lkml.org 
[lkml]   [2009]   [Jun]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 2/2] convert to syscall tracepoints

* Jason Baron <jbaron@redhat.com> wrote:

> On Mon, Jun 08, 2009 at 10:40:56PM +0200, Ingo Molnar wrote:
> > * Jason Baron <jbaron@redhat.com> wrote:
> >
> > > +#ifdef __NR_time
> > > +trace_event_syscall(1, time, time_t __user *, tloc);
> > > +#endif
> > > +
> > > +#ifdef __NR_stime
> > > +trace_event_syscall(1, stime, time_t __user *, tptr);
> > > +#endif
> > > +
> > > +#ifdef __NR_gettimeofday
> > > +trace_event_syscall(2, gettimeofday, struct timeval __user *, tv, struct timezone __user *, tz);
> > > +#endif
> >
> > This could be reduced to a single line: just add a Kconfig entry
> > (say TRACE_SYSCALL_TRACEPOINTS) wether an arch supports syscall
> > tracepoints, enable it on a sane arch, make sure it has all the
> > syscalls and list them ...
> >
> > As more architectures turn on SYSCALL_TRACEPOINTS, they'll have to
> > resolve any deviations in syscall entry points. Ideally we'd have
> > one generic table that covers 95% of all syscalls, and the remaining
> > 5% in some architecture specific #ifdef section.
> >
>
> true, but this implementation works for all arches now, why would
> want to slowly add this over time? [...]

Because the current solution is butt-ugly ...

> [...] I think its unnecessary work that could be error prone.

This area needs cleanups - making it messier doesnt help. (I've
Cc:-ed hpa - he has expressed interest in auto-generating all the
syscall related details from another angle ...)

> > But, more generally, i'm not at all convinced that we need _any_
> > of this enumeration. Look how much the above lines duplicate
> > DEFINE_SYSCALL macros. Why arent those macros re-used?
>
> The DEFINE_SYSCALL() are located all over the code in various .c files.

yes, and that's good.

> Thus, if we define the tracpoints via the DEFINE_SYSCALL() macros
> we are going to have 'static inline functions' (which is how
> tracepoints are implemented) defined in all these .c files. Now, I
> need to call all these 'static inline functions' from ptrace.c.
> How do I do that? [...]

And that's bad.

We dont want a per syscall tracepoint call site. AT ALL.

We want to collect the record information, we want to construct
/debug/tracing/events/syscalls/ directories with all the proper
tracepoint-lookalike entries, and then we want to use the
_existing_, _zero overhead_ method implemented by Frederic to get
per syscall functionality.

Have you looked at how the syscall attributes information is
constructed by using .section tricks? See:
kernel/trace/trace_syscalls.c.

Ingo


\
 
 \ /
  Last update: 2009-06-08 23:29    [W:0.092 / U:0.064 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site