arch/powerpc/kernel/machine_kexec_64.c - arm/linux-arm64-legacy - Git at Google

 /*
  * PPC64 code to handle Linux booting another kernel.
  *
  * Copyright (C) 2004-2005, IBM Corp.
  *
  * Created by: Milton D Miller II
  *
  * This source code is licensed under the GNU General Public License,
  * Version 2.  See the file COPYING for more details.
  */


 #include <linux/kexec.h>
 #include <linux/smp.h>
 #include <linux/thread_info.h>
 #include <linux/init_task.h>
 #include <linux/errno.h>
 #include <linux/kernel.h>
 #include <linux/cpu.h>

 #include <asm/page.h>
 #include <asm/current.h>
 #include <asm/machdep.h>
 #include <asm/cacheflush.h>
 #include <asm/paca.h>
 #include <asm/mmu.h>
 #include <asm/sections.h>	/* _end */
 #include <asm/prom.h>
 #include <asm/smp.h>
 #include <asm/hw_breakpoint.h>

 int default_machine_kexec_prepare(struct kimage *image)
 {
 	int i;
 	unsigned long begin, end;	/* limits of segment */
 	unsigned long low, high;	/* limits of blocked memory range */
 	struct device_node *node;
 	const unsigned long *basep;
 	const unsigned int *sizep;

 	if (!ppc_md.hpte_clear_all)
 		return -ENOENT;

 	/*
 	 * Since we use the kernel fault handlers and paging code to
 	 * handle the virtual mode, we must make sure no destination
 	 * overlaps kernel static data or bss.
 	 */
 	for (i = 0; i < image->nr_segments; i++)
 		if (image->segment[i].mem < __pa(_end))
 			return -ETXTBSY;

 	/*
 	 * For non-LPAR, we absolutely can not overwrite the mmu hash
 	 * table, since we are still using the bolted entries in it to
 	 * do the copy.  Check that here.
 	 *
 	 * It is safe if the end is below the start of the blocked
 	 * region (end <= low), or if the beginning is after the
 	 * end of the blocked region (begin >= high).  Use the
 	 * boolean identity !(a || b)  === (!a && !b).
 	 */
 	if (htab_address) {
 		low = __pa(htab_address);
 		high = low + htab_size_bytes;

 		for (i = 0; i < image->nr_segments; i++) {
 			begin = image->segment[i].mem;
 			end = begin + image->segment[i].memsz;

 			if ((begin < high) && (end > low))
 				return -ETXTBSY;
 		}
 	}

 	/* We also should not overwrite the tce tables */
 	for_each_node_by_type(node, "pci") {
 		basep = of_get_property(node, "linux,tce-base", NULL);
 		sizep = of_get_property(node, "linux,tce-size", NULL);
 		if (basep == NULL || sizep == NULL)
 			continue;

 		low = *basep;
 		high = low + (*sizep);

 		for (i = 0; i < image->nr_segments; i++) {
 			begin = image->segment[i].mem;
 			end = begin + image->segment[i].memsz;

 			if ((begin < high) && (end > low))
 				return -ETXTBSY;
 		}
 	}

 	return 0;
 }

 #define IND_FLAGS (IND_DESTINATION | IND_INDIRECTION | IND_DONE | IND_SOURCE)

 static void copy_segments(unsigned long ind)
 {
 	unsigned long entry;
 	unsigned long *ptr;
 	void *dest;
 	void *addr;

 	/*
 	 * We rely on kexec_load to create a lists that properly
 	 * initializes these pointers before they are used.
 	 * We will still crash if the list is wrong, but at least
 	 * the compiler will be quiet.
 	 */
 	ptr = NULL;
 	dest = NULL;

 	for (entry = ind; !(entry & IND_DONE); entry = *ptr++) {
 		addr = __va(entry & PAGE_MASK);

 		switch (entry & IND_FLAGS) {
 		case IND_DESTINATION:
 			dest = addr;
 			break;
 		case IND_INDIRECTION:
 			ptr = addr;
 			break;
 		case IND_SOURCE:
 			copy_page(dest, addr);
 			dest += PAGE_SIZE;
 		}
 	}
 }

 void kexec_copy_flush(struct kimage *image)
 {
 	long i, nr_segments = image->nr_segments;
 	struct  kexec_segment ranges[KEXEC_SEGMENT_MAX];

 	/* save the ranges on the stack to efficiently flush the icache */
 	memcpy(ranges, image->segment, sizeof(ranges));

