/***
*ehprolg3a.c - Define the _EH_prolog3* compiler helpers for aligned frames
*
*       Copyright (c) Microsoft Corporation. All rights reserved.
*
*Purpose:
*       EH prologue helpers for the EH security cookie cases, where the cookie
*       must be initialized before the EH node is installed.  Also defines the
*       complementary EH epilogue helpers.
*
*       The helpers should be compiled /Gy, at least in retail CRTs, so they
*       will be compiled as comdats, and only the ones used will be pulled into
*       a release build.
*
*       These helpers are for setting up dynamically aligned frames, where the
*       local stack allocation must be 8-byte (or better) aligned, either for
*       performance reasons (making sure doubles don't cross cache lines) or
*       correctness (making sure some SSE types don't cross cache lines).
*
*       There are 4 different prologue helpers, to deal with the various
*       combinations of a 12-byte -vs- 16-byte exception registration node and
*       the presence or absence of a /GS local security cookie.
*
*       _EH_prolog3_align
*       _EH_prolog3_catch_align
*       _EH_prolog3_GS_align
*       _EH_prolog3_catch_GS_align
*
*       There are 2 different epilogue helpers:
*
*       _EH_epilog3_align
*       _EH_epilog3_GS_align
****/

#include <vcruntime_internal.h>

/*
 * Ignore warnings about unreferenced formal parameters and unsafe FS:0
 * assignments.
 */

#pragma warning(disable:4100 4733)

/***
*_EH_prolog3_align - Set up C++ EH call frame variation
*
*Purpose:
*   Sets up the call frame for a C++ EH function that:
*   + uses a 12-byte EH node (function has unwinds, no catch blocks)
*   + does not have a local /GS cookie
*   + uses an EBX/EBP frame (no FPO)
*   + needs dynamic stack alignment
*
*Entry:
*   EAX = address of EH handler thunk.
*   LocalAllocation = local stack allocation requirement (hereafter, 'N').
*       This is the space required after EBX is pushed below the EH node.
*   Alignment = alignment requirement.
*
*   Incoming stack frame has:
*       [ESP+12] callee's return address
*       [ESP+8]  alignment requirement
*       [ESP+4]  local stack allocation requirement
*       [ESP+0]  _EH_prolog3_align's return address
*
*Exit:
*   EAX = destroyed
*   EBX = ESP on entry + 4 (pointer to callee's parameters)
*   EBP = aligned pointer to callee's locals
*   ESP = EBP on exit - 28 - N
*   All other registers except CC preserved
*
*   FS:[0] = set to EBP on exit - 12 to create new link in the EH chain
*
*   Stack frame has been set up as follows:
*       [EBX+4]     (entry [ESP+12]) callee's return address
*       [EBX+0]     saved EBX
*       padding to align stack (if needed)
*       [EBP+4]     callee's return address (copy of entry [ESP+12])
*       [EBP+0]     saved EBP
*       [EBP-4]     EH record state index, initialized to -1
*       [EBP-8]     address of EH handler thunk
*       [EBP-12]    saved FS:[0]
*       [EBP-16]    saved value of EBX on exit
*       padding to realign stack (if needed)
*       ...
*       [EBP-16-N]  base of locals allocation
*       [EBP-20-N]  saved ESI
*       [EBP-24-N]  saved EDI
*       [EBP-28-N]  local EH cookie, XORed with value of EBP on exit
*
*******************************************************************************/

extern void __declspec(naked)
_EH_prolog3_align(
    unsigned long LocalAllocation,
    unsigned long Alignment
    )
{
    __asm
    {
        ; stack has:
        ;   callee's return addr
        ;   alignment requirement
        ;   allocation size
        ;   ret addr    <== ESP

        push    ecx             ; we need an extra reg, so save ECX
        mov     ecx, [esp+12]   ; get the alignment requirement
        mov     [esp+12], ebx   ; save EBX in its final position
        lea     ebx, [esp+12]   ; * and set the new EBX for addressing params
        push    eax             ; save the handler thunk addr, free EAX for use

        ; stack has:
        ;   callee's return addr
        ;   saved EBX   <== EBX
        ;   allocation size
        ;   ret addr
        ;   saved ECX
        ;   handler thunk addr  <== ESP
        ;
        ; Now calculate the aligned stack pointer, which will be returned in
        ; EBP.  Depending on the padding required, it will point at the ret
        ; addr in the above stack, or somewhere below that.

        lea     eax, [esp+8]
        neg     ecx
        and     eax, ecx
        lea     esp, [eax-8]

        ; ESP now points at or below its position in the previous comment,
        ; and ESP+8 has the required alignment.  Everything below the saved
        ; EBX is potentially overlapped by the aligned stack frame we're about
        ; to create, so move those items to safety.

        mov     eax, [ebx-16]   ; the handler thunk address can be moved into
        mov     [esp], eax      ; * its final position (might not move)
        mov     eax, [ebx-8]    ; copy down the ret addr
        push    eax
        mov     eax, [ebx-4]    ; get the allocation size for later
        mov     ecx, [ebx-12]   ; restore the original ECX

        ; stack has:
        ;   callee's return addr
        ;   saved EBX   <== EBX
        ;   ... possible padding to align stack ...
        ;   (uninitialized) callee's return addr
        ;   (uninitialized) saved EBP (aligned stack location)
        ;   (uninitialized) EH state index
        ;   handler thunk addr
        ;   ret addr    <== ESP

        mov     [esp+12], ebp   ; save old EBP and set new EBP frame pointer
        lea     ebp, [esp+12]   ; * for addressing locals
        mov     dword ptr [esp+8], -1 ; initialize the EH state index

        ; stack has:
        ;   callee's return addr
        ;   saved EBX   <== EBX
        ;   ... possible padding to align stack ...
        ;   (uninitialized) callee's return addr
        ;   saved EBP   <== EBP (aligned stack location)
        ;   initial EH state index of -1
        ;   handler thunk addr
        ;   ret addr    <== ESP

        push    ebx             ; save copy of EBX at EBP-16 for funclet use
        sub     esp, eax        ; allocate the locals allocation space
        push    esi             ; save callee-saved regs
        push    edi

        ; stack has:
        ;   callee's return addr
        ;   saved EBX   <== EBX
        ;   ... possible padding to align stack ...
        ;   (uninitialized) callee's return addr
        ;   saved EBP   <== EBP (aligned stack location)
        ;   initial EH state index of -1
        ;   handler thunk addr
        ;   ret addr
        ;   saved value of EBX on exit
        ;   locals allocation area
        ;   saved ESI
        ;   saved EDI   <== ESP

        mov     eax, __security_cookie
        xor     eax, ebp        ; generate local EH cookie
        push    eax
        mov     eax, [ebx+4]    ; copy callee's return addr above saved EBP
        mov     [ebp+4], eax    ; * so EBP-based stackwalks work better
        push    [ebp-12]        ; move the return address to final position
        mov     eax, fs:[0]     ; set link to next node in EH chain
        mov     [ebp-12], eax

        ; stack has:
        ;   callee's return addr
        ;   saved EBX   <== EBX
        ;   ... possible padding to align stack ...
        ;   callee's return addr
        ;   saved EBP   <== EBP (aligned stack location)
        ;   initial EH state index of -1
        ;   handler thunk addr
        ;   saved FS:[0]
        ;   saved value of EBX on exit
        ;   locals allocation area
        ;   saved ESI
        ;   saved EDI
        ;   local EH security cookie
        ;   ret addr    <== ESP

        lea     eax, [ebp-12]   ; all done - link in the EH node
        mov     fs:[0], eax

        ret
    }
}

/***
*_EH_prolog3_catch_align - Set up C++ EH call frame variation
*
*Purpose:
*   Sets up the call frame for a C++ EH function that:
*   + uses a 16-byte EH node (function has catch blocks)
*   + does not have a local /GS cookie
*   + uses an EBX/EBP frame (no FPO)
*   + needs dynamic stack alignment
*
*Entry:
*   EAX = address of EH handler thunk.
*   LocalAllocation = local stack allocation requirement (hereafter, 'N').
*       This is the space required after EBX is pushed below the EH node.
*   Alignment = alignment requirement.
*
*   Incoming stack frame has:
*       [ESP+12] callee's return address
*       [ESP+8]  alignment requirement
*       [ESP+4]  local stack allocation requirement
*       [ESP+0]  _EH_prolog3_catch_align's return address
*
*Exit:
*   EAX = destroyed
*   EBX = ESP on entry + 4 (pointer to callee's parameters)
*   EBP = aligned pointer to callee's locals
*   ESP = EBP on exit - 32 - N
*   All other registers except CC preserved
*
*   FS:[0] = set to EBP on exit - 12 to create new link in the EH chain
*
*   Stack frame has been set up as follows:
*       [EBX+4]     (entry [ESP+12]) callee's return address
*       [EBX+0]     saved EBX
*       padding to align stack (if needed)
*       [EBP+4]     callee's return address (copy of entry [ESP+12])
*       [EBP+0]     saved EBP
*       [EBP-4]     EH record state index, initialized to -1
*       [EBP-8]     address of EH handler thunk
*       [EBP-12]    saved FS:[0]
*       [EBP-16]    saved final ESP return value
*       [EBP-20]    saved value of EBX on exit
*       padding to realign stack (if needed)
*       ...
*       [EBP-20-N]  base of locals allocation
*       [EBP-24-N]  saved ESI
*       [EBP-28-N]  saved EDI
*       [EBP-32-N]  local EH cookie, XORed with value of EBP on exit
*
*******************************************************************************/

