arch/x86/kernel/machine_kexec_64.c - kernel/common.git - Git at Google

 /*
  * handle transition of Linux booting another kernel
  * Copyright (C) 2002-2005 Eric Biederman  <ebiederm@xmission.com>
  *
  * This source code is licensed under the GNU General Public License,
  * Version 2.  See the file COPYING for more details.
  */

 #define pr_fmt(fmt)	"kexec: " fmt

 #include <linux/mm.h>
 #include <linux/kexec.h>
 #include <linux/string.h>
 #include <linux/gfp.h>
 #include <linux/reboot.h>
 #include <linux/numa.h>
 #include <linux/ftrace.h>
 #include <linux/io.h>
 #include <linux/suspend.h>
 #include <linux/vmalloc.h>

 #include <asm/init.h>
 #include <asm/pgtable.h>
 #include <asm/tlbflush.h>
 #include <asm/mmu_context.h>
 #include <asm/io_apic.h>
 #include <asm/debugreg.h>
 #include <asm/kexec-bzimage64.h>
 #include <asm/setup.h>

 #ifdef CONFIG_KEXEC_FILE
 static struct kexec_file_ops *kexec_file_loaders[] = {
 		&kexec_bzImage64_ops,
 };
 #endif

 static void free_transition_pgtable(struct kimage *image)
 {
 	free_page((unsigned long)image->arch.pud);
 	free_page((unsigned long)image->arch.pmd);
 	free_page((unsigned long)image->arch.pte);
 }

 static int init_transition_pgtable(struct kimage *image, pgd_t *pgd)
 {
 	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *pte;
 	unsigned long vaddr, paddr;
 	int result = -ENOMEM;

 	vaddr = (unsigned long)relocate_kernel;
 	paddr = __pa(page_address(image->control_code_page)+PAGE_SIZE);
 	pgd += pgd_index(vaddr);
 	if (!pgd_present(*pgd)) {
 		pud = (pud_t *)get_zeroed_page(GFP_KERNEL);
 		if (!pud)
 			goto err;
 		image->arch.pud = pud;
 		set_pgd(pgd, __pgd(__pa(pud) | _KERNPG_TABLE));
 	}
 	pud = pud_offset(pgd, vaddr);
 	if (!pud_present(*pud)) {
 		pmd = (pmd_t *)get_zeroed_page(GFP_KERNEL);
 		if (!pmd)
 			goto err;
 		image->arch.pmd = pmd;
 		set_pud(pud, __pud(__pa(pmd) | _KERNPG_TABLE));
 	}
 	pmd = pmd_offset(pud, vaddr);
 	if (!pmd_present(*pmd)) {
 		pte = (pte_t *)get_zeroed_page(GFP_KERNEL);
 		if (!pte)
 			goto err;
 		image->arch.pte = pte;
 		set_pmd(pmd, __pmd(__pa(pte) | _KERNPG_TABLE));
 	}
 	pte = pte_offset_kernel(pmd, vaddr);
 	set_pte(pte, pfn_pte(paddr >> PAGE_SHIFT, PAGE_KERNEL_EXEC));
 	return 0;
 err:
 	free_transition_pgtable(image);
 	return result;
 }

 static void *alloc_pgt_page(void *data)
 {
 	struct kimage *image = (struct kimage *)data;
 	struct page *page;
 	void *p = NULL;

 	page = kimage_alloc_control_pages(image, 0);
 	if (page) {
 		p = page_address(page);
 		clear_page(p);
 	}

 	return p;
 }

 static int init_pgtable(struct kimage *image, unsigned long start_pgtable)
 {
 	struct x86_mapping_info info = {
 		.alloc_pgt_page	= alloc_pgt_page,
 		.context	= image,
 		.pmd_flag	= __PAGE_KERNEL_LARGE_EXEC,
 	};
 	unsigned long mstart, mend;
 	pgd_t *level4p;
 	int result;
 	int i;

 	level4p = (pgd_t *)__va(start_pgtable);
 	clear_page(level4p);
 	for (i = 0; i < nr_pfn_mapped; i++) {
 		mstart = pfn_mapped[i].start << PAGE_SHIFT;
 		mend   = pfn_mapped[i].end << PAGE_SHIFT;

 		result = kernel_ident_mapping_init(&info,
 						 level4p, mstart, mend);
 		if (result)
 			return result;
 	}

