path: root/src/Native/Runtime/arm64/ExceptionHandling.asm

;; Licensed to the .NET Foundation under one or more agreements.
;; The .NET Foundation licenses this file to you under the MIT license.
;; See the LICENSE file in the project root for more information.

#include "AsmMacros.h"

        TEXTAREA

#define STACKSIZEOF_ExInfo ((SIZEOF__ExInfo + 15)&(~15))

#define HARDWARE_EXCEPTION 1
#define SOFTWARE_EXCEPTION 0

;; -----------------------------------------------------------------------------
;; Macro used to create frame of exception throwing helpers (RhpThrowEx, RhpThrowHwEx)
    MACRO
        ALLOC_THROW_FRAME $exceptionType

        PROLOG_NOP mov x3, sp
 
        ;; Setup a PAL_LIMITED_CONTEXT on the stack {
        IF $exceptionType == HARDWARE_EXCEPTION
            PROLOG_NOP sub sp,sp,#0x50
            PROLOG_NOP stp x3, x1, [sp]   ; x3 is the SP and x1 is the IP of the fault site 
            PROLOG_PUSH_MACHINE_FRAME
        ELSE
            PROLOG_STACK_ALLOC 0x50
            PROLOG_NOP stp x3, lr, [sp]   ; x3 is the SP and lr is the IP of the fault site 
        ENDIF
        PROLOG_NOP stp d8, d9, [sp, #0x10]
        PROLOG_NOP stp d10, d11, [sp, #0x20]
        PROLOG_NOP stp d12, d13, [sp, #0x30]
        PROLOG_NOP stp d14, d15, [sp, #0x40]
        PROLOG_SAVE_REG_PAIR fp, lr, #-0x70!
        PROLOG_NOP stp xzr, xzr, [sp, #0x10] ; locations reserved for return value, not used for exception handling
        PROLOG_SAVE_REG_PAIR x19, x20, #0x20
        PROLOG_SAVE_REG_PAIR x21, x22, #0x30
        PROLOG_SAVE_REG_PAIR x23, x24, #0x40
        PROLOG_SAVE_REG_PAIR x25, x26, #0x50
        PROLOG_SAVE_REG_PAIR x27, x28, #0x60
        ;; } end PAL_LIMITED_CONTEXT
 
        PROLOG_STACK_ALLOC STACKSIZEOF_ExInfo 
    MEND 

;; -----------------------------------------------------------------------------
;; Macro used to create frame of funclet calling helpers (RhpCallXXXXFunclet)
;; $extraStackSize - extra stack space that the user of the macro can use to
;;                   store additional registers
    MACRO 
        ALLOC_CALL_FUNCLET_FRAME $extraStackSize

        ; Using below prolog instead of PROLOG_SAVE_REG_PAIR fp,lr, #-60!
        ; is intentional. Above statement would also emit instruction to save
        ; sp in fp. If sp is saved in fp in prolog then it is not expected that fp can change in the body
        ; of method. However, this method needs to be able to change fp before calling funclet.
        ; This is required to access locals in funclet.
        PROLOG_SAVE_REG_PAIR_NO_FP fp,lr, #-0x60!
        PROLOG_SAVE_REG_PAIR x19, x20, #0x10
        PROLOG_SAVE_REG_PAIR x21, x22, #0x20
        PROLOG_SAVE_REG_PAIR x23, x24, #0x30
        PROLOG_SAVE_REG_PAIR x25, x26, #0x40
        PROLOG_SAVE_REG_PAIR x27, x28, #0x50
        PROLOG_NOP mov fp, sp

        IF $extraStackSize != 0
            PROLOG_STACK_ALLOC $extraStackSize
        ENDIF
    MEND

;; -----------------------------------------------------------------------------
;; Macro used to free frame of funclet calling helpers (RhpCallXXXXFunclet)
;; $extraStackSize - extra stack space that the user of the macro can use to
;;                   store additional registers.
;;                   It needs to match the value passed to the corresponding
;;                   ALLOC_CALL_FUNCLET_FRAME.
    MACRO 
        FREE_CALL_FUNCLET_FRAME $extraStackSize

        IF $extraStackSize != 0
            EPILOG_STACK_FREE $extraStackSize
        ENDIF

