llvm::AArch64PAuth Namespace Reference

Enumerations
enum class	AuthCheckMethod {   None , DummyLoad , HighBitsNoTBI , XPACHint ,   XPAC }
	Variants of check performed on an authenticated pointer. More...
enum class	PtrauthCheckMode { Unchecked , Poison , Trap }
	Ways to check pointer authentication auth/resign failures. More...
enum class	SetRAStateMode { Never , PAuthLR , Always }
	Control the emission of .cfi_set_ra_state, which replaces the deprecated .cfi_negate_ra_state_with_pc [1]. More...

Functions
unsigned	getCheckerSizeInBytes (AuthCheckMethod Method)
	Returns the number of bytes added by checkAuthenticatedRegister.

Variables
constexpr AArch64PACKey::ID	InitFiniKey = AArch64PACKey::IA
	PAuth key to be used with function pointers in .init_array and .fini_array.
constexpr unsigned	InitFiniPointerConstantDiscriminator = 0xD9D4
	Constant discriminator to be used with function pointers in .init_array and .fini_array.

Enumeration Type Documentation

AuthCheckMethod

enum class llvm::AArch64PAuth::AuthCheckMethod

strong

Variants of check performed on an authenticated pointer.

In cases such as authenticating the LR value when performing a tail call or when re-signing a signed pointer with a different signing schema, a failed authentication may not generate an exception on its own and may create an authentication or signing oracle if not checked explicitly.

A number of check methods modify control flow in a similar way by rewriting the code

<authenticate LR>
<more instructions>

as follows:

  <authenticate LR>
  <method-specific checker>
on_fail:
  brk <code>
on_success:
  <more instructions>

Enumerator
None	Do not check the value at all.
DummyLoad	Perform a load to a temporary register.
HighBitsNoTBI	Check by comparing bits 62 and 61 of the authenticated address. This method modifies control flow and inserts the following checker: eor Xtmp, Xn, Xn, lsl #1 tbz Xtmp, #62, on_success
XPACHint	Check by comparing the authenticated value with an XPAC-ed one without using PAuth instructions not encoded as HINT. Can only be applied to LR. This method modifies control flow and inserts the following checker: mov Xtmp, LR xpaclri ; encoded as "hint #7" ; Note: at this point, the LR register contains the address as if ; the authentication succeeded and the temporary register contains the ; *real* result of authentication. cmp Xtmp, LR b.eq on_success
XPAC	Similar to XPACHint but using Armv8.3-only XPAC instruction, thus not restricted to LR: mov Xtmp, Xn xpac(i|d) Xn cmp Xtmp, Xn b.eq on_success

Definition at line 50 of file AArch64PointerAuth.h.

PtrauthCheckMode

enum class llvm::AArch64PAuth::PtrauthCheckMode

strong

Ways to check pointer authentication auth/resign failures.

Enumerator
Unchecked
Poison
Trap

Definition at line 95 of file AArch64PointerAuth.h.

SetRAStateMode

enum class llvm::AArch64PAuth::SetRAStateMode

strong

Control the emission of .cfi_set_ra_state, which replaces the deprecated .cfi_negate_ra_state_with_pc [1].

The latter is fundamentally unable to express some program orders [2], as the dwarf 'program' reads functions in a linear scan of their addresses to reconstruct the state of the frame, whereas control flow may enter and exit such regions arbitrarily (such as in hot-cold-split, and shrinkwrapped fucntions), and thus the negate-based cfi is unable to encode the address of the signing instruciton in all program orders.

Since .cfi_negate_ra_state is still sufficient for describing ptrauth-returns=pauth, we default to using the new CFI only for PAuth_LR, as DW_CFA_AARCH64_negate_ra_state has a smaller encoding than DW_CFA_AARCH64_set_ra_state.

1: https://github.com/ARM-software/abi-aa/pull/346 2: https://github.com/ARM-software/abi-aa/issues/327

Enumerator
Never
PAuthLR
Always

Definition at line 114 of file AArch64PointerAuth.h.

Function Documentation

getCheckerSizeInBytes()

unsigned llvm::AArch64PAuth::getCheckerSizeInBytes

(

AuthCheckMethod

Method

)

Returns the number of bytes added by checkAuthenticatedRegister.

Definition at line 452 of file AArch64PointerAuth.cpp.

References DummyLoad, HighBitsNoTBI, llvm_unreachable, None, XPAC, and XPACHint.

Referenced by llvm::AArch64InstrInfo::getInstSizeInBytes().

Variable Documentation

InitFiniKey

AArch64PACKey::ID llvm::AArch64PAuth::InitFiniKey = AArch64PACKey::IA

constexpr

PAuth key to be used with function pointers in .init_array and .fini_array.

Definition at line 18 of file AArch64PointerAuth.h.

InitFiniPointerConstantDiscriminator

unsigned llvm::AArch64PAuth::InitFiniPointerConstantDiscriminator = 0xD9D4

constexpr

Constant discriminator to be used with function pointers in .init_array and .fini_array.

The value is ptrauth_string_discriminator("init_fini")

Definition at line 22 of file AArch64PointerAuth.h.