in mm/fault.c [46:59]
static int store_updates_sp(struct pt_regs *regs)
{
unsigned int inst;
if (get_user(inst, (unsigned int __user *)regs->pc))
return 0;
/* check for 1 in the rD field */
if (((inst >> 21) & 0x1f) != 1)
return 0;
/* check for store opcodes */
if ((inst & 0xd0000000) == 0xd0000000)
return 1;
return 0;
}