        EPILOG_RESTORE_REG_PAIR x19, x20, #0x10
        EPILOG_RESTORE_REG_PAIR x21, x22, #0x20
        EPILOG_RESTORE_REG_PAIR x23, x24, #0x30
        EPILOG_RESTORE_REG_PAIR x25, x26, #0x40
        EPILOG_RESTORE_REG_PAIR x27, x28, #0x50
        EPILOG_RESTORE_REG_PAIR fp, lr, #0x60!
    MEND

;; -----------------------------------------------------------------------------
;; Macro used to restore preserved general purpose and FP registers from REGDISPLAY
;; $regdisplayReg - register pointing to the REGDISPLAY structure
    MACRO
        RESTORE_PRESERVED_REGISTERS $regdisplayReg

        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX19]
        ldr         x19, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX20]
        ldr         x20, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX21]
        ldr         x21, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX22]
        ldr         x22, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX23]
        ldr         x23, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX24]
        ldr         x24, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX25]
        ldr         x25, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX26]
        ldr         x26, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX27]
        ldr         x27, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX28]
        ldr         x28, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pFP]
        ldr         fp,  [x12]
        ;;
        ;; load FP preserved regs
        ;;
        add         x12, $regdisplayReg, #OFFSETOF__REGDISPLAY__D
        ldp         d8, d9,   [x12, #0x00]
        ldp         d10, d11, [x12, #0x10]
        ldp         d12, d13, [x12, #0x20]
        ldp         d14, d15, [x12, #0x30]
    MEND

;; -----------------------------------------------------------------------------
;; Macro used to save preserved general purpose and FP registers to REGDISPLAY
;; $regdisplayReg - register pointing to the REGDISPLAY structure
    MACRO
        SAVE_PRESERVED_REGISTERS $regdisplayReg

        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX19]
        str         x19, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX20]
        str         x20, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX21]
        str         x21, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX22]
        str         x22, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX23]
        str         x23, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX24]
        str         x24, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX25]
        str         x25, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX26]
        str         x26, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX27]
        str         x27, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX28]
        str         x28, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pFP]
        str         fp,  [x12]
        ;;
        ;; store vfp preserved regs
        ;;
        add         x12, $regdisplayReg, #OFFSETOF__REGDISPLAY__D
        stp         d8, d9,   [x12, #0x00]
        stp         d10, d11, [x12, #0x10]
        stp         d12, d13, [x12, #0x20]
        stp         d14, d15, [x12, #0x30]
    MEND

;; -----------------------------------------------------------------------------
;; Macro used to thrash preserved general purpose registers in REGDISPLAY
;; to make sure nobody uses them
;; $regdisplayReg - register pointing to the REGDISPLAY structure
    MACRO
        TRASH_PRESERVED_REGISTERS_STORAGE $regdisplayReg

#if 0 // def _DEBUG  ;; @TODO: temporarily removed because trashing the frame pointer breaks the debugger
        movz        x3, #0xbaad, LSL #48
        movk        x3, #0xdeed, LSL #32
        movk        x3, #0xbaad, LSL #16
        movk        x3, #0xdeed
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX19]
        str         x3, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX20]
        str         x3, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX21]
        str         x3, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX22]
        str         x3, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX23]
        str         x3, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX24]
        str         x3, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX25]
        str         x3, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX26]
        str         x3, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX27]
        str         x3, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pX28]
        str         x3, [x12]
        ldr         x12, [$regdisplayReg, #OFFSETOF__REGDISPLAY__pFP]
        str         x3, [x12]
#endif // _DEBUG
    MEND

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; RhpThrowHwEx
;;
;; INPUT:  W0:  exception code of fault
;;         X1:  faulting IP
;;
;; OUTPUT:
;; 
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    NESTED_ENTRY RhpThrowHwEx

#define rsp_offsetof_ExInfo  0
#define rsp_offsetof_Context STACKSIZEOF_ExInfo

        ALLOC_THROW_FRAME HARDWARE_EXCEPTION

        ;; x2 = GetThread(), TRASHES x1
        INLINE_GETTHREAD x2, x1

        add         x1, sp, #rsp_offsetof_ExInfo                    ;; x1 <- ExInfo*
        str         xzr, [x1, #OFFSETOF__ExInfo__m_exception]       ;; pExInfo->m_exception = null
        mov         w3, #1
        strb        w3, [x1, #OFFSETOF__ExInfo__m_passNumber]       ;; pExInfo->m_passNumber = 1
        mov         w3, #0xFFFFFFFF
        str         w3, [x1, #OFFSETOF__ExInfo__m_idxCurClause]     ;; pExInfo->m_idxCurClause = MaxTryRegionIdx
        mov         w3, #2
        strb        w3, [x1, #OFFSETOF__ExInfo__m_kind]             ;; pExInfo->m_kind = ExKind.HardwareFault