 	/*
 	 * segments's mem ranges could be outside 0 ~ max_pfn,
 	 * for example when jump back to original kernel from kexeced kernel.
 	 * or first kernel is booted with user mem map, and second kernel
 	 * could be loaded out of that range.
 	 */
 	for (i = 0; i < image->nr_segments; i++) {
 		mstart = image->segment[i].mem;
 		mend   = mstart + image->segment[i].memsz;

 		result = kernel_ident_mapping_init(&info,
 						 level4p, mstart, mend);

 		if (result)
 			return result;
 	}

 	return init_transition_pgtable(image, level4p);
 }

 static void set_idt(void *newidt, u16 limit)
 {
 	struct desc_ptr curidt;

 	/* x86-64 supports unaliged loads & stores */
 	curidt.size    = limit;
 	curidt.address = (unsigned long)newidt;

 	__asm__ __volatile__ (
 		"lidtq %0\n"
 		: : "m" (curidt)
 		);
 };


 static void set_gdt(void *newgdt, u16 limit)
 {
 	struct desc_ptr curgdt;

 	/* x86-64 supports unaligned loads & stores */
 	curgdt.size    = limit;
 	curgdt.address = (unsigned long)newgdt;

 	__asm__ __volatile__ (
 		"lgdtq %0\n"
 		: : "m" (curgdt)
 		);
 };

 static void load_segments(void)
 {
 	__asm__ __volatile__ (
 		"\tmovl %0,%%ds\n"
 		"\tmovl %0,%%es\n"
 		"\tmovl %0,%%ss\n"
 		"\tmovl %0,%%fs\n"
 		"\tmovl %0,%%gs\n"
 		: : "a" (__KERNEL_DS) : "memory"
 		);
 }

 #ifdef CONFIG_KEXEC_FILE
 /* Update purgatory as needed after various image segments have been prepared */
 static int arch_update_purgatory(struct kimage *image)
 {
 	int ret = 0;

 	if (!image->file_mode)
 		return 0;

 	/* Setup copying of backup region */
 	if (image->type == KEXEC_TYPE_CRASH) {
 		ret = kexec_purgatory_get_set_symbol(image, "backup_dest",
 				&image->arch.backup_load_addr,
 				sizeof(image->arch.backup_load_addr), 0);
 		if (ret)
 			return ret;

 		ret = kexec_purgatory_get_set_symbol(image, "backup_src",
 				&image->arch.backup_src_start,
 				sizeof(image->arch.backup_src_start), 0);
 		if (ret)
 			return ret;

 		ret = kexec_purgatory_get_set_symbol(image, "backup_sz",
 				&image->arch.backup_src_sz,
 				sizeof(image->arch.backup_src_sz), 0);
 		if (ret)
 			return ret;
 	}

 	return ret;
 }
 #else /* !CONFIG_KEXEC_FILE */
 static inline int arch_update_purgatory(struct kimage *image)
 {
 	return 0;
 }
 #endif /* CONFIG_KEXEC_FILE */

 int machine_kexec_prepare(struct kimage *image)
 {
 	unsigned long start_pgtable;
 	int result;

 	/* Calculate the offsets */
 	start_pgtable = page_to_pfn(image->control_code_page) << PAGE_SHIFT;

 	/* Setup the identity mapped 64bit page table */
 	result = init_pgtable(image, start_pgtable);
 	if (result)
 		return result;

 	/* update purgatory as needed */
 	result = arch_update_purgatory(image);
 	if (result)
 		return result;

 	return 0;
 }

 void machine_kexec_cleanup(struct kimage *image)
 {
 	free_transition_pgtable(image);
 }

 /*
  * Do not allocate memory (or fail in any way) in machine_kexec().
  * We are past the point of no return, committed to rebooting now.
  */
 void machine_kexec(struct kimage *image)
 {
 	unsigned long page_list[PAGES_NR];
 	void *control_page;
 	int save_ftrace_enabled;

 #ifdef CONFIG_KEXEC_JUMP
 	if (image->preserve_context)
 		save_processor_state();
 #endif

 	save_ftrace_enabled = __ftrace_enabled_save();

