alistair23-linux/arch/x86/kernel/setup.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  Copyright (C) 1995  Linus Torvalds
 *
 *  Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
 *
 *  Memory region support
 *	David Parsons <orc@pell.chi.il.us>, July-August 1999
 *
 *  Added E820 sanitization routine (removes overlapping memory regions);
 *  Brian Moyle <bmoyle@mvista.com>, February 2001
 *
 * Moved CPU detection code to cpu/${cpu}.c
 *    Patrick Mochel <mochel@osdl.org>, March 2002
 *
 *  Provisions for empty E820 memory regions (reported by certain BIOSes).
 *  Alex Achenbach <xela@slit.de>, December 2002.
 *
 */

/*
 * This file handles the architecture-dependent parts of initialization
 */

#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/mmzone.h>
#include <linux/screen_info.h>
#include <linux/ioport.h>
#include <linux/acpi.h>
#include <linux/sfi.h>
#include <linux/apm_bios.h>
#include <linux/initrd.h>
#include <linux/memblock.h>
#include <linux/seq_file.h>
#include <linux/console.h>
#include <linux/root_dev.h>
#include <linux/highmem.h>
#include <linux/export.h>
#include <linux/efi.h>
#include <linux/init.h>
#include <linux/edd.h>
#include <linux/iscsi_ibft.h>
#include <linux/nodemask.h>
#include <linux/kexec.h>
#include <linux/dmi.h>
#include <linux/pfn.h>
#include <linux/pci.h>
#include <asm/pci-direct.h>
#include <linux/init_ohci1394_dma.h>
#include <linux/kvm_para.h>
#include <linux/dma-contiguous.h>
#include <xen/xen.h>
#include <uapi/linux/mount.h>

#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/ptrace.h>
#include <linux/user.h>
#include <linux/delay.h>

#include <linux/kallsyms.h>
#include <linux/cpufreq.h>
#include <linux/dma-mapping.h>
#include <linux/ctype.h>
#include <linux/uaccess.h>

#include <linux/percpu.h>
#include <linux/crash_dump.h>
#include <linux/tboot.h>
#include <linux/jiffies.h>
#include <linux/mem_encrypt.h>
#include <linux/sizes.h>

#include <linux/usb/xhci-dbgp.h>
#include <video/edid.h>

#include <asm/mtrr.h>
#include <asm/apic.h>
#include <asm/realmode.h>
#include <asm/e820/api.h>
#include <asm/mpspec.h>
#include <asm/setup.h>
#include <asm/efi.h>
#include <asm/timer.h>
#include <asm/i8259.h>
#include <asm/sections.h>
#include <asm/io_apic.h>
#include <asm/ist.h>
#include <asm/setup_arch.h>
#include <asm/bios_ebda.h>
#include <asm/cacheflush.h>
#include <asm/processor.h>
#include <asm/bugs.h>
#include <asm/kasan.h>

#include <asm/vsyscall.h>
#include <asm/cpu.h>
#include <asm/desc.h>
#include <asm/dma.h>
#include <asm/iommu.h>
#include <asm/gart.h>
#include <asm/mmu_context.h>
#include <asm/proto.h>

#include <asm/paravirt.h>
#include <asm/hypervisor.h>
#include <asm/olpc_ofw.h>

#include <asm/percpu.h>
#include <asm/topology.h>
#include <asm/apicdef.h>
#include <asm/amd_nb.h>
#include <asm/mce.h>
#include <asm/alternative.h>
#include <asm/prom.h>
#include <asm/microcode.h>
#include <asm/kaslr.h>
#include <asm/unwind.h>

/*
 * max_low_pfn_mapped: highest direct mapped pfn under 4GB
 * max_pfn_mapped:     highest direct mapped pfn over 4GB
 *
 * The direct mapping only covers E820_TYPE_RAM regions, so the ranges and gaps are
 * represented by pfn_mapped
 */
unsigned long max_low_pfn_mapped;
unsigned long max_pfn_mapped;

#ifdef CONFIG_DMI
RESERVE_BRK(dmi_alloc, 65536);
#endif


static __initdata unsigned long _brk_start = (unsigned long)__brk_base;
unsigned long _brk_end = (unsigned long)__brk_base;

struct boot_params boot_params;

/*
 * Machine setup..
 */
static struct resource data_resource = {
	.name	= "Kernel data",
	.start	= 0,
	.end	= 0,
	.flags	= IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM
};

static struct resource code_resource = {
	.name	= "Kernel code",
	.start	= 0,
	.end	= 0,
	.flags	= IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM
};

static struct resource bss_resource = {
	.name	= "Kernel bss",
	.start	= 0,
	.end	= 0,
	.flags	= IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM
};


#ifdef CONFIG_X86_32
/* cpu data as detected by the assembly code in head_32.S */
struct cpuinfo_x86 new_cpu_data;

/* common cpu data for all cpus */
struct cpuinfo_x86 boot_cpu_data __read_mostly;
EXPORT_SYMBOL(boot_cpu_data);

unsigned int def_to_bigsmp;

/* for MCA, but anyone else can use it if they want */
unsigned int machine_id;
unsigned int machine_submodel_id;
unsigned int BIOS_revision;

struct apm_info apm_info;
EXPORT_SYMBOL(apm_info);

