[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>

1 files changed, 76 insertions, 5 deletions

diff --git a/arch/powerpc/platforms/pseries/phyp_dump.c b/arch/powerpc/platforms/pseries/phyp_dump.c
index 230286cafffe..f355f052a56c 100644
--- 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;
 }