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[PAuth] Use different discriminators for __int128_t / __uint128_t / _BitInt(n) #140276

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[PAuth] Use different discriminators for __int128_t / __uint128_t / _BitInt(n) #140276

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[PAuth] Use different discriminators for __int128_t / __uint128_t / _…
asl May 16, 2025
d511d02
Make type discrimination of 128-bit types optional
asl Jun 2, 2025
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1 change: 1 addition & 0 deletions clang/include/clang/Basic/Features.def
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Original file line number Diff line number Diff line change
Expand Up @@ -119,6 +119,7 @@ FEATURE(ptrauth_indirect_gotos, LangOpts.PointerAuthIndirectGotos)
FEATURE(ptrauth_init_fini, LangOpts.PointerAuthInitFini)
FEATURE(ptrauth_init_fini_address_discrimination, LangOpts.PointerAuthInitFiniAddressDiscrimination)
FEATURE(ptrauth_elf_got, LangOpts.PointerAuthELFGOT)
FEATURE(ptrauth_function_pointer_type_discrimination_128, LangOpts.PointerAuthFunctionTypeDiscrimination128)
EXTENSION(swiftcc,
PP.getTargetInfo().checkCallingConvention(CC_Swift) ==
clang::TargetInfo::CCCR_OK)
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2 changes: 2 additions & 0 deletions clang/include/clang/Basic/LangOptions.def
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Expand Up @@ -172,6 +172,8 @@ LANGOPT(PointerAuthVTPtrTypeDiscrimination, 1, 0, "incorporate type discriminati
LANGOPT(PointerAuthTypeInfoVTPtrDiscrimination, 1, 0, "incorporate type and address discrimination in authenticated vtable pointers for std::type_info")
BENIGN_LANGOPT(PointerAuthFunctionTypeDiscrimination, 1, 0,
"Use type discrimination when signing function pointers")
LANGOPT(PointerAuthFunctionTypeDiscrimination128, 1, 1,
"Use different discriminators for __int128_t / __uint128_t / _BitInt(n) compared to other integer types when computing function pointer type discriminator")
LANGOPT(PointerAuthInitFini, 1, 0, "sign function pointers in init/fini arrays")
LANGOPT(PointerAuthInitFiniAddressDiscrimination, 1, 0,
"incorporate address discrimination in authenticated function pointers in init/fini arrays")
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2 changes: 2 additions & 0 deletions clang/include/clang/Driver/Options.td
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Expand Up @@ -4451,6 +4451,8 @@ defm ptrauth_init_fini_address_discrimination : OptInCC1FFlag<"ptrauth-init-fini
"Enable address discrimination of function pointers in init/fini arrays">;
defm ptrauth_elf_got : OptInCC1FFlag<"ptrauth-elf-got", "Enable authentication of pointers from GOT (ELF only)">;
defm aarch64_jump_table_hardening: OptInCC1FFlag<"aarch64-jump-table-hardening", "Use hardened lowering for jump-table dispatch">;
defm ptrauth_disable_128bit_type_discrimination : OptInCC1FFlag<"ptrauth-disable-128bit-type-discrimination",
"Do not use different discriminators for __int128_t / __uint128_t / _BitInt(n) compared to other integer types when computing function pointer type discriminator">;
}

def fenable_matrix : Flag<["-"], "fenable-matrix">, Group<f_Group>,
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23 changes: 19 additions & 4 deletions clang/lib/AST/ASTContext.cpp
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Expand Up @@ -3395,21 +3395,36 @@ static void encodeTypeForFunctionPointerAuth(const ASTContext &Ctx,

// Don't bother discriminating based on these types.
case Type::Pipe:
case Type::BitInt:
case Type::ConstantMatrix:
OS << "?";
return;

case Type::BitInt:
if (Ctx.getLangOpts().PointerAuthFunctionTypeDiscrimination128) {
const auto *BtTy = T->castAs<BitIntType>();
OS << "D" << (BtTy->isUnsigned() ? "U" : "B") << BtTy->getNumBits()
<< "_";
} else
OS << "?";
return;