#if defined(CONFIG_X86_SPEEDSTEP_SMI) || \
	defined(CONFIG_X86_SPEEDSTEP_SMI_MODULE)
struct ist_info ist_info;
EXPORT_SYMBOL(ist_info);
#else
struct ist_info ist_info;
#endif

#else
struct cpuinfo_x86 boot_cpu_data __read_mostly;
EXPORT_SYMBOL(boot_cpu_data);
#endif


#if !defined(CONFIG_X86_PAE) || defined(CONFIG_X86_64)
__visible unsigned long mmu_cr4_features __ro_after_init;
#else
__visible unsigned long mmu_cr4_features __ro_after_init = X86_CR4_PAE;
#endif

/* Boot loader ID and version as integers, for the benefit of proc_dointvec */
int bootloader_type, bootloader_version;

/*
 * Setup options
 */
struct screen_info screen_info;
EXPORT_SYMBOL(screen_info);
struct edid_info edid_info;
EXPORT_SYMBOL_GPL(edid_info);

extern int root_mountflags;

unsigned long saved_video_mode;

#define RAMDISK_IMAGE_START_MASK	0x07FF
#define RAMDISK_PROMPT_FLAG		0x8000
#define RAMDISK_LOAD_FLAG		0x4000

static char __initdata command_line[COMMAND_LINE_SIZE];
#ifdef CONFIG_CMDLINE_BOOL
static char __initdata builtin_cmdline[COMMAND_LINE_SIZE] = CONFIG_CMDLINE;
#endif

#if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)
struct edd edd;
#ifdef CONFIG_EDD_MODULE
EXPORT_SYMBOL(edd);
#endif
/**
 * copy_edd() - Copy the BIOS EDD information
 *              from boot_params into a safe place.
 *
 */
static inline void __init copy_edd(void)
{
     memcpy(edd.mbr_signature, boot_params.edd_mbr_sig_buffer,
	    sizeof(edd.mbr_signature));
     memcpy(edd.edd_info, boot_params.eddbuf, sizeof(edd.edd_info));
     edd.mbr_signature_nr = boot_params.edd_mbr_sig_buf_entries;
     edd.edd_info_nr = boot_params.eddbuf_entries;
}
#else
static inline void __init copy_edd(void)
{
}
#endif

void * __init extend_brk(size_t size, size_t align)
{
	size_t mask = align - 1;
	void *ret;

	BUG_ON(_brk_start == 0);
	BUG_ON(align & mask);

	_brk_end = (_brk_end + mask) & ~mask;
	BUG_ON((char *)(_brk_end + size) > __brk_limit);

	ret = (void *)_brk_end;
	_brk_end += size;

	memset(ret, 0, size);

	return ret;
}

#ifdef CONFIG_X86_32
static void __init cleanup_highmap(void)
{
}
#endif

static void __init reserve_brk(void)
{
	if (_brk_end > _brk_start)
		memblock_reserve(__pa_symbol(_brk_start),
				 _brk_end - _brk_start);

	/* Mark brk area as locked down and no longer taking any
	   new allocations */
	_brk_start = 0;
}

u64 relocated_ramdisk;

#ifdef CONFIG_BLK_DEV_INITRD

static u64 __init get_ramdisk_image(void)
{
	u64 ramdisk_image = boot_params.hdr.ramdisk_image;

	ramdisk_image |= (u64)boot_params.ext_ramdisk_image << 32;

	return ramdisk_image;
}
static u64 __init get_ramdisk_size(void)
{
	u64 ramdisk_size = boot_params.hdr.ramdisk_size;

	ramdisk_size |= (u64)boot_params.ext_ramdisk_size << 32;

	return ramdisk_size;
}

static void __init relocate_initrd(void)
{
	/* Assume only end is not page aligned */
	u64 ramdisk_image = get_ramdisk_image();
	u64 ramdisk_size  = get_ramdisk_size();
	u64 area_size     = PAGE_ALIGN(ramdisk_size);

	/* We need to move the initrd down into directly mapped mem */
	relocated_ramdisk = memblock_find_in_range(0, PFN_PHYS(max_pfn_mapped),
						   area_size, PAGE_SIZE);

	if (!relocated_ramdisk)
		panic("Cannot find place for new RAMDISK of size %lld\n",
		      ramdisk_size);

	/* Note: this includes all the mem currently occupied by
	   the initrd, we rely on that fact to keep the data intact. */
	memblock_reserve(relocated_ramdisk, area_size);
	initrd_start = relocated_ramdisk + PAGE_OFFSET;
	initrd_end   = initrd_start + ramdisk_size;
	printk(KERN_INFO "Allocated new RAMDISK: [mem %#010llx-%#010llx]\n",
	       relocated_ramdisk, relocated_ramdisk + ramdisk_size - 1);

	copy_from_early_mem((void *)initrd_start, ramdisk_image, ramdisk_size);

	printk(KERN_INFO "Move RAMDISK from [mem %#010llx-%#010llx] to"
		" [mem %#010llx-%#010llx]\n",
		ramdisk_image, ramdisk_image + ramdisk_size - 1,
		relocated_ramdisk, relocated_ramdisk + ramdisk_size - 1);
}

