https://github.com/ojhunt created
https://github.com/llvm/llvm-project/pull/98276
Updates codegen for global destructors and raising exceptions to ensure that
the function pointers being passed are signed using the correct schema.
Notably this requires that CodeGenFunction::createAtExitStub to return an
opaque Constant* rather than a Function* as the value being emitted is no
longer necessarily a raw function pointer depending on the configured ABI.
>From 4b92c4af87a1a381dad09b243db4d3ec71d64738 Mon Sep 17 00:00:00 2001
From: John McCall <rjmcc...@apple.com>
Date: Wed, 18 Sep 2019 02:21:37 -0400
Subject: [PATCH 1/3] Sign function pointers passed to atexit and __cxa_atexit.
Patch by Akira Hatanaka.
---
clang/lib/CodeGen/CGDeclCXX.cpp | 9 +++++--
clang/lib/CodeGen/CodeGenFunction.h | 2 +-
clang/lib/CodeGen/ItaniumCXXABI.cpp | 10 ++++++-
.../CodeGenCXX/ptrauth-static-destructors.cpp | 26 +++++++++++++++++++
4 files changed, 43 insertions(+), 4 deletions(-)
create mode 100644 clang/test/CodeGenCXX/ptrauth-static-destructors.cpp
diff --git a/clang/lib/CodeGen/CGDeclCXX.cpp b/clang/lib/CodeGen/CGDeclCXX.cpp
index 05dd7ddb86fa6..36248a9c75188 100644
--- a/clang/lib/CodeGen/CGDeclCXX.cpp
+++ b/clang/lib/CodeGen/CGDeclCXX.cpp
@@ -232,7 +232,7 @@ void CodeGenFunction::EmitCXXGlobalVarDeclInit(const
VarDecl &D,
/// Create a stub function, suitable for being passed to atexit,
/// which passes the given address to the given destructor function.
-llvm::Function *CodeGenFunction::createAtExitStub(const VarDecl &VD,
+llvm::Constant *CodeGenFunction::createAtExitStub(const VarDecl &VD,
llvm::FunctionCallee dtor,
llvm::Constant *addr) {
// Get the destructor function type, void(*)(void).
@@ -264,7 +264,12 @@ llvm::Function *CodeGenFunction::createAtExitStub(const
VarDecl &VD,
CGF.FinishFunction();
- return fn;
+ // Get a proper function pointer.
+ FunctionProtoType::ExtProtoInfo EPI(getContext().getDefaultCallingConvention(
+ /*IsVariadic=*/false, /*IsCXXMethod=*/false));
+ QualType fnType = getContext().getFunctionType(getContext().VoidTy,
+ {getContext().VoidPtrTy},
EPI);
+ return CGM.getFunctionPointer(fn, fnType);
}
/// Create a stub function, suitable for being passed to __pt_atexit_np,
diff --git a/clang/lib/CodeGen/CodeGenFunction.h
b/clang/lib/CodeGen/CodeGenFunction.h
index 13f12b5d878a6..e33267c4787fd 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -4862,7 +4862,7 @@ class CodeGenFunction : public CodeGenTypeCache {
void EmitCXXGlobalVarDeclInit(const VarDecl &D, llvm::GlobalVariable *GV,
bool PerformInit);
- llvm::Function *createAtExitStub(const VarDecl &VD, llvm::FunctionCallee
Dtor,
+ llvm::Constant *createAtExitStub(const VarDecl &VD, llvm::FunctionCallee
Dtor,
llvm::Constant *Addr);
llvm::Function *createTLSAtExitStub(const VarDecl &VD,
diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp
b/clang/lib/CodeGen/ItaniumCXXABI.cpp
index e1d056765a866..1924c07c1529d 100644
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -2699,6 +2699,14 @@ static void emitGlobalDtorWithCXAAtExit(CodeGenFunction
&CGF,
if (llvm::Function *fn = dyn_cast<llvm::Function>(atexit.getCallee()))
fn->setDoesNotThrow();
+ auto &Context = CGF.CGM.getContext();
+ FunctionProtoType::ExtProtoInfo EPI(Context.getDefaultCallingConvention(
+ /*IsVariadic=*/false, /*IsCXXMethod=*/false));
+ QualType fnType =
+ Context.getFunctionType(Context.VoidTy, {Context.VoidPtrTy}, EPI);
+ llvm::Constant *dtorCallee = cast<llvm::Constant>(dtor.getCallee());
+ dtorCallee = CGF.CGM.getFunctionPointer(dtorCallee, fnType);
+
if (!addr)
// addr is null when we are trying to register a dtor annotated with
// __attribute__((destructor)) in a constructor function. Using null here
is
@@ -2706,7 +2714,7 @@ static void emitGlobalDtorWithCXAAtExit(CodeGenFunction
&CGF,
// function.
