cregit-Linux how code gets into the kernel

Release 4.14 arch/powerpc/kernel/fadump.c

Directory: arch/powerpc/kernel
/*
 * Firmware Assisted dump: A robust mechanism to get reliable kernel crash
 * dump with assistance from firmware. This approach does not use kexec,
 * instead firmware assists in booting the kdump kernel while preserving
 * memory contents. The most of the code implementation has been adapted
 * from phyp assisted dump implementation written by Linas Vepstas and
 * Manish Ahuja
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright 2011 IBM Corporation
 * Author: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
 */


#undef DEBUG

#define pr_fmt(fmt) "fadump: " fmt

#include <linux/string.h>
#include <linux/memblock.h>
#include <linux/delay.h>
#include <linux/seq_file.h>
#include <linux/crash_dump.h>
#include <linux/kobject.h>
#include <linux/sysfs.h>

#include <asm/debugfs.h>
#include <asm/page.h>
#include <asm/prom.h>
#include <asm/rtas.h>
#include <asm/fadump.h>
#include <asm/setup.h>


static struct fw_dump fw_dump;

static struct fadump_mem_struct fdm;

static const struct fadump_mem_struct *fdm_active;

static DEFINE_MUTEX(fadump_mutex);

struct fad_crash_memory_ranges crash_memory_ranges[INIT_CRASHMEM_RANGES];

int crash_mem_ranges;

/* Scan the Firmware Assisted dump configuration details. */



int __init early_init_dt_scan_fw_dump(unsigned long node,
			const char *uname, int depth, void *data)
{
	const __be32 *sections;
	int i, num_sections;
	int size;
	const __be32 *token;

	if (depth != 1 || strcmp(uname, "rtas") != 0)
		return 0;

	/*
         * Check if Firmware Assisted dump is supported. if yes, check
         * if dump has been initiated on last reboot.
         */
	token = of_get_flat_dt_prop(node, "ibm,configure-kernel-dump", NULL);
	if (!token)
		return 1;

	fw_dump.fadump_supported = 1;
	fw_dump.ibm_configure_kernel_dump = be32_to_cpu(*token);

	/*
         * The 'ibm,kernel-dump' rtas node is present only if there is
         * dump data waiting for us.
         */
	fdm_active = of_get_flat_dt_prop(node, "ibm,kernel-dump", NULL);
	if (fdm_active)
		fw_dump.dump_active = 1;

	/* Get the sizes required to store dump data for the firmware provided
         * dump sections.
         * For each dump section type supported, a 32bit cell which defines
         * the ID of a supported section followed by two 32 bit cells which
         * gives teh size of the section in bytes.
         */
	sections = of_get_flat_dt_prop(node, "ibm,configure-kernel-dump-sizes",
					&size);

	if (!sections)
		return 1;

	num_sections = size / (3 * sizeof(u32));

	for (i = 0; i < num_sections; i++, sections += 3) {
		u32 type = (u32)of_read_number(sections, 1);

		switch (type) {
		case FADUMP_CPU_STATE_DATA:
			fw_dump.cpu_state_data_size =
					of_read_ulong(&sections[1], 2);
			break;
		case FADUMP_HPTE_REGION:
			fw_dump.hpte_region_size =
					of_read_ulong(&sections[1], 2);
			break;
		}
	}

	return 1;
}


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/*
 * If fadump is registered, check if the memory provided
 * falls within boot memory area.
 */



int is_fadump_boot_memory_area(u64 addr, ulong size)
{
	if (!fw_dump.dump_registered)
		return 0;

	return (addr + size) > RMA_START && addr <= fw_dump.boot_memory_size;
}


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int should_fadump_crash(void)
{
	if (!fw_dump.dump_registered || !fw_dump.fadumphdr_addr)
		return 0;
	return 1;
}


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int is_fadump_active(void)
{
	return fw_dump.dump_active;
}