 	/* Interrupts aren't acceptable while we reboot */
 	local_irq_disable();
 	hw_breakpoint_disable();

 	if (image->preserve_context) {
 #ifdef CONFIG_X86_IO_APIC
 		/*
 		 * We need to put APICs in legacy mode so that we can
 		 * get timer interrupts in second kernel. kexec/kdump
 		 * paths already have calls to disable_IO_APIC() in
 		 * one form or other. kexec jump path also need
 		 * one.
 		 */
 		disable_IO_APIC();
 #endif
 	}

 	control_page = page_address(image->control_code_page) + PAGE_SIZE;
 	memcpy(control_page, relocate_kernel, KEXEC_CONTROL_CODE_MAX_SIZE);

 	page_list[PA_CONTROL_PAGE] = virt_to_phys(control_page);
 	page_list[VA_CONTROL_PAGE] = (unsigned long)control_page;
 	page_list[PA_TABLE_PAGE] =
 	  (unsigned long)__pa(page_address(image->control_code_page));

 	if (image->type == KEXEC_TYPE_DEFAULT)
 		page_list[PA_SWAP_PAGE] = (page_to_pfn(image->swap_page)
 						<< PAGE_SHIFT);

 	/*
 	 * The segment registers are funny things, they have both a
 	 * visible and an invisible part.  Whenever the visible part is
 	 * set to a specific selector, the invisible part is loaded
 	 * with from a table in memory.  At no other time is the
 	 * descriptor table in memory accessed.
 	 *
 	 * I take advantage of this here by force loading the
 	 * segments, before I zap the gdt with an invalid value.
 	 */
 	load_segments();
 	/*
 	 * The gdt & idt are now invalid.
 	 * If you want to load them you must set up your own idt & gdt.
 	 */
 	set_gdt(phys_to_virt(0), 0);
 	set_idt(phys_to_virt(0), 0);

 	/* now call it */
 	image->start = relocate_kernel((unsigned long)image->head,
 				       (unsigned long)page_list,
 				       image->start,
 				       image->preserve_context);

 #ifdef CONFIG_KEXEC_JUMP
 	if (image->preserve_context)
 		restore_processor_state();
 #endif

 	__ftrace_enabled_restore(save_ftrace_enabled);
 }

 void arch_crash_save_vmcoreinfo(void)
 {
 	VMCOREINFO_SYMBOL(phys_base);
 	VMCOREINFO_SYMBOL(init_level4_pgt);

 #ifdef CONFIG_NUMA
 	VMCOREINFO_SYMBOL(node_data);
 	VMCOREINFO_LENGTH(node_data, MAX_NUMNODES);
 #endif
 	vmcoreinfo_append_str("KERNELOFFSET=%lx\n",
 			      kaslr_offset());
 }

 /* arch-dependent functionality related to kexec file-based syscall */

 #ifdef CONFIG_KEXEC_FILE
 int arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
 				  unsigned long buf_len)
 {
 	int i, ret = -ENOEXEC;
 	struct kexec_file_ops *fops;

 	for (i = 0; i < ARRAY_SIZE(kexec_file_loaders); i++) {
 		fops = kexec_file_loaders[i];
 		if (!fops || !fops->probe)
 			continue;

 		ret = fops->probe(buf, buf_len);
 		if (!ret) {
 			image->fops = fops;
 			return ret;
 		}
 	}

 	return ret;
 }

 void *arch_kexec_kernel_image_load(struct kimage *image)
 {
 	vfree(image->arch.elf_headers);
 	image->arch.elf_headers = NULL;

 	if (!image->fops || !image->fops->load)
 		return ERR_PTR(-ENOEXEC);

 	return image->fops->load(image, image->kernel_buf,
 				 image->kernel_buf_len, image->initrd_buf,
 				 image->initrd_buf_len, image->cmdline_buf,
 				 image->cmdline_buf_len);
 }

 int arch_kimage_file_post_load_cleanup(struct kimage *image)
 {
 	if (!image->fops || !image->fops->cleanup)
 		return 0;

 	return image->fops->cleanup(image->image_loader_data);
 }

 int arch_kexec_kernel_verify_sig(struct kimage *image, void *kernel,
 				 unsigned long kernel_len)
 {
 	if (!image->fops || !image->fops->verify_sig) {
 		pr_debug("kernel loader does not support signature verification.");
 		return -EKEYREJECTED;
 	}