case Type::Builtin: {
const auto *BTy = T->castAs<BuiltinType>();
switch (BTy->getKind()) {
const auto Kind = BTy->getKind();
switch (Kind) {
#define SIGNED_TYPE(Id, SingletonId) \
case BuiltinType::Id: \
OS << "i"; \
OS << (Kind == BuiltinType::Int128 && \
Ctx.getLangOpts().PointerAuthFunctionTypeDiscrimination128 \
? "n" \
: "i"); \
return;
#define UNSIGNED_TYPE(Id, SingletonId) \
case BuiltinType::Id: \
OS << "i"; \
OS << (Kind == BuiltinType::UInt128 && \
Ctx.getLangOpts().PointerAuthFunctionTypeDiscrimination128 \
? "o" \
: "i"); \
return;
#define PLACEHOLDER_TYPE(Id, SingletonId) case BuiltinType::Id:
#define BUILTIN_TYPE(Id, SingletonId)
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3 changes: 3 additions & 0 deletions clang/lib/Driver/ToolChains/Clang.cpp
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Expand Up @@ -1883,6 +1883,9 @@ void Clang::AddAArch64TargetArgs(const ArgList &Args,
Args.addOptInFlag(
CmdArgs, options::OPT_fptrauth_function_pointer_type_discrimination,
options::OPT_fno_ptrauth_function_pointer_type_discrimination);
Args.addOptInFlag(
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there's apple kernel flags in this function, but it looks like darwin args are actually set up in Toolchains/Darwin.cpp - can the apple invocation paths hit this? if not I think it's worth just having this as an opt out rather than an opt in. We might be constrained by ABI, but I don't think you have any reason to restrict this.

My request for a cli/langopt was so that we can stick with our existing ABI if need be, not because I thought you couldn't do this :D

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@asl ping ^

CmdArgs, options::OPT_fptrauth_disable_128bit_type_discrimination,
options::OPT_fno_ptrauth_disable_128bit_type_discrimination);

Args.addOptInFlag(CmdArgs, options::OPT_fptrauth_indirect_gotos,
options::OPT_fno_ptrauth_indirect_gotos);
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4 changes: 4 additions & 0 deletions clang/lib/Frontend/CompilerInvocation.cpp
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Expand Up @@ -3544,6 +3544,8 @@ static void GeneratePointerAuthArgs(const LangOptions &Opts,
GenerateArg(Consumer, OPT_fptrauth_type_info_vtable_pointer_discrimination);
if (Opts.PointerAuthFunctionTypeDiscrimination)
GenerateArg(Consumer, OPT_fptrauth_function_pointer_type_discrimination);
if (!Opts.PointerAuthFunctionTypeDiscrimination128)
GenerateArg(Consumer, OPT_fptrauth_disable_128bit_type_discrimination);
if (Opts.PointerAuthInitFini)
GenerateArg(Consumer, OPT_fptrauth_init_fini);
if (Opts.PointerAuthInitFiniAddressDiscrimination)
Expand All @@ -3569,6 +3571,8 @@ static void ParsePointerAuthArgs(LangOptions &Opts, ArgList &Args,
Args.hasArg(OPT_fptrauth_type_info_vtable_pointer_discrimination);
Opts.PointerAuthFunctionTypeDiscrimination =
Args.hasArg(OPT_fptrauth_function_pointer_type_discrimination);
Opts.PointerAuthFunctionTypeDiscrimination128 =
!Args.hasArg(OPT_fptrauth_disable_128bit_type_discrimination);
Opts.PointerAuthInitFini = Args.hasArg(OPT_fptrauth_init_fini);
Opts.PointerAuthInitFiniAddressDiscrimination =
Args.hasArg(OPT_fptrauth_init_fini_address_discrimination);
Expand Down
49 changes: 43 additions & 6 deletions clang/test/CodeGen/ptrauth-function-type-discriminator.c
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@@ -1,18 +1,20 @@
// RUN: %clang_cc1 -fptrauth-function-pointer-type-discrimination -triple arm64e-apple-ios13 -fptrauth-calls -fptrauth-intrinsics \
// RUN: -disable-llvm-passes -emit-llvm %s -o- | FileCheck --check-prefixes=CHECK,CHECKC %s
// RUN: -disable-llvm-passes -emit-llvm %s -o- | FileCheck --check-prefixes=CHECK,CHECKC,CHECK128 %s
// RUN: %clang_cc1 -fptrauth-function-pointer-type-discrimination -triple arm64e-apple-ios13 -fptrauth-calls -fptrauth-intrinsics \
// RUN: -disable-llvm-passes -emit-llvm -xc++ %s -o- | FileCheck --check-prefix=CHECK %s
// RUN: -disable-llvm-passes -emit-llvm -xc++ %s -o- | FileCheck --check-prefixes=CHECK,CHECK128 %s
// RUN: %clang_cc1 -fptrauth-function-pointer-type-discrimination -triple arm64-apple-ios -fptrauth-calls -fptrauth-intrinsics -emit-pch %s -o %t.ast
// RUN: %clang_cc1 -fptrauth-function-pointer-type-discrimination -triple arm64-apple-ios -fptrauth-calls -fptrauth-intrinsics \
// RUN: -emit-llvm -x ast -o - %t.ast | FileCheck --check-prefixes=CHECK,CHECKC %s
// RUN: -emit-llvm -x ast -o - %t.ast | FileCheck --check-prefixes=CHECK,CHECKC,CHECK128 %s
// RUN: %clang_cc1 -fptrauth-function-pointer-type-discrimination -triple arm64e-apple-ios13 -fptrauth-calls -fptrauth-intrinsics \
// RUN: -fptrauth-disable-128bit-type-discrimination -disable-llvm-passes -emit-llvm %s -o- | FileCheck --check-prefixes=CHECK,CHECKC,CHECKNO128 %s

