN: %clang -target armv6a--none-eabi -c %s -### -mharden-sls=none 2>&1 | \
+// RUN: FileCheck %s --check-prefix=SLS-SUPPORTED
+
+// RUN: %clang -target armv7a-linux-gnueabihf -c %s -### -mharden-sls=all 2>&1 | \
+// RUN: FileCheck %s --check-prefix=SLS-SUPPORTED
+
+// RUN: %clang -target armv8a-linux-gnueabihf -c %s -### -mharden-sls=all 2>&1 | \
+// RUN: FileCheck %s --check-prefix=SLS-SUPPORTED
+
+// SLS-NOT-SUPPORTED: -mharden-sls is only supported on armv7-a or later
+// SLS-SUPPORTED-NOT: mharden-sls
+