https://github.com/ojhunt created
https://github.com/llvm/llvm-project/pull/153700
Pointer auth protection of the block descriptor pointer is only supported in
some constrained environments so we do actually need it to be configurable.
We had made it non configurable in the first PR to protect block metadata
because we believed that was an option but subsequently realised it does need
to remain configurable.
This PR revives the flags that permit this.
>From 0ec32635312dd35a38d75df53d58541817a25c17 Mon Sep 17 00:00:00 2001
From: Oliver Hunt <oli...@apple.com>
Date: Sat, 9 Aug 2025 21:28:40 -0700
Subject: [PATCH] [clang][Obj-C][PAC] Make block descriptor pointer signing
configurable
Pointer auth protection of the block descriptor pointer is only
supported in some constrained environments so we do actually need
it to be configurable.
We had made it non configurable in the first PR to protect block
metadata because we believed that was an option but subsequently
realised it does need to remain configurable.
This PR revives the flags that permit this.
---
clang/include/clang/Basic/Features.def | 2 +-
clang/include/clang/Basic/LangOptions.def | 2 ++
clang/include/clang/Driver/Options.td | 1 +
clang/lib/Frontend/CompilerInvocation.cpp | 11 ++++++++---
.../CodeGenObjC/ptrauth-block-descriptor-pointer.m | 2 +-
clang/test/CodeGenObjC/ptrauth-block-isa.m | 2 +-
6 files changed, 14 insertions(+), 6 deletions(-)
diff --git a/clang/include/clang/Basic/Features.def
b/clang/include/clang/Basic/Features.def
index 0f6cd005bfd03..b9efc6a6a2e9d 100644
--- a/clang/include/clang/Basic/Features.def
+++ b/clang/include/clang/Basic/Features.def
@@ -155,7 +155,7 @@ FEATURE(ptrauth_vtable_pointer_address_discrimination,
LangOpts.PointerAuthVTPtr
FEATURE(ptrauth_vtable_pointer_type_discrimination,
LangOpts.PointerAuthVTPtrTypeDiscrimination)
FEATURE(ptrauth_type_info_vtable_pointer_discrimination,
LangOpts.PointerAuthTypeInfoVTPtrDiscrimination)
FEATURE(ptrauth_member_function_pointer_type_discrimination,
LangOpts.PointerAuthCalls)
-FEATURE(ptrauth_signed_block_descriptors, LangOpts.PointerAuthCalls)
+FEATURE(ptrauth_signed_block_descriptors,
LangOpts.PointerAuthBlockDescriptorPointers)
FEATURE(ptrauth_function_pointer_type_discrimination,
LangOpts.PointerAuthFunctionTypeDiscrimination)
FEATURE(ptrauth_indirect_gotos, LangOpts.PointerAuthIndirectGotos)
FEATURE(ptrauth_init_fini, LangOpts.PointerAuthInitFini)
diff --git a/clang/include/clang/Basic/LangOptions.def
b/clang/include/clang/Basic/LangOptions.def
index 08d98a77e0252..f094ba112988f 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -136,6 +136,8 @@ LANGOPT(PointerAuthObjcInterfaceSel, 1, 0, NotCompatible,
"authentication of SEL
LANGOPT(PointerAuthObjcInterfaceSelKey, 16, 0, NotCompatible, "authentication
key for SEL fields of ObjC interfaces")
LANGOPT(PointerAuthObjcClassROPointers, 1, 0, Benign, "class_ro_t pointer
authentication")
+LANGOPT(PointerAuthBlockDescriptorPointers, 1, 0, NotCompatible, "enable
signed block descriptors")
+
LANGOPT(DoubleSquareBracketAttributes, 1, 0, NotCompatible, "'[[]]' attributes
extension for all language standard modes")
LANGOPT(ExperimentalLateParseAttributes, 1, 0, NotCompatible, "experimental
late parsing of attributes")
diff --git a/clang/include/clang/Driver/Options.td
b/clang/include/clang/Driver/Options.td
index 7712a49cef154..858f37c392107 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -4546,6 +4546,7 @@ defm aarch64_jump_table_hardening:
OptInCC1FFlag<"aarch64-jump-table-hardening",
defm ptrauth_objc_isa : OptInCC1FFlag<"ptrauth-objc-isa", "Enable signing and
authentication of Objective-C object's 'isa' field">;
defm ptrauth_objc_interface_sel : OptInCC1FFlag<"ptrauth-objc-interface-sel",
"Enable signing and authentication of Objective-C object's 'SEL' fields">;
defm ptrauth_objc_class_ro : OptInCC1FFlag<"ptrauth-objc-class-ro", "Enable
signing and authentication for ObjC class_ro pointers">;
+defm ptrauth_block_descriptor_pointers :
OptInCC1FFlag<"ptrauth-block-descriptor-pointers", "Enable signing and