// RUN: %clang_cc1 -fptrauth-function-pointer-type-discrimination -triple aarch64-linux-gnu -fptrauth-calls -fptrauth-intrinsics \
// RUN: -disable-llvm-passes -emit-llvm %s -o- | FileCheck --check-prefixes=CHECK,CHECKC %s
// RUN: -disable-llvm-passes -emit-llvm %s -o- | FileCheck --check-prefixes=CHECK,CHECKC,CHECK128 %s
// RUN: %clang_cc1 -fptrauth-function-pointer-type-discrimination -triple aarch64-linux-gnu -fptrauth-calls -fptrauth-intrinsics \
// RUN: -disable-llvm-passes -emit-llvm -xc++ %s -o- | FileCheck --check-prefix=CHECK %s
// RUN: -disable-llvm-passes -emit-llvm -xc++ %s -o- | FileCheck --check-prefixes=CHECK,CHECK128 %s
// RUN: %clang_cc1 -fptrauth-function-pointer-type-discrimination -triple aarch64-linux-gnu -fptrauth-calls -fptrauth-intrinsics -emit-pch %s -o %t.ast
// RUN: %clang_cc1 -fptrauth-function-pointer-type-discrimination -triple aarch64-linux-gnu -fptrauth-calls -fptrauth-intrinsics \
// RUN: -emit-llvm -x ast -o - %t.ast | FileCheck --check-prefixes=CHECK,CHECKC %s
// RUN: -emit-llvm -x ast -o - %t.ast | FileCheck --check-prefixes=CHECK,CHECKC,CHECK128 %s

#ifdef __cplusplus
extern "C" {
Expand Down Expand Up @@ -65,6 +67,41 @@ void (*fptr3)(void) = __builtin_ptrauth_sign_constant(&external_function, 2, 26)
// CHECK: @fptr4 = global ptr ptrauth (ptr @external_function, i32 2, i64 26, ptr @fptr4)
void (*fptr4)(void) = __builtin_ptrauth_sign_constant(&external_function, 2, __builtin_ptrauth_blend_discriminator(&fptr4, 26));

extern void external_function_int(int);
extern void external_function_char(char);
extern void external_function_i128(__int128_t);
extern void external_function_u128(__uint128_t);
extern void external_function_b128(_BitInt(128));
extern void external_function_b8(_BitInt(8));

// Check discriminators of functions taking integer type arguments:

// - Builtin integer types should be discriminated equally (so, pointer to
// function taking int argument should accept function taking char argument
// - _BitInt types are guaranteed distinct and therefore should be discriminated
// differently
// - __int128_t / __uint128_t are passed differently than char / int / long
// (require two registers instead of one) and therefore should be discriminated
// differently.

// CHECK: @fptr5 = global ptr ptrauth (ptr @external_function_int, i32 0, i64 2712)
// CHECK: @fptr6 = global ptr ptrauth (ptr @external_function_char, i32 0, i64 2712)
void (*fptr5)(int) = external_function_int;
void (*fptr6)(char) = external_function_char;

// CHECK128: @fptr7 = global ptr ptrauth (ptr @external_function_i128, i32 0, i64 23141)
// CHECK128: @fptr8 = global ptr ptrauth (ptr @external_function_u128, i32 0, i64 45743)
// CHECK128: @fptr9 = global ptr ptrauth (ptr @external_function_b128, i32 0, i64 17854)
// CHECK128: @fptr10 = global ptr ptrauth (ptr @external_function_b8, i32 0, i64 26383)
// CHECKNO128: @fptr7 = global ptr ptrauth (ptr @external_function_i128, i32 0, i64 2712)
// CHECKNO128: @fptr8 = global ptr ptrauth (ptr @external_function_u128, i32 0, i64 2712)
// CHECKNO128: @fptr9 = global ptr ptrauth (ptr @external_function_b128, i32 0, i64 41228)
// CHECKNO128: @fptr10 = global ptr ptrauth (ptr @external_function_b8, i32 0, i64 41228)
void (*fptr7)(__int128_t) = external_function_i128;
void (*fptr8)(__uint128_t) = external_function_u128;
void (*fptr9)(_BitInt(128)) = external_function_b128;
void (*fptr10)(_BitInt(8)) = external_function_b8;

// CHECK-LABEL: define{{.*}} void @test_call()
void test_call() {
// CHECK: [[T0:%.*]] = load ptr, ptr @fnptr,
Expand Down
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