extern void __declspec(naked)
_EH_prolog3_catch_align(
    unsigned long LocalAllocation,
    unsigned long Alignment
    )
{
    __asm
    {
        ; stack has:
        ;   callee's return addr
        ;   alignment requirement
        ;   allocation size
        ;   ret addr    <== ESP

        push    ecx             ; we need an extra reg, so save ECX
        mov     ecx, [esp+12]   ; get the alignment requirement
        mov     [esp+12], ebx   ; save EBX in its final position
        lea     ebx, [esp+12]   ; * and set the new EBX for addressing params
        push    eax             ; save the handler thunk addr, free EAX for use

        ; stack has:
        ;   callee's return addr
        ;   saved EBX   <== EBX
        ;   allocation size
        ;   ret addr
        ;   saved ECX
        ;   handler thunk addr  <== ESP
        ;
        ; Now calculate the aligned stack pointer, which will be returned in
        ; EBP.  Depending on the padding required, it will point at the ret
        ; addr in the above stack, or somewhere below that.

        lea     eax, [esp+8]
        neg     ecx
        and     eax, ecx
        lea     esp, [eax-8]

        ; ESP now points at or below its position in the previous comment,
        ; and ESP+8 has the required alignment.  Everything below the saved
        ; EBX is potentially overlapped by the aligned stack frame we're about
        ; to create, so move those items to safety.

        mov     eax, [ebx-16]   ; the handler thunk address can be moved into
        mov     [esp], eax      ; * its final position (might not move)
        mov     eax, [ebx-8]    ; copy down the ret addr
        push    eax
        mov     eax, [ebx-4]    ; get the allocation size for later
        mov     ecx, [ebx-12]   ; restore the original ECX

        ; stack has:
        ;   callee's return addr
        ;   saved EBX   <== EBX
        ;   ... possible padding to align stack ...
        ;   (uninitialized) callee's return addr
        ;   (uninitialized) saved EBP (aligned stack location)
        ;   (uninitialized) EH state index
        ;   handler thunk addr
        ;   ret addr    <== ESP

        mov     [esp+12], ebp   ; save old EBP and set new EBP frame pointer
        lea     ebp, [esp+12]   ; * for addressing locals
        mov     dword ptr [esp+8], -1 ; initialize the EH state index

        ; stack has:
        ;   callee's return addr
        ;   saved EBX   <== EBX
        ;   ... possible padding to align stack ...
        ;   (uninitialized) callee's return addr
        ;   saved EBP   <== EBP (aligned stack location)
        ;   initial EH state index of -1
        ;   handler thunk addr
        ;   ret addr    <== ESP

        push    ecx             ; save space for saved ESP field of EH node
        push    ebx             ; save copy of EBX at EBP-20 for funclet use
        sub     esp, eax        ; allocate the locals allocation space
        push    esi             ; save callee-saved regs
        push    edi

        ; stack has:
        ;   callee's return addr
        ;   saved EBX   <== EBX
        ;   ... possible padding to align stack ...
        ;   (uninitialized) callee's return addr
        ;   saved EBP   <== EBP (aligned stack location)
        ;   initial EH state index of -1
        ;   handler thunk addr
        ;   ret addr
        ;   (uninitialized) saved ESP field of EH node
        ;   saved value of EBX on exit
        ;   locals allocation area
        ;   saved ESI
        ;   saved EDI   <== ESP

        mov     eax, __security_cookie
        xor     eax, ebp        ; generate local EH cookie
        push    eax
        mov     [ebp-16], esp   ; initialize the EH node's saved ESP field
        mov     eax, [ebx+4]    ; copy callee's return addr above saved EBP
        mov     [ebp+4], eax    ; * so EBP-based stackwalks work better
        push    [ebp-12]        ; move the return address to final position
        mov     eax, fs:[0]     ; set link to next node in EH chain
        mov     [ebp-12], eax

