Re: [PATCH v4 01/15] stacktrace/x86: add function for detecting reliable stack traces

Josh Poimboeuf
2017-01-27T17:19:19Z

On Fri, Jan 27, 2017 at 09:47:08AM +0100, Miroslav Benes wrote:
>
> > diff --git a/include/linux/stacktrace.h b/include/linux/stacktrace.h
> > index 0a34489..8e8b67b 100644
> > --- a/include/linux/stacktrace.h
> > +++ b/include/linux/stacktrace.h
> > @@ -18,6 +18,8 @@ extern void save_stack_trace_regs(struct pt_regs *regs,
> > struct stack_trace *trace);
> > extern void save_stack_trace_tsk(struct task_struct *tsk,
> > struct stack_trace *trace);
> > +extern int save_stack_trace_tsk_reliable(struct task_struct *tsk,
> > + struct stack_trace *trace);
> >
> > extern void print_stack_trace(struct stack_trace *trace, int spaces);
> > extern int snprint_stack_trace(char *buf, size_t size,
> > @@ -29,12 +31,12 @@ extern void save_stack_trace_user(struct stack_trace *trace);
> > # define save_stack_trace_user(trace) do { } while (0)
> > #endif
> >
> > -#else
> > +#else /* !CONFIG_STACKTRACE */
> > # define save_stack_trace(trace) do { } while (0)
> > # define save_stack_trace_tsk(tsk, trace) do { } while (0)
> > # define save_stack_trace_user(trace) do { } while (0)
> > # define print_stack_trace(trace, spaces) do { } while (0)
> > # define snprint_stack_trace(buf, size, trace, spaces) do { } while (0)
>
> Is there a reason you did not define empty save_stack_trace_tsk_reliable()
> here? Right, it should not be needed now as livepatching is the only user,
> but still.

Agreed, thanks. I'll make the stub return an error, since an empty
stack trace isn't very reliable.

--
Josh