[PATCH 2/2] kernel32: Set up a guard page at the bottom of the fiber stack.

[Alexandre Julliard]

Zebediah Figura <zfigura at codeweavers.com> writes:

> @@ -96,16 +98,19 @@ LPVOID WINAPI CreateFiberEx( SIZE_T stack_commit, SIZE_T stack_reserve, DWORD fl
>          return NULL;
>      }
>  
> +    GetSystemInfo(&si);
> +
>      /* FIXME: should use the thread stack allocation routines here */
>      /* some applications try to use more stack than they allocate */
> -    stack_reserve = max(stack_reserve, 1024 * 1024);
> -    if(!(fiber->stack_allocation = VirtualAlloc( 0, stack_reserve, MEM_COMMIT, PAGE_READWRITE )))
> +    stack_reserve = max(stack_reserve, 1024 * 1024 - 3 * si.dwPageSize);
> +    if(!(fiber->stack_allocation = VirtualAlloc( 0, stack_reserve + 3 * si.dwPageSize, MEM_COMMIT, PAGE_READWRITE )))
>      {
>          HeapFree( GetProcessHeap(), 0, fiber );
>          return NULL;
>      }
> -    fiber->stack_base  = (char *)fiber->stack_allocation + stack_reserve;
> -    fiber->stack_limit = fiber->stack_allocation;
> +    VirtualProtect(fiber->stack_allocation, 3 * si.dwPageSize, PAGE_NOACCESS, &prev);
> +    fiber->stack_base  = (char *)fiber->stack_allocation + 3 * si.dwPageSize + stack_reserve;
> +    fiber->stack_limit = (char *)fiber->stack_allocation + 3 * si.dwPageSize;

Like the FIXME says, this should reuse the thread stack allocation
routines, instead of reinventing them.

Currently it's implemented in virtual_alloc_thread_stack(), but this
could be adapted and exported as RtlCreateUserStack().

-- 
Alexandre Julliard
julliard at winehq.org