 	return image->fops->verify_sig(kernel, kernel_len);
 }

 /*
  * Apply purgatory relocations.
  *
  * ehdr: Pointer to elf headers
  * sechdrs: Pointer to section headers.
  * relsec: section index of SHT_RELA section.
  *
  * TODO: Some of the code belongs to generic code. Move that in kexec.c.
  */
 int arch_kexec_apply_relocations_add(const Elf64_Ehdr *ehdr,
 				     Elf64_Shdr *sechdrs, unsigned int relsec)
 {
 	unsigned int i;
 	Elf64_Rela *rel;
 	Elf64_Sym *sym;
 	void *location;
 	Elf64_Shdr *section, *symtabsec;
 	unsigned long address, sec_base, value;
 	const char *strtab, *name, *shstrtab;

 	/*
 	 * ->sh_offset has been modified to keep the pointer to section
 	 * contents in memory
 	 */
 	rel = (void *)sechdrs[relsec].sh_offset;

 	/* Section to which relocations apply */
 	section = &sechdrs[sechdrs[relsec].sh_info];

 	pr_debug("Applying relocate section %u to %u\n", relsec,
 		 sechdrs[relsec].sh_info);

 	/* Associated symbol table */
 	symtabsec = &sechdrs[sechdrs[relsec].sh_link];

 	/* String table */
 	if (symtabsec->sh_link >= ehdr->e_shnum) {
 		/* Invalid strtab section number */
 		pr_err("Invalid string table section index %d\n",
 		       symtabsec->sh_link);
 		return -ENOEXEC;
 	}

 	strtab = (char *)sechdrs[symtabsec->sh_link].sh_offset;

 	/* section header string table */
 	shstrtab = (char *)sechdrs[ehdr->e_shstrndx].sh_offset;

 	for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {

 		/*
 		 * rel[i].r_offset contains byte offset from beginning
 		 * of section to the storage unit affected.
 		 *
 		 * This is location to update (->sh_offset). This is temporary
 		 * buffer where section is currently loaded. This will finally
 		 * be loaded to a different address later, pointed to by
 		 * ->sh_addr. kexec takes care of moving it
 		 *  (kexec_load_segment()).
 		 */
 		location = (void *)(section->sh_offset + rel[i].r_offset);

 		/* Final address of the location */
 		address = section->sh_addr + rel[i].r_offset;

 		/*
 		 * rel[i].r_info contains information about symbol table index
 		 * w.r.t which relocation must be made and type of relocation
 		 * to apply. ELF64_R_SYM() and ELF64_R_TYPE() macros get
 		 * these respectively.
 		 */
 		sym = (Elf64_Sym *)symtabsec->sh_offset +
 				ELF64_R_SYM(rel[i].r_info);

 		if (sym->st_name)
 			name = strtab + sym->st_name;
 		else
 			name = shstrtab + sechdrs[sym->st_shndx].sh_name;

 		pr_debug("Symbol: %s info: %02x shndx: %02x value=%llx size: %llx\n",
 			 name, sym->st_info, sym->st_shndx, sym->st_value,
 			 sym->st_size);

 		if (sym->st_shndx == SHN_UNDEF) {
 			pr_err("Undefined symbol: %s\n", name);
 			return -ENOEXEC;
 		}

 		if (sym->st_shndx == SHN_COMMON) {
 			pr_err("symbol '%s' in common section\n", name);
 			return -ENOEXEC;
 		}

 		if (sym->st_shndx == SHN_ABS)
 			sec_base = 0;
 		else if (sym->st_shndx >= ehdr->e_shnum) {
 			pr_err("Invalid section %d for symbol %s\n",
 			       sym->st_shndx, name);
 			return -ENOEXEC;
 		} else
 			sec_base = sechdrs[sym->st_shndx].sh_addr;

 		value = sym->st_value;
 		value += sec_base;
 		value += rel[i].r_addend;

 		switch (ELF64_R_TYPE(rel[i].r_info)) {
 		case R_X86_64_NONE:
 			break;
 		case R_X86_64_64:
 			*(u64 *)location = value;
 			break;
 		case R_X86_64_32:
 			*(u32 *)location = value;
 			if (value != *(u32 *)location)
 				goto overflow;
 			break;
 		case R_X86_64_32S:
 			*(s32 *)location = value;
 			if ((s64)value != *(s32 *)location)
 				goto overflow;
 			break;
 		case R_X86_64_PC32:
 		case R_X86_64_PLT32:
 			value -= (u64)address;
 			*(u32 *)location = value;
 			break;
 		default:
 			pr_err("Unknown rela relocation: %llu\n",
 			       ELF64_R_TYPE(rel[i].r_info));
 			return -ENOEXEC;
 		}
 	}
 	return 0;

