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[POWERPC] pseries: phyp dump: Use sysfs to release reserved mem

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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: Linas Vepstas <linasvepstas@gmail.com>
Signed-off-by: Manish Ahuja <mahuja@us.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Manish Ahuja 2008-03-22 10:39:17 +11:00 committed by Paul Mackerras
parent 6ac26c8a7e
commit d5a29c7a36
1 changed files with 76 additions and 5 deletions
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81
arch/powerpc/platforms/pseries/phyp_dump.c
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@ -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)
}
}
/* ------------------------------------------------- */
/**
* 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)
{
unsigned long start_pfn, nr_pages;
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;
}