// 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 "unixasmmacros.inc"
#include "asmconstants.h"

.syntax unified
.thumb

//
// WARNING!!  These functions immediately ruin thread unwindability.  This is
// WARNING!!  OK as long as there is a mechanism for saving the thread context
// WARNING!!  prior to running these functions as well as a mechanism for
// WARNING!!  restoring the context prior to any stackwalk.  This means that
// WARNING!!  we need to ensure that no GC can occur while the stack is
// WARNING!!  unwalkable.  This further means that we cannot allow any exception
// WARNING!!  to occur when the stack is unwalkable
//

        // GSCookie + alignment padding
OFFSET_OF_FRAME=(4 + SIZEOF__GSCookie)

        .macro GenerateRedirectedStubWithFrame STUB, TARGET

        // 
        // This is the primary function to which execution will be redirected to.
        //
        NESTED_ENTRY \STUB, _TEXT, NoHandler

        //
        // IN: lr: original IP before redirect
        //

        PROLOG_PUSH  "{r4,r7,lr}"
        alloc_stack  OFFSET_OF_FRAME + SIZEOF__FaultingExceptionFrame

        // At this point, the stack maybe misaligned if the thread abort was asynchronously
        // triggered in the prolog or epilog of the managed method. For such a case, we must
        // align the stack before calling into the VM.
        //
        // Runtime check for 8-byte alignment. 
        PROLOG_STACK_SAVE r7
        // We lose stack unwindability here by configuring fp(r7) incorrectely
        // here.
        and r0, r7, #4
        sub sp, sp, r0

        // Save pointer to FEF for GetFrameFromRedirectedStubStackFrame
        add r4, sp, #OFFSET_OF_FRAME

        // Prepare to initialize to NULL
        mov r1,#0
        str r1, [r4]                                                        // Initialize vtbl (it is not strictly necessary)
        str r1, [r4, #FaultingExceptionFrame__m_fFilterExecuted]            // Initialize BOOL for personality routine

        mov r0, r4                      // move the ptr to FEF in R0
        
        // stack must be 8 byte aligned
        CHECK_STACK_ALIGNMENT       
        
        bl            C_FUNC(\TARGET)

        // Target should not return.
        EMIT_BREAKPOINT

        NESTED_END \STUB, _TEXT

        .endm

// ------------------------------------------------------------------

        // This helper enables us to call into a funclet after applying the non-volatiles
        NESTED_ENTRY CallEHFunclet, _TEXT, NoHandler

        PROLOG_PUSH  "{r4-r11, lr}"
        PROLOG_STACK_SAVE_OFFSET  r7, #12
        alloc_stack  4

        // On entry:
        //
        // R0 = throwable        
        // R1 = PC to invoke
        // R2 = address of R4 register in CONTEXT record// used to restore the non-volatile registers of CrawlFrame
        // R3 = address of the location where the SP of funclet's caller (i.e. this helper) should be saved.
        //
        // Save the SP of this function
        str sp, [r3]
        // apply the non-volatiles corresponding to the CrawlFrame
        ldm r2!, {r4-r6}
        add r2, r2, #4
        ldm r2!, {r8-r11}
        // Invoke the funclet
        blx r1

        free_stack   4
        EPILOG_POP   "{r4-r11, pc}"

        NESTED_END CallEHFunclet, _TEXT

        // This helper enables us to call into a filter funclet by passing it the CallerSP to lookup the 
        // frame pointer for accessing the locals in the parent method.
        NESTED_ENTRY CallEHFilterFunclet, _TEXT, NoHandler

        PROLOG_PUSH  "{r7, lr}"
        PROLOG_STACK_SAVE r7

        // On entry:
        //
        // R0 = throwable        
        // R1 = SP of the caller of the method/funclet containing the filter
        // R2 = PC to invoke
        // R3 = address of the location where the SP of funclet's caller (i.e. this helper) should be saved.
        //
        // Save the SP of this function
        str sp, [r3]
        // Invoke the filter funclet
        blx r2

        EPILOG_POP   "{r7, pc}"

        NESTED_END CallEHFilterFunclet, _TEXT