        ; stack has:
        ;   callee's return addr
        ;   saved EBX   <== EBX
        ;   ... possible padding to align stack ...
        ;   callee's return addr
        ;   saved EBP   <== EBP (aligned stack location)
        ;   initial EH state index of -1
        ;   handler thunk addr
        ;   saved FS:[0]
        ;   saved ESP field of EH node
        ;   saved value of EBX on exit
        ;   locals allocation area
        ;   saved ESI
        ;   saved EDI
        ;   local EH security cookie
        ;   ret addr    <== ESP

        lea     eax, [ebp-12]   ; all done - link in the EH node
        mov     fs:[0], eax

        ret
    }
}

/***
*_EH_prolog3_GS_align - Set up C++ EH call frame variation
*
*Purpose:
*   Sets up the call frame for a C++ EH function that:
*   + uses a 12-byte EH node (function has unwinds, no catch blocks)
*   + has a local /GS cookie
*   + uses an EBX/EBP frame (no FPO)
*   + needs dynamic stack alignment
*
*Entry:
*   EAX = address of EH handler thunk.
*   LocalAllocation = local stack allocation requirement (hereafter, 'N').
*       This is the space required after EBX is pushed below the EH node.
*   Alignment = alignment requirement.
*
*   Incoming stack frame has:
*       [ESP+12] callee's return address
*       [ESP+8]  alignment requirement
*       [ESP+4]  local stack allocation requirement
*       [ESP+0]  _EH_prolog3_GS_align's return address
*
*Exit:
*   EAX = destroyed
*   EBX = ESP on entry + 4 (pointer to callee's parameters)
*   EBP = aligned pointer to callee's locals
*   ESP = EBP on exit - 28 - N
*   All other registers except CC preserved
*
*   FS:[0] = set to EBP on exit - 12 to create new link in the EH chain
*
*   Stack frame has been set up as follows:
*       [EBX+4]     (entry [ESP+12]) callee's return address
*       [EBX+0]     saved EBX
*       padding to align stack (if needed)
*       [EBP+4]     callee's return address (copy of entry [ESP+12])
*       [EBP+0]     saved EBP
*       [EBP-4]     EH record state index, initialized to -1
*       [EBP-8]     address of EH handler thunk
*       [EBP-12]    saved FS:[0]
*       [EBP-16]    saved value of EBX on exit
*       padding to realign stack (if needed)
*       [EBP-???]   local GS cookie, XORed with value of EBP on exit
*       ...
*       [EBP-16-N]  base of locals allocation
*       [EBP-20-N]  saved ESI
*       [EBP-24-N]  saved EDI
*       [EBP-28-N]  local EH cookie, XORed with value of EBP on exit
*
*   The local GS cookie will be placed just below the first alignment point at
*   or below EBP-16.  That is, it is stored at [((EBP-16) & -Alignment)-4].
*
*******************************************************************************/

extern void __declspec(naked)
_EH_prolog3_GS_align(
    unsigned long LocalAllocation,
    unsigned long Alignment
    )
{
    __asm
    {
        ; stack has:
        ;   callee's return addr
        ;   alignment requirement
        ;   allocation size
        ;   ret addr    <== ESP

        push    ecx             ; we need an extra reg, so save ECX
        mov     ecx, [esp+12]   ; get the alignment requirement
        mov     [esp+12], ebx   ; save EBX in its final position
        lea     ebx, [esp+12]   ; * and set the new EBX for addressing params
        push    eax             ; save the handler thunk addr, free EAX for use

        ; stack has:
        ;   callee's return addr
        ;   saved EBX   <== EBX
        ;   allocation size
        ;   ret addr
        ;   saved ECX
        ;   handler thunk addr  <== ESP
        ;
        ; Now calculate the aligned stack pointer, which will be returned in
        ; EBP.  Depending on the padding required, it will point at the ret
        ; addr in the above stack, or somewhere below that.

        lea     eax, [esp+8]
        neg     ecx
        and     eax, ecx
        lea     esp, [eax-8]

