Re: [PATCH 4/9] kern/ieee1275/init: ppc64: Check early for sufficiently large chunk

[Daniel Kiper]

On Tue, Oct 31, 2023 at 01:50:26PM -0400, Stefan Berger wrote:
> If a single memory block is requested (GRUB_MM_ADD_REGION_CONSECUTIVE)
> then check early on whether the given block from the memory map is
> big enough to satisfy the request.
>
> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
> Cc: Hari Bathini <hbathini@linux.ibm.com>
> Cc: Pavithra Prakash <pavrampu@in.ibm.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Carolyn Scherrer <cpscherr@us.ibm.com>
> Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
> Cc: Sourabh Jain <sourabhjain@linux.ibm.com>
> ---
>  grub-core/kern/ieee1275/init.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/grub-core/kern/ieee1275/init.c b/grub-core/kern/ieee1275/init.c
> index e09db4192..a0ce9d55e 100644
> --- a/grub-core/kern/ieee1275/init.c
> +++ b/grub-core/kern/ieee1275/init.c
> @@ -328,6 +328,10 @@ regions_claim (grub_uint64_t addr, grub_uint64_t len, 
> grub_memory_type_t type,
>    if (type != GRUB_MEMORY_AVAILABLE)
>      return 0;
>
> +  /* If a specific size was requested: is this chunk big enough? */
> +  if (rcr->flags & GRUB_MM_ADD_REGION_CONSECUTIVE && len < rcr->total)
> +    return 0;

Do we really need that? Same check is a few lines below. If we need both
checks the commit message should explain why. And I would add comments
before ifs explaining what they do and why they are needed/different/...

Daniel