Re: [PATCH 0/1] MR5333: vcruntime140_1: Pass original frame to catch block on stack.

[Piotr Caban (＠piotr)]

Piotr Caban (@piotr) commented about dlls/msvcrt/handler4.c:
> }
>
> +typedef void* (__cdecl *handler_function)(ULONG64, ULONG64);
> +void* __cdecl catch_block_wrapper(handler_function handler, ULONG64 frame);
> +__ASM_GLOBAL_FUNC( catch_block_wrapper,
> -
>               "subq $0x28,%rsp\n\t"
> -
>               __ASM_CFI(".cfi_adjust_cfa_offset 0x28\n\t")
> -
>               __ASM_SEH(".seh_stackalloc 0x28\n\t")
> -
>               __ASM_SEH(".seh_endprologue\n\t")
> -
>               "movq %rcx, %rax\n\t"
> -
>               "movq %rdx, 0x10(%rsp)\n\t"  /* pass frame on stack in addition to register */
> -
>               "xorq %rcx, %rcx\n\t"
> -
>               "callq *%rax\n\t"            /* call catch(0, frame) */
> -
>               "addq $0x28,%rsp\n\t"
> -
>               __ASM_CFI(".cfi_adjust_cfa_offset -0x28\n\t")
> -
>               "ret")

While I don't understand why native works this way the patch looks good for me. I have injected custom catch handler so I can use it to obtain some information about how handler is called. I think it would be good to change other differences I've seen this way:
 - native executes handler with following parameters: handler(handler, frame)
 - we should copy more data to the stack

```suggestion:-11+0
__ASM_GLOBAL_FUNC( catch_block_wrapper,
                   "subq $0x28,%rsp\n\t"
                   __ASM_CFI(".cfi_adjust_cfa_offset 0x28\n\t")
                   __ASM_SEH(".seh_stackalloc 0x28\n\t")
                   __ASM_SEH(".seh_endprologue\n\t")
                   "movq %rcx, 0x0(%rsp)\n\t"
                   "movl $0x100, 0x8(%rsp)\n\t"
                   "movq %rdx, 0x10(%rsp)\n\t"  /* pass frame on stack in addition to register */
                   "callq *%rax\n\t"            /* call catch(catch, frame) */
                   "addq $0x28,%rsp\n\t"
                   __ASM_CFI(".cfi_adjust_cfa_offset -0x28\n\t")
                   "ret")
```