sdk/lib/crt/except/amd64/chkstk_ms.s

   1 /*
   2  * COPYRIGHT:         See COPYING in the top level directory
   3  * PROJECT:           ReactOS system libraries
   4  * PURPOSE:           Implementation of _chkstk and _alloca_probe
   5  * PROGRAMMERS        Richard Henderson <rth@redhat.com>
   6  *                    Kai Tietz <kai.tietz@onevision.com>
   7  *                    Timo Kreuzer (timo.kreuzer@reactos.org)
   8  */
   9
  10 /* INCLUDES ******************************************************************/
  11
  12 #include <asm.inc>
  13 #define PAGE_SIZE 4096
  14
  15 /* CODE **********************************************************************/
  16 .code64
  17
  18 PUBLIC __chkstk
  19 PUBLIC __alloca_probe
  20
  21 __alloca_probe:
  22 .PROC __chkstk
  23
  24     push rcx                    /* save temps */
  25     .pushreg rcx
  26     push rax
  27     .pushreg rax
  28     .endprolog
  29
  30     cmp rax, PAGE_SIZE          /* > 4k ?*/
  31     lea rcx, [rsp + 24]         /* point past return addr */
  32     jb l_LessThanAPage
  33
  34 l_MoreThanAPage:
  35     sub rcx, PAGE_SIZE          /* yes, move pointer down 4k */
  36     or byte ptr [rcx], 0        /* probe there */
  37     sub rax, PAGE_SIZE          /* decrement count */
  38
  39     cmp rax, PAGE_SIZE
  40     ja l_MoreThanAPage          /* and do it again */
  41
  42 l_LessThanAPage:
  43     sub rcx, rax
  44     or byte ptr [rcx], 0        /* less than 4k, just peek here */
  45
  46     pop rax
  47     pop rcx
  48     ret
  49
  50 .ENDP
  51
  52 END
  53 /* EOF */