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Commit d5a29c7a authored by Manish Ahuja's avatar Manish Ahuja Committed by Paul Mackerras
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[POWERPC] pseries: phyp dump: Use sysfs to release reserved mem 



Check to see if there actually is data from a previously
crashed kernel waiting.  If so, allow user-space tools to
grab the data (by reading /proc/kcore).  When user-space
finishes dumping a section, it must release that memory
by writing to sysfs. For example,

  echo "0x40000000 0x10000000" > /sys/kernel/release_region

will release 256MB starting at the 1GB.  The released memory
becomes free for general use.

Signed-off-by: default avatarLinas Vepstas <linasvepstas@gmail.com>
Signed-off-by: default avatarManish Ahuja <mahuja@us.ibm.com>
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
parent 6ac26c8a

arch/powerpc/platforms/pseries/phyp_dump.c

+76 −5
Original line number Diff line number Diff line
@@ -12,19 +12,24 @@ 
 */



#include <linux/init.h>

#include <linux/kobject.h>

#include <linux/mm.h>

#include <linux/of.h>

#include <linux/pfn.h>

#include <linux/swap.h>

#include <linux/sysfs.h>



#include <asm/page.h>

#include <asm/phyp_dump.h>

#include <asm/machdep.h>

#include <asm/prom.h>

#include <asm/rtas.h>



/* Variables, used to communicate data between early boot and late boot */

static struct phyp_dump phyp_dump_vars;

struct phyp_dump *phyp_dump_info = &phyp_dump_vars;



/* ------------------------------------------------- */

/**

 * release_memory_range -- release memory previously lmb_reserved

 * @start_pfn: starting physical frame number
@@ -54,18 +59,84 @@ release_memory_range(unsigned long start_pfn, unsigned long nr_pages) 
	}

}



static int __init phyp_dump_setup(void)

/* ------------------------------------------------- */

/**

 * sysfs_release_region -- sysfs interface to release memory range.

 *

 * Usage:

 *   "echo <start addr> <length> > /sys/kernel/release_region"

 *

 * Example:

 *   "echo 0x40000000 0x10000000 > /sys/kernel/release_region"

 *

 * will release 256MB starting at 1GB.

 */

static ssize_t store_release_region(struct kobject *kobj,

				struct kobj_attribute *attr,

				const char *buf, size_t count)

{

	unsigned long start_addr, length, end_addr;

	unsigned long start_pfn, nr_pages;

	ssize_t ret;



	ret = sscanf(buf, "%lx %lx", &start_addr, &length);

	if (ret != 2)

		return -EINVAL;



	/* Range-check - don't free any reserved memory that

	 * wasn't reserved for phyp-dump */

	if (start_addr < phyp_dump_info->init_reserve_start)

		start_addr = phyp_dump_info->init_reserve_start;



	end_addr = phyp_dump_info->init_reserve_start +

			phyp_dump_info->init_reserve_size;

	if (start_addr+length > end_addr)

		length = end_addr - start_addr;



	/* Release the region of memory assed in by user */

	start_pfn = PFN_DOWN(start_addr);

	nr_pages = PFN_DOWN(length);

	release_memory_range(start_pfn, nr_pages);



	return count;

}



static struct kobj_attribute rr = __ATTR(release_region, 0600,

					 NULL, store_release_region);



static int __init phyp_dump_setup(void)

{

	struct device_node *rtas;

	const int *dump_header = NULL;

	int header_len = 0;

	int rc;



	/* If no memory was reserved in early boot, there is nothing to do */

	if (phyp_dump_info->init_reserve_size == 0)

		return 0;



	/* Release memory that was reserved in early boot */

	start_pfn = PFN_DOWN(phyp_dump_info->init_reserve_start);

	nr_pages = PFN_DOWN(phyp_dump_info->init_reserve_size);

	release_memory_range(start_pfn, nr_pages);

	/* Return if phyp dump not supported */

	if (!phyp_dump_info->phyp_dump_configured)

		return -ENOSYS;



	/* Is there dump data waiting for us? */

	rtas = of_find_node_by_path("/rtas");

	if (rtas) {

		dump_header = of_get_property(rtas, "ibm,kernel-dump",

						&header_len);

		of_node_put(rtas);

	}



	if (dump_header == NULL)

		return 0;



	/* Should we create a dump_subsys, analogous to s390/ipl.c ? */

	rc = sysfs_create_file(kernel_kobj, &rr.attr);

	if (rc) {

		printk(KERN_ERR "phyp-dump: unable to create sysfs file (%d)\n",

									rc);

		return 0;

	}



	return 0;

}