 overflow:
 	pr_err("Overflow in relocation type %d value 0x%lx\n",
 	       (int)ELF64_R_TYPE(rel[i].r_info), value);
 	return -ENOEXEC;
 }
 #endif /* CONFIG_KEXEC_FILE */
	/*
	* handle transition of Linux booting another kernel
	* Copyright (C) 2002-2005 Eric Biederman <ebiederm@xmission.com>
	*
	* This source code is licensed under the GNU General Public License,
	* Version 2. See the file COPYING for more details.
	*/

	#define pr_fmt(fmt) "kexec: " fmt

	#include <linux/mm.h>
	#include <linux/kexec.h>
	#include <linux/string.h>
	#include <linux/gfp.h>
	#include <linux/reboot.h>
	#include <linux/numa.h>
	#include <linux/ftrace.h>
	#include <linux/io.h>
	#include <linux/suspend.h>
	#include <linux/vmalloc.h>

	#include <asm/init.h>
	#include <asm/pgtable.h>
	#include <asm/tlbflush.h>
	#include <asm/mmu_context.h>
	#include <asm/io_apic.h>
	#include <asm/debugreg.h>
	#include <asm/kexec-bzimage64.h>
	#include <asm/setup.h>

	#ifdef CONFIG_KEXEC_FILE
	static struct kexec_file_ops *kexec_file_loaders[] = {
	&kexec_bzImage64_ops,
	};
	#endif

	static void free_transition_pgtable(struct kimage *image)
	{
	free_page((unsigned long)image->arch.pud);
	free_page((unsigned long)image->arch.pmd);
	free_page((unsigned long)image->arch.pte);
	}

	static int init_transition_pgtable(struct kimage image, pgd_t pgd)
	{
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;
	unsigned long vaddr, paddr;
	int result = -ENOMEM;

	vaddr = (unsigned long)relocate_kernel;
	paddr = __pa(page_address(image->control_code_page)+PAGE_SIZE);
	pgd += pgd_index(vaddr);
	if (!pgd_present(*pgd)) {
	pud = (pud_t *)get_zeroed_page(GFP_KERNEL);
	if (!pud)
	goto err;
	image->arch.pud = pud;
	set_pgd(pgd, __pgd(__pa(pud) \| _KERNPG_TABLE));
	}
	pud = pud_offset(pgd, vaddr);
	if (!pud_present(*pud)) {
	pmd = (pmd_t *)get_zeroed_page(GFP_KERNEL);
	if (!pmd)
	goto err;
	image->arch.pmd = pmd;
	set_pud(pud, __pud(__pa(pmd) \| _KERNPG_TABLE));
	}
	pmd = pmd_offset(pud, vaddr);
	if (!pmd_present(*pmd)) {
	pte = (pte_t *)get_zeroed_page(GFP_KERNEL);
	if (!pte)
	goto err;
	image->arch.pte = pte;
	set_pmd(pmd, __pmd(__pa(pte) \| _KERNPG_TABLE));
	}
	pte = pte_offset_kernel(pmd, vaddr);
	set_pte(pte, pfn_pte(paddr >> PAGE_SHIFT, PAGE_KERNEL_EXEC));
	return 0;
	err:
	free_transition_pgtable(image);
	return result;
	}

	static void alloc_pgt_page(void data)
	{
	struct kimage image = (struct kimage )data;
	struct page *page;
	void *p = NULL;

	page = kimage_alloc_control_pages(image, 0);
	if (page) {
	p = page_address(page);
	clear_page(p);
	}

	return p;
	}

	static int init_pgtable(struct kimage *image, unsigned long start_pgtable)
	{
	struct x86_mapping_info info = {
	.alloc_pgt_page = alloc_pgt_page,
	.context = image,
	.pmd_flag = __PAGE_KERNEL_LARGE_EXEC,
	};
	unsigned long mstart, mend;
	pgd_t *level4p;
	int result;
	int i;

	level4p = (pgd_t *)__va(start_pgtable);
	clear_page(level4p);
	for (i = 0; i < nr_pfn_mapped; i++) {
	mstart = pfn_mapped[i].start << PAGE_SHIFT;
	mend = pfn_mapped[i].end << PAGE_SHIFT;

	result = kernel_ident_mapping_init(&info,
	level4p, mstart, mend);
	if (result)
	return result;
	}

