[linux-block.git] / drivers / firmware / efi / libstub / randomalloc.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2016 Linaro Ltd;  <ard.biesheuvel@linaro.org>
 */

#include <linux/efi.h>
#include <linux/log2.h>
#include <asm/efi.h>

#include "efistub.h"

/*
 * 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.
 */
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(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - 1,
			 (u64)ULONG_MAX);
	if (region_end < size)
		return 0;

	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 total_mirrored_slots = 0;
	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;

	size = round_up(size, 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;
		if (md->attribute & EFI_MEMORY_MORE_RELIABLE)
			total_mirrored_slots += slots;
	}

	/* consider only mirrored slots for randomization if any exist */
	if (total_mirrored_slots > 0)
		total_slots = total_mirrored_slots;

	/* find a random number between 0 and total_slots */
	target_slot = (total_slots * (u64)(random_seed & U32_MAX)) >> 32;

	/*
	 * 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 (total_mirrored_slots > 0 &&
		    !(md->attribute & EFI_MEMORY_MORE_RELIABLE))
			continue;

		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 = 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;
}
Commit	Line	Data
0ed02bda AB	1	// SPDX-License-Identifier: GPL-2.0
	2	/*
	3	* Copyright (C) 2016 Linaro Ltd; <ard.biesheuvel@linaro.org>
	4	*/
	5
	6	#include <linux/efi.h>
	7	#include <linux/log2.h>
	8	#include <asm/efi.h>
	9
	10	#include "efistub.h"
	11
	12	/*
	13	* Return the number of slots covered by this entry, i.e., the number of
	14	* addresses it covers that are suitably aligned and supply enough room
	15	* for the allocation.
	16	*/
	17	static unsigned long get_entry_num_slots(efi_memory_desc_t *md,
	18	unsigned long size,
	19	unsigned long align_shift)
	20	{
	21	unsigned long align = 1UL << align_shift;
	22	u64 first_slot, last_slot, region_end;
	23
	24	if (md->type != EFI_CONVENTIONAL_MEMORY)
	25	return 0;
	26
	27	if (efi_soft_reserve_enabled() &&
	28	(md->attribute & EFI_MEMORY_SP))
	29	return 0;
	30
	31	region_end = min(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - 1,
	32	(u64)ULONG_MAX);
4152433c BH	33	if (region_end < size)
4152433c BH	34	return 0;
0ed02bda AB	35
	36	first_slot = round_up(md->phys_addr, align);
	37	last_slot = round_down(region_end - size + 1, align);
	38
	39	if (first_slot > last_slot)
	40	return 0;
	41
	42	return ((unsigned long)(last_slot - first_slot) >> align_shift) + 1;
	43	}
	44
	45	/*
	46	* The UEFI memory descriptors have a virtual address field that is only used
	47	* when installing the virtual mapping using SetVirtualAddressMap(). Since it
	48	* is unused here, we can reuse it to keep track of each descriptor's slot
	49	* count.
	50	*/
	51	#define MD_NUM_SLOTS(md) ((md)->virt_addr)
	52
	53	efi_status_t efi_random_alloc(unsigned long size,
	54	unsigned long align,
	55	unsigned long *addr,
	56	unsigned long random_seed)
	57	{
	58	unsigned long map_size, desc_size, total_slots = 0, target_slot;
a6cfe03c	59	unsigned long total_mirrored_slots = 0;
0ed02bda AB	60	unsigned long buff_size;
	61	efi_status_t status;
	62	efi_memory_desc_t *memory_map;
	63	int map_offset;
	64	struct efi_boot_memmap map;
	65
	66	map.map = &memory_map;
	67	map.map_size = &map_size;
	68	map.desc_size = &desc_size;
	69	map.desc_ver = NULL;
	70	map.key_ptr = NULL;
	71	map.buff_size = &buff_size;
	72
	73	status = efi_get_memory_map(&map);
	74	if (status != EFI_SUCCESS)
	75	return status;
	76
	77	if (align < EFI_ALLOC_ALIGN)
	78	align = EFI_ALLOC_ALIGN;
	79
e1df73e2 AB	80	size = round_up(size, EFI_ALLOC_ALIGN);
e1df73e2 AB	81
0ed02bda AB	82	/* count the suitable slots in each memory map entry */
	83	for (map_offset = 0; map_offset < map_size; map_offset += desc_size) {
	84	efi_memory_desc_t md = (void )memory_map + map_offset;
	85	unsigned long slots;
	86
	87	slots = get_entry_num_slots(md, size, ilog2(align));
	88	MD_NUM_SLOTS(md) = slots;
	89	total_slots += slots;
a6cfe03c AB	90	if (md->attribute & EFI_MEMORY_MORE_RELIABLE)
a6cfe03c AB	91	total_mirrored_slots += slots;
0ed02bda AB	92	}
0ed02bda AB	93
a6cfe03c AB	94	/* consider only mirrored slots for randomization if any exist */
	95	if (total_mirrored_slots > 0)
	96	total_slots = total_mirrored_slots;
	97
0ed02bda	98	/* find a random number between 0 and total_slots */
c37c9162	99	target_slot = (total_slots * (u64)(random_seed & U32_MAX)) >> 32;
0ed02bda AB	100
	101	/*
	102	* target_slot is now a value in the range [0, total_slots), and so
	103	* it corresponds with exactly one of the suitable slots we recorded
	104	* when iterating over the memory map the first time around.
	105	*
	106	* So iterate over the memory map again, subtracting the number of
	107	* slots of each entry at each iteration, until we have found the entry
	108	* that covers our chosen slot. Use the residual value of target_slot
	109	* to calculate the randomly chosen address, and allocate it directly
	110	* using EFI_ALLOCATE_ADDRESS.
	111	*/
	112	for (map_offset = 0; map_offset < map_size; map_offset += desc_size) {
	113	efi_memory_desc_t md = (void )memory_map + map_offset;
	114	efi_physical_addr_t target;
	115	unsigned long pages;
	116
a6cfe03c AB	117	if (total_mirrored_slots > 0 &&
	118	!(md->attribute & EFI_MEMORY_MORE_RELIABLE))
	119	continue;
	120
0ed02bda AB	121	if (target_slot >= MD_NUM_SLOTS(md)) {
	122	target_slot -= MD_NUM_SLOTS(md);
	123	continue;
	124	}
	125
	126	target = round_up(md->phys_addr, align) + target_slot * align;
e1df73e2	127	pages = size / EFI_PAGE_SIZE;
0ed02bda AB	128
	129	status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS,
	130	EFI_LOADER_DATA, pages, &target);
	131	if (status == EFI_SUCCESS)
	132	*addr = target;
	133	break;
	134	}
	135
	136	efi_bs_call(free_pool, memory_map);
	137
	138	return status;
	139	}