Commit 71c989ae authored by Luke Cheeseman's avatar Luke Cheeseman
Browse files

[AArch64] Return address signing B key support 

- Add support to generate AUTIBSP, PACIBSP, RETAB instructions for return
  address signing
- The key used to sign the function is controlled by the function attribute
  "sign-return-address-key"

Differential Revision: https://reviews.llvm.org/D51427

llvm-svn: 345511
parent e2806f85

llvm/lib/Target/AArch64/AArch64FrameLowering.cpp

+20 −3
Original line number Diff line number Diff line
@@ -597,6 +597,17 @@ static void adaptForLdStOpt(MachineBasicBlock &MBB, 
  //

}



static bool ShouldSignWithAKey(MachineFunction &MF) {

  const Function &F = MF.getFunction();

  if (!F.hasFnAttribute("sign-return-address-key"))

    return true;



  const StringRef Key =

      F.getFnAttribute("sign-return-address-key").getValueAsString();

  assert(Key.equals_lower("a_key") || Key.equals_lower("b_key"));

  return Key.equals_lower("a_key");

}



void AArch64FrameLowering::emitPrologue(MachineFunction &MF,

                                        MachineBasicBlock &MBB) const {

  MachineBasicBlock::iterator MBBI = MBB.begin();
@@ -620,7 +631,9 @@ void AArch64FrameLowering::emitPrologue(MachineFunction &MF, 
  DebugLoc DL;



  if (ShouldSignReturnAddress(MF)) {

    BuildMI(MBB, MBBI, DL, TII->get(AArch64::PACIASP))

    BuildMI(

        MBB, MBBI, DL,

        TII->get(ShouldSignWithAKey(MF) ? AArch64::PACIASP : AArch64::PACIBSP))

        .setMIFlag(MachineInstr::FrameSetup);

  }
@@ -907,10 +920,14 @@ static void InsertReturnAddressAuth(MachineFunction &MF, 
  // instructions, namely RETA{A,B}, that can be used instead.

  if (Subtarget.hasV8_3aOps() && MBBI != MBB.end() &&

      MBBI->getOpcode() == AArch64::RET_ReallyLR) {

    BuildMI(MBB, MBBI, DL, TII->get(AArch64::RETAA)).copyImplicitOps(*MBBI);

    BuildMI(MBB, MBBI, DL,

            TII->get(ShouldSignWithAKey(MF) ? AArch64::RETAA : AArch64::RETAB))

        .copyImplicitOps(*MBBI);

    MBB.erase(MBBI);

  } else {

    BuildMI(MBB, MBBI, DL, TII->get(AArch64::AUTIASP))

    BuildMI(

        MBB, MBBI, DL,

        TII->get(ShouldSignWithAKey(MF) ? AArch64::AUTIASP : AArch64::AUTIBSP))

        .setMIFlag(MachineInstr::FrameDestroy);

  }

}

llvm/test/CodeGen/AArch64/sign-return-address.ll

+23 −0
Original line number Diff line number Diff line
@@ -84,3 +84,26 @@ define fastcc void @spill_lr_and_tail_call(i64 %x) "sign-return-address"="all" { 
  tail call fastcc i64 @bar(i64 %x)

  ret void

}



; CHECK-LABEL: @leaf_sign_all_a_key

; CHECK: paciasp

; CHECK: autiasp

define i32 @leaf_sign_all_a_key(i32 %x) "sign-return-address"="all" "sign-return-address-key"="a_key" {

  ret i32 %x

}



; CHECK-LABEL: @leaf_sign_all_b_key

; CHECK: pacibsp

; CHECK: autibsp

define i32 @leaf_sign_all_b_key(i32 %x) "sign-return-address"="all" "sign-return-address-key"="b_key" {

  ret i32 %x

}



; CHECK-LABEL: @leaf_sign_all_v83_b_key

; CHECK: pacibsp

; CHECK-NOT: ret

; CHECK: retab

; CHECK-NOT: ret

define i32 @leaf_sign_all_v83_b_key(i32 %x) "sign-return-address"="all" "target-features"="+v8.3a" "sign-return-address-key"="b_key" {

  ret i32 %x

}