        ; ESP now points at or below its position in the previous comment,
        ; and ESP+8 has the required alignment.  Everything below the saved
        ; EBX is potentially overlapped by the aligned stack frame we're about
        ; to create, so move those items to safety.

        mov     eax, [ebx-16]   ; the handler thunk address can be moved into
        mov     [esp], eax      ; * its final position (might not move)
        mov     eax, [ebx-8]    ; copy down the ret addr
        push    eax
        mov     eax, [ebx-12]   ; copy down the original ECX
        push    eax
        mov     eax, [ebx-4]    ; get the allocation size for later

        ; stack has:
        ;   callee's return addr
        ;   saved EBX   <== EBX
        ;   ... possible padding to align stack ...
        ;   (uninitialized) callee's return addr
        ;   (uninitialized) saved EBP (aligned stack location)
        ;   (uninitialized) EH state index
        ;   handler thunk addr
        ;   ret addr
        ;   saved ECX   <== ESP

        mov     [esp+16], ebp   ; save old EBP and set new EBP frame pointer
        lea     ebp, [esp+16]   ; * for addressing locals
        mov     dword ptr [esp+12], -1 ; initialize the EH state index

        ; stack has:
        ;   callee's return addr
        ;   saved EBX   <== EBX
        ;   ... possible padding to align stack ...
        ;   (uninitialized) callee's return addr
        ;   saved EBP   <== EBP (aligned stack location)
        ;   initial EH state index of -1
        ;   handler thunk addr
        ;   ret addr
        ;   saved ECX   <== ESP

        and     ecx, esp        ; get address of realignment point
        sub     esp, eax        ; allocate the locals allocation space
        push    esi             ; save callee-saved regs
        push    edi

        ; stack has:
        ;   callee's return addr
        ;   saved EBX   <== EBX
        ;   ... possible padding to align stack ...
        ;   (uninitialized) callee's return addr
        ;   saved EBP   <== EBP (aligned stack location)
        ;   initial EH state index of -1
        ;   handler thunk addr
        ;   ret addr
        ;   saved ECX
        ;   ... possible padding to realign stack ... <== ECX (aligned)
        ;   (uninitialized) local GS security cookie
        ;   locals allocation area
        ;   saved ESI
        ;   saved EDI   <== ESP

        mov     eax, __security_cookie
        xor     eax, ebp        ; generate local EH and GS cookies
        push    eax
        mov     [ecx-4], eax
        mov     ecx, [ebp-16]   ; restore the original ECX
        mov     [ebp-16], ebx   ; save copy of EBX for funclet use
        mov     eax, [ebx+4]    ; copy callee's return addr above saved EBP
        mov     [ebp+4], eax    ; * so EBP-based stackwalks work better
        push    [ebp-12]        ; move the return address to final position
        mov     eax, fs:[0]     ; set link to next node in EH chain
        mov     [ebp-12], eax

        ; stack has:
        ;   callee's return addr
        ;   saved EBX   <== EBX
        ;   ... possible padding to align stack ...
        ;   callee's return addr
        ;   saved EBP   <== EBP (aligned stack location)
        ;   initial EH state index of -1
        ;   handler thunk addr
        ;   saved FS:[0]
        ;   saved value of EBX on exit
        ;   ... possible padding to realign stack ...
        ;   local GS security cookie
        ;   locals allocation area
        ;   saved ESI
        ;   saved EDI
        ;   local EH security cookie
        ;   ret addr    <== ESP

        lea     eax, [ebp-12]   ; all done - link in the EH node
        mov     fs:[0], eax

