Got it, many thanks ;-)
On Fri, Aug 8, 2008 at 2:53 AM, Johannes Weiner <[EMAIL PROTECTED]> wrote:
> Hi,
>
> ZelluX <[EMAIL PROTECTED]> writes:
>
> > In Linux Kernel 2.6.11, the switch_to macro is defined as follows(on x86
> > platform)
> >
> > 15#define switch_to(prev,next,last) do {
> \
> > 16 unsigned long esi,edi;
> \
> > 17 asm volatile("pushfl\n\t"
> \
> > 18 "pushl %%ebp\n\t"
> \
> > 19 "movl %%esp,%0\n\t" /* save ESP */
> \
> > 20 "movl %5,%%esp\n\t" /* restore ESP */
> \
> > 21 "movl $1f,%1\n\t" /* save EIP */
> \
> > 22 "pushl %6\n\t" /* restore EIP */
> \
> > 23 "jmp __switch_to\n"
> \
> > 24 "1:\t"
> \
> > 25 "popl %%ebp\n\t"
> \
> > 26 "popfl"
> \
> > 27 :"=m" (prev->thread.esp),"=m" (prev->thread.eip),
> \
> > 28 "=a" (last),"=S" (esi),"=D" (edi)
> \
> > 29 :"m" (next->thread.esp),"m" (next->thread.eip),
> \
> > 30 "2" (prev), "d" (next));
> \
> > 31} while (0)
> >
> > In the middle of the code there's a movl instruction
> > 21 "movl $1f,%1\n\t" /* save EIP
> > */ \
> >
> > which saves the address labeled 1 in prev->thread.eip as ULK points out.
> >
> > My question is why there's an f after $1? Is there any specification to
> > this grammar?
>
> It specifies that the address referred to is further down the code
> sequence. If it would be before the movl, it'd be 1b.
>
> Hannes
>