static void __init early_reserve_initrd(void)
{
	/* Assume only end is not page aligned */
	u64 ramdisk_image = get_ramdisk_image();
	u64 ramdisk_size  = get_ramdisk_size();
	u64 ramdisk_end   = PAGE_ALIGN(ramdisk_image + ramdisk_size);

	if (!boot_params.hdr.type_of_loader ||
	    !ramdisk_image || !ramdisk_size)
		return;		/* No initrd provided by bootloader */

	memblock_reserve(ramdisk_image, ramdisk_end - ramdisk_image);
}
static void __init reserve_initrd(void)
{
	/* Assume only end is not page aligned */
	u64 ramdisk_image = get_ramdisk_image();
	u64 ramdisk_size  = get_ramdisk_size();
	u64 ramdisk_end   = PAGE_ALIGN(ramdisk_image + ramdisk_size);
	u64 mapped_size;

	if (!boot_params.hdr.type_of_loader ||
	    !ramdisk_image || !ramdisk_size)
		return;		/* No initrd provided by bootloader */

	initrd_start = 0;

	mapped_size = memblock_mem_size(max_pfn_mapped);
	if (ramdisk_size >= (mapped_size>>1))
		panic("initrd too large to handle, "
		       "disabling initrd (%lld needed, %lld available)\n",
		       ramdisk_size, mapped_size>>1);

	printk(KERN_INFO "RAMDISK: [mem %#010llx-%#010llx]\n", ramdisk_image,
			ramdisk_end - 1);

	if (pfn_range_is_mapped(PFN_DOWN(ramdisk_image),
				PFN_DOWN(ramdisk_end))) {
		/* All are mapped, easy case */
		initrd_start = ramdisk_image + PAGE_OFFSET;
		initrd_end = initrd_start + ramdisk_size;
		return;
	}

	relocate_initrd();

	memblock_free(ramdisk_image, ramdisk_end - ramdisk_image);
}

#else
static void __init early_reserve_initrd(void)
{
}
static void __init reserve_initrd(void)
{
}
#endif /* CONFIG_BLK_DEV_INITRD */

static void __init parse_setup_data(void)
{
	struct setup_data *data;
	u64 pa_data, pa_next;

	pa_data = boot_params.hdr.setup_data;
	while (pa_data) {
		u32 data_len, data_type;

		data = early_memremap(pa_data, sizeof(*data));
		data_len = data->len + sizeof(struct setup_data);
		data_type = data->type;
		pa_next = data->next;
		early_memunmap(data, sizeof(*data));

		switch (data_type) {
		case SETUP_E820_EXT:
			e820__memory_setup_extended(pa_data, data_len);
			break;
		case SETUP_DTB:
			add_dtb(pa_data);
			break;
		case SETUP_EFI:
			parse_efi_setup(pa_data, data_len);
			break;
		default:
			break;
		}
		pa_data = pa_next;
	}
}

static void __init memblock_x86_reserve_range_setup_data(void)
{
	struct setup_data *data;
	u64 pa_data;

	pa_data = boot_params.hdr.setup_data;
	while (pa_data) {
		data = early_memremap(pa_data, sizeof(*data));
		memblock_reserve(pa_data, sizeof(*data) + data->len);
		pa_data = data->next;
		early_memunmap(data, sizeof(*data));
	}
}

/*
 * --------- Crashkernel reservation ------------------------------
 */

#ifdef CONFIG_KEXEC_CORE

/* 16M alignment for crash kernel regions */
#define CRASH_ALIGN		SZ_16M

/*
 * Keep the crash kernel below this limit.  On 32 bits earlier kernels
 * would limit the kernel to the low 512 MiB due to mapping restrictions.
 */
#ifdef CONFIG_X86_32
# define CRASH_ADDR_LOW_MAX	SZ_512M
# define CRASH_ADDR_HIGH_MAX	SZ_512M
#else
# define CRASH_ADDR_LOW_MAX	SZ_4G
# define CRASH_ADDR_HIGH_MAX	MAXMEM
#endif

static int __init reserve_crashkernel_low(void)
{
#ifdef CONFIG_X86_64
	unsigned long long base, low_base = 0, low_size = 0;
	unsigned long total_low_mem;
	int ret;

	total_low_mem = memblock_mem_size(1UL << (32 - PAGE_SHIFT));

	/* crashkernel=Y,low */
	ret = parse_crashkernel_low(boot_command_line, total_low_mem, &low_size, &base);
	if (ret) {
		/*
		 * two parts from lib/swiotlb.c:
		 * -swiotlb size: user-specified with swiotlb= or default.
		 *
		 * -swiotlb overflow buffer: now hardcoded to 32k. We round it
		 * to 8M for other buffers that may need to stay low too. Also
		 * make sure we allocate enough extra low memory so that we
		 * don't run out of DMA buffers for 32-bit devices.
		 */
		low_size = max(swiotlb_size_or_default() + (8UL << 20), 256UL << 20);
	} else {
		/* passed with crashkernel=0,low ? */
		if (!low_size)
			return 0;
	}

	low_base = memblock_find_in_range(0, 1ULL << 32, low_size, CRASH_ALIGN);
	if (!low_base) {
		pr_err("Cannot reserve %ldMB crashkernel low memory, please try smaller size.\n",
		       (unsigned long)(low_size >> 20));
		return -ENOMEM;
	}