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/*
 * Returns 1, if there are no holes in boot memory area,
 * 0 otherwise.
 */



static int is_boot_memory_area_contiguous(void)
{
	struct memblock_region *reg;
	unsigned long tstart, tend;
	unsigned long start_pfn = PHYS_PFN(RMA_START);
	unsigned long end_pfn = PHYS_PFN(RMA_START + fw_dump.boot_memory_size);
	unsigned int ret = 0;

	for_each_memblock(memory, reg) {
		tstart = max(start_pfn, memblock_region_memory_base_pfn(reg));
		tend = min(end_pfn, memblock_region_memory_end_pfn(reg));
		if (tstart < tend) {
			/* Memory hole from start_pfn to tstart */
			if (tstart > start_pfn)
				break;

			if (tend == end_pfn) {
				ret = 1;
				break;
			}

			start_pfn = tend + 1;
		}
	}

	return ret;
}


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/* Print firmware assisted dump configurations for debugging purpose. */



static void fadump_show_config(void)
{
	pr_debug("Support for firmware-assisted dump (fadump): %s\n",
			(fw_dump.fadump_supported ? "present" : "no support"));

	if (!fw_dump.fadump_supported)
		return;

	pr_debug("Fadump enabled    : %s\n",
				(fw_dump.fadump_enabled ? "yes" : "no"));
	pr_debug("Dump Active       : %s\n",
				(fw_dump.dump_active ? "yes" : "no"));
	pr_debug("Dump section sizes:\n");
	pr_debug("    CPU state data size: %lx\n", fw_dump.cpu_state_data_size);
	pr_debug("    HPTE region size   : %lx\n", fw_dump.hpte_region_size);
	pr_debug("Boot memory size  : %lx\n", fw_dump.boot_memory_size);
}


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static unsigned long init_fadump_mem_struct(struct fadump_mem_struct *fdm,
				unsigned long addr)
{
	if (!fdm)
		return 0;

	memset(fdm, 0, sizeof(struct fadump_mem_struct));
	addr = addr & PAGE_MASK;

	fdm->header.dump_format_version = cpu_to_be32(0x00000001);
	fdm->header.dump_num_sections = cpu_to_be16(3);
	fdm->header.dump_status_flag = 0;
	fdm->header.offset_first_dump_section =
		cpu_to_be32((u32)offsetof(struct fadump_mem_struct, cpu_state_data));

	/*
         * Fields for disk dump option.
         * We are not using disk dump option, hence set these fields to 0.
         */
	fdm->header.dd_block_size = 0;
	fdm->header.dd_block_offset = 0;
	fdm->header.dd_num_blocks = 0;
	fdm->header.dd_offset_disk_path = 0;

	/* set 0 to disable an automatic dump-reboot. */
	fdm->header.max_time_auto = 0;

	/* Kernel dump sections */
	/* cpu state data section. */
	fdm->cpu_state_data.request_flag = cpu_to_be32(FADUMP_REQUEST_FLAG);
	fdm->cpu_state_data.source_data_type = cpu_to_be16(FADUMP_CPU_STATE_DATA);
	fdm->cpu_state_data.source_address = 0;
	fdm->cpu_state_data.source_len = cpu_to_be64(fw_dump.cpu_state_data_size);
	fdm->cpu_state_data.destination_address = cpu_to_be64(addr);
	addr += fw_dump.cpu_state_data_size;

	/* hpte region section */
	fdm->hpte_region.request_flag = cpu_to_be32(FADUMP_REQUEST_FLAG);
	fdm->hpte_region.source_data_type = cpu_to_be16(FADUMP_HPTE_REGION);
	fdm->hpte_region.source_address = 0;
	fdm->hpte_region.source_len = cpu_to_be64(fw_dump.hpte_region_size);
	fdm->hpte_region.destination_address = cpu_to_be64(addr);
	addr += fw_dump.hpte_region_size;

	/* RMA region section */
	fdm->rmr_region.request_flag = cpu_to_be32(FADUMP_REQUEST_FLAG);
	fdm->rmr_region.source_data_type = cpu_to_be16(FADUMP_REAL_MODE_REGION);
	fdm->rmr_region.source_address = cpu_to_be64(RMA_START);
	fdm->rmr_region.source_len = cpu_to_be64(fw_dump.boot_memory_size);
	fdm->rmr_region.destination_address = cpu_to_be64(addr);
	addr += fw_dump.boot_memory_size;

	return addr;
}


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/**
 * fadump_calculate_reserve_size(): reserve variable boot area 5% of System RAM
 *
 * Function to find the largest memory size we need to reserve during early
 * boot process. This will be the size of the memory that is required for a
 * kernel to boot successfully.
 *
 * This function has been taken from phyp-assisted dump feature implementation.
 *
 * returns larger of 256MB or 5% rounded down to multiples of 256MB.
 *
 * TODO: Come up with better approach to find out more accurate memory size
 * that is required for a kernel to boot successfully.
 *
 */



static inline unsigned long fadump_calculate_reserve_size(void)
{
	int ret;
	unsigned long long base, size;

	if (fw_dump.reserve_bootvar)
		pr_warn("'fadump_reserve_mem=' parameter is deprecated in favor of 'crashkernel=' parameter.\n");