	/*
	* segments's mem ranges could be outside 0 ~ max_pfn,
	* for example when jump back to original kernel from kexeced kernel.
	* or first kernel is booted with user mem map, and second kernel
	* could be loaded out of that range.
	*/
	for (i = 0; i < image->nr_segments; i++) {
	mstart = image->segment[i].mem;
	mend = mstart + image->segment[i].memsz;

	result = kernel_ident_mapping_init(&info,
	level4p, mstart, mend);

	if (result)
	return result;
	}

	return init_transition_pgtable(image, level4p);
	}

	static void set_idt(void *newidt, u16 limit)
	{
	struct desc_ptr curidt;

	/* x86-64 supports unaliged loads & stores */
	curidt.size = limit;
	curidt.address = (unsigned long)newidt;

	__asm__ __volatile__ (
	"lidtq %0\n"
	: : "m" (curidt)
	);
	};


	static void set_gdt(void *newgdt, u16 limit)
	{
	struct desc_ptr curgdt;

	/* x86-64 supports unaligned loads & stores */
	curgdt.size = limit;
	curgdt.address = (unsigned long)newgdt;

	__asm__ __volatile__ (
	"lgdtq %0\n"
	: : "m" (curgdt)
	);
	};

	static void load_segments(void)
	{
	__asm__ __volatile__ (
	"\tmovl %0,%%ds\n"
	"\tmovl %0,%%es\n"
	"\tmovl %0,%%ss\n"
	"\tmovl %0,%%fs\n"
	"\tmovl %0,%%gs\n"
	: : "a" (__KERNEL_DS) : "memory"
	);
	}

	#ifdef CONFIG_KEXEC_FILE
	/* Update purgatory as needed after various image segments have been prepared */
	static int arch_update_purgatory(struct kimage *image)
	{
	int ret = 0;

	if (!image->file_mode)
	return 0;

	/* Setup copying of backup region */
	if (image->type == KEXEC_TYPE_CRASH) {
	ret = kexec_purgatory_get_set_symbol(image, "backup_dest",
	&image->arch.backup_load_addr,
	sizeof(image->arch.backup_load_addr), 0);
	if (ret)
	return ret;

	ret = kexec_purgatory_get_set_symbol(image, "backup_src",
	&image->arch.backup_src_start,
	sizeof(image->arch.backup_src_start), 0);
	if (ret)
	return ret;

	ret = kexec_purgatory_get_set_symbol(image, "backup_sz",
	&image->arch.backup_src_sz,
	sizeof(image->arch.backup_src_sz), 0);
	if (ret)
	return ret;
	}

	return ret;
	}
	#else /* !CONFIG_KEXEC_FILE */
	static inline int arch_update_purgatory(struct kimage *image)
	{
	return 0;
	}
	#endif /* CONFIG_KEXEC_FILE */

	int machine_kexec_prepare(struct kimage *image)
	{
	unsigned long start_pgtable;
	int result;

	/* Calculate the offsets */
	start_pgtable = page_to_pfn(image->control_code_page) << PAGE_SHIFT;

	/* Setup the identity mapped 64bit page table */
	result = init_pgtable(image, start_pgtable);
	if (result)
	return result;

	/* update purgatory as needed */
	result = arch_update_purgatory(image);
	if (result)
	return result;

	return 0;
	}

	void machine_kexec_cleanup(struct kimage *image)
	{
	free_transition_pgtable(image);
	}

	/*
	* Do not allocate memory (or fail in any way) in machine_kexec().
	* We are past the point of no return, committed to rebooting now.
	*/
	void machine_kexec(struct kimage *image)
	{
	unsigned long page_list[PAGES_NR];
	void *control_page;
	int save_ftrace_enabled;

	#ifdef CONFIG_KEXEC_JUMP
	if (image->preserve_context)
	save_processor_state();
	#endif

	save_ftrace_enabled = __ftrace_enabled_save();