authentication of block descriptors">;
}
def fenable_matrix : Flag<["-"], "fenable-matrix">, Group<f_Group>,
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp
b/clang/lib/Frontend/CompilerInvocation.cpp
index a4d18966be35f..da96352e1d82c 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1548,9 +1548,10 @@ void CompilerInvocation::setDefaultPointerAuthOptions(
PointerAuthSchema(Key::ASIA, true, Discrimination::None);
Opts.BlockByrefHelperFunctionPointers =
PointerAuthSchema(Key::ASIA, true, Discrimination::None);
- Opts.BlockDescriptorPointers =
- PointerAuthSchema(Key::ASDA, true, Discrimination::Constant,
- BlockDescriptorConstantDiscriminator);
+ if (LangOpts.PointerAuthBlockDescriptorPointers)
+ Opts.BlockDescriptorPointers =
+ PointerAuthSchema(Key::ASDA, true, Discrimination::Constant,
+ BlockDescriptorConstantDiscriminator);
Opts.ObjCMethodListFunctionPointers =
PointerAuthSchema(Key::ASIA, true, Discrimination::None);
@@ -3608,6 +3609,8 @@ static void GeneratePointerAuthArgs(const LangOptions
&Opts,
GenerateArg(Consumer, OPT_fptrauth_objc_interface_sel);
if (Opts.PointerAuthObjcClassROPointers)
GenerateArg(Consumer, OPT_fptrauth_objc_class_ro);
+ if (Opts.PointerAuthBlockDescriptorPointers)
+ GenerateArg(Consumer, OPT_fptrauth_block_descriptor_pointers);
}
static void ParsePointerAuthArgs(LangOptions &Opts, ArgList &Args,
@@ -3631,6 +3634,8 @@ static void ParsePointerAuthArgs(LangOptions &Opts,
ArgList &Args,
Opts.PointerAuthELFGOT = Args.hasArg(OPT_fptrauth_elf_got);
Opts.AArch64JumpTableHardening =
Args.hasArg(OPT_faarch64_jump_table_hardening);
+ Opts.PointerAuthBlockDescriptorPointers =
+ Args.hasArg(OPT_fptrauth_block_descriptor_pointers);
Opts.PointerAuthObjcIsa = Args.hasArg(OPT_fptrauth_objc_isa);
Opts.PointerAuthObjcClassROPointers =
Args.hasArg(OPT_fptrauth_objc_class_ro);
Opts.PointerAuthObjcInterfaceSel =
diff --git a/clang/test/CodeGenObjC/ptrauth-block-descriptor-pointer.m
b/clang/test/CodeGenObjC/ptrauth-block-descriptor-pointer.m
index 559cddfd4e866..f852c6d93fd58 100644
--- a/clang/test/CodeGenObjC/ptrauth-block-descriptor-pointer.m
+++ b/clang/test/CodeGenObjC/ptrauth-block-descriptor-pointer.m
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fobjc-arc -fblocks -fptrauth-calls -triple
arm64e-apple-ios -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -fobjc-arc -fblocks -fptrauth-calls
-fptrauth-block-descriptor-pointers -triple arm64e-apple-ios -emit-llvm -o -
%s | FileCheck %s
_Static_assert(__has_feature(ptrauth_signed_block_descriptors),
"-fptrauth-block-descriptor-pointers should set
ptrauth_signed_block_descriptors");
diff --git a/clang/test/CodeGenObjC/ptrauth-block-isa.m
b/clang/test/CodeGenObjC/ptrauth-block-isa.m
index c37fe8b0d7fec..248e57769ba1e 100644
--- a/clang/test/CodeGenObjC/ptrauth-block-isa.m
+++ b/clang/test/CodeGenObjC/ptrauth-block-isa.m
@@ -2,7 +2,7 @@
void (^globalblock)(void) = ^{};
// CHECK: [[BLOCK_DESCRIPTOR_NAME:@"__block_descriptor_.*"]] = linkonce_odr
hidden unnamed_addr constant { i64, i64, ptr, ptr } { i64 0, i64 32, ptr @.str,
ptr null }, comdat, align 8
-// CHECK: @__block_literal_global = internal constant { ptr, i32, i32, ptr,
ptr } { ptr ptrauth (ptr @_NSConcreteGlobalBlock, i32 2, i64 27361, ptr
@__block_literal_global), i32 1342177280, i32 0, ptr ptrauth (ptr
@globalblock_block_invoke, i32 0, i64 0, ptr getelementptr inbounds ({ ptr,
i32, i32, ptr, ptr }, ptr @__block_literal_global, i32 0, i32 3)), ptr ptrauth
(ptr [[BLOCK_DESCRIPTOR_NAME]], i32 2, i64 49339, ptr getelementptr inbounds ({
ptr, i32, i32, ptr, ptr }, ptr @__block_literal_global, i32 0, i32 4)) }
+// CHECK: @__block_literal_global = internal constant { ptr, i32, i32, ptr,
ptr } { ptr ptrauth (ptr @_NSConcreteGlobalBlock, i32 2, i64 27361, ptr
@__block_literal_global), i32 1342177280, i32 0, ptr ptrauth (ptr
@globalblock_block_invoke, i32 0, i64 0, ptr getelementptr inbounds ({ ptr,
i32, i32, ptr, ptr }, ptr @__block_literal_global, i32 0, i32 3)), ptr
[[BLOCK_DESCRIPTOR_NAME]] }
@interface A
- (int) count;
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