Re: [RFC PATCH v2 4/6] tracing/fprobe: Enable fprobe events with CONFIG_DYNAMIC_FTRACE_WITH_ARGS

[Masami Hiramatsu (Google) <mhiramat@kernel.org>]

On Wed, 9 Aug 2023 17:38:00 +0200
Florent Revest <revest@chromium.org> wrote:

> On Wed, Aug 9, 2023 at 4:45 PM Masami Hiramatsu <mhiramat@kernel.org> wrote:
> > > > --- a/kernel/trace/trace_fprobe.c
> > > > +++ b/kernel/trace/trace_fprobe.c
> > > > @@ -132,25 +132,30 @@ static int
> > > >  process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
> > > >                    void *base)
> > > >  {
> > > > -       struct pt_regs *regs = rec;
> > > > -       unsigned long val;
> > > > +       struct ftrace_regs *fregs = rec;
> > > > +       unsigned long val, *stackp;
> > > >         int ret;
> > > >
> > > >  retry:
> > > >         /* 1st stage: get value from context */
> > > >         switch (code->op) {
> > > >         case FETCH_OP_STACK:
> > > > -               val = regs_get_kernel_stack_nth(regs, code->param);
> > > > +               stackp = (unsigned long *)ftrace_regs_get_stack_pointer(fregs);
> > > > +               if (((unsigned long)(stackp + code->param) & ~(THREAD_SIZE - 1)) ==
> > > > +                   ((unsigned long)stackp & ~(THREAD_SIZE - 1)))
> > >
> > > Maybe it'd be worth extracting a local
> > > "ftrace_regs_get_kernel_stack_nth_addr" helper function and/or
> > > "ftrace_regs_within_kernel_stack" ?
> >
> > Yeah, maybe we can make it a generic inline function in linux/ftrace.h.
> 
> Or even just above this function if there are low chances it would get
> used elsewhere :)

Thanks, but since regs_get_kernel_stack_nth() is defined in asm/ptrace.h,
I think ftrace_regs_get_kernel_stack_nth() is better defined in
linux/ftrace.h. :)

Thank you!

-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>