	/* Interrupts aren't acceptable while we reboot */
	local_irq_disable();
	hw_breakpoint_disable();

	if (image->preserve_context) {
	#ifdef CONFIG_X86_IO_APIC
	/*
	* We need to put APICs in legacy mode so that we can
	* get timer interrupts in second kernel. kexec/kdump
	* paths already have calls to disable_IO_APIC() in
	* one form or other. kexec jump path also need
	* one.
	*/
	disable_IO_APIC();
	#endif
	}

	control_page = page_address(image->control_code_page) + PAGE_SIZE;
	memcpy(control_page, relocate_kernel, KEXEC_CONTROL_CODE_MAX_SIZE);

	page_list[PA_CONTROL_PAGE] = virt_to_phys(control_page);
	page_list[VA_CONTROL_PAGE] = (unsigned long)control_page;
	page_list[PA_TABLE_PAGE] =
	(unsigned long)__pa(page_address(image->control_code_page));

	if (image->type == KEXEC_TYPE_DEFAULT)
	page_list[PA_SWAP_PAGE] = (page_to_pfn(image->swap_page)
	<< PAGE_SHIFT);

	/*
	* The segment registers are funny things, they have both a
	* visible and an invisible part. Whenever the visible part is
	* set to a specific selector, the invisible part is loaded
	* with from a table in memory. At no other time is the
	* descriptor table in memory accessed.
	*
	* I take advantage of this here by force loading the
	* segments, before I zap the gdt with an invalid value.
	*/
	load_segments();
	/*
	* The gdt & idt are now invalid.
	* If you want to load them you must set up your own idt & gdt.
	*/
	set_gdt(phys_to_virt(0), 0);
	set_idt(phys_to_virt(0), 0);

	/* now call it */
	image->start = relocate_kernel((unsigned long)image->head,
	(unsigned long)page_list,
	image->start,
	image->preserve_context);

	#ifdef CONFIG_KEXEC_JUMP
	if (image->preserve_context)
	restore_processor_state();
	#endif

	__ftrace_enabled_restore(save_ftrace_enabled);
	}

	void arch_crash_save_vmcoreinfo(void)
	{
	VMCOREINFO_SYMBOL(phys_base);
	VMCOREINFO_SYMBOL(init_level4_pgt);

	#ifdef CONFIG_NUMA
	VMCOREINFO_SYMBOL(node_data);
	VMCOREINFO_LENGTH(node_data, MAX_NUMNODES);
	#endif
	vmcoreinfo_append_str("KERNELOFFSET=%lx\n",
	kaslr_offset());
	}

	/* arch-dependent functionality related to kexec file-based syscall */

	#ifdef CONFIG_KEXEC_FILE
	int arch_kexec_kernel_image_probe(struct kimage image, void buf,
	unsigned long buf_len)
	{
	int i, ret = -ENOEXEC;
	struct kexec_file_ops *fops;

	for (i = 0; i < ARRAY_SIZE(kexec_file_loaders); i++) {
	fops = kexec_file_loaders[i];
	if (!fops \|\| !fops->probe)
	continue;

	ret = fops->probe(buf, buf_len);
	if (!ret) {
	image->fops = fops;
	return ret;
	}
	}

	return ret;
	}

	void arch_kexec_kernel_image_load(struct kimage image)
	{
	vfree(image->arch.elf_headers);
	image->arch.elf_headers = NULL;

	if (!image->fops \|\| !image->fops->load)
	return ERR_PTR(-ENOEXEC);

	return image->fops->load(image, image->kernel_buf,
	image->kernel_buf_len, image->initrd_buf,
	image->initrd_buf_len, image->cmdline_buf,
	image->cmdline_buf_len);
	}

	int arch_kimage_file_post_load_cleanup(struct kimage *image)
	{
	if (!image->fops \|\| !image->fops->cleanup)
	return 0;

	return image->fops->cleanup(image->image_loader_data);
	}

	int arch_kexec_kernel_verify_sig(struct kimage image, void kernel,
	unsigned long kernel_len)
	{
	if (!image->fops \|\| !image->fops->verify_sig) {
	pr_debug("kernel loader does not support signature verification.");
	return -EKEYREJECTED;
	}

	return image->fops->verify_sig(kernel, kernel_len);
	}

	/*
	* Apply purgatory relocations.
	*
	* ehdr: Pointer to elf headers
	* sechdrs: Pointer to section headers.
	* relsec: section index of SHT_RELA section.
	*
	* TODO: Some of the code belongs to generic code. Move that in kexec.c.
	*/
	int arch_kexec_apply_relocations_add(const Elf64_Ehdr *ehdr,
	Elf64_Shdr *sechdrs, unsigned int relsec)
	{
	unsigned int i;
	Elf64_Rela *rel;
	Elf64_Sym *sym;
	void *location;
	Elf64_Shdr section, symtabsec;
	unsigned long address, sec_base, value;
	const char strtab, name, *shstrtab;

