On Wed, Jun 23, 2010 at 11:26:26AM -0400, Steven Rostedt wrote:
> On Wed, 2010-06-23 at 20:02 +1000, Ian Munsie wrote:
> > From: Jason Baron <jba...@redhat.com>
> >
> > Add core support to event tracing for compat syscalls. The basic idea is
> > that we
> > check if we have a compat task via 'is_compat_task()'. If so, we lookup in
> > the
> > new compat_syscalls_metadata table, the corresponding struct
> > syscall_metadata, to
> > check syscall arguments and whether or not we are enabled.
> >
> > Signed-off-by: Jason Baron <jba...@redhat.com>
> > Signed-off-by: Ian Munsie <imun...@au1.ibm.com>
> > ---
> > include/linux/compat.h | 2 +
> > include/trace/syscall.h | 4 ++
> > kernel/trace/trace.h | 2 +
> > kernel/trace/trace_syscalls.c | 86
> > +++++++++++++++++++++++++++++++++++++----
> > 4 files changed, 86 insertions(+), 8 deletions(-)
> >
> > diff --git a/include/linux/compat.h b/include/linux/compat.h
> > index ab638e9..a94f13d 100644
> > --- a/include/linux/compat.h
> > +++ b/include/linux/compat.h
> > @@ -363,6 +363,8 @@ extern ssize_t compat_rw_copy_check_uvector(int type,
> >
> > #else /* CONFIG_COMPAT */
> >
> > +#define NR_syscalls_compat 0
> > +
> > static inline int is_compat_task(void)
> > {
> > return 0;
> > diff --git a/include/trace/syscall.h b/include/trace/syscall.h
> > index 75f3dce..67d4e64 100644
> > --- a/include/trace/syscall.h
> > +++ b/include/trace/syscall.h
> > @@ -22,6 +22,7 @@
> > struct syscall_metadata {
> > const char *name;
> > int syscall_nr;
> > + int compat_syscall_nr;
>
> This is also bloating the kernel. I don't like to add fields to the
> syscall_metadata lightly.
>
> You're adding 4 more bytes to this structure to handle a few items. Find
> a better way to do this.
This is for cases when the compat and normal handlers are the same.
I haven't checked whether such case happen enough to make this a
benefit. I suspect it's not. Moreover I guess this adds more
complexity to the code.
May be this should be simply dropped.
> > int nb_args;
> > const char **types;
> > const char **args;
> > @@ -38,6 +39,9 @@ struct syscall_metadata {
> >
> > #ifdef CONFIG_FTRACE_SYSCALLS
> > extern unsigned long arch_syscall_addr(int nr);
> > +#ifdef CONFIG_COMPAT
> > +extern unsigned long arch_compat_syscall_addr(int nr);
> > +#endif
> > extern int init_syscall_trace(struct ftrace_event_call *call);
> >
> > extern int reg_event_syscall_enter(struct ftrace_event_call *call);
> > diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> > index 01ce088..53ace4b 100644
> > --- a/kernel/trace/trace.h
> > +++ b/kernel/trace/trace.h
> > @@ -79,12 +79,14 @@ enum trace_type {
> > struct syscall_trace_enter {
> > struct trace_entry ent;
> > int nr;
> > + int compat;
>
> You're adding 4 bytes to a trace (taking up precious buffer space) for a
> single flag. If anything, set the 31st bit of nr if it is compat.
That too can be dropped I think. compat syscalls and normal syscalls are
different events, so the difference can be made in the event id or name.
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