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efi/libstub: Add limit argument to efi_random_alloc()

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x86 will need to limit the kernel memory allocation to the lowest 512
MiB of memory, to match the behavior of the existing bare metal KASLR
physical randomization logic. So in preparation for that, add a limit
parameter to efi_random_alloc() and wire it up.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230807162720.545787-22-ardb@kernel.org
This commit is contained in:
Ard Biesheuvel
2023-08-07 18:27:18 +02:00
committed by Borislav Petkov (AMD)
parent 8338151935
commit bc5ddceff4
4 changed files with 9 additions and 7 deletions
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10
drivers/firmware/efi/libstub/randomalloc.c
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@@ -16,7 +16,8 @@
*/
static unsigned long get_entry_num_slots(efi_memory_desc_t *md,
unsigned long size,
unsigned long align_shift)
unsigned long align_shift,
u64 alloc_limit)
{
unsigned long align = 1UL << align_shift;
u64 first_slot, last_slot, region_end;
@@ -29,7 +30,7 @@ static unsigned long get_entry_num_slots(efi_memory_desc_t *md,
return 0;
region_end = min(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - 1,
(u64)EFI_ALLOC_LIMIT);
alloc_limit);
if (region_end < size)
return 0;
@@ -54,7 +55,8 @@ efi_status_t efi_random_alloc(unsigned long size,
unsigned long align,
unsigned long *addr,
unsigned long random_seed,
int memory_type)
int memory_type,
unsigned long alloc_limit)
{
unsigned long total_slots = 0, target_slot;
unsigned long total_mirrored_slots = 0;
@@ -76,7 +78,7 @@ efi_status_t efi_random_alloc(unsigned long size,
efi_memory_desc_t *md = (void *)map->map + map_offset;
unsigned long slots;
slots = get_entry_num_slots(md, size, ilog2(align));
slots = get_entry_num_slots(md, size, ilog2(align), alloc_limit);
MD_NUM_SLOTS(md) = slots;
total_slots += slots;
if (md->attribute & EFI_MEMORY_MORE_RELIABLE)