Re: [Xen-devel] [PATCH 1/5] xen: add tainted state and show warning is gcov is enabled

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Sep 02, 2016 at 05:56:49AM -0600, Jan Beulich wrote:
> >>> On 02.09.16 at 13:47, <wei.liu2@xxxxxxxxxx> wrote:
> 
> Since this is a config option - why bother issuing a warning and
> tainting the hypervisor?
> 

Because there isn't a clear indicator if gcov is enabled.

I think it would be valuable to just tell from the backtrace or console
log that gcov is enabled, then we can legitimately refuse to provide
(security) support for such builds.

> > --- a/xen/common/gcov/gcov.c
> > +++ b/xen/common/gcov/gcov.c
> > @@ -23,6 +23,11 @@
> >  #include <public/xen.h>
> >  #include <public/gcov.h>
> >  
> > +const char __initconst warning_gcov[] =
> > +    "WARNING: GCOV SUPPORT IS ENABLED\n"
> > +    "This option is *ONLY* intended to aid testing of Xen.\n"
> > +    "Please *DO NOT* use this in production.\n";
> 
> Note the type (const) difference between this and ...
> 
> > --- a/xen/drivers/char/console.c
> > +++ b/xen/drivers/char/console.c
> > @@ -792,6 +792,10 @@ void __init console_init_postirq(void)
> >      console_init_ring();
> >  }
> >  
> > +#ifdef CONFIG_GCOV
> > +extern char warning_gcov[];
> > +#endif
> 
> ... this. That's one of the reasons declarations of stuff defined in
> C sources should be put in a header, which then gets included by
> both producer and consumer(s). But ...
> 
> > @@ -802,6 +806,11 @@ void __init console_endboot(void)
> >          printk(" (Rate-limited: %s)", 
> > loglvl_str(xenlog_guest_upper_thresh));
> >      printk("\n");
> >  
> > +#ifdef CONFIG_GCOV
> > +    warning_add(warning_gcov);
> > +    add_taint(TAINT_GCOV);
> > +#endif
> 
> ... (if we want this in the first place) how about
> 
> #ifdef CONFIG_GCOV
>     {
>         static const char __initconst warning_gcov[] = "...";
> 
>         warning_add(warning_gcov);
>         add_taint(TAINT_GCOV);
>     }
> #endif
> 

Fine with me.

Wei.

> Jan
> 

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