	/*
         * Check if the size is specified through crashkernel= cmdline
         * option. If yes, then use that but ignore base as fadump reserves
         * memory at a predefined offset.
         */
	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
				&size, &base);
	if (ret == 0 && size > 0) {
		unsigned long max_size;

		if (fw_dump.reserve_bootvar)
			pr_info("Using 'crashkernel=' parameter for memory reservation.\n");

		fw_dump.reserve_bootvar = (unsigned long)size;

		/*
                 * Adjust if the boot memory size specified is above
                 * the upper limit.
                 */
		max_size = memblock_phys_mem_size() / MAX_BOOT_MEM_RATIO;
		if (fw_dump.reserve_bootvar > max_size) {
			fw_dump.reserve_bootvar = max_size;
			pr_info("Adjusted boot memory size to %luMB\n",
				(fw_dump.reserve_bootvar >> 20));
		}

		return fw_dump.reserve_bootvar;
	} else if (fw_dump.reserve_bootvar) {
		/*
                 * 'fadump_reserve_mem=' is being used to reserve memory
                 * for firmware-assisted dump.
                 */
		return fw_dump.reserve_bootvar;
	}

	/* divide by 20 to get 5% of value */
	size = memblock_phys_mem_size() / 20;

	/* round it down in multiples of 256 */
	size = size & ~0x0FFFFFFFUL;

	/* Truncate to memory_limit. We don't want to over reserve the memory.*/
	if (memory_limit && size > memory_limit)
		size = memory_limit;

	return (size > MIN_BOOT_MEM ? size : MIN_BOOT_MEM);
}


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/*
 * Calculate the total memory size required to be reserved for
 * firmware-assisted dump registration.
 */



static unsigned long get_fadump_area_size(void)
{
	unsigned long size = 0;

	size += fw_dump.cpu_state_data_size;
	size += fw_dump.hpte_region_size;
	size += fw_dump.boot_memory_size;
	size += sizeof(struct fadump_crash_info_header);
	size += sizeof(struct elfhdr); /* ELF core header.*/
	size += sizeof(struct elf_phdr); /* place holder for cpu notes */
	/* Program headers for crash memory regions. */
	size += sizeof(struct elf_phdr) * (memblock_num_regions(memory) + 2);

	size = PAGE_ALIGN(size);
	return size;
}


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int __init fadump_reserve_mem(void)
{
	unsigned long base, size, memory_boundary;

	if (!fw_dump.fadump_enabled)
		return 0;

	if (!fw_dump.fadump_supported) {
		printk(KERN_INFO "Firmware-assisted dump is not supported on"
				" this hardware\n");
		fw_dump.fadump_enabled = 0;
		return 0;
	}
	/*
         * Initialize boot memory size
         * If dump is active then we have already calculated the size during
         * first kernel.
         */
	if (fdm_active)
		fw_dump.boot_memory_size = be64_to_cpu(fdm_active->rmr_region.source_len);
	else
		fw_dump.boot_memory_size = fadump_calculate_reserve_size();

	/*
         * Calculate the memory boundary.
         * If memory_limit is less than actual memory boundary then reserve
         * the memory for fadump beyond the memory_limit and adjust the
         * memory_limit accordingly, so that the running kernel can run with
         * specified memory_limit.
         */
	if (memory_limit && memory_limit < memblock_end_of_DRAM()) {
		size = get_fadump_area_size();
		if ((memory_limit + size) < memblock_end_of_DRAM())
			memory_limit += size;
		else
			memory_limit = memblock_end_of_DRAM();
		printk(KERN_INFO "Adjusted memory_limit for firmware-assisted"
				" dump, now %#016llx\n", memory_limit);
	}
	if (memory_limit)
		memory_boundary = memory_limit;
	else
		memory_boundary = memblock_end_of_DRAM();

