kernel/arch/x86/platform/efi/fake_mem.c

// SPDX-License-Identifier: GPL-2.0
/*
 * fake_mem.c
 *
 * Copyright (C) 2015 FUJITSU LIMITED
 * Author: Taku Izumi <izumi.taku@jp.fujitsu.com>
 *
 * This code introduces new boot option named "efi_fake_mem"
 * By specifying this parameter, you can add arbitrary attribute to
 * specific memory range by updating original (firmware provided) EFI
 * memmap.
 */

#include <linux/kernel.h>
#include <linux/efi.h>
#include <linux/init.h>
#include <linux/memblock.h>
#include <linux/types.h>
#include <linux/sort.h>
#include <asm/e820/api.h>
#include <asm/efi.h>

#define EFI_MAX_FAKEMEM CONFIG_EFI_MAX_FAKE_MEM

static struct efi_mem_range efi_fake_mems[EFI_MAX_FAKEMEM];
static int nr_fake_mem;

static int __init cmp_fake_mem(const void *x1, const void *x2)
{
	const struct efi_mem_range *m1 = x1;
	const struct efi_mem_range *m2 = x2;

	if (m1->range.start < m2->range.start)
		return -1;
	if (m1->range.start > m2->range.start)
		return 1;
	return 0;
}

static void __init efi_fake_range(struct efi_mem_range *efi_range)
{
	struct efi_memory_map_data data = { 0 };
	int new_nr_map = efi.memmap.nr_map;
	efi_memory_desc_t *md;
	void *new_memmap;

	/* count up the number of EFI memory descriptor */
	for_each_efi_memory_desc(md)
		new_nr_map += efi_memmap_split_count(md, &efi_range->range);

	/* allocate memory for new EFI memmap */
	if (efi_memmap_alloc(new_nr_map, &data) != 0)
		return;

	/* create new EFI memmap */
	new_memmap = early_memremap(data.phys_map, data.size);
	if (!new_memmap) {
		__efi_memmap_free(data.phys_map, data.size, data.flags);
		return;
	}

	efi_memmap_insert(&efi.memmap, new_memmap, efi_range);

	/* swap into new EFI memmap */
	early_memunmap(new_memmap, data.size);

	efi_memmap_install(&data);
}

void __init efi_fake_memmap(void)
{
	int i;

	if (!efi_enabled(EFI_MEMMAP) || !nr_fake_mem)
		return;

	for (i = 0; i < nr_fake_mem; i++)
		efi_fake_range(&efi_fake_mems[i]);

	/* print new EFI memmap */
	efi_print_memmap();
}

static int __init setup_fake_mem(char *p)
{
	u64 start = 0, mem_size = 0, attribute = 0;
	int i;

	if (!p)
		return -EINVAL;

	while (*p != '\0') {
		mem_size = memparse(p, &p);
		if (*p == '@')
			start = memparse(p+1, &p);
		else
			break;

		if (*p == ':')
			attribute = simple_strtoull(p+1, &p, 0);
		else
			break;

		if (nr_fake_mem >= EFI_MAX_FAKEMEM)
			break;

		efi_fake_mems[nr_fake_mem].range.start = start;
		efi_fake_mems[nr_fake_mem].range.end = start + mem_size - 1;
		efi_fake_mems[nr_fake_mem].attribute = attribute;
		nr_fake_mem++;

		if (*p == ',')
			p++;
	}

	sort(efi_fake_mems, nr_fake_mem, sizeof(struct efi_mem_range),
	     cmp_fake_mem, NULL);

	for (i = 0; i < nr_fake_mem; i++)
		pr_info("efi_fake_mem: add attr=0x%016llx to [mem 0x%016llx-0x%016llx]",
			efi_fake_mems[i].attribute, efi_fake_mems[i].range.start,
			efi_fake_mems[i].range.end);

	return *p == '\0' ? 0 : -EINVAL;
}

early_param("efi_fake_mem", setup_fake_mem);

void __init efi_fake_memmap_early(void)
{
	int i;

	/*
	 * The late efi_fake_mem() call can handle all requests if
	 * EFI_MEMORY_SP support is disabled.
	 */
	if (!efi_soft_reserve_enabled())
		return;

	if (!efi_enabled(EFI_MEMMAP) || !nr_fake_mem)
		return;

	/*
	 * Given that efi_fake_memmap() needs to perform memblock
	 * allocations it needs to run after e820__memblock_setup().
	 * However, if efi_fake_mem specifies EFI_MEMORY_SP for a given
	 * address range that potentially needs to mark the memory as
	 * reserved prior to e820__memblock_setup(). Update e820
	 * directly if EFI_MEMORY_SP is specified for an
	 * EFI_CONVENTIONAL_MEMORY descriptor.
	 */
	for (i = 0; i < nr_fake_mem; i++) {
		struct efi_mem_range *mem = &efi_fake_mems[i];
		efi_memory_desc_t *md;
		u64 m_start, m_end;

		if ((mem->attribute & EFI_MEMORY_SP) == 0)
			continue;

		m_start = mem->range.start;
		m_end = mem->range.end;
		for_each_efi_memory_desc(md) {
			u64 start, end, size;

			if (md->type != EFI_CONVENTIONAL_MEMORY)
				continue;

			start = md->phys_addr;
			end = md->phys_addr + (md->num_pages << EFI_PAGE_SHIFT) - 1;

			if (m_start <= end && m_end >= start)
				/* fake range overlaps descriptor */;
			else
				continue;

			/*
			 * Trim the boundary of the e820 update to the
			 * descriptor in case the fake range overlaps
			 * !EFI_CONVENTIONAL_MEMORY
			 */
			start = max(start, m_start);
			end = min(end, m_end);
			size = end - start + 1;

			if (end <= start)
				continue;

			/*
			 * Ensure each efi_fake_mem instance results in
			 * a unique e820 resource
			 */
			e820__range_remove(start, size, E820_TYPE_RAM, 1);
			e820__range_add(start, size, E820_TYPE_SOFT_RESERVED);
			e820__update_table(e820_table);
		}
	}
}