 	/*
 	 * After this call we may not use anything allocated in dynamic
 	 * memory, including *image.
 	 *
 	 * Only globals and the stack are allowed.
 	 */
 	copy_segments(image->head);

 	/*
 	 * we need to clear the icache for all dest pages sometime,
 	 * including ones that were in place on the original copy
 	 */
 	for (i = 0; i < nr_segments; i++)
 		flush_icache_range((unsigned long)__va(ranges[i].mem),
 			(unsigned long)__va(ranges[i].mem + ranges[i].memsz));
 }

 #ifdef CONFIG_SMP

 static int kexec_all_irq_disabled = 0;

 static void kexec_smp_down(void *arg)
 {
 	local_irq_disable();
 	hard_irq_disable();

 	mb(); /* make sure our irqs are disabled before we say they are */
 	get_paca()->kexec_state = KEXEC_STATE_IRQS_OFF;
 	while(kexec_all_irq_disabled == 0)
 		cpu_relax();
 	mb(); /* make sure all irqs are disabled before this */
 	hw_breakpoint_disable();
 	/*
 	 * Now every CPU has IRQs off, we can clear out any pending
 	 * IPIs and be sure that no more will come in after this.
 	 */
 	if (ppc_md.kexec_cpu_down)
 		ppc_md.kexec_cpu_down(0, 1);

 	kexec_smp_wait();
 	/* NOTREACHED */
 }

 static void kexec_prepare_cpus_wait(int wait_state)
 {
 	int my_cpu, i, notified=-1;

 	hw_breakpoint_disable();
 	my_cpu = get_cpu();
 	/* Make sure each CPU has at least made it to the state we need.
 	 *
 	 * FIXME: There is a (slim) chance of a problem if not all of the CPUs
 	 * are correctly onlined.  If somehow we start a CPU on boot with RTAS
 	 * start-cpu, but somehow that CPU doesn't write callin_cpu_map[] in
 	 * time, the boot CPU will timeout.  If it does eventually execute
 	 * stuff, the secondary will start up (paca[].cpu_start was written) and
 	 * get into a peculiar state.  If the platform supports
 	 * smp_ops->take_timebase(), the secondary CPU will probably be spinning
 	 * in there.  If not (i.e. pseries), the secondary will continue on and
 	 * try to online itself/idle/etc. If it survives that, we need to find
 	 * these possible-but-not-online-but-should-be CPUs and chaperone them
 	 * into kexec_smp_wait().
 	 */
 	for_each_online_cpu(i) {
 		if (i == my_cpu)
 			continue;

 		while (paca[i].kexec_state < wait_state) {
 			barrier();
 			if (i != notified) {
 				printk(KERN_INFO "kexec: waiting for cpu %d "
 				       "(physical %d) to enter %i state\n",
 				       i, paca[i].hw_cpu_id, wait_state);
 				notified = i;
 			}
 		}
 	}
 	mb();
 }

 /*
  * We need to make sure each present CPU is online.  The next kernel will scan
  * the device tree and assume primary threads are online and query secondary
  * threads via RTAS to online them if required.  If we don't online primary
  * threads, they will be stuck.  However, we also online secondary threads as we
  * may be using 'cede offline'.  In this case RTAS doesn't see the secondary
  * threads as offline -- and again, these CPUs will be stuck.
  *
  * So, we online all CPUs that should be running, including secondary threads.
  */
 static void wake_offline_cpus(void)
 {
 	int cpu = 0;

 	for_each_present_cpu(cpu) {
 		if (!cpu_online(cpu)) {
 			printk(KERN_INFO "kexec: Waking offline cpu %d.\n",
 			       cpu);
 			cpu_up(cpu);
 		}
 	}
 }

 static void kexec_prepare_cpus(void)
 {
 	wake_offline_cpus();
 	smp_call_function(kexec_smp_down, NULL, /* wait */0);
 	local_irq_disable();
 	hard_irq_disable();

 	mb(); /* make sure IRQs are disabled before we say they are */
 	get_paca()->kexec_state = KEXEC_STATE_IRQS_OFF;

 	kexec_prepare_cpus_wait(KEXEC_STATE_IRQS_OFF);
 	/* we are sure every CPU has IRQs off at this point */
 	kexec_all_irq_disabled = 1;

 	/* after we tell the others to go down */
 	if (ppc_md.kexec_cpu_down)
 		ppc_md.kexec_cpu_down(0, 0);