	if (fw_dump.dump_active) {
		printk(KERN_INFO "Firmware-assisted dump is active.\n");
		/*
                 * If last boot has crashed then reserve all the memory
                 * above boot_memory_size so that we don't touch it until
                 * dump is written to disk by userspace tool. This memory
                 * will be released for general use once the dump is saved.
                 */
		base = fw_dump.boot_memory_size;
		size = memory_boundary - base;
		memblock_reserve(base, size);
		printk(KERN_INFO "Reserved %ldMB of memory at %ldMB "
				"for saving crash dump\n",
				(unsigned long)(size >> 20),
				(unsigned long)(base >> 20));

		fw_dump.fadumphdr_addr =
				be64_to_cpu(fdm_active->rmr_region.destination_address) +
				be64_to_cpu(fdm_active->rmr_region.source_len);
		pr_debug("fadumphdr_addr = %p\n",
				(void *) fw_dump.fadumphdr_addr);
	} else {
		size = get_fadump_area_size();

		/*
                 * Reserve memory at an offset closer to bottom of the RAM to
                 * minimize the impact of memory hot-remove operation. We can't
                 * use memblock_find_in_range() here since it doesn't allocate
                 * from bottom to top.
                 */
		for (base = fw_dump.boot_memory_size;
		     base <= (memory_boundary - size);
		     base += size) {
			if (memblock_is_region_memory(base, size) &&
			    !memblock_is_region_reserved(base, size))
				break;
		}
		if ((base > (memory_boundary - size)) ||
		    memblock_reserve(base, size)) {
			pr_err("Failed to reserve memory\n");
			return 0;
		}

		pr_info("Reserved %ldMB of memory at %ldMB for firmware-"
			"assisted dump (System RAM: %ldMB)\n",
			(unsigned long)(size >> 20),
			(unsigned long)(base >> 20),
			(unsigned long)(memblock_phys_mem_size() >> 20));
	}

	fw_dump.reserve_dump_area_start = base;
	fw_dump.reserve_dump_area_size = size;
	return 1;
}


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unsigned long __init arch_reserved_kernel_pages(void)
{
	return memblock_reserved_size() / PAGE_SIZE;
}


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/* Look for fadump= cmdline option. */



static int __init early_fadump_param(char *p)
{
	if (!p)
		return 1;

	if (strncmp(p, "on", 2) == 0)
		fw_dump.fadump_enabled = 1;
	else if (strncmp(p, "off", 3) == 0)
		fw_dump.fadump_enabled = 0;

	return 0;
}

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early_param("fadump", early_fadump_param);

/*
 * Look for fadump_reserve_mem= cmdline option
 * TODO: Remove references to 'fadump_reserve_mem=' parameter,
 *       the sooner 'crashkernel=' parameter is accustomed to.
 */



static int __init early_fadump_reserve_mem(char *p)
{
	if (p)
		fw_dump.reserve_bootvar = memparse(p, &p);
	return 0;
}

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early_param("fadump_reserve_mem", early_fadump_reserve_mem);




static int register_fw_dump(struct fadump_mem_struct *fdm)
{
	int rc, err;
	unsigned int wait_time;

	pr_debug("Registering for firmware-assisted kernel dump...\n");

	/* TODO: Add upper time limit for the delay */
	do {
		rc = rtas_call(fw_dump.ibm_configure_kernel_dump, 3, 1, NULL,
			FADUMP_REGISTER, fdm,
			sizeof(struct fadump_mem_struct));

		wait_time = rtas_busy_delay_time(rc);
		if (wait_time)
			mdelay(wait_time);

	} while (wait_time);

	err = -EIO;
	switch (rc) {
	default:
		pr_err("Failed to register. Unknown Error(%d).\n", rc);
		break;
	case -1:
		printk(KERN_ERR "Failed to register firmware-assisted kernel"
			" dump. Hardware Error(%d).\n", rc);
		break;
	case -3:
		if (!is_boot_memory_area_contiguous())
			pr_err("Can't have holes in boot memory area while "
			       "registering fadump\n");

		printk(KERN_ERR "Failed to register firmware-assisted kernel"
			" dump. Parameter Error(%d).\n", rc);
		err = -EINVAL;
		break;
	case -9:
		printk(KERN_ERR "firmware-assisted kernel dump is already "
			" registered.");
		fw_dump.dump_registered = 1;
		err = -EEXIST;
		break;
	case 0:
		printk(KERN_INFO "firmware-assisted kernel dump registration"
			" is successful\n");
		fw_dump.dump_registered = 1;
		err = 0;
		break;
	}
	return err;
}


