[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)EFI_ALLOC_LIMIT);
	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,
			      int memory_type)
{
	unsigned long total_slots = 0, target_slot;
	unsigned long total_mirrored_slots = 0;
	struct efi_boot_memmap *map;
	efi_status_t status;
	int map_offset;

	status = efi_get_memory_map(&map, false);
	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->map_size; map_offset += map->desc_size) {
		efi_memory_desc_t *md = (void *)map->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.
	 */
	status = EFI_OUT_OF_RESOURCES;
	for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) {
		efi_memory_desc_t *md = (void *)map->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,
				     memory_type, pages, &target);
		if (status == EFI_SUCCESS)
			*addr = target;
		break;
	}

	efi_bs_call(free_pool, 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,
a37dac5c	32	(u64)EFI_ALLOC_LIMIT);
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,
9cf42bca AB	56	unsigned long random_seed,
9cf42bca AB	57	int memory_type)
0ed02bda	58	{
eab31265	59	unsigned long total_slots = 0, target_slot;
a6cfe03c	60	unsigned long total_mirrored_slots = 0;
eab31265	61	struct efi_boot_memmap *map;
0ed02bda	62	efi_status_t status;
0ed02bda	63	int map_offset;
0ed02bda	64
171539f5	65	status = efi_get_memory_map(&map, false);
0ed02bda AB	66	if (status != EFI_SUCCESS)
	67	return status;
	68
	69	if (align < EFI_ALLOC_ALIGN)
	70	align = EFI_ALLOC_ALIGN;
	71
e1df73e2 AB	72	size = round_up(size, EFI_ALLOC_ALIGN);
e1df73e2 AB	73
0ed02bda	74	/* count the suitable slots in each memory map entry */
eab31265 AB	75	for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) {
eab31265 AB	76	efi_memory_desc_t md = (void )map->map + map_offset;
0ed02bda AB	77	unsigned long slots;
	78
	79	slots = get_entry_num_slots(md, size, ilog2(align));
	80	MD_NUM_SLOTS(md) = slots;
	81	total_slots += slots;
a6cfe03c AB	82	if (md->attribute & EFI_MEMORY_MORE_RELIABLE)
a6cfe03c AB	83	total_mirrored_slots += slots;
0ed02bda AB	84	}
0ed02bda AB	85
a6cfe03c AB	86	/* consider only mirrored slots for randomization if any exist */
	87	if (total_mirrored_slots > 0)
	88	total_slots = total_mirrored_slots;
	89
0ed02bda	90	/* find a random number between 0 and total_slots */
c37c9162	91	target_slot = (total_slots * (u64)(random_seed & U32_MAX)) >> 32;
0ed02bda AB	92
	93	/*
	94	* target_slot is now a value in the range [0, total_slots), and so
	95	* it corresponds with exactly one of the suitable slots we recorded
	96	* when iterating over the memory map the first time around.
	97	*
	98	* So iterate over the memory map again, subtracting the number of
	99	* slots of each entry at each iteration, until we have found the entry
	100	* that covers our chosen slot. Use the residual value of target_slot
	101	* to calculate the randomly chosen address, and allocate it directly
	102	* using EFI_ALLOCATE_ADDRESS.
	103	*/
0b1d9deb	104	status = EFI_OUT_OF_RESOURCES;
eab31265 AB	105	for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) {
eab31265 AB	106	efi_memory_desc_t md = (void )map->map + map_offset;
0ed02bda AB	107	efi_physical_addr_t target;
	108	unsigned long pages;
	109
a6cfe03c AB	110	if (total_mirrored_slots > 0 &&
	111	!(md->attribute & EFI_MEMORY_MORE_RELIABLE))
	112	continue;
	113
0ed02bda AB	114	if (target_slot >= MD_NUM_SLOTS(md)) {
	115	target_slot -= MD_NUM_SLOTS(md);
	116	continue;
	117	}
	118
	119	target = round_up(md->phys_addr, align) + target_slot * align;
e1df73e2	120	pages = size / EFI_PAGE_SIZE;
0ed02bda AB	121
0ed02bda AB	122	status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS,
9cf42bca	123	memory_type, pages, &target);
0ed02bda AB	124	if (status == EFI_SUCCESS)
	125	*addr = target;
	126	break;
	127	}
	128
eab31265	129	efi_bs_call(free_pool, map);
0ed02bda AB	130
	131	return status;
	132	}