 	/*
 	 * Before removing MMU mappings make sure all CPUs have entered real
 	 * mode:
 	 */
 	kexec_prepare_cpus_wait(KEXEC_STATE_REAL_MODE);

 	put_cpu();
 }

 #else /* ! SMP */

 static void kexec_prepare_cpus(void)
 {
 	/*
 	 * move the secondarys to us so that we can copy
 	 * the new kernel 0-0x100 safely
 	 *
 	 * do this if kexec in setup.c ?
 	 *
 	 * We need to release the cpus if we are ever going from an
 	 * UP to an SMP kernel.
 	 */
 	smp_release_cpus();
 	if (ppc_md.kexec_cpu_down)
 		ppc_md.kexec_cpu_down(0, 0);
 	local_irq_disable();
 	hard_irq_disable();
 }

 #endif /* SMP */

 /*
  * kexec thread structure and stack.
  *
  * We need to make sure that this is 16384-byte aligned due to the
  * way process stacks are handled.  It also must be statically allocated
  * or allocated as part of the kimage, because everything else may be
  * overwritten when we copy the kexec image.  We piggyback on the
  * "init_task" linker section here to statically allocate a stack.
  *
  * We could use a smaller stack if we don't care about anything using
  * current, but that audit has not been performed.
  */
 static union thread_union kexec_stack __init_task_data =
 	{ };

 /*
  * For similar reasons to the stack above, the kexecing CPU needs to be on a
  * static PACA; we switch to kexec_paca.
  */
 struct paca_struct kexec_paca;

 /* Our assembly helper, in kexec_stub.S */
 extern void kexec_sequence(void *newstack, unsigned long start,
 			   void *image, void *control,
 			   void (*clear_all)(void)) __noreturn;

 /* too late to fail here */
 void default_machine_kexec(struct kimage *image)
 {
 	/* prepare control code if any */

 	/*
         * If the kexec boot is the normal one, need to shutdown other cpus
         * into our wait loop and quiesce interrupts.
         * Otherwise, in the case of crashed mode (crashing_cpu >= 0),
         * stopping other CPUs and collecting their pt_regs is done before
         * using debugger IPI.
         */

 	if (crashing_cpu == -1)
 		kexec_prepare_cpus();

 	pr_debug("kexec: Starting switchover sequence.\n");

 	/* switch to a staticly allocated stack.  Based on irq stack code.
 	 * XXX: the task struct will likely be invalid once we do the copy!
 	 */
 	kexec_stack.thread_info.task = current_thread_info()->task;
 	kexec_stack.thread_info.flags = 0;

 	/* We need a static PACA, too; copy this CPU's PACA over and switch to
 	 * it.  Also poison per_cpu_offset to catch anyone using non-static
 	 * data.
 	 */
 	memcpy(&kexec_paca, get_paca(), sizeof(struct paca_struct));
 	kexec_paca.data_offset = 0xedeaddeadeeeeeeeUL;
 	paca = (struct paca_struct *)RELOC_HIDE(&kexec_paca, 0) -
 		kexec_paca.paca_index;
 	setup_paca(&kexec_paca);

 	/* XXX: If anyone does 'dynamic lppacas' this will also need to be
 	 * switched to a static version!
 	 */

 	/* Some things are best done in assembly.  Finding globals with
 	 * a toc is easier in C, so pass in what we can.
 	 */
 	kexec_sequence(&kexec_stack, image->start, image,
 			page_address(image->control_code_page),
 			ppc_md.hpte_clear_all);
 	/* NOTREACHED */
 }

 /* Values we need to export to the second kernel via the device tree. */
 static unsigned long htab_base;

 static struct property htab_base_prop = {
 	.name = "linux,htab-base",
 	.length = sizeof(unsigned long),
 	.value = &htab_base,
 };

 static struct property htab_size_prop = {
 	.name = "linux,htab-size",
 	.length = sizeof(unsigned long),
 	.value = &htab_size_bytes,
 };

 static int __init export_htab_values(void)
 {
 	struct device_node *node;
 	struct property *prop;

 	/* On machines with no htab htab_address is NULL */
 	if (!htab_address)
 		return -ENODEV;

 	node = of_find_node_by_path("/chosen");
 	if (!node)
 		return -ENODEV;

