On Mon, Mar 28, 2022 at 05:22:28PM +1100, Daniel Axtens wrote:
> On x86_64-efi (at least) regions seem to be added from top down. The mm
> code will merge a new region with an existing region that comes
> immediately before the new region. This allows larger allocations to be
> satisfied that would otherwise be the case.
>
> On powerpc-ieee1275, however, regions are added from bottom up. So if
> we add 3x 32MB regions, we can still only satisfy a 32MB allocation,
> rather than the 96MB allocation we might otherwise be able to satisfy.
>
> * Define 'post_size' as being bytes lost to the end of an allocation
> due to being given weird sizes from firmware that are not multiples
> of GRUB_MM_ALIGN.
>
> * Allow merging of regions immediately _after_ existing regions, not
> just before. As with the other approach, we create an allocated
> block to represent the new space and the pass it to grub_free() to
> get the metadata right.
>
> Tested-by: Stefan Berger <stef...@linux.ibm.com>
This tag should be added by Stefan in a reply to the email(s) send to
the grub-devel. Though I will accept it this time. And it should be
behind SOB.
> Signed-off-by: Daniel Axtens <d...@axtens.net>
Reviewed-by: Daniel Kiper <daniel.ki...@oracle.com>
But there some nits below...
> ---
> v2: Thanks Daniel K for feedback.
> ---
> grub-core/kern/mm.c | 123 +++++++++++++++++++++++---------------
> include/grub/mm_private.h | 9 +++
> 2 files changed, 85 insertions(+), 47 deletions(-)
>
> diff --git a/grub-core/kern/mm.c b/grub-core/kern/mm.c
> index 079c28da7cdf..94e78f9a910d 100644
> --- a/grub-core/kern/mm.c
> +++ b/grub-core/kern/mm.c
> @@ -130,53 +130,81 @@ grub_mm_init_region (void *addr, grub_size_t size)
>
> /* Attempt to merge this region with every existing region */
> for (p = &grub_mm_base, q = *p; q; p = &(q->next), q = *p)
> - /*
> - * Is the new region immediately below an existing region? That
> - * is, is the address of the memory we're adding now (addr) + size
> - * of the memory we're adding (size) + the bytes we couldn't use
> - * at the start of the region we're considering (q->pre_size)
> - * equal to the address of q? In other words, does the memory
> - * looks like this?
> - *
> - * addr q
> - * |----size-----|-q->pre_size-|<q region>|
> - */
> - if ((grub_uint8_t *) addr + size + q->pre_size == (grub_uint8_t *) q)
> - {
> - /*
> - * Yes, we can merge the memory starting at addr into the
> - * existing region from below. Align up addr to GRUB_MM_ALIGN
> - * so that our new region has proper alignment.
> - */
> - r = (grub_mm_region_t) ALIGN_UP ((grub_addr_t) addr, GRUB_MM_ALIGN);
> - /* Copy the region data across */
> - *r = *q;
> - /* Consider all the new size as pre-size */
> - r->pre_size += size;
> -
> - /*
> - * If we have enough pre-size to create a block, create a
> - * block with it. Mark it as allocated and pass it to
> - * grub_free (), which will sort out getting it into the free
> - * list.
> - */
> - if (r->pre_size >> GRUB_MM_ALIGN_LOG2)
> - {
> - h = (grub_mm_header_t) (r + 1);
> - /* block size is pre-size converted to cells */
> - h->size = (r->pre_size >> GRUB_MM_ALIGN_LOG2);
> - h->magic = GRUB_MM_ALLOC_MAGIC;
> - /* region size grows by block size converted back to bytes */
> - r->size += h->size << GRUB_MM_ALIGN_LOG2;
> - /* adjust pre_size to be accurate */
> - r->pre_size &= (GRUB_MM_ALIGN - 1);
> - *p = r;
> - grub_free (h + 1);
> - }
> - /* Replace the old region with the new region */
> - *p = r;
> - return;
> - }
> + {
> + /*
> + * Is the new region immediately below an existing region? That
> + * is, is the address of the memory we're adding now (addr) + size
> + * of the memory we're adding (size) + the bytes we couldn't use
> + * at the start of the region we're considering (q->pre_size)
> + * equal to the address of q? In other words, does the memory
> + * looks like this?
> + *
> + * addr q
> + * |----size-----|-q->pre_size-|<q region>|
> + */
> + if ((grub_uint8_t *) addr + size + q->pre_size == (grub_uint8_t *) q)
> + {
> + /*
> + * Yes, we can merge the memory starting at addr into the
> + * existing region from below. Align up addr to GRUB_MM_ALIGN
> + * so that our new region has proper alignment.
> + */
> + r = (grub_mm_region_t) ALIGN_UP ((grub_addr_t) addr,
> GRUB_MM_ALIGN);
> + /* Copy the region data across */
> + *r = *q;
> + /* Consider all the new size as pre-size */
> + r->pre_size += size;
> +
> + /*
> + * If we have enough pre-size to create a block, create a
> + * block with it. Mark it as allocated and pass it to
> + * grub_free (), which will sort out getting it into the free
> + * list.
> + */
> + if (r->pre_size >> GRUB_MM_ALIGN_LOG2)
> + {
> + h = (grub_mm_header_t) (r + 1);
> + /* block size is pre-size converted to cells */
> + h->size = (r->pre_size >> GRUB_MM_ALIGN_LOG2);
> + h->magic = GRUB_MM_ALLOC_MAGIC;
> + /* region size grows by block size converted back to bytes */
> + r->size += h->size << GRUB_MM_ALIGN_LOG2;
> + /* adjust pre_size to be accurate */
> + r->pre_size &= (GRUB_MM_ALIGN - 1);
> + *p = r;
> + grub_free (h + 1);
> + }
> + /* Replace the old region with the new region */
> + *p = r;
> + return;
> + }
> +
> + /*
> + * Is the new region immediately above an existing region? That
> + * is:
> + * q addr
> + * |<q region>|-q->post_size-|----size-----|
> + */
> + if ((grub_uint8_t *)q + sizeof(*q) + q->size + q->post_size ==
> + (grub_uint8_t *) addr)
> + {
> + /*
> + * Yes! Follow a similar pattern to above, but simpler.
> + * Our header starts at address - post_size, which should align us
> + * to a cell boundary.
> + */
> + h = (grub_mm_header_t) ((grub_uint8_t *)addr - q->post_size);
> + /* our size is the allocated size plus post_size, in cells */
> + h->size = (size + q->post_size) >> GRUB_MM_ALIGN_LOG2;
> + h->magic = GRUB_MM_ALLOC_MAGIC;
> + /* region size grows by block size converted back to bytes */
> + q->size += h->size << GRUB_MM_ALIGN_LOG2;
> + /* adjust new post_size to be accurate */
Comments and code are incorrectly aligned...
Anyway, I can fix this before committing.
Daniel
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