	ret = memblock_reserve(low_base, low_size);
	if (ret) {
		pr_err("%s: Error reserving crashkernel low memblock.\n", __func__);
		return ret;
	}

	pr_info("Reserving %ldMB of low memory at %ldMB for crashkernel (System low RAM: %ldMB)\n",
		(unsigned long)(low_size >> 20),
		(unsigned long)(low_base >> 20),
		(unsigned long)(total_low_mem >> 20));

	crashk_low_res.start = low_base;
	crashk_low_res.end   = low_base + low_size - 1;
	insert_resource(&iomem_resource, &crashk_low_res);
#endif
	return 0;
}

static void __init reserve_crashkernel(void)
{
	unsigned long long crash_size, crash_base, total_mem;
	bool high = false;
	int ret;

	total_mem = memblock_phys_mem_size();

	/* crashkernel=XM */
	ret = parse_crashkernel(boot_command_line, total_mem, &crash_size, &crash_base);
	if (ret != 0 || crash_size <= 0) {
		/* crashkernel=X,high */
		ret = parse_crashkernel_high(boot_command_line, total_mem,
					     &crash_size, &crash_base);
		if (ret != 0 || crash_size <= 0)
			return;
		high = true;
	}

	if (xen_pv_domain()) {
		pr_info("Ignoring crashkernel for a Xen PV domain\n");
		return;
	}

	/* 0 means: find the address automatically */
	if (!crash_base) {
		/*
		 * Set CRASH_ADDR_LOW_MAX upper bound for crash memory,
		 * crashkernel=x,high reserves memory over 4G, also allocates
		 * 256M extra low memory for DMA buffers and swiotlb.
		 * But the extra memory is not required for all machines.
		 * So try low memory first and fall back to high memory
		 * unless "crashkernel=size[KMG],high" is specified.
		 */
		if (!high)
			crash_base = memblock_find_in_range(CRASH_ALIGN,
						CRASH_ADDR_LOW_MAX,
						crash_size, CRASH_ALIGN);
		if (!crash_base)
			crash_base = memblock_find_in_range(CRASH_ALIGN,
						CRASH_ADDR_HIGH_MAX,
						crash_size, CRASH_ALIGN);
		if (!crash_base) {
			pr_info("crashkernel reservation failed - No suitable area found.\n");
			return;
		}
	} else {
		unsigned long long start;

		start = memblock_find_in_range(crash_base,
					       crash_base + crash_size,
					       crash_size, 1 << 20);
		if (start != crash_base) {
			pr_info("crashkernel reservation failed - memory is in use.\n");
			return;
		}
	}
	ret = memblock_reserve(crash_base, crash_size);
	if (ret) {
		pr_err("%s: Error reserving crashkernel memblock.\n", __func__);
		return;
	}

	if (crash_base >= (1ULL << 32) && reserve_crashkernel_low()) {
		memblock_free(crash_base, crash_size);
		return;
	}

	pr_info("Reserving %ldMB of memory at %ldMB for crashkernel (System RAM: %ldMB)\n",
		(unsigned long)(crash_size >> 20),
		(unsigned long)(crash_base >> 20),
		(unsigned long)(total_mem >> 20));

	crashk_res.start = crash_base;
	crashk_res.end   = crash_base + crash_size - 1;
	insert_resource(&iomem_resource, &crashk_res);
}
#else
static void __init reserve_crashkernel(void)
{
}
#endif

static struct resource standard_io_resources[] = {
	{ .name = "dma1", .start = 0x00, .end = 0x1f,
		.flags = IORESOURCE_BUSY | IORESOURCE_IO },
	{ .name = "pic1", .start = 0x20, .end = 0x21,
		.flags = IORESOURCE_BUSY | IORESOURCE_IO },
	{ .name = "timer0", .start = 0x40, .end = 0x43,
		.flags = IORESOURCE_BUSY | IORESOURCE_IO },
	{ .name = "timer1", .start = 0x50, .end = 0x53,
		.flags = IORESOURCE_BUSY | IORESOURCE_IO },
	{ .name = "keyboard", .start = 0x60, .end = 0x60,
		.flags = IORESOURCE_BUSY | IORESOURCE_IO },
	{ .name = "keyboard", .start = 0x64, .end = 0x64,
		.flags = IORESOURCE_BUSY | IORESOURCE_IO },
	{ .name = "dma page reg", .start = 0x80, .end = 0x8f,
		.flags = IORESOURCE_BUSY | IORESOURCE_IO },
	{ .name = "pic2", .start = 0xa0, .end = 0xa1,
		.flags = IORESOURCE_BUSY | IORESOURCE_IO },
	{ .name = "dma2", .start = 0xc0, .end = 0xdf,
		.flags = IORESOURCE_BUSY | IORESOURCE_IO },
	{ .name = "fpu", .start = 0xf0, .end = 0xff,
		.flags = IORESOURCE_BUSY | IORESOURCE_IO }
};

void __init reserve_standard_io_resources(void)
{
	int i;

	/* request I/O space for devices used on all i[345]86 PCs */
	for (i = 0; i < ARRAY_SIZE(standard_io_resources); i++)
		request_resource(&ioport_resource, &standard_io_resources[i]);