 	/* remove any stale propertys so ours can be found */
 	prop = of_find_property(node, htab_base_prop.name, NULL);
 	if (prop)
 		of_remove_property(node, prop);
 	prop = of_find_property(node, htab_size_prop.name, NULL);
 	if (prop)
 		of_remove_property(node, prop);

 	htab_base = __pa(htab_address);
 	of_add_property(node, &htab_base_prop);
 	of_add_property(node, &htab_size_prop);

 	of_node_put(node);
 	return 0;
 }
 late_initcall(export_htab_values);
	/*
	* PPC64 code to handle Linux booting another kernel.
	*
	* Copyright (C) 2004-2005, IBM Corp.
	*
	* Created by: Milton D Miller II
	*
	* This source code is licensed under the GNU General Public License,
	* Version 2. See the file COPYING for more details.
	*/


	#include <linux/kexec.h>
	#include <linux/smp.h>
	#include <linux/thread_info.h>
	#include <linux/init_task.h>
	#include <linux/errno.h>
	#include <linux/kernel.h>
	#include <linux/cpu.h>

	#include <asm/page.h>
	#include <asm/current.h>
	#include <asm/machdep.h>
	#include <asm/cacheflush.h>
	#include <asm/paca.h>
	#include <asm/mmu.h>
	#include <asm/sections.h> /* _end */
	#include <asm/prom.h>
	#include <asm/smp.h>
	#include <asm/hw_breakpoint.h>

	int default_machine_kexec_prepare(struct kimage *image)
	{
	int i;
	unsigned long begin, end; /* limits of segment */
	unsigned long low, high; /* limits of blocked memory range */
	struct device_node *node;
	const unsigned long *basep;
	const unsigned int *sizep;

	if (!ppc_md.hpte_clear_all)
	return -ENOENT;

	/*
	* Since we use the kernel fault handlers and paging code to
	* handle the virtual mode, we must make sure no destination
	* overlaps kernel static data or bss.
	*/
	for (i = 0; i < image->nr_segments; i++)
	if (image->segment[i].mem < __pa(_end))
	return -ETXTBSY;

	/*
	* For non-LPAR, we absolutely can not overwrite the mmu hash
	* table, since we are still using the bolted entries in it to
	* do the copy. Check that here.
	*
	* It is safe if the end is below the start of the blocked
	* region (end <= low), or if the beginning is after the
	* end of the blocked region (begin >= high). Use the
	* boolean identity !(a \|\| b) === (!a && !b).
	*/
	if (htab_address) {
	low = __pa(htab_address);
	high = low + htab_size_bytes;

	for (i = 0; i < image->nr_segments; i++) {
	begin = image->segment[i].mem;
	end = begin + image->segment[i].memsz;

	if ((begin < high) && (end > low))
	return -ETXTBSY;
	}
	}

	/* We also should not overwrite the tce tables */
	for_each_node_by_type(node, "pci") {
	basep = of_get_property(node, "linux,tce-base", NULL);
	sizep = of_get_property(node, "linux,tce-size", NULL);
	if (basep == NULL \|\| sizep == NULL)
	continue;

	low = *basep;
	high = low + (*sizep);

	for (i = 0; i < image->nr_segments; i++) {
	begin = image->segment[i].mem;
	end = begin + image->segment[i].memsz;

	if ((begin < high) && (end > low))
	return -ETXTBSY;
	}
	}

	return 0;
	}

	#define IND_FLAGS (IND_DESTINATION \| IND_INDIRECTION \| IND_DONE \| IND_SOURCE)

	static void copy_segments(unsigned long ind)
	{
	unsigned long entry;
	unsigned long *ptr;
	void *dest;
	void *addr;

	/*
	* We rely on kexec_load to create a lists that properly
	* initializes these pointers before they are used.
	* We will still crash if the list is wrong, but at least
	* the compiler will be quiet.
	*/
	ptr = NULL;
	dest = NULL;

	for (entry = ind; !(entry & IND_DONE); entry = *ptr++) {
	addr = __va(entry & PAGE_MASK);

	switch (entry & IND_FLAGS) {
	case IND_DESTINATION:
	dest = addr;
	break;
	case IND_INDIRECTION:
	ptr = addr;
	break;
	case IND_SOURCE:
	copy_page(dest, addr);
	dest += PAGE_SIZE;
	}
	}
	}

	void kexec_copy_flush(struct kimage *image)
	{
	long i, nr_segments = image->nr_segments;
	struct kexec_segment ranges[KEXEC_SEGMENT_MAX];