        ret
    }
}

/***
*_EH_prolog3_catch_GS_align - Set up C++ EH call frame variation
*
*Purpose:
*   Sets up the call frame for a C++ EH function that:
*   + uses a 16-byte EH node (function has catch blocks)
*   + has a local /GS cookie
*   + uses an EBX/EBP frame (no FPO)
*   + needs dynamic stack alignment
*
*Entry:
*   EAX = address of EH handler thunk.
*   LocalAllocation = local stack allocation requirement (hereafter, 'N').
*       This is the space required after EBX is pushed below the EH node.
*   Alignment = alignment requirement.
*
*   Incoming stack frame has:
*       [ESP+12] callee's return address
*       [ESP+8]  alignment requirement
*       [ESP+4]  local stack allocation requirement
*       [ESP+0]  _EH_prolog3_catch_GS_align's return address
*
*Exit:
*   EAX = destroyed
*   EBX = ESP on entry + 4 (pointer to callee's parameters)
*   EBP = aligned pointer to callee's locals
*   ESP = EBP on exit - 32 - N
*   All other registers except CC preserved
*
*   FS:[0] = set to EBP on exit - 12 to create new link in the EH chain
*
*   Stack frame has been set up as follows:
*       [EBX+4]     (entry [ESP+12]) callee's return address
*       [EBX+0]     saved EBX
*       padding to align stack (if needed)
*       [EBP+4]     callee's return address (copy of entry [ESP+12])
*       [EBP+0]     saved EBP
*       [EBP-4]     EH record state index, initialized to -1
*       [EBP-8]     address of EH handler thunk
*       [EBP-12]    saved FS:[0]
*       [EBP-16]    saved final ESP return value
*       [EBP-20]    saved value of EBX on exit
*       padding to realign stack (if needed)
*       [EBP-???]   local GS cookie, XORed with value of EBP on exit
*       ...
*       [EBP-20-N]  base of locals allocation
*       [EBP-24-N]  saved ESI
*       [EBP-28-N]  saved EDI
*       [EBP-32-N]  local EH cookie, XORed with value of EBP on exit
*
*   The local GS cookie will be placed just below the first alignment point at
*   or below EBP-16.  That is, it is stored at [((EBP-16) & -Alignment)-4].
*
*******************************************************************************/

extern void __declspec(naked)
_EH_prolog3_catch_GS_align(
    unsigned long LocalAllocation,
    unsigned long Alignment
    )
{
    __asm
    {
        ; stack has:
        ;   callee's return addr
        ;   alignment requirement
        ;   allocation size
        ;   ret addr    <== ESP

        push    ecx             ; we need an extra reg, so save ECX
        mov     ecx, [esp+12]   ; get the alignment requirement
        mov     [esp+12], ebx   ; save EBX in its final position
        lea     ebx, [esp+12]   ; * and set the new EBX for addressing params
        push    eax             ; save the handler thunk addr, free EAX for use

        ; stack has:
        ;   callee's return addr
        ;   saved EBX   <== EBX
        ;   allocation size
        ;   ret addr
        ;   saved ECX
        ;   handler thunk addr  <== ESP
        ;
        ; Now calculate the aligned stack pointer, which will be returned in
        ; EBP.  Depending on the padding required, it will point at the ret
        ; addr in the above stack, or somewhere below that.

        lea     eax, [esp+8]
        neg     ecx
        and     eax, ecx
        lea     esp, [eax-8]

        ; ESP now points at or below its position in the previous comment,
        ; and ESP+8 has the required alignment.  Everything below the saved
        ; EBX is potentially overlapped by the aligned stack frame we're about
        ; to create, so move those items to safety.

        mov     eax, [ebx-16]   ; the handler thunk address can be moved into
        mov     [esp], eax      ; * its final position (might not move)
        mov     eax, [ebx-8]    ; copy down the ret addr
        push    eax
        mov     eax, [ebx-12]   ; copy down the original ECX
        push    eax
        mov     eax, [ebx-4]    ; get the allocation size for later

        ; stack has:
        ;   callee's return addr
        ;   saved EBX   <== EBX
        ;   ... possible padding to align stack ...
        ;   (uninitialized) callee's return addr
        ;   (uninitialized) saved EBP (aligned stack location)
        ;   (uninitialized) EH state index
        ;   handler thunk addr
        ;   ret addr
        ;   saved ECX   <== ESP

        mov     [esp+16], ebp   ; save old EBP and set new EBP frame pointer
        lea     ebp, [esp+16]   ; * for addressing locals
        mov     dword ptr [esp+12], -1 ; initialize the EH state index

        ; stack has:
        ;   callee's return addr
        ;   saved EBX   <== EBX
        ;   ... possible padding to align stack ...
        ;   (uninitialized) callee's return addr
        ;   saved EBP   <== EBP (aligned stack location)
        ;   initial EH state index of -1
        ;   handler thunk addr
        ;   ret addr
        ;   saved ECX   <== ESP

        push    ebx             ; save copy of EBX at EBP-16 for funclet use
        and     ecx, esp        ; get address of realignment point
        sub     esp, eax        ; allocate the locals allocation space
        push    esi             ; save callee-saved regs
        push    edi