        ;; link the ExInfo into the thread's ExInfo chain
        ldr         x3, [x2, #OFFSETOF__Thread__m_pExInfoStackHead]
        str         x3, [x1, #OFFSETOF__ExInfo__m_pPrevExInfo]      ;; pExInfo->m_pPrevExInfo = m_pExInfoStackHead
        str         x1, [x2, #OFFSETOF__Thread__m_pExInfoStackHead] ;; m_pExInfoStackHead = pExInfo

        ;; set the exception context field on the ExInfo
        add         x2, sp, #rsp_offsetof_Context                   ;; x2 <- PAL_LIMITED_CONTEXT*
        str         x2, [x1, #OFFSETOF__ExInfo__m_pExContext]       ;; pExInfo->m_pExContext = pContext

        ;; w0: exception code
        ;; x1: ExInfo*
        bl          RhThrowHwEx        

    EXPORT_POINTER_TO_ADDRESS PointerToRhpThrowHwEx2
        
        ;; no return
        EMIT_BREAKPOINT

    NESTED_END RhpThrowHwEx

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; RhpThrowEx
;;
;; INPUT:  X0:  exception object
;;
;; OUTPUT:
;; 
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    NESTED_ENTRY RhpThrowEx

        ALLOC_THROW_FRAME SOFTWARE_EXCEPTION

        ;; x2 = GetThread(), TRASHES x1
        INLINE_GETTHREAD x2, x1

        ;; There is runtime C# code that can tail call to RhpThrowEx using a binder intrinsic.  So the return 
        ;; address could have been hijacked when we were in that C# code and we must remove the hijack and
        ;; reflect the correct return address in our exception context record.  The other throw helpers don't
        ;; need this because they cannot be tail-called from C#.

        ;; NOTE: we cannot use INLINE_THREAD_UNHIJACK because it will write into the stack at the location 
        ;; where the tail-calling thread had saved LR, which may not match where we have saved LR.

        ldr         x1, [x2, #OFFSETOF__Thread__m_pvHijackedReturnAddress]
        cbz         x1, NotHijacked

        ldr         x3, [x2, #OFFSETOF__Thread__m_ppvHijackedReturnAddressLocation]

        ;; x0: exception object
        ;; x1: hijacked return address
        ;; x2: pThread
        ;; x3: hijacked return address location

        add         x12, sp, #(STACKSIZEOF_ExInfo + SIZEOF__PAL_LIMITED_CONTEXT)        ;; re-compute SP at callsite
        cmp         x3, x12             ;; if (m_ppvHijackedReturnAddressLocation < SP at callsite)
        blo         TailCallWasHijacked

        ;; normal case where a valid return address location is hijacked
        str         x1, [x3]
        b           ClearThreadState

TailCallWasHijacked

        ;; Abnormal case where the return address location is now invalid because we ended up here via a tail 
        ;; call.  In this case, our hijacked return address should be the correct caller of this method.
        ;; 

        ;; stick the previous return address in LR as well as in the right spots in our PAL_LIMITED_CONTEXT.
        mov         lr, x1
        str         lr, [sp, #(rsp_offsetof_Context + OFFSETOF__PAL_LIMITED_CONTEXT__LR)]
        str         lr, [sp, #(rsp_offsetof_Context + OFFSETOF__PAL_LIMITED_CONTEXT__IP)]

ClearThreadState

        ;; clear the Thread's hijack state
        str         xzr, [x2, #OFFSETOF__Thread__m_ppvHijackedReturnAddressLocation]
        str         xzr, [x2, #OFFSETOF__Thread__m_pvHijackedReturnAddress]