	/* save the ranges on the stack to efficiently flush the icache */
	memcpy(ranges, image->segment, sizeof(ranges));

	/*
	* After this call we may not use anything allocated in dynamic
	* memory, including *image.
	*
	* Only globals and the stack are allowed.
	*/
	copy_segments(image->head);

	/*
	* we need to clear the icache for all dest pages sometime,
	* including ones that were in place on the original copy
	*/
	for (i = 0; i < nr_segments; i++)
	flush_icache_range((unsigned long)__va(ranges[i].mem),
	(unsigned long)__va(ranges[i].mem + ranges[i].memsz));
	}

	#ifdef CONFIG_SMP

	static int kexec_all_irq_disabled = 0;

	static void kexec_smp_down(void *arg)
	{
	local_irq_disable();
	hard_irq_disable();

	mb(); /* make sure our irqs are disabled before we say they are */
	get_paca()->kexec_state = KEXEC_STATE_IRQS_OFF;
	while(kexec_all_irq_disabled == 0)
	cpu_relax();
	mb(); /* make sure all irqs are disabled before this */
	hw_breakpoint_disable();
	/*
	* Now every CPU has IRQs off, we can clear out any pending
	* IPIs and be sure that no more will come in after this.
	*/
	if (ppc_md.kexec_cpu_down)
	ppc_md.kexec_cpu_down(0, 1);

	kexec_smp_wait();
	/* NOTREACHED */
	}

	static void kexec_prepare_cpus_wait(int wait_state)
	{
	int my_cpu, i, notified=-1;

	hw_breakpoint_disable();
	my_cpu = get_cpu();
	/* Make sure each CPU has at least made it to the state we need.
	*
	* FIXME: There is a (slim) chance of a problem if not all of the CPUs
	* are correctly onlined. If somehow we start a CPU on boot with RTAS
	* start-cpu, but somehow that CPU doesn't write callin_cpu_map[] in
	* time, the boot CPU will timeout. If it does eventually execute
	* stuff, the secondary will start up (paca[].cpu_start was written) and
	* get into a peculiar state. If the platform supports
	* smp_ops->take_timebase(), the secondary CPU will probably be spinning
	* in there. If not (i.e. pseries), the secondary will continue on and
	* try to online itself/idle/etc. If it survives that, we need to find
	* these possible-but-not-online-but-should-be CPUs and chaperone them
	* into kexec_smp_wait().
	*/
	for_each_online_cpu(i) {
	if (i == my_cpu)
	continue;

	while (paca[i].kexec_state < wait_state) {
	barrier();
	if (i != notified) {
	printk(KERN_INFO "kexec: waiting for cpu %d "
	"(physical %d) to enter %i state\n",
	i, paca[i].hw_cpu_id, wait_state);
	notified = i;
	}
	}
	}
	mb();
	}

	/*
	* We need to make sure each present CPU is online. The next kernel will scan
	* the device tree and assume primary threads are online and query secondary
	* threads via RTAS to online them if required. If we don't online primary
	* threads, they will be stuck. However, we also online secondary threads as we
	* may be using 'cede offline'. In this case RTAS doesn't see the secondary
	* threads as offline -- and again, these CPUs will be stuck.
	*
	* So, we online all CPUs that should be running, including secondary threads.
	*/
	static void wake_offline_cpus(void)
	{
	int cpu = 0;

	for_each_present_cpu(cpu) {
	if (!cpu_online(cpu)) {
	printk(KERN_INFO "kexec: Waking offline cpu %d.\n",
	cpu);
	cpu_up(cpu);
	}
	}
	}

	static void kexec_prepare_cpus(void)
	{
	wake_offline_cpus();
	smp_call_function(kexec_smp_down, NULL, /* wait */0);
	local_irq_disable();
	hard_irq_disable();

	mb(); /* make sure IRQs are disabled before we say they are */
	get_paca()->kexec_state = KEXEC_STATE_IRQS_OFF;

	kexec_prepare_cpus_wait(KEXEC_STATE_IRQS_OFF);
	/* we are sure every CPU has IRQs off at this point */
	kexec_all_irq_disabled = 1;

	/* after we tell the others to go down */
	if (ppc_md.kexec_cpu_down)
	ppc_md.kexec_cpu_down(0, 0);

	/*
	* Before removing MMU mappings make sure all CPUs have entered real
	* mode:
	*/
	kexec_prepare_cpus_wait(KEXEC_STATE_REAL_MODE);

	put_cpu();
	}

	#else /* ! SMP */

	static void kexec_prepare_cpus(void)
	{
	/*
	* move the secondarys to us so that we can copy
	* the new kernel 0-0x100 safely
	*
	* do this if kexec in setup.c ?
	*
	* We need to release the cpus if we are ever going from an
	* UP to an SMP kernel.
	*/
	smp_release_cpus();
	if (ppc_md.kexec_cpu_down)
	ppc_md.kexec_cpu_down(0, 0);
	local_irq_disable();
	hard_irq_disable();
	}

	#endif /* SMP */

	/*
	* kexec thread structure and stack.
	*
	* We need to make sure that this is 16384-byte aligned due to the
	* way process stacks are handled. It also must be statically allocated
	* or allocated as part of the kimage, because everything else may be
	* overwritten when we copy the kexec image. We piggyback on the
	* "init_task" linker section here to statically allocate a stack.
	*
	* We could use a smaller stack if we don't care about anything using
	* current, but that audit has not been performed.
	*/
	static union thread_union kexec_stack __init_task_data =
	{ };

	/*
	* For similar reasons to the stack above, the kexecing CPU needs to be on a
	* static PACA; we switch to kexec_paca.
	*/
	struct paca_struct kexec_paca;

	/* Our assembly helper, in kexec_stub.S */
	extern void kexec_sequence(void *newstack, unsigned long start,
	void image, void control,
	void (*clear_all)(void)) __noreturn;

	/* too late to fail here */
	void default_machine_kexec(struct kimage *image)
	{
	/* prepare control code if any */

	/*
	* If the kexec boot is the normal one, need to shutdown other cpus
	* into our wait loop and quiesce interrupts.
	* Otherwise, in the case of crashed mode (crashing_cpu >= 0),
	* stopping other CPUs and collecting their pt_regs is done before
	* using debugger IPI.
	*/

	if (crashing_cpu == -1)
	kexec_prepare_cpus();

	pr_debug("kexec: Starting switchover sequence.\n");

	/* switch to a staticly allocated stack. Based on irq stack code.
	* XXX: the task struct will likely be invalid once we do the copy!
	*/
	kexec_stack.thread_info.task = current_thread_info()->task;
	kexec_stack.thread_info.flags = 0;

	/* We need a static PACA, too; copy this CPU's PACA over and switch to
	* it. Also poison per_cpu_offset to catch anyone using non-static
	* data.
	*/
	memcpy(&kexec_paca, get_paca(), sizeof(struct paca_struct));
	kexec_paca.data_offset = 0xedeaddeadeeeeeeeUL;
	paca = (struct paca_struct *)RELOC_HIDE(&kexec_paca, 0) -
	kexec_paca.paca_index;
	setup_paca(&kexec_paca);

	/* XXX: If anyone does 'dynamic lppacas' this will also need to be
	* switched to a static version!
	*/

	/* Some things are best done in assembly. Finding globals with
	* a toc is easier in C, so pass in what we can.
	*/
	kexec_sequence(&kexec_stack, image->start, image,
	page_address(image->control_code_page),
	ppc_md.hpte_clear_all);
	/* NOTREACHED */
	}

	/* Values we need to export to the second kernel via the device tree. */
	static unsigned long htab_base;

	static struct property htab_base_prop = {
	.name = "linux,htab-base",
	.length = sizeof(unsigned long),
	.value = &htab_base,
	};

	static struct property htab_size_prop = {
	.name = "linux,htab-size",
	.length = sizeof(unsigned long),
	.value = &htab_size_bytes,
	};

	static int __init export_htab_values(void)
	{
	struct device_node *node;
	struct property *prop;

	/* On machines with no htab htab_address is NULL */
	if (!htab_address)
	return -ENODEV;

	node = of_find_node_by_path("/chosen");
	if (!node)
	return -ENODEV;

	/* remove any stale propertys so ours can be found */
	prop = of_find_property(node, htab_base_prop.name, NULL);
	if (prop)
	of_remove_property(node, prop);
	prop = of_find_property(node, htab_size_prop.name, NULL);
	if (prop)
	of_remove_property(node, prop);

	htab_base = __pa(htab_address);
	of_add_property(node, &htab_base_prop);
	of_add_property(node, &htab_size_prop);

	of_node_put(node);
	return 0;
	}
	late_initcall(export_htab_values);