[clang] [clang][RISCV] Introduce preprocessor macro when Zicfiss-based shadow stack is enabled (PR #127592)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-risc-v

Author: Ming-Yi Lai (mylai-mtk)

<details>
<summary>Changes</summary>

The `-fcf-protection=[full|return]` flag enables shadow stack implementation based on RISC-V Zicfiss extension. This patch adds the `__riscv_shadow_stack` predefined macro to preprocessing when such a shadow stack implementation is enabled.

---
Full diff: https://github.com/llvm/llvm-project/pull/127592.diff


4 Files Affected:

- (modified) clang/include/clang/Basic/LangOptions.def (+1) 
- (modified) clang/lib/Basic/Targets/RISCV.cpp (+3) 
- (modified) clang/lib/Frontend/CompilerInvocation.cpp (+6-1) 
- (added) clang/test/Preprocessor/riscv-cf-protection-return.c (+44) 


``````````diff
diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
index bfab0baa089cf..383440ddbc0ea 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -365,6 +365,7 @@ LANGOPT(ObjCDisableDirectMethodsForTesting, 1, 0,
 LANGOPT(CFProtectionBranch , 1, 0, "Control-Flow Branch Protection enabled")
 ENUM_LANGOPT(CFBranchLabelScheme, CFBranchLabelSchemeKind, 2, CFBranchLabelSchemeKind::Default,
              "Control-Flow Branch Protection Label Scheme")
+LANGOPT(CFProtectionReturn, 1, 0, "Control-Flow Return Protection enabled")
 LANGOPT(FakeAddressSpaceMap , 1, 0, "OpenCL fake address space map")
 ENUM_LANGOPT(AddressSpaceMapMangling , AddrSpaceMapMangling, 2, ASMM_Target, "OpenCL address space map mangling mode")
 LANGOPT(IncludeDefaultHeader, 1, 0, "Include default header file for OpenCL")
diff --git a/clang/lib/Basic/Targets/RISCV.cpp b/clang/lib/Basic/Targets/RISCV.cpp
index b4aa3206fcfab..dff990d15dd62 100644
--- a/clang/lib/Basic/Targets/RISCV.cpp
+++ b/clang/lib/Basic/Targets/RISCV.cpp
@@ -238,6 +238,9 @@ void RISCVTargetInfo::getTargetDefines(const LangOptions &Opts,
     else
       Builder.defineMacro("__riscv_32e");
   }
+
+  if (Opts.CFProtectionReturn && ISAInfo->hasExtension("zicfiss"))
+    Builder.defineMacro("__riscv_shadow_stack");
 }
 
 static constexpr int NumRVVBuiltins =
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 014e629c959e2..b9a5c0589ebc4 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -4048,8 +4048,13 @@ bool CompilerInvocation::ParseLangArgs(LangOptions &Opts, ArgList &Args,
 
   if (const Arg *A = Args.getLastArg(OPT_fcf_protection_EQ)) {
     StringRef Name = A->getValue();
-    if (Name == "full" || Name == "branch") {
+    if (Name == "full") {
+      Opts.CFProtectionBranch = 1;
+      Opts.CFProtectionReturn = 1;
+    } else if (Name == "branch") {
       Opts.CFProtectionBranch = 1;
+    } else if (Name == "return") {
+      Opts.CFProtectionReturn = 1;
     }
   }
 
diff --git a/clang/test/Preprocessor/riscv-cf-protection-return.c b/clang/test/Preprocessor/riscv-cf-protection-return.c
new file mode 100644
index 0000000000000..3a93a88fa6839
--- /dev/null
+++ b/clang/test/Preprocessor/riscv-cf-protection-return.c
@@ -0,0 +1,44 @@
+// RUN: %clang --target=riscv32 -E -dM %s -o - | \
+// RUN: FileCheck --check-prefixes=NO-MACRO %s
+
+// RUN: %clang --target=riscv32 -fcf-protection=return -E -dM %s -o - | \
+// RUN: FileCheck --check-prefixes=NO-MACRO %s
+
+// RUN: %clang --target=riscv32 -fcf-protection=full -E -dM %s -o - | \
+// RUN: FileCheck --check-prefixes=NO-MACRO %s
+
+// RUN: %clang --target=riscv32 -march=rv32i_zicfiss1p0 \
+// RUN: -menable-experimental-extensions -E -dM %s -o - | \
+// RUN: FileCheck --check-prefixes=NO-MACRO %s
+
+// RUN: %clang --target=riscv32 -march=rv32i_zicfiss1p0 \
+// RUN: -menable-experimental-extensions -fcf-protection=return -E -dM %s \
+// RUN: -o - | FileCheck --check-prefixes=SHSTK-MACRO %s
+
+// RUN: %clang --target=riscv32 -march=rv32i_zicfiss1p0 \
+// RUN: -menable-experimental-extensions -fcf-protection=full -E -dM %s -o - \
+// RUN: | FileCheck --check-prefixes=SHSTK-MACRO %s
+
+// RUN: %clang --target=riscv64 -E -dM %s -o - | \
+// RUN: FileCheck --check-prefixes=NO-MACRO %s
+
+// RUN: %clang --target=riscv64 -fcf-protection=return -E -dM %s -o - | \
+// RUN: FileCheck --check-prefixes=NO-MACRO %s
+
+// RUN: %clang --target=riscv64 -fcf-protection=full -E -dM %s -o - | \
+// RUN: FileCheck --check-prefixes=NO-MACRO %s
+
+// RUN: %clang --target=riscv64 -march=rv64i_zicfiss1p0 \
+// RUN: -menable-experimental-extensions -E -dM %s -o - | \
+// RUN: FileCheck --check-prefixes=NO-MACRO %s
+
+// RUN: %clang --target=riscv64 -march=rv64i_zicfiss1p0 \
+// RUN: -menable-experimental-extensions -fcf-protection=return -E -dM %s \
+// RUN: -o - | FileCheck --check-prefixes=SHSTK-MACRO %s
+
+// RUN: %clang --target=riscv64 -march=rv64i_zicfiss1p0 \
+// RUN: -menable-experimental-extensions -fcf-protection=full -E -dM %s -o - \
+// RUN: | FileCheck --check-prefixes=SHSTK-MACRO %s
+
+// SHSTK-MACRO: __riscv_shadow_stack 1{{$}}
+// NO-MACRO-NOT: __riscv_shadow_stack

``````````

</details>


https://github.com/llvm/llvm-project/pull/127592