	/*
	* ->sh_offset has been modified to keep the pointer to section
	* contents in memory
	*/
	rel = (void *)sechdrs[relsec].sh_offset;

	/* Section to which relocations apply */
	section = &sechdrs[sechdrs[relsec].sh_info];

	pr_debug("Applying relocate section %u to %u\n", relsec,
	sechdrs[relsec].sh_info);

	/* Associated symbol table */
	symtabsec = &sechdrs[sechdrs[relsec].sh_link];

	/* String table */
	if (symtabsec->sh_link >= ehdr->e_shnum) {
	/* Invalid strtab section number */
	pr_err("Invalid string table section index %d\n",
	symtabsec->sh_link);
	return -ENOEXEC;
	}

	strtab = (char *)sechdrs[symtabsec->sh_link].sh_offset;

	/* section header string table */
	shstrtab = (char *)sechdrs[ehdr->e_shstrndx].sh_offset;

	for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {

	/*
	* rel[i].r_offset contains byte offset from beginning
	* of section to the storage unit affected.
	*
	* This is location to update (->sh_offset). This is temporary
	* buffer where section is currently loaded. This will finally
	* be loaded to a different address later, pointed to by
	* ->sh_addr. kexec takes care of moving it
	* (kexec_load_segment()).
	*/
	location = (void *)(section->sh_offset + rel[i].r_offset);

	/* Final address of the location */
	address = section->sh_addr + rel[i].r_offset;

	/*
	* rel[i].r_info contains information about symbol table index
	* w.r.t which relocation must be made and type of relocation
	* to apply. ELF64_R_SYM() and ELF64_R_TYPE() macros get
	* these respectively.
	*/
	sym = (Elf64_Sym *)symtabsec->sh_offset +
	ELF64_R_SYM(rel[i].r_info);

	if (sym->st_name)
	name = strtab + sym->st_name;
	else
	name = shstrtab + sechdrs[sym->st_shndx].sh_name;

	pr_debug("Symbol: %s info: %02x shndx: %02x value=%llx size: %llx\n",
	name, sym->st_info, sym->st_shndx, sym->st_value,
	sym->st_size);

	if (sym->st_shndx == SHN_UNDEF) {
	pr_err("Undefined symbol: %s\n", name);
	return -ENOEXEC;
	}

	if (sym->st_shndx == SHN_COMMON) {
	pr_err("symbol '%s' in common section\n", name);
	return -ENOEXEC;
	}

	if (sym->st_shndx == SHN_ABS)
	sec_base = 0;
	else if (sym->st_shndx >= ehdr->e_shnum) {
	pr_err("Invalid section %d for symbol %s\n",
	sym->st_shndx, name);
	return -ENOEXEC;
	} else
	sec_base = sechdrs[sym->st_shndx].sh_addr;

	value = sym->st_value;
	value += sec_base;
	value += rel[i].r_addend;

	switch (ELF64_R_TYPE(rel[i].r_info)) {
	case R_X86_64_NONE:
	break;
	case R_X86_64_64:
	(u64 )location = value;
	break;
	case R_X86_64_32:
	(u32 )location = value;
	if (value != (u32 )location)
	goto overflow;
	break;
	case R_X86_64_32S:
	(s32 )location = value;
	if ((s64)value != (s32 )location)
	goto overflow;
	break;
	case R_X86_64_PC32:
	case R_X86_64_PLT32:
	value -= (u64)address;
	(u32 )location = value;
	break;
	default:
	pr_err("Unknown rela relocation: %llu\n",
	ELF64_R_TYPE(rel[i].r_info));
	return -ENOEXEC;
	}
	}
	return 0;

	overflow:
	pr_err("Overflow in relocation type %d value 0x%lx\n",
	(int)ELF64_R_TYPE(rel[i].r_info), value);
	return -ENOEXEC;
	}
	#endif /* CONFIG_KEXEC_FILE */