}

static __init void reserve_ibft_region(void)
{
	unsigned long addr, size = 0;

	addr = find_ibft_region(&size);

	if (size)
		memblock_reserve(addr, size);
}

static bool __init snb_gfx_workaround_needed(void)
{
#ifdef CONFIG_PCI
	int i;
	u16 vendor, devid;
	static const __initconst u16 snb_ids[] = {
		0x0102,
		0x0112,
		0x0122,
		0x0106,
		0x0116,
		0x0126,
		0x010a,
	};

	/* Assume no if something weird is going on with PCI */
	if (!early_pci_allowed())
		return false;

	vendor = read_pci_config_16(0, 2, 0, PCI_VENDOR_ID);
	if (vendor != 0x8086)
		return false;

	devid = read_pci_config_16(0, 2, 0, PCI_DEVICE_ID);
	for (i = 0; i < ARRAY_SIZE(snb_ids); i++)
		if (devid == snb_ids[i])
			return true;
#endif

	return false;
}

/*
 * Sandy Bridge graphics has trouble with certain ranges, exclude
 * them from allocation.
 */
static void __init trim_snb_memory(void)
{
	static const __initconst unsigned long bad_pages[] = {
		0x20050000,
		0x20110000,
		0x20130000,
		0x20138000,
		0x40004000,
	};
	int i;

	if (!snb_gfx_workaround_needed())
		return;

	printk(KERN_DEBUG "reserving inaccessible SNB gfx pages\n");

	/*
	 * Reserve all memory below the 1 MB mark that has not
	 * already been reserved.
	 */
	memblock_reserve(0, 1<<20);
	
	for (i = 0; i < ARRAY_SIZE(bad_pages); i++) {
		if (memblock_reserve(bad_pages[i], PAGE_SIZE))
			printk(KERN_WARNING "failed to reserve 0x%08lx\n",
			       bad_pages[i]);
	}
}

/*
 * Here we put platform-specific memory range workarounds, i.e.
 * memory known to be corrupt or otherwise in need to be reserved on
 * specific platforms.
 *
 * If this gets used more widely it could use a real dispatch mechanism.
 */
static void __init trim_platform_memory_ranges(void)
{
	trim_snb_memory();
}

static void __init trim_bios_range(void)
{
	/*
	 * A special case is the first 4Kb of memory;
	 * This is a BIOS owned area, not kernel ram, but generally
	 * not listed as such in the E820 table.
	 *
	 * This typically reserves additional memory (64KiB by default)
	 * since some BIOSes are known to corrupt low memory.  See the
	 * Kconfig help text for X86_RESERVE_LOW.
	 */
	e820__range_update(0, PAGE_SIZE, E820_TYPE_RAM, E820_TYPE_RESERVED);

	/*
	 * special case: Some BIOSen report the PC BIOS
	 * area (640->1Mb) as ram even though it is not.
	 * take them out.
	 */
	e820__range_remove(BIOS_BEGIN, BIOS_END - BIOS_BEGIN, E820_TYPE_RAM, 1);

	e820__update_table(e820_table);
}

/* called before trim_bios_range() to spare extra sanitize */
static void __init e820_add_kernel_range(void)
{
	u64 start = __pa_symbol(_text);
	u64 size = __pa_symbol(_end) - start;

	/*
	 * Complain if .text .data and .bss are not marked as E820_TYPE_RAM and
	 * attempt to fix it by adding the range. We may have a confused BIOS,
	 * or the user may have used memmap=exactmap or memmap=xxM$yyM to
	 * exclude kernel range. If we really are running on top non-RAM,
	 * we will crash later anyways.
	 */
	if (e820__mapped_all(start, start + size, E820_TYPE_RAM))
		return;

	pr_warn(".text .data .bss are not marked as E820_TYPE_RAM!\n");
	e820__range_remove(start, size, E820_TYPE_RAM, 0);
	e820__range_add(start, size, E820_TYPE_RAM);
}

static unsigned reserve_low = CONFIG_X86_RESERVE_LOW << 10;

static int __init parse_reservelow(char *p)
{
	unsigned long long size;

	if (!p)
		return -EINVAL;

	size = memparse(p, &p);

	if (size < 4096)
		size = 4096;

	if (size > 640*1024)
		size = 640*1024;

	reserve_low = size;

	return 0;
}

early_param("reservelow", parse_reservelow);

static void __init trim_low_memory_range(void)
{
	memblock_reserve(0, ALIGN(reserve_low, PAGE_SIZE));
}
	
/*
 * Dump out kernel offset information on panic.
 */
static int
dump_kernel_offset(struct notifier_block *self, unsigned long v, void *p)
{
	if (kaslr_enabled()) {
		pr_emerg("Kernel Offset: 0x%lx from 0x%lx (relocation range: 0x%lx-0x%lx)\n",
			 kaslr_offset(),
			 __START_KERNEL,
			 __START_KERNEL_map,
			 MODULES_VADDR-1);
	} else {
		pr_emerg("Kernel Offset: disabled\n");
	}

	return 0;
}

/*
 * Determine if we were loaded by an EFI loader.  If so, then we have also been
 * passed the efi memmap, systab, etc., so we should use these data structures
 * for initialization.  Note, the efi init code path is determined by the
 * global efi_enabled. This allows the same kernel image to be used on existing
 * systems (with a traditional BIOS) as well as on EFI systems.
 */
/*
 * setup_arch - architecture-specific boot-time initializations
 *
 * Note: On x86_64, fixmaps are ready for use even before this is called.
 */

void __init setup_arch(char **cmdline_p)
{
	memblock_reserve(__pa_symbol(_text),
			 (unsigned long)__bss_stop - (unsigned long)_text);

