sys/i386/i386/exception.s RELENG_4 help to understand several lines

[Andrey Simonenko]

Hi,

Help me to understand several lines from RELENG_4
src/sys/i386/i386/exception.s,v 1.65.2.3 file:

   214	calltrap:
   215		FAKE_MCOUNT(_btrap)		/* init "from" _btrap -> calltrap */
   216		MPLOCKED incl _cnt+V_TRAP
   217		MP_LOCK
   218		movl	_cpl,%ebx		/* keep orig. cpl here during trap() */
   219		call	_trap
      	
   220		/*
   221		 * Return via _doreti to handle ASTs.  Have to change trap frame
   222		 * to interrupt frame.
   223		 */
   224		pushl	%ebx			/* cpl to restore */
   225		subl	$4,%esp			/* dummy unit to finish intr frame */
   226		incb	_intr_nesting_level
   227		MEXITCOUNT
   228		jmp	_doreti

Is everything correct with 218, 219 and 224 lines (or comments are wrong)?

I checked several places in exception.s and vm86bios.s in sys/i386/i386/
and in all places _cpl is saved in the stack, trap() need frame{} in the
stack, so here we can't put _cpl into stack, but it is unclear for
me how above listed lines works.

How can %ebx contain saved _cpl after trap()?

TIA