Re: [PATCH v2 7/8] mmap: Add grub_mmap_get_lowest() and grub_mmap_get_highest()

[ross . philipson]

On 9/19/24 3:02 PM, Sergii Dmytruk wrote:
> From: Daniel Kiper <daniel.kiper@oracle.com>
>
> The functions calculate lowest and highest available RAM
> addresses respectively.

It seems that the functions do a bit more than this. They find the 
lowest and highest values wrt to the limit you pass in. In the case of 
passing a low limit of 0 and a high limit of ~0, it seems the above 
functionality would be achieved. The commit message should reflect this.

Thanks
Ross

> Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
> Signed-off-by: Sergii Dmytruk <sergii.dmytruk@3mdeb.com>
> ---
>   grub-core/mmap/mmap.c | 83 +++++++++++++++++++++++++++++++++++++++++++
>   include/grub/memory.h |  3 ++
>   2 files changed, 86 insertions(+)
>
> diff --git a/grub-core/mmap/mmap.c b/grub-core/mmap/mmap.c
> index c8c8312c5..80d6c60b8 100644
> --- a/grub-core/mmap/mmap.c
> +++ b/grub-core/mmap/mmap.c
> @@ -26,6 +26,7 @@
>   #include <grub/command.h>
>   #include <grub/dl.h>
>   #include <grub/i18n.h>
> +#include <grub/safemath.h>
>   
>   GRUB_MOD_LICENSE ("GPLv3+");
>   
> @@ -343,6 +344,88 @@ grub_mmap_unregister (int handle)
>   
>   #endif /* ! GRUB_MMAP_REGISTER_BY_FIRMWARE */
>   
> +typedef struct
> +{
> +  grub_uint64_t addr;
> +  grub_uint64_t limit;
> +} addr_limit_t;
> +
> +/* Helper for grub_mmap_get_lowest(). */
> +static int
> +lowest_hook (grub_uint64_t addr, grub_uint64_t size, grub_memory_type_t type,
> +             void *data)
> +{
> +  addr_limit_t *al = data;
> +  grub_uint64_t end;
> +
> +  if (type != GRUB_MEMORY_AVAILABLE)
> +    return 0;
> +
> +  if (grub_add (addr, size, &end))
> +    return 0;
> +
> +  if (addr >= al->limit)
> +    al->addr = grub_min (al->addr, addr);
> +
> +  if ((addr < al->limit) && (end > al->limit))
> +    al->addr = al->limit;
> +
> +  return 0;
> +}
> +
> +/*
> + * This function calculates lowest available RAM address that is at or above
> + * the passed limit.  If no RAM exists above the limit, ~0 is returned.
> + */
> +grub_uint64_t
> +grub_mmap_get_lowest (grub_uint64_t limit)
> +{
> +  addr_limit_t al = {~0, limit};
> +
> +  grub_mmap_iterate (lowest_hook, &al);
> +
> +  return al.addr;
> +}
> +
> +/* Helper for grub_mmap_get_highest(). */
> +static int
> +highest_hook (grub_uint64_t addr, grub_uint64_t size, grub_memory_type_t type,
> +              void *data)
> +{
> +  addr_limit_t *al = data;
> +  grub_uint64_t end;
> +
> +  if (type != GRUB_MEMORY_AVAILABLE)
> +    return 0;
> +
> +  if (grub_add (addr, size, &end))
> +    return 0;
> +
> +  if (end < al->limit)
> +    al->addr = grub_max (al->addr, end);
> +
> +  if ((addr < al->limit) && (end >= al->limit))
> +    al->addr = al->limit;
> +
> +  return 0;
> +}
> +
> +/*
> + * This function calculates highest available RAM address that is below the
> + * passed limit.  Returned address is either one byte after last byte of RAM or
> + * equal to limit, whichever is lower.  If no RAM exists below limit, 0 is
> + * returned.
> + */
> +grub_uint64_t
> +grub_mmap_get_highest (grub_uint64_t limit)
> +{
> +  addr_limit_t al = {0, limit};
> +
> +  grub_mmap_iterate (highest_hook, &al);
> +
> +  return al.addr;
> +}
> +
>   #define CHUNK_SIZE    0x400
>   
>   struct badram_entry {
> diff --git a/include/grub/memory.h b/include/grub/memory.h
> index 6da114a1b..8f22f7525 100644
> --- a/include/grub/memory.h
> +++ b/include/grub/memory.h
> @@ -69,6 +69,9 @@ void *grub_mmap_malign_and_register (grub_uint64_t align, 
> grub_uint64_t size,
>   
>   void grub_mmap_free_and_unregister (int handle);
>   
> +extern grub_uint64_t grub_mmap_get_lowest (grub_uint64_t limit);
> +extern grub_uint64_t grub_mmap_get_highest (grub_uint64_t limit);
> +
>   #ifndef GRUB_MMAP_REGISTER_BY_FIRMWARE
>   
>   struct grub_mmap_region