	/*
	 * Make sure page 0 is always reserved because on systems with
	 * L1TF its contents can be leaked to user processes.
	 */
	memblock_reserve(0, PAGE_SIZE);

	early_reserve_initrd();

	/*
	 * At this point everything still needed from the boot loader
	 * or BIOS or kernel text should be early reserved or marked not
	 * RAM in e820. All other memory is free game.
	 */

#ifdef CONFIG_X86_32
	memcpy(&boot_cpu_data, &new_cpu_data, sizeof(new_cpu_data));

	/*
	 * copy kernel address range established so far and switch
	 * to the proper swapper page table
	 */
	clone_pgd_range(swapper_pg_dir     + KERNEL_PGD_BOUNDARY,
			initial_page_table + KERNEL_PGD_BOUNDARY,
			KERNEL_PGD_PTRS);

	load_cr3(swapper_pg_dir);
	/*
	 * Note: Quark X1000 CPUs advertise PGE incorrectly and require
	 * a cr3 based tlb flush, so the following __flush_tlb_all()
	 * will not flush anything because the cpu quirk which clears
	 * X86_FEATURE_PGE has not been invoked yet. Though due to the
	 * load_cr3() above the TLB has been flushed already. The
	 * quirk is invoked before subsequent calls to __flush_tlb_all()
	 * so proper operation is guaranteed.
	 */
	__flush_tlb_all();
#else
	printk(KERN_INFO "Command line: %s\n", boot_command_line);
	boot_cpu_data.x86_phys_bits = MAX_PHYSMEM_BITS;
#endif

	/*
	 * If we have OLPC OFW, we might end up relocating the fixmap due to
	 * reserve_top(), so do this before touching the ioremap area.
	 */
	olpc_ofw_detect();

	idt_setup_early_traps();
	early_cpu_init();
	arch_init_ideal_nops();
	jump_label_init();
	early_ioremap_init();

	setup_olpc_ofw_pgd();

	ROOT_DEV = old_decode_dev(boot_params.hdr.root_dev);
	screen_info = boot_params.screen_info;
	edid_info = boot_params.edid_info;
#ifdef CONFIG_X86_32
	apm_info.bios = boot_params.apm_bios_info;
	ist_info = boot_params.ist_info;
#endif
	saved_video_mode = boot_params.hdr.vid_mode;
	bootloader_type = boot_params.hdr.type_of_loader;
	if ((bootloader_type >> 4) == 0xe) {
		bootloader_type &= 0xf;
		bootloader_type |= (boot_params.hdr.ext_loader_type+0x10) << 4;
	}
	bootloader_version  = bootloader_type & 0xf;
	bootloader_version |= boot_params.hdr.ext_loader_ver << 4;

#ifdef CONFIG_BLK_DEV_RAM
	rd_image_start = boot_params.hdr.ram_size & RAMDISK_IMAGE_START_MASK;
	rd_prompt = ((boot_params.hdr.ram_size & RAMDISK_PROMPT_FLAG) != 0);
	rd_doload = ((boot_params.hdr.ram_size & RAMDISK_LOAD_FLAG) != 0);
#endif
#ifdef CONFIG_EFI
	if (!strncmp((char *)&boot_params.efi_info.efi_loader_signature,
		     EFI32_LOADER_SIGNATURE, 4)) {
		set_bit(EFI_BOOT, &efi.flags);
	} else if (!strncmp((char *)&boot_params.efi_info.efi_loader_signature,
		     EFI64_LOADER_SIGNATURE, 4)) {
		set_bit(EFI_BOOT, &efi.flags);
		set_bit(EFI_64BIT, &efi.flags);
	}
#endif

	x86_init.oem.arch_setup();

	iomem_resource.end = (1ULL << boot_cpu_data.x86_phys_bits) - 1;
	e820__memory_setup();
	parse_setup_data();

	copy_edd();

	if (!boot_params.hdr.root_flags)
		root_mountflags &= ~MS_RDONLY;
	init_mm.start_code = (unsigned long) _text;
	init_mm.end_code = (unsigned long) _etext;
	init_mm.end_data = (unsigned long) _edata;
	init_mm.brk = _brk_end;

	mpx_mm_init(&init_mm);

	code_resource.start = __pa_symbol(_text);
	code_resource.end = __pa_symbol(_etext)-1;
	data_resource.start = __pa_symbol(_etext);
	data_resource.end = __pa_symbol(_edata)-1;
	bss_resource.start = __pa_symbol(__bss_start);
	bss_resource.end = __pa_symbol(__bss_stop)-1;

#ifdef CONFIG_CMDLINE_BOOL
#ifdef CONFIG_CMDLINE_OVERRIDE
	strlcpy(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
#else
	if (builtin_cmdline[0]) {
		/* append boot loader cmdline to builtin */
		strlcat(builtin_cmdline, " ", COMMAND_LINE_SIZE);
		strlcat(builtin_cmdline, boot_command_line, COMMAND_LINE_SIZE);
		strlcpy(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
	}
#endif
#endif

	strlcpy(command_line, boot_command_line, COMMAND_LINE_SIZE);
	*cmdline_p = command_line;

	/*
	 * x86_configure_nx() is called before parse_early_param() to detect
	 * whether hardware doesn't support NX (so that the early EHCI debug
	 * console setup can safely call set_fixmap()). It may then be called
	 * again from within noexec_setup() during parsing early parameters
	 * to honor the respective command line option.
	 */
	x86_configure_nx();

	parse_early_param();

	if (efi_enabled(EFI_BOOT))
		efi_memblock_x86_reserve_range();
#ifdef CONFIG_MEMORY_HOTPLUG
	/*
	 * Memory used by the kernel cannot be hot-removed because Linux
	 * cannot migrate the kernel pages. When memory hotplug is
	 * enabled, we should prevent memblock from allocating memory
	 * for the kernel.
	 *
	 * ACPI SRAT records all hotpluggable memory ranges. But before
	 * SRAT is parsed, we don't know about it.
	 *
	 * The kernel image is loaded into memory at very early time. We
	 * cannot prevent this anyway. So on NUMA system, we set any
	 * node the kernel resides in as un-hotpluggable.
	 *
	 * Since on modern servers, one node could have double-digit
	 * gigabytes memory, we can assume the memory around the kernel
	 * image is also un-hotpluggable. So before SRAT is parsed, just
	 * allocate memory near the kernel image to try the best to keep
	 * the kernel away from hotpluggable memory.
	 */
	if (movable_node_is_enabled())
		memblock_set_bottom_up(true);
#endif

	x86_report_nx();

	/* after early param, so could get panic from serial */
	memblock_x86_reserve_range_setup_data();

	if (acpi_mps_check()) {
#ifdef CONFIG_X86_LOCAL_APIC
		disable_apic = 1;
#endif
		setup_clear_cpu_cap(X86_FEATURE_APIC);
	}

	e820__reserve_setup_data();
	e820__finish_early_params();

	if (efi_enabled(EFI_BOOT))
		efi_init();

	dmi_setup();

	/*
	 * VMware detection requires dmi to be available, so this
	 * needs to be done after dmi_setup(), for the boot CPU.
	 */
	init_hypervisor_platform();

	tsc_early_init();
	x86_init.resources.probe_roms();

	/* after parse_early_param, so could debug it */
	insert_resource(&iomem_resource, &code_resource);
	insert_resource(&iomem_resource, &data_resource);
	insert_resource(&iomem_resource, &bss_resource);

	e820_add_kernel_range();
	trim_bios_range();
#ifdef CONFIG_X86_32
	if (ppro_with_ram_bug()) {
		e820__range_update(0x70000000ULL, 0x40000ULL, E820_TYPE_RAM,
				  E820_TYPE_RESERVED);
		e820__update_table(e820_table);
		printk(KERN_INFO "fixed physical RAM map:\n");
		e820__print_table("bad_ppro");
	}
#else
	early_gart_iommu_check();
#endif

	/*
	 * partially used pages are not usable - thus
	 * we are rounding upwards:
	 */
	max_pfn = e820__end_of_ram_pfn();

	/* update e820 for memory not covered by WB MTRRs */
	mtrr_bp_init();
	if (mtrr_trim_uncached_memory(max_pfn))
		max_pfn = e820__end_of_ram_pfn();

	max_possible_pfn = max_pfn;

	/*
	 * This call is required when the CPU does not support PAT. If
	 * mtrr_bp_init() invoked it already via pat_init() the call has no
	 * effect.
	 */
	init_cache_modes();

	/*
	 * Define random base addresses for memory sections after max_pfn is
	 * defined and before each memory section base is used.
	 */
	kernel_randomize_memory();

#ifdef CONFIG_X86_32
	/* max_low_pfn get updated here */
	find_low_pfn_range();
#else
	check_x2apic();

	/* How many end-of-memory variables you have, grandma! */
	/* need this before calling reserve_initrd */
	if (max_pfn > (1UL<<(32 - PAGE_SHIFT)))
		max_low_pfn = e820__end_of_low_ram_pfn();
	else
		max_low_pfn = max_pfn;

	high_memory = (void *)__va(max_pfn * PAGE_SIZE - 1) + 1;
#endif

	/*
	 * Find and reserve possible boot-time SMP configuration:
	 */
	find_smp_config();

	reserve_ibft_region();

	early_alloc_pgt_buf();

	/*
	 * Need to conclude brk, before e820__memblock_setup()
	 *  it could use memblock_find_in_range, could overlap with
	 *  brk area.
	 */
	reserve_brk();

	cleanup_highmap();

	memblock_set_current_limit(ISA_END_ADDRESS);
	e820__memblock_setup();

	reserve_bios_regions();

	if (efi_enabled(EFI_MEMMAP)) {
		efi_fake_memmap();
		efi_find_mirror();
		efi_esrt_init();

