Re: [PATCH 09/10] kern: Make it possible to subtract conditions from debug=

[Daniel Kiper]

On Fri, Mar 13, 2020 at 08:16:59PM +0100, Javier Martinez Canillas wrote:
> From: Peter Jones <address@hidden>
>
> This makes it so you can do set debug to "all,-scripting,-lexer" and get the
> obvious outcome.  Any negation present will take preference over that
> conditional, so "all,-scripting,scripting" is the same thing as
> "all,-scripting".
>
> Signed-off-by: Peter Jones <address@hidden>
> Signed-off-by: Javier Martinez Canillas <address@hidden>
>
> ---
>
>  grub-core/kern/misc.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/grub-core/kern/misc.c b/grub-core/kern/misc.c
> index ce92ddd076d..e5fd8c1915f 100644
> --- a/grub-core/kern/misc.c
> +++ b/grub-core/kern/misc.c
> @@ -162,12 +162,24 @@ int
>  grub_debug_enabled (const char * condition)
>  {
>    const char *debug;
> +  char *negcond;
> +  int negated = 0;
>
>    debug = grub_env_get ("debug");
>    if (!debug)
>      return 0;
>
> -  if (grub_strword (debug, "all") || grub_strword (debug, condition))
> +  negcond = grub_zalloc (grub_strlen (condition) + 2);

I would use grub_malloc() here and zero last char... And in general
I would try to avoid grub_malloc()/grub_free(). Static buffer? This
is part of debug function and calling into memory allocator can have
bad impact on debugging capabilities. So, it has to be simple as much
as possible.

> +  if (negcond)
> +    {
> +      grub_strcpy (negcond, "-");

         *negcond = '-';

The function can be called thousand times. So, this change can matter here.

> +      grub_strcpy (negcond+1, condition);

                      negcond + 1

Or we can avoid copying at all by using grub_strword((debug, condition)
and checking backwards for "-". Or maybe /,[ \t]*-/ (perlre)...

> +      negated = grub_strword (debug, negcond);
> +      grub_free (negcond);
> +    }
> +
> +  if (!negated &&
> +      (grub_strword (debug, "all") || grub_strword (debug, condition)))
>      return 1;
>
>    return 0;

Daniel