Re: [PATCH 17/19] [not for merge] print more debug info in mm

[Daniel Kiper]

CC-ing Glenn...

On Tue, Oct 12, 2021 at 06:30:06PM +1100, Daniel Axtens wrote:
> This is handy for debugging - I'm including it in case anyone else hacking
> on this area finds it helpful.
>
> Signed-off-by: Daniel Axtens <dja@axtens.net>
> ---
>  grub-core/kern/mm.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/grub-core/kern/mm.c b/grub-core/kern/mm.c
> index 58d5b89e8860..811df1ab5ebb 100644
> --- a/grub-core/kern/mm.c
> +++ b/grub-core/kern/mm.c
> @@ -135,6 +135,9 @@ grub_mm_init_region (void *addr, grub_size_t size)
>    for (p = &grub_mm_base, q = *p; q; p = &(q->next), q = *p)
>      {
>        /* Does this region come _before_ an existing region? */
> +      grub_printf ("Extending w/ before %p + %" PRIxGRUB_SIZE " + %" 
> PRIxGRUB_SIZE " = %p ? %s\n",
> +              (grub_uint8_t *)addr, size, q->pre_size, (grub_uint8_t *)q,
> +              (grub_uint8_t *)addr + size + q->pre_size == (grub_uint8_t *) 
> q ? "yes" : "no");

I think this kind of messages can be useful. Same applies to patch #18.
Though I would use grub_dprintf() instead which should be wrapped with
#ifdef MM_DEBUG. However, we have to be very careful with printing any
messages from mm and do not exeecec 255 chars message length. If we go
above that limit then we will trigger dynamic allocation in grub_dprintf()
from mm which may lead to a recursion...

Additionally, I think Glenn's patch allowing us to disable logging from
certain subsystem would be useful here. Glenn, could you take a look at
it once again?

Daniel