NotHijacked

        add         x1, sp, #rsp_offsetof_ExInfo                    ;; x1 <- ExInfo*
        str         xzr, [x1, #OFFSETOF__ExInfo__m_exception]       ;; pExInfo->m_exception = null
        mov         w3, #1
        strb        w3, [x1, #OFFSETOF__ExInfo__m_passNumber]       ;; pExInfo->m_passNumber = 1
        mov         w3, #0xFFFFFFFF
        str         w3, [x1, #OFFSETOF__ExInfo__m_idxCurClause]     ;; pExInfo->m_idxCurClause = MaxTryRegionIdx
        mov         w3, #1
        strb        w3, [x1, #OFFSETOF__ExInfo__m_kind]             ;; pExInfo->m_kind = ExKind.Throw

        ;; link the ExInfo into the thread's ExInfo chain
        ldr         x3, [x2, #OFFSETOF__Thread__m_pExInfoStackHead]
        str         x3, [x1, #OFFSETOF__ExInfo__m_pPrevExInfo]      ;; pExInfo->m_pPrevExInfo = m_pExInfoStackHead
        str         x1, [x2, #OFFSETOF__Thread__m_pExInfoStackHead] ;; m_pExInfoStackHead = pExInfo

        ;; set the exception context field on the ExInfo
        add         x2, sp, #rsp_offsetof_Context                   ;; x2 <- PAL_LIMITED_CONTEXT*
        str         x2, [x1, #OFFSETOF__ExInfo__m_pExContext]       ;; pExInfo->m_pExContext = pContext

        ;; x0: exception object
        ;; x1: ExInfo*
        bl          RhThrowEx

    EXPORT_POINTER_TO_ADDRESS PointerToRhpThrowEx2

        ;; no return
        EMIT_BREAKPOINT
    NESTED_END RhpThrowEx

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; void FASTCALL RhpRethrow()
;;
;; SUMMARY:  Similar to RhpThrowEx, except that it passes along the currently active ExInfo
;;
;; INPUT:
;;
;; OUTPUT:
;; 
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    NESTED_ENTRY RhpRethrow

        ALLOC_THROW_FRAME SOFTWARE_EXCEPTION

        ;; x2 = GetThread(), TRASHES x1
        INLINE_GETTHREAD x2, x1

        add         x1, sp, #rsp_offsetof_ExInfo                    ;; x1 <- ExInfo*
        str         xzr, [x1, #OFFSETOF__ExInfo__m_exception]       ;; pExInfo->m_exception = null
        strb        wzr, [x1, #OFFSETOF__ExInfo__m_kind]            ;; init to a deterministic value (ExKind.None)
        mov         w3, #1
        strb        w3, [x1, #OFFSETOF__ExInfo__m_passNumber]       ;; pExInfo->m_passNumber = 1
        mov         w3, #0xFFFFFFFF
        str         w3, [x1, #OFFSETOF__ExInfo__m_idxCurClause]     ;; pExInfo->m_idxCurClause = MaxTryRegionIdx

        ;; link the ExInfo into the thread's ExInfo chain
        ldr         x3, [x2, #OFFSETOF__Thread__m_pExInfoStackHead]
        mov         x0, x3                                          ;; x0 <- current ExInfo
        str         x3, [x1, #OFFSETOF__ExInfo__m_pPrevExInfo]      ;; pExInfo->m_pPrevExInfo = m_pExInfoStackHead
        str         x1, [x2, #OFFSETOF__Thread__m_pExInfoStackHead] ;; m_pExInfoStackHead = pExInfo

        ;; set the exception context field on the ExInfo
        add         x2, sp, #rsp_offsetof_Context                   ;; x2 <- PAL_LIMITED_CONTEXT*
        str         x2, [x1, #OFFSETOF__ExInfo__m_pExContext]       ;; pExInfo->m_pExContext = pContext

        ;; x0 contains the currently active ExInfo
        ;; x1 contains the address of the new ExInfo
        bl          RhRethrow

    EXPORT_POINTER_TO_ADDRESS PointerToRhpRethrow2

        ;; no return
        EMIT_BREAKPOINT
    NESTED_END RhpRethrow

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; void* FASTCALL RhpCallCatchFunclet(RtuObjectRef exceptionObj, void* pHandlerIP, REGDISPLAY* pRegDisplay,
;;                                    ExInfo* pExInfo)
;;
;; INPUT:  X0:  exception object
;;         X1:  handler funclet address
;;         X2:  REGDISPLAY*
;;         X3:  ExInfo*
;;
;; OUTPUT:
;; 
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    NESTED_ENTRY RhpCallCatchFunclet

