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path: root/drivers/firmware/efi/libstub/random.c
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Diffstat (limited to 'drivers/firmware/efi/libstub/random.c')
-rw-r--r--drivers/firmware/efi/libstub/random.c136
1 files changed, 23 insertions, 113 deletions
diff --git a/drivers/firmware/efi/libstub/random.c b/drivers/firmware/efi/libstub/random.c
index 316ce9ff0193..24aa37535372 100644
--- a/drivers/firmware/efi/libstub/random.c
+++ b/drivers/firmware/efi/libstub/random.c
@@ -4,7 +4,6 @@
*/
#include <linux/efi.h>
-#include <linux/log2.h>
#include <asm/efi.h>
#include "efistub.h"
@@ -26,6 +25,17 @@ union efi_rng_protocol {
} mixed_mode;
};
+/**
+ * efi_get_random_bytes() - fill a buffer with random bytes
+ * @size: size of the buffer
+ * @out: caller allocated buffer to receive the random bytes
+ *
+ * The call will fail if either the firmware does not implement the
+ * EFI_RNG_PROTOCOL or there are not enough random bytes available to fill
+ * the buffer.
+ *
+ * Return: status code
+ */
efi_status_t efi_get_random_bytes(unsigned long size, u8 *out)
{
efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID;
@@ -39,119 +49,19 @@ efi_status_t efi_get_random_bytes(unsigned long size, u8 *out)
return efi_call_proto(rng, get_rng, NULL, size, out);
}
-/*
- * Return the number of slots covered by this entry, i.e., the number of
- * addresses it covers that are suitably aligned and supply enough room
- * for the allocation.
+/**
+ * efi_random_get_seed() - provide random seed as configuration table
+ *
+ * The EFI_RNG_PROTOCOL is used to read random bytes. These random bytes are
+ * saved as a configuration table which can be used as entropy by the kernel
+ * for the initialization of its pseudo random number generator.
+ *
+ * If the EFI_RNG_PROTOCOL is not available or there are not enough random bytes
+ * available, the configuration table will not be installed and an error code
+ * will be returned.
+ *
+ * Return: status code
*/
-static unsigned long get_entry_num_slots(efi_memory_desc_t *md,
- unsigned long size,
- unsigned long align_shift)
-{
- unsigned long align = 1UL << align_shift;
- u64 first_slot, last_slot, region_end;
-
- if (md->type != EFI_CONVENTIONAL_MEMORY)
- return 0;
-
- if (efi_soft_reserve_enabled() &&
- (md->attribute & EFI_MEMORY_SP))
- return 0;
-
- region_end = min((u64)ULONG_MAX, md->phys_addr + md->num_pages*EFI_PAGE_SIZE - 1);
-
- first_slot = round_up(md->phys_addr, align);
- last_slot = round_down(region_end - size + 1, align);
-
- if (first_slot > last_slot)
- return 0;
-
- return ((unsigned long)(last_slot - first_slot) >> align_shift) + 1;
-}
-
-/*
- * The UEFI memory descriptors have a virtual address field that is only used
- * when installing the virtual mapping using SetVirtualAddressMap(). Since it
- * is unused here, we can reuse it to keep track of each descriptor's slot
- * count.
- */
-#define MD_NUM_SLOTS(md) ((md)->virt_addr)
-
-efi_status_t efi_random_alloc(unsigned long size,
- unsigned long align,
- unsigned long *addr,
- unsigned long random_seed)
-{
- unsigned long map_size, desc_size, total_slots = 0, target_slot;
- unsigned long buff_size;
- efi_status_t status;
- efi_memory_desc_t *memory_map;
- int map_offset;
- struct efi_boot_memmap map;
-
- map.map = &memory_map;
- map.map_size = &map_size;
- map.desc_size = &desc_size;
- map.desc_ver = NULL;
- map.key_ptr = NULL;
- map.buff_size = &buff_size;
-
- status = efi_get_memory_map(&map);
- if (status != EFI_SUCCESS)
- return status;
-
- if (align < EFI_ALLOC_ALIGN)
- align = EFI_ALLOC_ALIGN;
-
- /* count the suitable slots in each memory map entry */
- for (map_offset = 0; map_offset < map_size; map_offset += desc_size) {
- efi_memory_desc_t *md = (void *)memory_map + map_offset;
- unsigned long slots;
-
- slots = get_entry_num_slots(md, size, ilog2(align));
- MD_NUM_SLOTS(md) = slots;
- total_slots += slots;
- }
-
- /* find a random number between 0 and total_slots */
- target_slot = (total_slots * (u16)random_seed) >> 16;
-
- /*
- * target_slot is now a value in the range [0, total_slots), and so
- * it corresponds with exactly one of the suitable slots we recorded
- * when iterating over the memory map the first time around.
- *
- * So iterate over the memory map again, subtracting the number of
- * slots of each entry at each iteration, until we have found the entry
- * that covers our chosen slot. Use the residual value of target_slot
- * to calculate the randomly chosen address, and allocate it directly
- * using EFI_ALLOCATE_ADDRESS.
- */
- for (map_offset = 0; map_offset < map_size; map_offset += desc_size) {
- efi_memory_desc_t *md = (void *)memory_map + map_offset;
- efi_physical_addr_t target;
- unsigned long pages;
-
- if (target_slot >= MD_NUM_SLOTS(md)) {
- target_slot -= MD_NUM_SLOTS(md);
- continue;
- }
-
- target = round_up(md->phys_addr, align) + target_slot * align;
- pages = round_up(size, EFI_PAGE_SIZE) / EFI_PAGE_SIZE;
-
- status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS,
- EFI_LOADER_DATA, pages, &target);
- if (status == EFI_SUCCESS)
- *addr = target;
- break;
- }
-
- efi_bs_call(free_pool, memory_map);
-
- return status;
-}
-
efi_status_t efi_random_get_seed(void)
{
efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID;