arch/arm64/kernel/setup.c - arm/linux - Git at Google

 /*
  * Based on arch/arm/kernel/setup.c
  *
  * Copyright (C) 1995-2001 Russell King
  * Copyright (C) 2012 ARM Ltd.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */

 #include <linux/acpi.h>
 #include <linux/export.h>
 #include <linux/kernel.h>
 #include <linux/stddef.h>
 #include <linux/ioport.h>
 #include <linux/delay.h>
 #include <linux/utsname.h>
 #include <linux/initrd.h>
 #include <linux/console.h>
 #include <linux/cache.h>
 #include <linux/bootmem.h>
 #include <linux/screen_info.h>
 #include <linux/init.h>
 #include <linux/kexec.h>
 #include <linux/root_dev.h>
 #include <linux/cpu.h>
 #include <linux/interrupt.h>
 #include <linux/smp.h>
 #include <linux/fs.h>
 #include <linux/proc_fs.h>
 #include <linux/memblock.h>
 #include <linux/of_fdt.h>
 #include <linux/efi.h>
 #include <linux/psci.h>
 #include <linux/sched/task.h>
 #include <linux/mm.h>

 #include <asm/acpi.h>
 #include <asm/fixmap.h>
 #include <asm/cpu.h>
 #include <asm/cputype.h>
 #include <asm/elf.h>
 #include <asm/cpufeature.h>
 #include <asm/cpu_ops.h>
 #include <asm/kasan.h>
 #include <asm/numa.h>
 #include <asm/sections.h>
 #include <asm/setup.h>
 #include <asm/smp_plat.h>
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
 #include <asm/traps.h>
 #include <asm/memblock.h>
 #include <asm/efi.h>
 #include <asm/xen/hypervisor.h>
 #include <asm/mmu_context.h>

 phys_addr_t __fdt_pointer __initdata;

 /*
  * Standard memory resources
  */
 static struct resource mem_res[] = {
 	{
 		.name = "Kernel code",
 		.start = 0,
 		.end = 0,
 		.flags = IORESOURCE_SYSTEM_RAM
 	},
 	{
 		.name = "Kernel data",
 		.start = 0,
 		.end = 0,
 		.flags = IORESOURCE_SYSTEM_RAM
 	}
 };

 #define kernel_code mem_res[0]
 #define kernel_data mem_res[1]

 /*
  * The recorded values of x0 .. x3 upon kernel entry.
  */
 u64 __cacheline_aligned boot_args[4];

 void __init smp_setup_processor_id(void)
 {
 	u64 mpidr = read_cpuid_mpidr() & MPIDR_HWID_BITMASK;
 	cpu_logical_map(0) = mpidr;

 	/*
 	 * clear __my_cpu_offset on boot CPU to avoid hang caused by
 	 * using percpu variable early, for example, lockdep will
 	 * access percpu variable inside lock_release
 	 */
 	set_my_cpu_offset(0);
 	pr_info("Booting Linux on physical CPU 0x%lx\n", (unsigned long)mpidr);
 }

 bool arch_match_cpu_phys_id(int cpu, u64 phys_id)
 {
 	return phys_id == cpu_logical_map(cpu);
 }

 struct mpidr_hash mpidr_hash;
 /**
  * smp_build_mpidr_hash - Pre-compute shifts required at each affinity
  *			  level in order to build a linear index from an
  *			  MPIDR value. Resulting algorithm is a collision
  *			  free hash carried out through shifting and ORing
  */
 static void __init smp_build_mpidr_hash(void)
 {
 	u32 i, affinity, fs[4], bits[4], ls;
 	u64 mask = 0;
 	/*
 	 * Pre-scan the list of MPIDRS and filter out bits that do
 	 * not contribute to affinity levels, ie they never toggle.
 	 */
 	for_each_possible_cpu(i)
 		mask |= (cpu_logical_map(i) ^ cpu_logical_map(0));
 	pr_debug("mask of set bits %#llx\n", mask);
 	/*
 	 * Find and stash the last and first bit set at all affinity levels to
 	 * check how many bits are required to represent them.
 	 */
 	for (i = 0; i < 4; i++) {
 		affinity = MPIDR_AFFINITY_LEVEL(mask, i);
 		/*
 		 * Find the MSB bit and LSB bits position
 		 * to determine how many bits are required
 		 * to express the affinity level.
 		 */
 		ls = fls(affinity);
 		fs[i] = affinity ? ffs(affinity) - 1 : 0;
 		bits[i] = ls - fs[i];
 	}
 	/*
 	 * An index can be created from the MPIDR_EL1 by isolating the
 	 * significant bits at each affinity level and by shifting
 	 * them in order to compress the 32 bits values space to a
 	 * compressed set of values. This is equivalent to hashing
 	 * the MPIDR_EL1 through shifting and ORing. It is a collision free
 	 * hash though not minimal since some levels might contain a number
 	 * of CPUs that is not an exact power of 2 and their bit
 	 * representation might contain holes, eg MPIDR_EL1[7:0] = {0x2, 0x80}.
 	 */
 	mpidr_hash.shift_aff[0] = MPIDR_LEVEL_SHIFT(0) + fs[0];
 	mpidr_hash.shift_aff[1] = MPIDR_LEVEL_SHIFT(1) + fs[1] - bits[0];
 	mpidr_hash.shift_aff[2] = MPIDR_LEVEL_SHIFT(2) + fs[2] -
 						(bits[1] + bits[0]);
 	mpidr_hash.shift_aff[3] = MPIDR_LEVEL_SHIFT(3) +
 				  fs[3] - (bits[2] + bits[1] + bits[0]);
 	mpidr_hash.mask = mask;
 	mpidr_hash.bits = bits[3] + bits[2] + bits[1] + bits[0];
 	pr_debug("MPIDR hash: aff0[%u] aff1[%u] aff2[%u] aff3[%u] mask[%#llx] bits[%u]\n",
 		mpidr_hash.shift_aff[0],
 		mpidr_hash.shift_aff[1],
 		mpidr_hash.shift_aff[2],
 		mpidr_hash.shift_aff[3],
 		mpidr_hash.mask,
 		mpidr_hash.bits);
 	/*
 	 * 4x is an arbitrary value used to warn on a hash table much bigger
 	 * than expected on most systems.
 	 */
 	if (mpidr_hash_size() > 4 * num_possible_cpus())
 		pr_warn("Large number of MPIDR hash buckets detected\n");
 }

 static void __init setup_machine_fdt(phys_addr_t dt_phys)
 {
 	void *dt_virt = fixmap_remap_fdt(dt_phys);
 	const char *name;

 	if (!dt_virt || !early_init_dt_scan(dt_virt)) {
 		pr_crit("\n"
 			"Error: invalid device tree blob at physical address %pa (virtual address 0x%p)\n"
 			"The dtb must be 8-byte aligned and must not exceed 2 MB in size\n"
 			"\nPlease check your bootloader.",
 			&dt_phys, dt_virt);

 		while (true)
 			cpu_relax();
 	}

 	name = of_flat_dt_get_machine_name();
 	if (!name)
 		return;

 	pr_info("Machine model: %s\n", name);
 	dump_stack_set_arch_desc("%s (DT)", name);
 }

 static void __init request_standard_resources(void)
 {
 	struct memblock_region *region;
 	struct resource *res;

 	kernel_code.start   = __pa_symbol(_text);
 	kernel_code.end     = __pa_symbol(__init_begin - 1);
 	kernel_data.start   = __pa_symbol(_sdata);
 	kernel_data.end     = __pa_symbol(_end - 1);

 	for_each_memblock(memory, region) {
 		res = alloc_bootmem_low(sizeof(*res));
 		if (memblock_is_nomap(region)) {
 			res->name  = "reserved";
 			res->flags = IORESOURCE_MEM;
 		} else {
 			res->name  = "System RAM";
 			res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
 		}
 		res->start = __pfn_to_phys(memblock_region_memory_base_pfn(region));
 		res->end = __pfn_to_phys(memblock_region_memory_end_pfn(region)) - 1;

 		request_resource(&iomem_resource, res);

 		if (kernel_code.start >= res->start &&
 		    kernel_code.end <= res->end)
 			request_resource(res, &kernel_code);
 		if (kernel_data.start >= res->start &&
 		    kernel_data.end <= res->end)
 			request_resource(res, &kernel_data);
 #ifdef CONFIG_KEXEC_CORE
 		/* Userspace will find "Crash kernel" region in /proc/iomem. */
 		if (crashk_res.end && crashk_res.start >= res->start &&
 		    crashk_res.end <= res->end)
 			request_resource(res, &crashk_res);
 #endif
 	}
 }

 u64 __cpu_logical_map[NR_CPUS] = { [0 ... NR_CPUS-1] = INVALID_HWID };

 void __init setup_arch(char **cmdline_p)
 {
 	pr_info("Boot CPU: AArch64 Processor [%08x]\n", read_cpuid_id());

 	sprintf(init_utsname()->machine, UTS_MACHINE);
 	init_mm.start_code = (unsigned long) _text;
 	init_mm.end_code   = (unsigned long) _etext;
 	init_mm.end_data   = (unsigned long) _edata;
 	init_mm.brk	   = (unsigned long) _end;

 	*cmdline_p = boot_command_line;

 	early_fixmap_init();
 	early_ioremap_init();

 	setup_machine_fdt(__fdt_pointer);

 	parse_early_param();

 	/*
 	 *  Unmask asynchronous aborts after bringing up possible earlycon.
 	 * (Report possible System Errors once we can report this occurred)
 	 */
 	local_async_enable();

 	/*
 	 * TTBR0 is only used for the identity mapping at this stage. Make it
 	 * point to zero page to avoid speculatively fetching new entries.
 	 */
 	cpu_uninstall_idmap();

 	xen_early_init();
 	efi_init();
 	arm64_memblock_init();

 	paging_init();

 	acpi_table_upgrade();

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

 	if (acpi_disabled)
 		unflatten_device_tree();

 	bootmem_init();

 	kasan_init();

 	request_standard_resources();

 	early_ioremap_reset();

 	if (acpi_disabled)
 		psci_dt_init();
 	else
 		psci_acpi_init();

 	cpu_read_bootcpu_ops();
 	smp_init_cpus();
 	smp_build_mpidr_hash();

 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
 	/*
 	 * Make sure init_thread_info.ttbr0 always generates translation
 	 * faults in case uaccess_enable() is inadvertently called by the init
 	 * thread.
 	 */
 	init_task.thread_info.ttbr0 = __pa_symbol(empty_zero_page);
 #endif

 #ifdef CONFIG_VT
 #if defined(CONFIG_VGA_CONSOLE)
 	conswitchp = &vga_con;
 #elif defined(CONFIG_DUMMY_CONSOLE)
 	conswitchp = &dummy_con;
 #endif
 #endif
 	if (boot_args[1] || boot_args[2] || boot_args[3]) {
 		pr_err("WARNING: x1-x3 nonzero in violation of boot protocol:\n"
 			"\tx1: %016llx\n\tx2: %016llx\n\tx3: %016llx\n"
 			"This indicates a broken bootloader or old kernel\n",
 			boot_args[1], boot_args[2], boot_args[3]);
 	}
 }

 static int __init topology_init(void)
 {
 	int i;

 	for_each_online_node(i)
 		register_one_node(i);

 	for_each_possible_cpu(i) {
 		struct cpu *cpu = &per_cpu(cpu_data.cpu, i);
 		cpu->hotpluggable = 1;
 		register_cpu(cpu, i);
 	}

 	return 0;
 }
 subsys_initcall(topology_init);

 /*
  * Dump out kernel offset information on panic.
  */
 static int dump_kernel_offset(struct notifier_block *self, unsigned long v,
 			      void *p)
 {
 	const unsigned long offset = kaslr_offset();

 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && offset > 0) {
 		pr_emerg("Kernel Offset: 0x%lx from 0x%lx\n",
 			 offset, KIMAGE_VADDR);
 	} else {
 		pr_emerg("Kernel Offset: disabled\n");
 	}
 	return 0;
 }

 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);
	/*
	* Based on arch/arm/kernel/setup.c
	*
	* Copyright (C) 1995-2001 Russell King
	* Copyright (C) 2012 ARM Ltd.
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program. If not, see <http://www.gnu.org/licenses/>.
	*/

	#include <linux/acpi.h>
	#include <linux/export.h>
	#include <linux/kernel.h>
	#include <linux/stddef.h>
	#include <linux/ioport.h>
	#include <linux/delay.h>
	#include <linux/utsname.h>
	#include <linux/initrd.h>
	#include <linux/console.h>
	#include <linux/cache.h>
	#include <linux/bootmem.h>
	#include <linux/screen_info.h>
	#include <linux/init.h>
	#include <linux/kexec.h>
	#include <linux/root_dev.h>
	#include <linux/cpu.h>
	#include <linux/interrupt.h>
	#include <linux/smp.h>
	#include <linux/fs.h>
	#include <linux/proc_fs.h>
	#include <linux/memblock.h>
	#include <linux/of_fdt.h>
	#include <linux/efi.h>
	#include <linux/psci.h>
	#include <linux/sched/task.h>
	#include <linux/mm.h>

	#include <asm/acpi.h>
	#include <asm/fixmap.h>
	#include <asm/cpu.h>
	#include <asm/cputype.h>
	#include <asm/elf.h>
	#include <asm/cpufeature.h>
	#include <asm/cpu_ops.h>
	#include <asm/kasan.h>
	#include <asm/numa.h>
	#include <asm/sections.h>
	#include <asm/setup.h>
	#include <asm/smp_plat.h>
	#include <asm/cacheflush.h>
	#include <asm/tlbflush.h>
	#include <asm/traps.h>
	#include <asm/memblock.h>
	#include <asm/efi.h>
	#include <asm/xen/hypervisor.h>
	#include <asm/mmu_context.h>

	phys_addr_t __fdt_pointer __initdata;

	/*
	* Standard memory resources
	*/
	static struct resource mem_res[] = {
	{
	.name = "Kernel code",
	.start = 0,
	.end = 0,
	.flags = IORESOURCE_SYSTEM_RAM
	},
	{
	.name = "Kernel data",
	.start = 0,
	.end = 0,
	.flags = IORESOURCE_SYSTEM_RAM
	}
	};

	#define kernel_code mem_res[0]
	#define kernel_data mem_res[1]

	/*
	* The recorded values of x0 .. x3 upon kernel entry.
	*/
	u64 __cacheline_aligned boot_args[4];

	void __init smp_setup_processor_id(void)
	{
	u64 mpidr = read_cpuid_mpidr() & MPIDR_HWID_BITMASK;
	cpu_logical_map(0) = mpidr;

	/*
	* clear __my_cpu_offset on boot CPU to avoid hang caused by
	* using percpu variable early, for example, lockdep will
	* access percpu variable inside lock_release
	*/
	set_my_cpu_offset(0);
	pr_info("Booting Linux on physical CPU 0x%lx\n", (unsigned long)mpidr);
	}

	bool arch_match_cpu_phys_id(int cpu, u64 phys_id)
	{
	return phys_id == cpu_logical_map(cpu);
	}

	struct mpidr_hash mpidr_hash;
	/**
	* smp_build_mpidr_hash - Pre-compute shifts required at each affinity
	* level in order to build a linear index from an
	* MPIDR value. Resulting algorithm is a collision
	* free hash carried out through shifting and ORing
	*/
	static void __init smp_build_mpidr_hash(void)
	{
	u32 i, affinity, fs[4], bits[4], ls;
	u64 mask = 0;
	/*
	* Pre-scan the list of MPIDRS and filter out bits that do
	* not contribute to affinity levels, ie they never toggle.
	*/
	for_each_possible_cpu(i)
	mask \|= (cpu_logical_map(i) ^ cpu_logical_map(0));
	pr_debug("mask of set bits %#llx\n", mask);
	/*
	* Find and stash the last and first bit set at all affinity levels to
	* check how many bits are required to represent them.
	*/
	for (i = 0; i < 4; i++) {
	affinity = MPIDR_AFFINITY_LEVEL(mask, i);
	/*
	* Find the MSB bit and LSB bits position
	* to determine how many bits are required
	* to express the affinity level.
	*/
	ls = fls(affinity);
	fs[i] = affinity ? ffs(affinity) - 1 : 0;
	bits[i] = ls - fs[i];
	}
	/*
	* An index can be created from the MPIDR_EL1 by isolating the
	* significant bits at each affinity level and by shifting
	* them in order to compress the 32 bits values space to a
	* compressed set of values. This is equivalent to hashing
	* the MPIDR_EL1 through shifting and ORing. It is a collision free
	* hash though not minimal since some levels might contain a number
	* of CPUs that is not an exact power of 2 and their bit
	* representation might contain holes, eg MPIDR_EL1[7:0] = {0x2, 0x80}.
	*/
	mpidr_hash.shift_aff[0] = MPIDR_LEVEL_SHIFT(0) + fs[0];
	mpidr_hash.shift_aff[1] = MPIDR_LEVEL_SHIFT(1) + fs[1] - bits[0];
	mpidr_hash.shift_aff[2] = MPIDR_LEVEL_SHIFT(2) + fs[2] -
	(bits[1] + bits[0]);
	mpidr_hash.shift_aff[3] = MPIDR_LEVEL_SHIFT(3) +
	fs[3] - (bits[2] + bits[1] + bits[0]);
	mpidr_hash.mask = mask;
	mpidr_hash.bits = bits[3] + bits[2] + bits[1] + bits[0];
	pr_debug("MPIDR hash: aff0[%u] aff1[%u] aff2[%u] aff3[%u] mask[%#llx] bits[%u]\n",
	mpidr_hash.shift_aff[0],
	mpidr_hash.shift_aff[1],
	mpidr_hash.shift_aff[2],
	mpidr_hash.shift_aff[3],
	mpidr_hash.mask,
	mpidr_hash.bits);
	/*
	* 4x is an arbitrary value used to warn on a hash table much bigger
	* than expected on most systems.
	*/
	if (mpidr_hash_size() > 4 * num_possible_cpus())
	pr_warn("Large number of MPIDR hash buckets detected\n");
	}

	static void __init setup_machine_fdt(phys_addr_t dt_phys)
	{
	void *dt_virt = fixmap_remap_fdt(dt_phys);
	const char *name;

	if (!dt_virt \|\| !early_init_dt_scan(dt_virt)) {
	pr_crit("\n"
	"Error: invalid device tree blob at physical address %pa (virtual address 0x%p)\n"
	"The dtb must be 8-byte aligned and must not exceed 2 MB in size\n"
	"\nPlease check your bootloader.",
	&dt_phys, dt_virt);

	while (true)
	cpu_relax();
	}

	name = of_flat_dt_get_machine_name();
	if (!name)
	return;

	pr_info("Machine model: %s\n", name);
	dump_stack_set_arch_desc("%s (DT)", name);
	}

	static void __init request_standard_resources(void)
	{
	struct memblock_region *region;
	struct resource *res;

	kernel_code.start = __pa_symbol(_text);
	kernel_code.end = __pa_symbol(__init_begin - 1);
	kernel_data.start = __pa_symbol(_sdata);
	kernel_data.end = __pa_symbol(_end - 1);

	for_each_memblock(memory, region) {
	res = alloc_bootmem_low(sizeof(*res));
	if (memblock_is_nomap(region)) {
	res->name = "reserved";
	res->flags = IORESOURCE_MEM;
	} else {
	res->name = "System RAM";
	res->flags = IORESOURCE_SYSTEM_RAM \| IORESOURCE_BUSY;
	}
	res->start = __pfn_to_phys(memblock_region_memory_base_pfn(region));
	res->end = __pfn_to_phys(memblock_region_memory_end_pfn(region)) - 1;

	request_resource(&iomem_resource, res);

	if (kernel_code.start >= res->start &&
	kernel_code.end <= res->end)
	request_resource(res, &kernel_code);
	if (kernel_data.start >= res->start &&
	kernel_data.end <= res->end)
	request_resource(res, &kernel_data);
	#ifdef CONFIG_KEXEC_CORE
	/* Userspace will find "Crash kernel" region in /proc/iomem. */
	if (crashk_res.end && crashk_res.start >= res->start &&
	crashk_res.end <= res->end)
	request_resource(res, &crashk_res);
	#endif
	}
	}

	u64 __cpu_logical_map[NR_CPUS] = { [0 ... NR_CPUS-1] = INVALID_HWID };

	void __init setup_arch(char **cmdline_p)
	{
	pr_info("Boot CPU: AArch64 Processor [%08x]\n", read_cpuid_id());

	sprintf(init_utsname()->machine, UTS_MACHINE);
	init_mm.start_code = (unsigned long) _text;
	init_mm.end_code = (unsigned long) _etext;
	init_mm.end_data = (unsigned long) _edata;
	init_mm.brk = (unsigned long) _end;

	*cmdline_p = boot_command_line;

	early_fixmap_init();
	early_ioremap_init();

	setup_machine_fdt(__fdt_pointer);

	parse_early_param();

	/*
	* Unmask asynchronous aborts after bringing up possible earlycon.
	* (Report possible System Errors once we can report this occurred)
	*/
	local_async_enable();

	/*
	* TTBR0 is only used for the identity mapping at this stage. Make it
	* point to zero page to avoid speculatively fetching new entries.
	*/
	cpu_uninstall_idmap();

	xen_early_init();
	efi_init();
	arm64_memblock_init();

	paging_init();

	acpi_table_upgrade();

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

	if (acpi_disabled)
	unflatten_device_tree();

	bootmem_init();

	kasan_init();

	request_standard_resources();

	early_ioremap_reset();

	if (acpi_disabled)
	psci_dt_init();
	else
	psci_acpi_init();

	cpu_read_bootcpu_ops();
	smp_init_cpus();
	smp_build_mpidr_hash();

	#ifdef CONFIG_ARM64_SW_TTBR0_PAN
	/*
	* Make sure init_thread_info.ttbr0 always generates translation
	* faults in case uaccess_enable() is inadvertently called by the init
	* thread.
	*/
	init_task.thread_info.ttbr0 = __pa_symbol(empty_zero_page);
	#endif

	#ifdef CONFIG_VT
	#if defined(CONFIG_VGA_CONSOLE)
	conswitchp = &vga_con;
	#elif defined(CONFIG_DUMMY_CONSOLE)
	conswitchp = &dummy_con;
	#endif
	#endif
	if (boot_args[1] \|\| boot_args[2] \|\| boot_args[3]) {
	pr_err("WARNING: x1-x3 nonzero in violation of boot protocol:\n"
	"\tx1: %016llx\n\tx2: %016llx\n\tx3: %016llx\n"
	"This indicates a broken bootloader or old kernel\n",
	boot_args[1], boot_args[2], boot_args[3]);
	}
	}

	static int __init topology_init(void)
	{
	int i;

	for_each_online_node(i)
	register_one_node(i);

	for_each_possible_cpu(i) {
	struct cpu *cpu = &per_cpu(cpu_data.cpu, i);
	cpu->hotpluggable = 1;
	register_cpu(cpu, i);
	}

	return 0;
	}
	subsys_initcall(topology_init);

	/*
	* Dump out kernel offset information on panic.
	*/
	static int dump_kernel_offset(struct notifier_block *self, unsigned long v,
	void *p)
	{
	const unsigned long offset = kaslr_offset();

	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && offset > 0) {
	pr_emerg("Kernel Offset: 0x%lx from 0x%lx\n",
	offset, KIMAGE_VADDR);
	} else {
	pr_emerg("Kernel Offset: disabled\n");
	}
	return 0;
	}

	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);