Re: [PATCH v2 04/12] module: Add printk format to add module build ID to stacktraces

[Petr Mladek]

On Wed 2021-03-24 15:28:43, Stephen Boyd wrote:
> Quoting Rasmus Villemoes (2021-03-24 15:21:34)
> > On 24/03/2021 20.11, Stephen Boyd wrote:
> > > Quoting Rasmus Villemoes (2021-03-24 02:57:13)
> > 
> > >>
> > >> Is there any reason you didn't just make b an optional flag that could
> > >> be specified with or without R? I suppose the parsing is more difficult
> > >> with several orthogonal flags (see escaped_string()), but it's a little
> > >> easier to understand. Dunno, it's not like we're gonna think of 10 other
> > >> things that could be printed for a symbol, so perhaps it's fine.
> > >>
> > > 
> > > I think I follow. So %pSb or %pSRb? If it's easier to understand then
> > > sure. I was trying to avoid checking another character beyond fmt[1] but
> > > it should be fine if fmt[1] is already 'R'.
> 
> I'm inclined to use %pSb and %pSRb. The code looks to simpler and I
> suppose we can worry about different ordering/combination problems if it
> comes to it.
>
> ---8<---
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 41ddc353ebb8..0e94cba5ba20 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -968,6 +968,8 @@ char *symbol_string(char *buf, char *end, void *ptr,
>  #ifdef CONFIG_KALLSYMS
>         if (*fmt == 'B')
>                 sprint_backtrace(sym, value);
> +       else if (*fmt == 'S' && (fmt[1] == 'b' || (fmt[1] == 'R' && fmt[2] == 'b')))
> +               sprint_symbol_stacktrace(sym, value);
>         else if (*fmt != 's')
>                 sprint_symbol(sym, value);
>         else

I prefer the extra "b" flag as well. It helps me to understand and
memorize[*] the meaning.

[*] at least short-time memorize ;-)

Best Regards,
Petr