syscall trace at kernel land

[mohit verma]

thanks  rajat,
and of course mulyadi , sorry for the confusion.
@ mulyadi : u got me right as u always do. :)
except system dependencies is there anything which should be taken care of
before implementing this  task??

On Tue, Jan 11, 2011 at 3:40 PM, Rajat Sharma <fs.rajat at gmail.com> wrote:

> > is there any procedure in kernel to check for the interrupt vector number
> which caused it to be invoked?
> Its actually very architecture dependent, on x86, its 'int $0x80'
> which causes user space to call system calls handlers. Recent intel
> architectures have callgate mechanism to enter into system call, look
> for sysenter instruction.
> Anyways, are you interested in interrupt number or the system call number?
>
> > i mean like one of my friends said that when  kernel is about to restart
> a
> > syscall then it raises signal -ERESTARTSYS signal for signal handler.
>
> Thats totally wrong. Like any other error code, its just an error code
> which waiting API return if process was interrupted while waiting on
> semaphore, e.g.
>
> rc = wait_event_inetrruptible(..);
> if (rc == -ERESTARTSYS) {
>    /*
>     * your driver should take corrective measure, may be to retry the
> code path again,
>     * or do some error recovery and send appropriate error code to user
> space.
>     * Note that conventionally -ERESTARTSYS should never be returned
> to user space
>     */
> }
>
> Although name is misleading, its an internal kernel error and is not
> at all related to system call restart.
>
> Rajat
>
> On Tue, Jan 11, 2011 at 1:09 PM, Mulyadi Santosa
> <mulyadi.santosa at gmail.com> wrote:
> > just to avoid confusion 1st...
> >
> > On Tue, Jan 11, 2011 at 14:06, mohit verma <mohit89mlnc at gmail.com>
> wrote:
> >> i mean like one of my friends said that when  kernel is about to restart
> a
> >> syscall then it raises signal -ERESTARTSYS signal for signal handler.
> but i
> >> think it is for
> >> something went wrong and kernel wanna start the syscall again. but in
> >> between a syscall  routine is it possible to get vector number (i repeat
> >> ,sorry) ??
> >
> > allow me to rephrase it: if an interrupt crosses by during the
> > execution of that code path, you wanna find out the interrupt number?
> >
> > --
> > regards,
> >
> > Mulyadi Santosa
> > Freelance Linux trainer and consultant
> >
> > blog: the-hydra.blogspot.com
> > training: mulyaditraining.blogspot.com
> >
> > _______________________________________________
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> >
>



-- 
........................
*MOHIT VERMA*
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