addr = llvm::Constant::getNullValue(CGF.Int8PtrTy);
- llvm::Value *args[] = {dtor.getCallee(), addr, handle};
+ llvm::Value *args[] = {dtorCallee, addr, handle};
CGF.EmitNounwindRuntimeCall(atexit, args);
}
diff --git a/clang/test/CodeGenCXX/ptrauth-static-destructors.cpp
b/clang/test/CodeGenCXX/ptrauth-static-destructors.cpp
new file mode 100644
index 0000000000000..6c8d0c560681a
--- /dev/null
+++ b/clang/test/CodeGenCXX/ptrauth-static-destructors.cpp
@@ -0,0 +1,26 @@
+// RUN: %clang_cc1 -triple arm64-apple-ios -fptrauth-calls -emit-llvm
-std=c++11 %s -o - \
+// RUN: | FileCheck %s --check-prefix=CXAATEXIT
+
+// RUN: %clang_cc1 -triple arm64-apple-ios -fptrauth-calls -emit-llvm
-std=c++11 %s -o - \
+// RUN: -fno-use-cxa-atexit \
+// RUN: | FileCheck %s --check-prefix=ATEXIT
+
+class Foo {
+ public:
+ ~Foo() {
+ }
+};
+
+Foo global;
+
+// CXAATEXIT: @_ZN3FooD1Ev.ptrauth = private constant { i8*, i32, i64, i64 } {
i8* bitcast (%class.Foo* (%class.Foo*)* @_ZN3FooD1Ev to i8*), i32 0, i64 0, i64
0 }, section "llvm.ptrauth", align 8
+// CXAATEXIT: define internal void @__cxx_global_var_init()
+// CXAATEXIT: call i32 @__cxa_atexit(void (i8*)* bitcast ({ i8*, i32, i64,
i64 }* @_ZN3FooD1Ev.ptrauth to void (i8*)*), i8* getelementptr inbounds
(%class.Foo, %class.Foo* @global, i32 0, i32 0), i8* @__dso_handle)
+
+
+// ATEXIT: @__dtor_global.ptrauth = private constant { i8*, i32, i64, i64 } {
i8* bitcast (void ()* @__dtor_global to i8*), i32 0, i64 0, i64 0 }, section
"llvm.ptrauth", align 8
+// ATEXIT: define internal void @__cxx_global_var_init()
+// ATEXIT: %{{.*}} = call i32 @atexit(void ()* bitcast ({ i8*, i32, i64, i64
}* @__dtor_global.ptrauth to void ()*))
+
+// ATEXIT: define internal void @__dtor_global() {{.*}} section
"__TEXT,__StaticInit,regular,pure_instructions" {
+// ATEXIT: %{{.*}} = call %class.Foo* @_ZN3FooD1Ev(%class.Foo* @global)
>From a128071334090973a8bb922cca418b283efb5148 Mon Sep 17 00:00:00 2001
From: Oliver Hunt <oli...@apple.com>
Date: Tue, 9 Jul 2024 23:22:07 -0700
Subject: [PATCH 2/3] Fix build and tests for upstream
---
clang/lib/CodeGen/CGDeclCXX.cpp | 2 +-
clang/lib/CodeGen/ItaniumCXXABI.cpp | 2 +-
clang/test/CodeGenCXX/ptrauth-static-destructors.cpp | 8 +++-----
3 files changed, 5 insertions(+), 7 deletions(-)
diff --git a/clang/lib/CodeGen/CGDeclCXX.cpp b/clang/lib/CodeGen/CGDeclCXX.cpp
index 36248a9c75188..7a6e380f111e4 100644
--- a/clang/lib/CodeGen/CGDeclCXX.cpp
+++ b/clang/lib/CodeGen/CGDeclCXX.cpp
@@ -338,7 +338,7 @@ void CodeGenFunction::registerGlobalDtorWithLLVM(const
VarDecl &VD,
llvm::FunctionCallee Dtor,
llvm::Constant *Addr) {
// Create a function which calls the destructor.