        ALLOC_CALL_FUNCLET_FRAME 0x60
        stp d8, d9,   [sp, #0x00]
        stp d10, d11, [sp, #0x10]
        stp d12, d13, [sp, #0x20]
        stp d14, d15, [sp, #0x30]
        stp x0, x2,   [sp, #0x40]  ;; x0, x2 & x3 are saved so we have the exception object, REGDISPLAY and 
        stp x3, xzr,  [sp, #0x50]  ;; ExInfo later, xzr makes space for the local "is_not_handling_thread_abort"

#define rsp_offset_is_not_handling_thread_abort 0x58
#define rsp_offset_x2 0x48
#define rsp_offset_x3 0x50

        ;;
        ;; clear the DoNotTriggerGc flag, trashes x4-x6
        ;;
        INLINE_GETTHREAD    x5, x6      ;; x5 <- Thread*, x6 <- trashed

        ldr         x4, [x5, #OFFSETOF__Thread__m_threadAbortException]
        sub         x4, x4, x0
        str         x4, [sp, #rsp_offset_is_not_handling_thread_abort] ;; Non-zero if the exception is not ThreadAbortException

        add         x12, x5, #OFFSETOF__Thread__m_ThreadStateFlags

ClearRetry_Catch
        ldxr        w4, [x12]
        bic         w4, w4, #TSF_DoNotTriggerGc
        stxr        w6, w4, [x12]
        cbz         w6, ClearSuccess_Catch
        b           ClearRetry_Catch
ClearSuccess_Catch

        ;;
        ;; set preserved regs to the values expected by the funclet
        ;;
        RESTORE_PRESERVED_REGISTERS x2
        ;;
        ;; trash the values at the old homes to make sure nobody uses them
        ;;
        TRASH_PRESERVED_REGISTERS_STORAGE x2

        ;;
        ;; call the funclet
        ;; 
        ;; x0 still contains the exception object
        blr         x1

        EXPORT_POINTER_TO_ADDRESS PointerToRhpCallCatchFunclet2

        ;; x0 contains resume IP

        ldr         x2, [sp, #rsp_offset_x2]                    ;; x2 <- REGDISPLAY*

;; @TODO: add debug-only validation code for ExInfo pop

        INLINE_GETTHREAD x1, x3                                 ;; x1 <- Thread*, x3 <- trashed

        ;; We must unhijack the thread at this point because the section of stack where the hijack is applied
        ;; may go dead.  If it does, then the next time we try to unhijack the thread, it will corrupt the stack.
        INLINE_THREAD_UNHIJACK x1, x3, x12                      ;; Thread in x1, trashes x3 and x12

        ldr         x3, [sp, #rsp_offset_x3]                    ;; x3 <- current ExInfo*
        ldr         x2, [x2, #OFFSETOF__REGDISPLAY__SP]         ;; x2 <- resume SP value

PopExInfoLoop
        ldr         x3, [x3, #OFFSETOF__ExInfo__m_pPrevExInfo]  ;; x3 <- next ExInfo
        cbz         x3, DonePopping                             ;; if (pExInfo == null) { we're done }
        cmp         x3, x2
        blt         PopExInfoLoop                               ;; if (pExInfo < resume SP} { keep going }

DonePopping
        str         x3, [x1, #OFFSETOF__Thread__m_pExInfoStackHead]     ;; store the new head on the Thread

        ldr         x3, =RhpTrapThreads
        ldr         w3, [x3]
        tbz         x3, #TrapThreadsFlags_AbortInProgress_Bit, NoAbort

        ldr         x3, [sp, #rsp_offset_is_not_handling_thread_abort]
        cbnz        x3, NoAbort

        ;; It was the ThreadAbortException, so rethrow it
        ;; reset SP
        mov         x1, x0                                     ;; x1 <- continuation address as exception PC
        mov         w0, #STATUS_REDHAWK_THREAD_ABORT
        mov         sp, x2
        b           RhpThrowHwEx

NoAbort
        ;; reset SP and jump to continuation address
        mov         sp, x2
        br          x0

    NESTED_END RhpCallCatchFunclet

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; void FASTCALL RhpCallFinallyFunclet(void* pHandlerIP, REGDISPLAY* pRegDisplay)
;;
;; INPUT:  X0:  handler funclet address
;;         X1:  REGDISPLAY*
;;
;; OUTPUT:
;; 
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    NESTED_ENTRY RhpCallFinallyFunclet