		/*
		 * The EFI specification says that boot service code won't be
		 * called after ExitBootServices(). This is, in fact, a lie.
		 */
		efi_reserve_boot_services();
	}

	/* preallocate 4k for mptable mpc */
	e820__memblock_alloc_reserved_mpc_new();

#ifdef CONFIG_X86_CHECK_BIOS_CORRUPTION
	setup_bios_corruption_check();
#endif

#ifdef CONFIG_X86_32
	printk(KERN_DEBUG "initial memory mapped: [mem 0x00000000-%#010lx]\n",
			(max_pfn_mapped<<PAGE_SHIFT) - 1);
#endif

	reserve_real_mode();

	trim_platform_memory_ranges();
	trim_low_memory_range();

	init_mem_mapping();

	idt_setup_early_pf();

	/*
	 * Update mmu_cr4_features (and, indirectly, trampoline_cr4_features)
	 * with the current CR4 value.  This may not be necessary, but
	 * auditing all the early-boot CR4 manipulation would be needed to
	 * rule it out.
	 *
	 * Mask off features that don't work outside long mode (just
	 * PCIDE for now).
	 */
	mmu_cr4_features = __read_cr4() & ~X86_CR4_PCIDE;

	memblock_set_current_limit(get_max_mapped());

	/*
	 * NOTE: On x86-32, only from this point on, fixmaps are ready for use.
	 */

#ifdef CONFIG_PROVIDE_OHCI1394_DMA_INIT
	if (init_ohci1394_dma_early)
		init_ohci1394_dma_on_all_controllers();
#endif
	/* Allocate bigger log buffer */
	setup_log_buf(1);

	if (efi_enabled(EFI_BOOT)) {
		switch (boot_params.secure_boot) {
		case efi_secureboot_mode_disabled:
			pr_info("Secure boot disabled\n");
			break;
		case efi_secureboot_mode_enabled:
			pr_info("Secure boot enabled\n");
			break;
		default:
			pr_info("Secure boot could not be determined\n");
			break;
		}
	}

	reserve_initrd();

	acpi_table_upgrade();

	vsmp_init();

	io_delay_init();

	early_platform_quirks();

	/*
	 * Parse the ACPI tables for possible boot-time SMP configuration.
	 */
	acpi_boot_table_init();

	early_acpi_boot_init();

	initmem_init();
	dma_contiguous_reserve(max_pfn_mapped << PAGE_SHIFT);

	/*
	 * Reserve memory for crash kernel after SRAT is parsed so that it
	 * won't consume hotpluggable memory.
	 */
	reserve_crashkernel();

	memblock_find_dma_reserve();

	if (!early_xdbc_setup_hardware())
		early_xdbc_register_console();

	x86_init.paging.pagetable_init();

	kasan_init();

	/*
	 * Sync back kernel address range.
	 *
	 * FIXME: Can the later sync in setup_cpu_entry_areas() replace
	 * this call?
	 */
	sync_initial_page_table();

	tboot_probe();

	map_vsyscall();

	generic_apic_probe();

	early_quirks();

	/*
	 * Read APIC and some other early information from ACPI tables.
	 */
	acpi_boot_init();
	sfi_init();
	x86_dtb_init();

	/*
	 * get boot-time SMP configuration:
	 */
	get_smp_config();

	/*
	 * Systems w/o ACPI and mptables might not have it mapped the local
	 * APIC yet, but prefill_possible_map() might need to access it.
	 */
	init_apic_mappings();

	prefill_possible_map();

	init_cpu_to_node();

	io_apic_init_mappings();

	x86_init.hyper.guest_late_init();

	e820__reserve_resources();
	e820__register_nosave_regions(max_pfn);

	x86_init.resources.reserve_resources();

	e820__setup_pci_gap();

#ifdef CONFIG_VT
#if defined(CONFIG_VGA_CONSOLE)
	if (!efi_enabled(EFI_BOOT) || (efi_mem_type(0xa0000) != EFI_CONVENTIONAL_MEMORY))
		conswitchp = &vga_con;
#elif defined(CONFIG_DUMMY_CONSOLE)
	conswitchp = &dummy_con;
#endif
#endif
	x86_init.oem.banner();

	x86_init.timers.wallclock_init();

	mcheck_init();

	register_refined_jiffies(CLOCK_TICK_RATE);

#ifdef CONFIG_EFI
	if (efi_enabled(EFI_BOOT))
		efi_apply_memmap_quirks();
#endif

	unwind_init();
}

#ifdef CONFIG_X86_32

static struct resource video_ram_resource = {
	.name	= "Video RAM area",
	.start	= 0xa0000,
	.end	= 0xbffff,
	.flags	= IORESOURCE_BUSY | IORESOURCE_MEM
};

void __init i386_reserve_resources(void)
{
	request_resource(&iomem_resource, &video_ram_resource);
	reserve_standard_io_resources();
}

#endif /* CONFIG_X86_32 */

static struct notifier_block kernel_offset_notifier = {
	.notifier_call = dump_kernel_offset
};

static int __init register_kernel_offset_dumper(void)
{
	atomic_notifier_chain_register(&panic_notifier_list,
					&kernel_offset_notifier);
	return 0;
}
__initcall(register_kernel_offset_dumper);