- llvm::Function *dtorStub = createAtExitStub(VD, Dtor, Addr);
+ llvm::Constant *dtorStub = createAtExitStub(VD, Dtor, Addr);
CGM.AddGlobalDtor(dtorStub);
}
diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp
b/clang/lib/CodeGen/ItaniumCXXABI.cpp
index 1924c07c1529d..317fdd1e01a6c 100644
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -4915,7 +4915,7 @@ void XLCXXABI::registerGlobalDtor(CodeGenFunction &CGF,
const VarDecl &D,
}
// Create __dtor function for the var decl.
- llvm::Function *DtorStub = CGF.createAtExitStub(D, Dtor, Addr);
+ llvm::Constant *DtorStub = CGF.createAtExitStub(D, Dtor, Addr);
// Register above __dtor with atexit().
CGF.registerGlobalDtorWithAtExit(DtorStub);
diff --git a/clang/test/CodeGenCXX/ptrauth-static-destructors.cpp
b/clang/test/CodeGenCXX/ptrauth-static-destructors.cpp
index 6c8d0c560681a..cad43dc0746df 100644
--- a/clang/test/CodeGenCXX/ptrauth-static-destructors.cpp
+++ b/clang/test/CodeGenCXX/ptrauth-static-destructors.cpp
@@ -13,14 +13,12 @@ class Foo {
Foo global;
-// CXAATEXIT: @_ZN3FooD1Ev.ptrauth = private constant { i8*, i32, i64, i64 } {
i8* bitcast (%class.Foo* (%class.Foo*)* @_ZN3FooD1Ev to i8*), i32 0, i64 0, i64
0 }, section "llvm.ptrauth", align 8
// CXAATEXIT: define internal void @__cxx_global_var_init()
-// CXAATEXIT: call i32 @__cxa_atexit(void (i8*)* bitcast ({ i8*, i32, i64,
i64 }* @_ZN3FooD1Ev.ptrauth to void (i8*)*), i8* getelementptr inbounds
(%class.Foo, %class.Foo* @global, i32 0, i32 0), i8* @__dso_handle)
+// CXAATEXIT: call i32 @__cxa_atexit(ptr ptrauth (ptr @_ZN3FooD1Ev, i32 0),
ptr @global, ptr @__dso_handle)
-// ATEXIT: @__dtor_global.ptrauth = private constant { i8*, i32, i64, i64 } {
i8* bitcast (void ()* @__dtor_global to i8*), i32 0, i64 0, i64 0 }, section
"llvm.ptrauth", align 8
// ATEXIT: define internal void @__cxx_global_var_init()
-// ATEXIT: %{{.*}} = call i32 @atexit(void ()* bitcast ({ i8*, i32, i64, i64
}* @__dtor_global.ptrauth to void ()*))
+// ATEXIT: %{{.*}} = call i32 @atexit(ptr ptrauth (ptr @__dtor_global, i32
0))
// ATEXIT: define internal void @__dtor_global() {{.*}} section
"__TEXT,__StaticInit,regular,pure_instructions" {
-// ATEXIT: %{{.*}} = call %class.Foo* @_ZN3FooD1Ev(%class.Foo* @global)
+// ATEXIT: %{{.*}} = call ptr @_ZN3FooD1Ev(ptr @global)
>From 011060a516d5bafc60304c40e2b3587a3fe0ad41 Mon Sep 17 00:00:00 2001
From: Ahmed Bougacha <ah...@bougacha.org>
Date: Mon, 27 Sep 2021 08:00:00 -0700
Subject: [PATCH 3/3] [clang] Sign the dtor passed to __cxa_throw as a
void(*)(void*) fptr.