        ALLOC_CALL_FUNCLET_FRAME 0x50
        stp d8, d9,   [sp, #0x00]
        stp d10, d11, [sp, #0x10]
        stp d12, d13, [sp, #0x20]
        stp d14, d15, [sp, #0x30]
        stp x0, x1,   [sp, #0x40]   ;; x1 is saved so we have the REGDISPLAY later, x0 is just alignment padding

#define rsp_offset_x1 0x48

        ;;
        ;; We want to suppress hijacking between invocations of subsequent finallys.  We do this because we
        ;; cannot tolerate a GC after one finally has run (and possibly side-effected the GC state of the
        ;; method) and then been popped off the stack, leaving behind no trace of its effect.
        ;;
        ;; So we clear the state before and set it after invocation of the handler.
        ;;

        ;;
        ;; clear the DoNotTriggerGc flag, trashes x2-x4
        ;;
        INLINE_GETTHREAD    x2, x3      ;; x2 <- Thread*, x3 <- trashed

        add         x12, x2, #OFFSETOF__Thread__m_ThreadStateFlags

ClearRetry
        ldxr        w4, [x12]
        bic         w4, w4, #TSF_DoNotTriggerGc
        stxr        w3, w4, [x12]
        cbz         w3, ClearSuccess
        b           ClearRetry
ClearSuccess

        ;;
        ;; set preserved regs to the values expected by the funclet
        ;;
        RESTORE_PRESERVED_REGISTERS x1
        ;;
        ;; trash the values at the old homes to make sure nobody uses them
        ;;
        TRASH_PRESERVED_REGISTERS_STORAGE x1

        ;;
        ;; call the funclet
        ;; 
        blr         x0

    EXPORT_POINTER_TO_ADDRESS PointerToRhpCallFinallyFunclet2

        ldr         x1, [sp, #rsp_offset_x1]        ;; reload REGDISPLAY pointer

        ;;
        ;; save new values of preserved regs into REGDISPLAY
        ;;
        SAVE_PRESERVED_REGISTERS x1

        ;;
        ;; set the DoNotTriggerGc flag, trashes x1-x3
        ;;
        INLINE_GETTHREAD    x2, x3      ;; x2 <- Thread*, x3 <- trashed

        add         x12, x2, #OFFSETOF__Thread__m_ThreadStateFlags
SetRetry
        ldxr        w1, [x12]
        orr         w1, w1, #TSF_DoNotTriggerGc
        stxr        w3, w1, [x12]
        cbz         w3, SetSuccess
        b           SetRetry
SetSuccess

        ldp         d8, d9,   [sp, #0x00] 
        ldp         d10, d11, [sp, #0x10]
        ldp         d12, d13, [sp, #0x20]
        ldp         d14, d15, [sp, #0x30]

        FREE_CALL_FUNCLET_FRAME 0x50
        EPILOG_RETURN

    NESTED_END RhpCallFinallyFunclet


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; void* FASTCALL RhpCallFilterFunclet(RtuObjectRef exceptionObj, void* pFilterIP, REGDISPLAY* pRegDisplay)
;;
;; INPUT:  X0:  exception object
;;         X1:  filter funclet address
;;         X2:  REGDISPLAY*
;;
;; OUTPUT:
;; 
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
    NESTED_ENTRY RhpCallFilterFunclet
        ALLOC_CALL_FUNCLET_FRAME 0x40
        stp d8, d9,   [sp, #0x00]
        stp d10, d11, [sp, #0x10]
        stp d12, d13, [sp, #0x20]
        stp d14, d15, [sp, #0x30]

        ldr         x12, [x2, #OFFSETOF__REGDISPLAY__pFP]
        ldr         fp, [x12]

        ;;
        ;; call the funclet
        ;; 
        ;; x0 still contains the exception object
        blr         x1

    EXPORT_POINTER_TO_ADDRESS PointerToRhpCallFilterFunclet2

        ldp         d8, d9,   [sp, #0x00]
        ldp         d10, d11, [sp, #0x10]
        ldp         d12, d13, [sp, #0x20]
        ldp         d14, d15, [sp, #0x30]

        FREE_CALL_FUNCLET_FRAME 0x40
        EPILOG_RETURN

    NESTED_END RhpCallFilterFunclet

    INLINE_GETTHREAD_CONSTANT_POOL

    end