        ; stack has:
        ;   callee's return addr
        ;   saved EBX   <== EBX
        ;   ... possible padding to align stack ...
        ;   (uninitialized) callee's return addr
        ;   saved EBP   <== EBP (aligned stack location)
        ;   initial EH state index of -1
        ;   handler thunk addr
        ;   ret addr
        ;   saved ECX
        ;   saved value of EBX on exit
        ;   ... possible padding to realign stack ... <== ECX (aligned)
        ;   (uninitialized) local GS security cookie
        ;   locals allocation area
        ;   saved ESI
        ;   saved EDI   <== ESP

        mov     eax, __security_cookie
        xor     eax, ebp        ; generate local EH and GS cookies
        push    eax
        mov     [ecx-4], eax
        mov     ecx, [ebp-16]   ; restore the original ECX
        mov     [ebp-16], esp   ; initialize the EH node's saved ESP field
        mov     eax, [ebx+4]    ; copy callee's return addr above saved EBP
        mov     [ebp+4], eax    ; * so EBP-based stackwalks work better
        push    [ebp-12]        ; move the return address to final position
        mov     eax, fs:[0]     ; set link to next node in EH chain
        mov     [ebp-12], eax

        ; stack has:
        ;   callee's return addr
        ;   saved EBX   <== EBX
        ;   ... possible padding to align stack ...
        ;   callee's return addr
        ;   saved EBP   <== EBP (aligned stack location)
        ;   initial EH state index of -1
        ;   handler thunk addr
        ;   saved FS:[0]
        ;   saved ESP field of EH node
        ;   saved value of EBX on exit
        ;   ... possible padding to realign stack ...
        ;   local GS security cookie
        ;   locals allocation area
        ;   saved ESI
        ;   saved EDI
        ;   local EH security cookie
        ;   ret addr    <== ESP

        lea     eax, [ebp-12]   ; all done - link in the EH node
        mov     fs:[0], eax

        ret
    }
}

/***
*_EH_epilog3_align - Tear down C++ EH call frame variation
*
*Purpose:
*   Destroy a call frame set up by _EH_prolog3_align or _EH_prolog3_catch_align.
*
*Entry:
*   ESP = value it had on return from _EH_prolog3_align or
*         _EH_prolog3_catch_align
*   EBP = value it had on return from _EH_prolog3_align or
*         _EH_prolog3_catch_align
*   EBX = value it had on return from _EH_prolog3_align or
*         _EH_prolog3_catch_align
*
*Exit:
*   ESP = pointer to the callee's return address
*   EBX, ESI, EDI, EBP restored from frame
*   ECX destroyed
*   All other registers except CC preserved
*
*******************************************************************************/

extern void __declspec(naked)
_EH_epilog3_align(
    void
    )
{
    __asm
    {
        mov     ecx, [ebp-12]   ; remove EH node from EH chain
        mov     fs:[0], ecx
        pop     ecx             ; save return address
        pop     edi             ; pop and ignore the EH cookie
        pop     edi             ; restore callee-saves
        pop     esi
        mov     esp, ebp        ; free aligned stack
        pop     ebp             ; restore local frame pointer
        mov     esp, ebx        ; free unaligned stack
        pop     ebx             ; restore parameter frame pointer
        push    ecx             ; push return address
        ret     0
    }
}

/***
*_EH_epilog3_GS_align - Tear down C++ EH call frame variation
*
*Purpose:
*   Destroy a call frame set up by _EH_prolog3_GS_align or
*   _EH_prolog3_catch_align, after first checking that the local /GS security
*   cookie is correct.
*
*   This helper version does not load the cookie itself because it doesn't
*   know where it's located.  It would need to be passed the alignment to know
*   that, so it might as well be passed the cookie value directly.
*
*Entry:
*   ESP = value it had on return from _EH_prolog3_GS
*   EBP = value it had on return from _EH_prolog3_GS
*   EBX = value it had on return from _EH_prolog3_GS
*   ECX = GS cookie from callee's frame
*
*Exit:
*   ESP = pointer to the callee's return address
*   EBX, ESI, EDI, EBP restored from frame
*   ECX destroyed
*   All other registers except CC preserved
*
*******************************************************************************/

extern void __declspec(naked)
_EH_epilog3_GS_align(
    void
    )
{
    __asm
    {
        xor     ecx, ebp                ; rematerialize the global cookie and
        call    __security_check_cookie ; * check its validity
        jmp     _EH_epilog3_align       ; go tear down the frame
    }
}