On Fri, May 31, 2019 at 02:25:15PM +0200, Miroslav Benes wrote:
> On Fri, 31 May 2019, Petr Mladek wrote:
>
> > WARN_ONCE() in the generic save_stack_trace_tsk_reliable() is superfluous.
> >
> > The information is passed also via the return value. The only current
> > user klp_check_stack() writes its own warning when the reliable stack
> > traces are not supported. Other eventual users might want its own error
> > handling as well.
> >
> > Signed-off-by: Petr Mladek <pmladek@xxxxxxxx>
> > Acked-by: Miroslav Benes <mbenes@xxxxxxx>
> > Reviewed-by: Kamalesh Babulal <kamalesh@xxxxxxxxxxxxxxxxxx>
> > ---
> > kernel/stacktrace.c | 1 -
> > 1 file changed, 1 deletion(-)
> >
> > diff --git a/kernel/stacktrace.c b/kernel/stacktrace.c
> > index 5667f1da3ede..8d088408928d 100644
> > --- a/kernel/stacktrace.c
> > +++ b/kernel/stacktrace.c
> > @@ -259,7 +259,6 @@ __weak int
> > save_stack_trace_tsk_reliable(struct task_struct *tsk,
> > struct stack_trace *trace)
> > {
> > - WARN_ONCE(1, KERN_INFO "save_stack_tsk_reliable() not implemented yet.\n");
> > return -ENOSYS;
> > }
>
> Do we even need the weak function now after Thomas' changes to
> kernel/stacktrace.c?
>
> - livepatch is the only user and it calls stack_trace_save_tsk_reliable()
> - x86 defines CONFIG_ARCH_STACKWALK and CONFIG_HAVE_RELIABLE_STACKTRACE,
> so it has stack_trace_save_tsk_reliable() implemented and it calls
> arch_stack_walk_reliable()
> - powerpc defines CONFIG_HAVE_RELIABLE_STACKTRACE and does not have
> CONFIG_ARCH_STACKWALK. It also has stack_trace_save_tsk_reliable()
> implemented and it calls save_stack_trace_tsk_reliable(), which is
> implemented in arch/powerpc/
> - all other archs do not have CONFIG_HAVE_RELIABLE_STACKTRACE and there is
> stack_trace_save_tsk_reliable() returning ENOSYS for these cases in
> include/linux/stacktrace.c
I think you're right. stack_trace_save_tsk_reliable() in stacktrace.h
returning -ENOSYS serves the same purpose as the old weak version of
save_stack_trace_tsk_reliable() which is no longer called directly.
--
Josh
