Re: [PATCH] stop_machine: Mark functions as notrace

[Atish Patra]

On Sat, Oct 31, 2020 at 12:42 AM Guo Ren <guoren@xxxxxxxxxx> wrote:
>
> On Sat, Oct 31, 2020 at 8:28 AM Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> >
> > On Fri, 30 Oct 2020 14:47:56 -0700
> > Atish Patra <atishp@xxxxxxxxxxxxxx> wrote:
> >
> > > > Look at arm64, they __kprobes flag and I guess it would also prevent
> > > > ftrace call site.
> > > >
> > >
> > > Are you sure about that ? __kprobes puts the code in .kprobes.text section
> > > which is under whitelist sections in recordmcount.pl & recordmcount.c.
> >
> > Correct, ftrace can trace functions marked with __kprobes. That said,
> I guess wrong, thx for correct me.
>
> > the instruction you are looking at here, is in a file that is
> > blacklisted from recordmcount.
> >
> >   CFLAGS_REMOVE_insn.o = $(CC_FLAGS_FTRACE)
> >
> > All ftrace flags are removed from the compiling of insn.c, and every
> > function in that file will not be traced.
> Yes, arm64 prevents the whole file from ftrace. My patch just use
> notrace flag setting on some functions.
>
> @Atish How do think:
> CFLAGS_REMOVE_cacheflush.o = $(CC_FLAGS_FTRACE)
> CFLAGS_REMOVE_sbi.o = $(CC_FLAGS_FTRACE)
>

Looks good to me. What should be done for copy_to_kernel_nofault ?
That is also in the calling path.

> --
> Best Regards
>  Guo Ren
>
> ML: https://lore.kernel.org/linux-csky/



-- 
Regards,
Atish