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void crash_fadump(struct pt_regs *regs, const char *str)
{
	struct fadump_crash_info_header *fdh = NULL;
	int old_cpu, this_cpu;

	if (!should_fadump_crash())
		return;

	/*
         * old_cpu == -1 means this is the first CPU which has come here,
         * go ahead and trigger fadump.
         *
         * old_cpu != -1 means some other CPU has already on it's way
         * to trigger fadump, just keep looping here.
         */
	this_cpu = smp_processor_id();
	old_cpu = cmpxchg(&crashing_cpu, -1, this_cpu);

	if (old_cpu != -1) {
		/*
                 * We can't loop here indefinitely. Wait as long as fadump
                 * is in force. If we race with fadump un-registration this
                 * loop will break and then we go down to normal panic path
                 * and reboot. If fadump is in force the first crashing
                 * cpu will definitely trigger fadump.
                 */
		while (fw_dump.dump_registered)
			cpu_relax();
		return;
	}

	fdh = __va(fw_dump.fadumphdr_addr);
	fdh->crashing_cpu = crashing_cpu;
	crash_save_vmcoreinfo();

	if (regs)
		fdh->regs = *regs;
	else
		ppc_save_regs(&fdh->regs);

	fdh->online_mask = *cpu_online_mask;

	/* Call ibm,os-term rtas call to trigger firmware assisted dump */
	rtas_os_term((char *)str);
}


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#define GPR_MASK	0xffffff0000000000



static inline int fadump_gpr_index(u64 id)
{
	int i = -1;
	char str[3];

	if ((id & GPR_MASK) == REG_ID("GPR")) {
		/* get the digits at the end */
		id &= ~GPR_MASK;
		id >>= 24;
		str[2] = '\0';
		str[1] = id & 0xff;
		str[0] = (id >> 8) & 0xff;
		sscanf(str, "%d", &i);
		if (i > 31)
			i = -1;
	}
	return i;
}


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static inline void fadump_set_regval(struct pt_regs *regs, u64 reg_id,
								u64 reg_val)
{
	int i;

	i = fadump_gpr_index(reg_id);
	if (i >= 0)
		regs->gpr[i] = (unsigned long)reg_val;
	else if (reg_id == REG_ID("NIA"))
		regs->nip = (unsigned long)reg_val;
	else if (reg_id == REG_ID("MSR"))
		regs->msr = (unsigned long)reg_val;
	else if (reg_id == REG_ID("CTR"))
		regs->ctr = (unsigned long)reg_val;
	else if (reg_id == REG_ID("LR"))
		regs->link = (unsigned long)reg_val;
	else if (reg_id == REG_ID("XER"))
		regs->xer = (unsigned long)reg_val;
	else if (reg_id == REG_ID("CR"))
		regs->ccr = (unsigned long)reg_val;
	else if (reg_id == REG_ID("DAR"))
		regs->dar = (unsigned long)reg_val;
	else if (reg_id == REG_ID("DSISR"))
		regs->dsisr = (unsigned long)reg_val;
}


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static struct fadump_reg_entry*

fadump_read_registers(struct fadump_reg_entry *reg_entry, struct pt_regs *regs)
{
	memset(regs, 0, sizeof(struct pt_regs));

	while (be64_to_cpu(reg_entry->reg_id) != REG_ID("CPUEND")) {
		fadump_set_regval(regs, be64_to_cpu(reg_entry->reg_id),
					be64_to_cpu(reg_entry->reg_value));
		reg_entry++;
	}
	reg_entry++;
	return reg_entry;
}


