.global ___chkstk
.global __alloca
.section .text
___chkstk:
__alloca:
pushl %ecx /* save temp */
leal 8(%esp), %ecx /* point past return addr */
cmpl $0x1000, %eax /* > 4k ?*/
jb Ldone
Lprobe:
subl $0x1000, %ecx /* yes, move pointer down 4k*/
orl $0x0, (%ecx) /* probe there */
subl $0x1000, %eax /* decrement count */
cmpl $0x1000, %eax
ja Lprobe /* and do it again */
Ldone:
subl %eax, %ecx
orl $0x0, (%ecx) /* less than 4k, just peek here */
movl %esp, %eax /* save old stack pointer */
movl %ecx, %esp /* decrement stack */
movl (%eax), %ecx /* recover saved temp */
movl 4(%eax), %eax /* recover return address */
/* Push the return value back. Doing this instead of just
jumping to %eax preserves the cached call-return stack
used by most modern processors. */
pushl %eax
ret