[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: Linas Vepstas <linasvepstas@gmail.com>
Signed-off-by: Manish Ahuja <mahuja@us.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

diff --git a/arch/powerpc/platforms/pseries/phyp_dump.c b/arch/powerpc/platforms/pseries/phyp_dump.c
index 230286c..f355f05 100644 (file)
--- a/arch/powerpc/platforms/pseries/phyp_dump.c
+++ b/arch/powerpc/platforms/pseries/phyp_dump.c
@@ -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;
 }