[llvm-branch-commits] [clang] release/19.x: [clang] Wire -fptrauth-returns to "ptrauth-returns" fn attribute. (#102416) (PR #102670)

[Tobias Hieta via llvm-branch-commits]

https://github.com/tru updated https://github.com/llvm/llvm-project/pull/102670

>From ccd8d0497a92c50e52933cd5d712a32a192ba6aa Mon Sep 17 00:00:00 2001
From: Ahmed Bougacha <ahmed at bougacha.org>
Date: Fri, 9 Aug 2024 11:49:50 -0700
Subject: [PATCH] [clang] Wire -fptrauth-returns to "ptrauth-returns" fn
 attribute. (#102416)

We already ended up with -fptrauth-returns, the feature macro, the lang
opt, and the actual backend lowering.

The only part left is threading it all through PointerAuthOptions, to
drive the addition of the "ptrauth-returns" attribute to generated
functions.
While there, do minor cleanup on ptrauth-function-attributes.c.

This also adds ptrauth_key_return_address to ptrauth.h.

(cherry picked from commit 2eb6e30fe83ccce3cf01e596e73fa6385facd44b)
---
 clang/include/clang/Basic/PointerAuthOptions.h   | 3 +++
 clang/lib/CodeGen/CodeGenFunction.cpp            | 2 ++
 clang/lib/Frontend/CompilerInvocation.cpp        | 4 +++-
 clang/lib/Headers/ptrauth.h                      | 6 ++++++
 clang/test/CodeGen/ptrauth-function-attributes.c | 9 +++++++--
 5 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/clang/include/clang/Basic/PointerAuthOptions.h b/clang/include/clang/Basic/PointerAuthOptions.h
index 417b4b00648c78..c0ab35bce5d84b 100644
--- a/clang/include/clang/Basic/PointerAuthOptions.h
+++ b/clang/include/clang/Basic/PointerAuthOptions.h
@@ -159,6 +159,9 @@ class PointerAuthSchema {
 };
 
 struct PointerAuthOptions {
+  /// Should return addresses be authenticated?
+  bool ReturnAddresses = false;
+
   /// Do indirect goto label addresses need to be authenticated?
   bool IndirectGotos = false;
 
diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index af201554898f31..4dc57d0ff5b269 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -880,6 +880,8 @@ void CodeGenFunction::StartFunction(GlobalDecl GD, QualType RetTy,
 
   // Add pointer authentication attributes.
   const CodeGenOptions &CodeGenOpts = CGM.getCodeGenOpts();
+  if (CodeGenOpts.PointerAuth.ReturnAddresses)
+    Fn->addFnAttr("ptrauth-returns");
   if (CodeGenOpts.PointerAuth.FunctionPointers)
     Fn->addFnAttr("ptrauth-calls");
   if (CodeGenOpts.PointerAuth.IndirectGotos)
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index f6b6c44a4cab6a..fa5d076c202a36 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1505,13 +1505,15 @@ void CompilerInvocation::setDefaultPointerAuthOptions(
         PointerAuthSchema(Key::ASIA, false, Discrimination::Type);
   }
   Opts.IndirectGotos = LangOpts.PointerAuthIndirectGotos;
+  Opts.ReturnAddresses = LangOpts.PointerAuthReturns;
 }
 
 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.PointerAuthReturns)
     return;
 
   CompilerInvocation::setDefaultPointerAuthOptions(Opts, LangOpts, Triple);
diff --git a/clang/lib/Headers/ptrauth.h b/clang/lib/Headers/ptrauth.h
index 4724155b0dc796..154b599862a8e2 100644
--- a/clang/lib/Headers/ptrauth.h
+++ b/clang/lib/Headers/ptrauth.h
@@ -28,6 +28,12 @@ typedef enum {
   /* A process-specific key which can be used to sign data pointers. */
   ptrauth_key_process_dependent_data = ptrauth_key_asdb,
 
+  /* The key used to sign return addresses on the stack.
+     The extra data is based on the storage address of the return address.
+     On AArch64, that is always the storage address of the return address + 8
+     (or, in other words, the value of the stack pointer on function entry) */
+  ptrauth_key_return_address = ptrauth_key_process_dependent_code,
+
   /* The key used to sign C function pointers.
      The extra data is always 0. */
   ptrauth_key_function_pointer = ptrauth_key_process_independent_code,
diff --git a/clang/test/CodeGen/ptrauth-function-attributes.c b/clang/test/CodeGen/ptrauth-function-attributes.c
index 6a09cd37bf4854..17ebf9d6e2e01c 100644
--- a/clang/test/CodeGen/ptrauth-function-attributes.c
+++ b/clang/test/CodeGen/ptrauth-function-attributes.c
@@ -1,11 +1,14 @@
+// RUN: %clang_cc1 -triple arm64-apple-ios                    -emit-llvm %s  -o - | FileCheck %s --check-prefixes=ALL,OFF
 // RUN: %clang_cc1 -triple arm64e-apple-ios                   -emit-llvm %s  -o - | FileCheck %s --check-prefixes=ALL,OFF
 // RUN: %clang_cc1 -triple aarch64-linux-gnu                  -emit-llvm %s  -o - | FileCheck %s --check-prefixes=ALL,OFF
 
-// RUN: %clang_cc1 -triple arm64-apple-ios  -fptrauth-calls   -emit-llvm %s  -o - | FileCheck %s --check-prefixes=ALL,CALLS
+// RUN: %clang_cc1 -triple arm64-apple-ios   -fptrauth-calls  -emit-llvm %s  -o - | FileCheck %s --check-prefixes=ALL,CALLS
 // RUN: %clang_cc1 -triple aarch64-linux-gnu -fptrauth-calls  -emit-llvm %s  -o - | FileCheck %s --check-prefixes=ALL,CALLS
 
+// RUN: %clang_cc1 -triple arm64-apple-ios   -fptrauth-returns -emit-llvm %s -o - | FileCheck %s --check-prefixes=ALL,RETS
+// RUN: %clang_cc1 -triple aarch64-linux-gnu -fptrauth-returns -emit-llvm %s -o - | FileCheck %s --check-prefixes=ALL,RETS
+
 // RUN: %clang_cc1 -triple arm64-apple-ios   -fptrauth-indirect-gotos -emit-llvm %s -o - | FileCheck %s --check-prefixes=ALL,GOTOS
-// 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
 
 // ALL: define {{(dso_local )?}}void @test() #0
@@ -14,6 +17,8 @@ void test() {
 
 // CALLS: attributes #0 = {{{.*}} "ptrauth-calls" {{.*}}}
 
+// RETS: attributes #0 = {{{.*}} "ptrauth-returns" {{.*}}}
+
 // GOTOS: attributes #0 = {{{.*}} "ptrauth-indirect-gotos" {{.*}}}
 
 // OFF-NOT: attributes {{.*}} "ptrauth-