__cxa_throw is declared to take its destructor as void (*)(void *). We
must match that if function pointers can be authenticated with
a discriminator based on their type.
---
clang/lib/CodeGen/ItaniumCXXABI.cpp | 8 ++++++++
clang/test/CodeGenCXX/ptrauth-throw.cpp | 20 ++++++++++++++++++++
2 files changed, 28 insertions(+)
create mode 100644 clang/test/CodeGenCXX/ptrauth-throw.cpp
diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp
b/clang/lib/CodeGen/ItaniumCXXABI.cpp
index 317fdd1e01a6c..2ab753bb78640 100644
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -1321,8 +1321,16 @@ void ItaniumCXXABI::emitThrow(CodeGenFunction &CGF,
const CXXThrowExpr *E) {
if (const RecordType *RecordTy = ThrowType->getAs<RecordType>()) {
CXXRecordDecl *Record = cast<CXXRecordDecl>(RecordTy->getDecl());
if (!Record->hasTrivialDestructor()) {
+ // __cxa_throw is declared to take its destructor as void (*)(void *). We
+ // must match that if function pointers can be authenticated with a
+ // discriminator based on their type.
+ ASTContext &Ctx = getContext();
+ QualType DtorTy = Ctx.getFunctionType(Ctx.VoidTy, {Ctx.VoidPtrTy},
+ FunctionProtoType::ExtProtoInfo());
+
CXXDestructorDecl *DtorD = Record->getDestructor();
Dtor = CGM.getAddrOfCXXStructor(GlobalDecl(DtorD, Dtor_Complete));
+ Dtor = CGM.getFunctionPointer(Dtor, DtorTy);
}
}
if (!Dtor) Dtor = llvm::Constant::getNullValue(CGM.Int8PtrTy);
diff --git a/clang/test/CodeGenCXX/ptrauth-throw.cpp
b/clang/test/CodeGenCXX/ptrauth-throw.cpp
new file mode 100644
index 0000000000000..0e143433ee5a3
--- /dev/null
+++ b/clang/test/CodeGenCXX/ptrauth-throw.cpp
@@ -0,0 +1,20 @@
+// RUN: %clang_cc1 -triple arm64-apple-ios -fptrauth-calls -fcxx-exceptions
-emit-llvm %s -o - | FileCheck %s
+
+class Foo {
+ public:
+ ~Foo() {
+ }
+};
+
+// CHECK-LABEL: define void @_Z1fv()
+// CHECK: call void @__cxa_throw(ptr %{{.*}}, ptr @_ZTI3Foo, ptr ptrauth (ptr
@_ZN3FooD1Ev, i32 0))
+void f() {
+ throw Foo();
+}
+
+// __cxa_throw is defined to take its destructor as "void (*)(void *)" in the
ABI.
+// CHECK-LABEL: define void @__cxa_throw({{.*}})
+// CHECK: call void {{%.*}}(ptr noundef {{%.*}}) [ "ptrauth"(i32 0, i64 0) ]
+extern "C" void __cxa_throw(void *exception, void *, void (*dtor)(void *)) {
+ dtor(exception);
+}
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