[clang] Implement -fptrauth-auth-traps.

[ahmedbougacha]

This provides -fptrauth-auth-traps, which at the frontend level only controls the addition of the "ptrauth-auth-traps" function attribute. The attribute in turn controls various aspects of backend codegen, by providing the guarantee that every "auth" operation generated will trap on failure. This can either be delegated to the hardware (if FPAC is known to be available), in which case this attribute doesn't change codegen. Or, if FPAC isn't available, the backend emits additional instructions to check and trap on auth failure.

[llvmbot]

@llvm/pr-subscribers-clang

@llvm/pr-subscribers-clang-codegen

Author: Ahmed Bougacha (ahmedbougacha)

Changes

This provides -fptrauth-auth-traps, which at the frontend level only controls the addition of the "ptrauth-auth-traps" function attribute. The attribute in turn controls various aspects of backend codegen, by providing the guarantee that every "auth" operation generated will trap on failure. This can either be delegated to the hardware (if FPAC is known to be available), in which case this attribute doesn't change codegen. Or, if FPAC isn't available, the backend emits additional instructions to check and trap on auth failure.

---

Full diff: https://github.com/llvm/llvm-project/pull/102417.diff

4 Files Affected:

• (modified) clang/include/clang/Basic/PointerAuthOptions.h (+3)
• (modified) clang/lib/CodeGen/CodeGenFunction.cpp (+2)
• (modified) clang/lib/Frontend/CompilerInvocation.cpp (+3-1)
• (modified) clang/test/CodeGen/ptrauth-function-attributes.c (+5)

diff --git a/clang/include/clang/Basic/PointerAuthOptions.h b/clang/include/clang/Basic/PointerAuthOptions.h
index 8f63cf2ad2bf27..74caa26b10b1fa 100644
--- a/clang/include/clang/Basic/PointerAuthOptions.h
+++ b/clang/include/clang/Basic/PointerAuthOptions.h
@@ -166,6 +166,9 @@ struct PointerAuthOptions {
   /// Do indirect goto label addresses need to be authenticated?
   bool IndirectGotos = false;
 
+  /// Do authentication failures cause a trap?
+  bool AuthTraps = false;
+
   /// The ABI for C function pointers.
   PointerAuthSchema FunctionPointers;
 
diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index af201554898f31..2b7a03a9a3b902 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -884,6 +884,8 @@ void CodeGenFunction::StartFunction(GlobalDecl GD, QualType RetTy,
     Fn->addFnAttr("ptrauth-calls");
   if (CodeGenOpts.PointerAuth.IndirectGotos)
     Fn->addFnAttr("ptrauth-indirect-gotos");
+  if (CodeGenOpts.PointerAuth.AuthTraps)
+    Fn->addFnAttr("ptrauth-auth-traps");
 
   // Apply xray attributes to the function (as a string, for now)
   bool AlwaysXRayAttr = false;
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 225bd6416ce5fc..86e24929c6b63f 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1511,13 +1511,15 @@ void CompilerInvocation::setDefaultPointerAuthOptions(
     }
   }
   Opts.IndirectGotos = LangOpts.PointerAuthIndirectGotos;
+  Opts.AuthTraps = LangOpts.PointerAuthAuthTraps;
 }
 
 static void parsePointerAuthOptions(PointerAuthOptions &Opts,
                                     const LangOptions &LangOpts,
                                     const llvm::Triple &Triple,
                                     DiagnosticsEngine &Diags) {
-  if (!LangOpts.PointerAuthCalls && !LangOpts.PointerAuthIndirectGotos)
+  if (!LangOpts.PointerAuthCalls && !LangOpts.PointerAuthIndirectGotos &&
+      !LangOpts.PointerAuthAuthTraps)
     return;
 
   CompilerInvocation::setDefaultPointerAuthOptions(Opts, LangOpts, Triple);
diff --git a/clang/test/CodeGen/ptrauth-function-attributes.c b/clang/test/CodeGen/ptrauth-function-attributes.c
index 6a09cd37bf4854..b7da5bba887dbf 100644
--- a/clang/test/CodeGen/ptrauth-function-attributes.c
+++ b/clang/test/CodeGen/ptrauth-function-attributes.c
@@ -8,6 +8,9 @@
 // RUN: %clang_cc1 -triple arm64e-apple-ios  -fptrauth-indirect-gotos -emit-llvm %s -o - | FileCheck %s --check-prefixes=ALL,GOTOS
 // RUN: %clang_cc1 -triple aarch64-linux-gnu -fptrauth-indirect-gotos -emit-llvm %s -o - | FileCheck %s --check-prefixes=ALL,GOTOS
 
+// RUN: %clang_cc1 -triple arm64e-apple-ios  -fptrauth-auth-traps -emit-llvm %s -o - | FileCheck %s --check-prefixes=ALL,TRAPS
+// RUN: %clang_cc1 -triple aarch64-linux-gnu -fptrauth-auth-traps -emit-llvm %s -o - | FileCheck %s --check-prefixes=ALL,TRAPS
+
 // ALL: define {{(dso_local )?}}void @test() #0
 void test() {
 }
@@ -16,4 +19,6 @@ void test() {
 
 // GOTOS: attributes #0 = {{{.*}} "ptrauth-indirect-gotos" {{.*}}}
 
+// TRAPS: attributes #0 = {{{.*}} "ptrauth-auth-traps" {{.*}}}
+
 // OFF-NOT: attributes {{.*}} "ptrauth-

[asl]

/cherry-pick d179acd

[llvmbot]

Failed to cherry-pick: d179acd

https://github.com/llvm/llvm-project/actions/runs/10324823761

Please manually backport the fix and push it to your github fork. Once this is done, please create a pull request

[asl]

Failed to cherry-pick: d179acd

https://github.com/llvm/llvm-project/actions/runs/10324823761

Please manually backport the fix and push it to your github fork. Once this is done, please create a pull request

Depends on #102670

[asl]

/cherry-pick d179acd

[llvmbot]

/pull-request #102938