path: root/arch/x86/kernel/e820.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Low level x86 E820 memory map handling functions.
 *
 * The firmware and bootloader passes us the "E820 table", which is the primary
 * physical memory layout description available about x86 systems.
 *
 * The kernel takes the E820 memory layout and optionally modifies it with
 * quirks and other tweaks, and feeds that into the generic Linux memory
 * allocation code routines via a platform independent interface (memblock, etc.).
 */
#include <linux/crash_dump.h>
#include <linux/memblock.h>
#include <linux/suspend.h>
#include <linux/acpi.h>
#include <linux/firmware-map.h>
#include <linux/sort.h>
#include <linux/memory_hotplug.h>

#include <asm/e820/api.h>
#include <asm/setup.h>

/*
 * We organize the E820 table into three main data structures:
 *
 * - 'e820_table_firmware': the original firmware version passed to us by the
 *   bootloader - not modified by the kernel. It is composed of two parts:
 *   the first 128 E820 memory entries in boot_params.e820_table and the remaining
 *   (if any) entries of the SETUP_E820_EXT nodes. We use this to:
 *
 *       - the hibernation code uses it to generate a kernel-independent CRC32
 *         checksum of the physical memory layout of a system.
 *
 * - 'e820_table_kexec': a slightly modified (by the kernel) firmware version
 *   passed to us by the bootloader - the major difference between
 *   e820_table_firmware[] and this one is that e820_table_kexec[]
 *   might be modified by the kexec itself to fake an mptable.
 *   We use this to:
 *
 *       - kexec, which is a bootloader in disguise, uses the original E820
 *         layout to pass to the kexec-ed kernel. This way the original kernel
 *         can have a restricted E820 map while the kexec()-ed kexec-kernel
 *         can have access to full memory - etc.
 *
 *         Export the memory layout via /sys/firmware/memmap. kexec-tools uses
 *         the entries to create an E820 table for the kexec kernel.
 *
 *         kexec_file_load in-kernel code uses the table for the kexec kernel.
 *
 * - 'e820_table': this is the main E820 table that is massaged by the
 *   low level x86 platform code, or modified by boot parameters, before
 *   passed on to higher level MM layers.
 *
 * Once the E820 map has been converted to the standard Linux memory layout
 * information its role stops - modifying it has no effect and does not get
 * re-propagated. So its main role is a temporary bootstrap storage of firmware
 * specific memory layout data during early bootup.
 */
static struct e820_table e820_table_init		__initdata;
static struct e820_table e820_table_kexec_init		__initdata;
static struct e820_table e820_table_firmware_init	__initdata;

struct e820_table *e820_table __refdata			= &e820_table_init;
struct e820_table *e820_table_kexec __refdata		= &e820_table_kexec_init;
struct e820_table *e820_table_firmware __refdata	= &e820_table_firmware_init;

/* For PCI or other memory-mapped resources */
unsigned long pci_mem_start = 0xaeedbabe;
#ifdef CONFIG_PCI
EXPORT_SYMBOL(pci_mem_start);
#endif

/*
 * This function checks if any part of the range <start,end> is mapped
 * with type.
 */
static bool _e820__mapped_any(struct e820_table *table,
			      u64 start, u64 end, enum e820_type type)
{
	int i;

	for (i = 0; i < table->nr_entries; i++) {
		struct e820_entry *entry = &table->entries[i];

		if (type && entry->type != type)
			continue;
		if (entry->addr >= end || entry->addr + entry->size <= start)
			continue;
		return true;
	}
	return false;
}

bool e820__mapped_raw_any(u64 start, u64 end, enum e820_type type)
{
	return _e820__mapped_any(e820_table_firmware, start, end, type);
}
EXPORT_SYMBOL_GPL(e820__mapped_raw_any);

bool e820__mapped_any(u64 start, u64 end, enum e820_type type)
{
	return _e820__mapped_any(e820_table, start, end, type);
}
EXPORT_SYMBOL_GPL(e820__mapped_any);

/*
 * This function checks if the entire <start,end> range is mapped with 'type'.
 *
 * Note: this function only works correctly once the E820 table is sorted and
 * not-overlapping (at least for the range specified), which is the case normally.
 */
static struct e820_entry *__e820__mapped_all(u64 start, u64 end,
					     enum e820_type