From 41a9e53500c4317da7fa0d0b52322ea5df78a796 Mon Sep 17 00:00:00 2001 From: Luke Cheeseman Date: Fri, 21 Dec 2018 10:45:08 +0000 Subject: [Dwarf/AArch64] Return address signing B key dwarf support - When signing return addresses with -msign-return-address={+}, either the A key instructions or the B key instructions can be used. To correctly authenticate the return address, the unwinder/debugger must know which key was used to sign the return address. - When and exception is thrown or a break point reached, it may be necessary to unwind the stack. To accomplish this, the unwinder/debugger must be able to first authenticate an the return address if it has been signed. - To enable this, the augmentation string of CIEs has been extended to allow inclusion of a 'B' character. Functions that are signed using the B key variant of the instructions should have and FDE whose associated CIE has a 'B' in the augmentation string. - One must also be able to preserve these semantics when first stepping from a high level language into assembly and then, as a second step, into an object file. To achieve this, I have introduced a new assembly directive '.cfi_b_key_frame ', that tells the assembler the current frame uses return address signing with the B key. - This ensures that the FDE is associated with a CIE that has 'B' in the augmentation string. Differential Revision: https://reviews.llvm.org/D51798 llvm-svn: 349895 --- llvm/lib/Target/AArch64/AArch64FrameLowering.cpp | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) (limited to 'llvm/lib/Target/AArch64/AArch64FrameLowering.cpp') diff --git a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp index 800dd449b49..538a8d7e8fb 100644 --- a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp +++ b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp @@ -816,10 +816,15 @@ void AArch64FrameLowering::emitPrologue(MachineFunction &MF, DebugLoc DL; if (ShouldSignReturnAddress(MF)) { - BuildMI( - MBB, MBBI, DL, - TII->get(ShouldSignWithAKey(MF) ? AArch64::PACIASP : AArch64::PACIBSP)) - .setMIFlag(MachineInstr::FrameSetup); + if (ShouldSignWithAKey(MF)) + BuildMI(MBB, MBBI, DL, TII->get(AArch64::PACIASP)) + .setMIFlag(MachineInstr::FrameSetup); + else { + BuildMI(MBB, MBBI, DL, TII->get(AArch64::EMITBKEY)) + .setMIFlag(MachineInstr::FrameSetup); + BuildMI(MBB, MBBI, DL, TII->get(AArch64::PACIBSP)) + .setMIFlag(MachineInstr::FrameSetup); + } unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::createNegateRAState(nullptr)); -- cgit v1.2.3