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Hari Bathini912.00%150.00%


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static u32 *fadump_regs_to_elf_notes(u32 *buf, struct pt_regs *regs)
{
	struct elf_prstatus prstatus;

	memset(&prstatus, 0, sizeof(prstatus));
	/*
         * FIXME: How do i get PID? Do I really need it?
         * prstatus.pr_pid = ????
         */
	elf_core_copy_kernel_regs(&prstatus.pr_reg, regs);
	buf = append_elf_note(buf, CRASH_CORE_NOTE_NAME, NT_PRSTATUS,
			      &prstatus, sizeof(prstatus));
	return buf;
}


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Mahesh Salgaonkar6496.97%150.00%


Hari Bathini23.03%150.00%


Total66100.00%2100.00%






static void fadump_update_elfcore_header(char *bufp)
{
	struct elfhdr *elf;
	struct elf_phdr *phdr;

	elf = (struct elfhdr *)bufp;
	bufp += sizeof(struct elfhdr);

	/* First note is a place holder for cpu notes info. */
	phdr = (struct elf_phdr *)bufp;

	if (phdr->p_type == PT_NOTE) {
		phdr->p_paddr = fw_dump.cpu_notes_buf;
		phdr->p_offset	= phdr->p_paddr;
		phdr->p_filesz	= fw_dump.cpu_notes_buf_size;
		phdr->p_memsz = fw_dump.cpu_notes_buf_size;
	}
	return;
}


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Mahesh Salgaonkar90100.00%1100.00%


Total90100.00%1100.00%






static void *fadump_cpu_notes_buf_alloc(unsigned long size)
{
	void *vaddr;
	struct page *page;
	unsigned long order, count, i;

	order = get_order(size);
	vaddr = (void *)__get_free_pages(GFP_KERNEL|__GFP_ZERO, order);
	if (!vaddr)
		return NULL;

	count = 1 << order;
	page = virt_to_page(vaddr);
	for (i = 0; i < count; i++)
		SetPageReserved(page + i);
	return vaddr;
}


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Mahesh Salgaonkar94100.00%1100.00%


Total94100.00%1100.00%






static void fadump_cpu_notes_buf_free(unsigned long vaddr, unsigned long size)
{
	struct page *page;
	unsigned long order, count, i;

	order = get_order(size);
	count = 1 << order;
	page = virt_to_page(vaddr);
	for (i = 0; i < count; i++)
		ClearPageReserved(page + i);
	__free_pages(page, order);
}


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Mahesh Salgaonkar74100.00%1100.00%


Total74100.00%1100.00%



/*
 * Read CPU state dump data and convert it into ELF notes.
 * The CPU dump starts with magic number "REGSAVE". NumCpusOffset should be
 * used to access the data to allow for additional fields to be added without
 * affecting compatibility. Each list of registers for a CPU starts with
 * "CPUSTRT" and ends with "CPUEND". Each register entry is of 16 bytes,
 * 8 Byte ASCII identifier and 8 Byte register value. The register entry
 * with identifier "CPUSTRT" and "CPUEND" contains 4 byte cpu id as part
 * of register value. For more details refer to PAPR document.
 *
 * Only for the crashing cpu we ignore the CPU dump data and get exact
 * state from fadump crash info structure populated by first kernel at the
 * time of crash.
 */



static int __init fadump_build_cpu_notes(const struct fadump_mem_struct *fdm)
{
	struct fadump_reg_save_area_header *reg_header;
	struct fadump_reg_entry *reg_entry;
	struct fadump_crash_info_header *fdh = NULL;
	void *vaddr;
	unsigned long addr;
	u32 num_cpus, *note_buf;
	struct pt_regs regs;
	int i, rc = 0, cpu = 0;

	if (!fdm->cpu_state_data.bytes_dumped)
		return -EINVAL;

	addr = be64_to_cpu(fdm->cpu_state_data.destination_address);
	vaddr = __va(addr);

	reg_header = vaddr;
	if (be64_to_cpu(reg_header->magic_number) != REGSAVE_AREA_MAGIC) {
		printk(KERN_ERR "Unable to read register save area.\n");
		return -ENOENT;
	}
	pr_debug("--------CPU State Data------------\n");
	pr_debug("Magic Number: %llx\n", be64_to_cpu(reg_header->magic_number));
	pr_debug("NumCpuOffset: %x\n", be32_to_cpu(reg_header->num_cpu_offset));

	vaddr += be32_to_cpu(reg_header->num_cpu_offset);
	num_cpus = be32_to_cpu(*((__be32 *)(vaddr)));
	pr_debug