[PAC][ELF] Place AUTH constants in .data.rel.ro for position dependent code

llvm/lib/Target/TargetLoweringObjectFile.cpp

@@ -17,6 +17,7 @@
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Function.h"
+#include "llvm/IR/GlobalValue.h"
 #include "llvm/IR/GlobalVariable.h"
 #include "llvm/IR/Mangler.h"
 #include "llvm/IR/Module.h"
@@ -226,6 +227,20 @@ void TargetLoweringObjectFile::emitPseudoProbeDescMetadata(
   }
 }
 
+static bool containsConstantPtrAuth(const Constant *C) {
+  if (isa<ConstantPtrAuth>(C))
+    return true;
+
+  if (isa<BlockAddress>(C) || isa<GlobalValue>(C))
+    return false;
+
+  for (const Value *Op : C->operands())
+    if (containsConstantPtrAuth(cast<Constant>(Op)))
+      return true;
+
+  return false;
+}
+
 /// getKindForGlobal - This is a top-level target-independent classifier for
 /// a global object.  Given a global variable and information from the TM, this
 /// function classifies the global in a target independent manner. This function
@@ -327,6 +342,10 @@ SectionKind TargetLoweringObjectFile::getKindForGlobal(const GlobalObject *GO,
       }
 
     } else {
+      // The dynamic linker always needs to fix PtrAuth relocations up.
+      if (containsConstantPtrAuth(C))
+        return SectionKind::getReadOnlyWithRel();
+
       // In static, ROPI and RWPI relocation models, the linker will resolve
       // all addresses, so the relocation entries will actually be constants by
       // the time the app starts up.  However, we can't put this into a

llvm/test/CodeGen/AArch64/ptrauth-global-no-pic.ll

@@ -0,0 +1,51 @@
+; RUN: llc -mtriple aarch64-elf --relocation-model=static         -mattr=+pauth < %s | FileCheck %s
+; RUN: llc -mtriple aarch64-elf --relocation-model=dynamic-no-pic -mattr=+pauth < %s | FileCheck %s
+
+;; A constant value, use .rodata
+; CHECK:         .section        .rodata,"a",@progbits
+; CHECK:         .globl  Const
+; CHECK: Const:
+; CHECK:         .xword  37
+
+;; An AUTH reloc is needed, use .data.rel.ro
+; CHECK:         .section        .data.rel.ro,"aw",@progbits
+; CHECK:         .globl  PtrAuthExtern
+; CHECK: PtrAuthExtern:
+; CHECK:         .xword  ConstExtern@AUTH(da,0)
+
+; CHECK:         .globl  PtrAuth
+; CHECK: PtrAuth:
+; CHECK:         .xword  Const@AUTH(da,0)
+
+; CHECK:         .globl  PtrAuthExternNested1
+; CHECK: PtrAuthExternNested1:
+; CHECK:         .xword  ConstExtern@AUTH(da,0)
+
+;; The address could be filled statically, use .rodata
+; CHECK:         .section        .rodata,"a",@progbits
+; CHECK:         .globl  PtrAuthExternNested2
+; CHECK: PtrAuthExternNested2:
+; CHECK:         .xword  PtrAuthExtern
+
+;; An AUTH reloc is needed, use .data.rel.ro
+; CHECK:         .section        .data.rel.ro,"aw",@progbits
+; CHECK:         .globl  PtrAuthNested1
+; CHECK: PtrAuthNested1:
+; CHECK:         .xword  Const@AUTH(da,0)
+
+;; The address could be filled statically, use .rodata
+; CHECK:         .section        .rodata,"a",@progbits
+; CHECK:         .globl  PtrAuthNested2
+; CHECK: PtrAuthNested2:
+; CHECK:         .xword  PtrAuth
+
+@ConstExtern = external global i64
+@Const       = constant i64 37
+
+@PtrAuthExtern = constant ptr ptrauth (ptr @ConstExtern, i32 2)
+@PtrAuth       = constant ptr ptrauth (ptr @Const,  i32 2)
+
+@PtrAuthExternNested1 = constant { ptr } { ptr ptrauth (ptr @ConstExtern, i32 2) }
+@PtrAuthExternNested2 = constant { ptr } { ptr @PtrAuthExtern }
+@PtrAuthNested1       = constant { ptr } { ptr ptrauth (ptr @Const, i32 2) }
+@PtrAuthNested2       = constant { ptr } { ptr @PtrAuth }