From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: Daniel Axtens Date: Thu, 21 Apr 2022 15:24:15 +1000 Subject: [PATCH] mm: When adding a region, merge with region after as well as before 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. Signed-off-by: Daniel Axtens Tested-by: Stefan Berger Reviewed-by: Daniel Kiper Tested-by: Patrick Steinhardt (cherry picked from commit 052e6068be622ff53f1238b449c300dbd0a8abcd) --- grub-core/kern/mm.c | 128 +++++++++++++++++++++++++++++----------------- include/grub/mm_private.h | 9 ++++ 2 files changed, 91 insertions(+), 46 deletions(-) diff --git a/grub-core/kern/mm.c b/grub-core/kern/mm.c index 1cbf98c7ab..7be33e23bf 100644 --- a/grub-core/kern/mm.c +++ b/grub-core/kern/mm.c @@ -130,53 +130,88 @@ 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-|| - */ - 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; + { + /* + * 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-|| + */ + 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; - } + /* + * 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->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. + * + * Cast to (void *) first to avoid the following build error: + * kern/mm.c: In function ‘grub_mm_init_region’: + * kern/mm.c:211:15: error: cast increases required alignment of target type [-Werror=cast-align] + * 211 | h = (grub_mm_header_t) ((grub_uint8_t *) addr - q->post_size); + * | ^ + * It is safe to do that because proper alignment is enforced in grub_mm_size_sanity_check(). + */ + h = (grub_mm_header_t)(void *) ((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 */ + q->post_size = (q->post_size + size) & (GRUB_MM_ALIGN - 1); + grub_free (h + 1); + return; + } + } /* Allocate a region from the head. */ r = (grub_mm_region_t) ALIGN_UP ((grub_addr_t) addr, GRUB_MM_ALIGN); @@ -195,6 +230,7 @@ grub_mm_init_region (void *addr, grub_size_t size) r->first = h; r->pre_size = (grub_addr_t) r - (grub_addr_t) addr; r->size = (h->size << GRUB_MM_ALIGN_LOG2); + r->post_size = size - r->size; /* Find where to insert this region. Put a smaller one before bigger ones, to prevent fragmentation. */ diff --git a/include/grub/mm_private.h b/include/grub/mm_private.h index a688b92a83..96c2d816be 100644 --- a/include/grub/mm_private.h +++ b/include/grub/mm_private.h @@ -81,8 +81,17 @@ typedef struct grub_mm_region */ grub_size_t pre_size; + /* + * Likewise, the post-size is the number of bytes we wasted at the end + * of the allocation because it wasn't a multiple of GRUB_MM_ALIGN + */ + grub_size_t post_size; + /* How many bytes are in this region? (free and allocated) */ grub_size_t size; + + /* pad to a multiple of cell size */ + char padding[3 * GRUB_CPU_SIZEOF_VOID_P]; } *grub_mm_region_t;