[PATCH] kdump: Accessing dump file in linear raw format (/dev/oldmem)
Hariprasad Nellitheertha <hari@in.ibm.com>
This patch contains the code that enables us to access the previous kernel's
memory as /dev/oldmem.
Signed-off-by: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index e3085b2..01b3c17 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -23,6 +23,8 @@
#include <linux/devfs_fs_kernel.h>
#include <linux/ptrace.h>
#include <linux/device.h>
+#include <linux/highmem.h>
+#include <linux/crash_dump.h>
#include <linux/backing-dev.h>
#include <asm/uaccess.h>
@@ -273,6 +275,62 @@
return mmap_mem(file, vma);
}
+#ifdef CONFIG_CRASH_DUMP
+/*
+ * Read memory corresponding to the old kernel.
+ * If we are reading from the reserved section, which is
+ * actually used by the current kernel, we just return zeroes.
+ * Or if we are reading from the first 640k, we return from the
+ * backed up area.
+ */
+static ssize_t read_oldmem(struct file * file, char * buf,
+ size_t count, loff_t *ppos)
+{
+ unsigned long pfn;
+ unsigned backup_start, backup_end, relocate_start;
+ size_t read=0, csize;
+
+ backup_start = CRASH_BACKUP_BASE / PAGE_SIZE;
+ backup_end = backup_start + (CRASH_BACKUP_SIZE / PAGE_SIZE);
+ relocate_start = (CRASH_BACKUP_BASE + CRASH_BACKUP_SIZE) / PAGE_SIZE;
+
+ while(count) {
+ pfn = *ppos / PAGE_SIZE;
+
+ csize = (count > PAGE_SIZE) ? PAGE_SIZE : count;
+
+ /* Perform translation (see comment above) */
+ if ((pfn >= backup_start) && (pfn < backup_end)) {
+ if (clear_user(buf, csize)) {
+ read = -EFAULT;
+ goto done;
+ }
+
+ goto copy_done;
+ } else if (pfn < (CRASH_RELOCATE_SIZE / PAGE_SIZE))
+ pfn += relocate_start;
+
+ if (pfn > saved_max_pfn) {
+ read = 0;
+ goto done;
+ }
+
+ if (copy_oldmem_page(pfn, buf, csize, 1)) {
+ read = -EFAULT;
+ goto done;
+ }
+
+copy_done:
+ buf += csize;
+ *ppos += csize;
+ read += csize;
+ count -= csize;
+ }
+done:
+ return read;
+}
+#endif
+
extern long vread(char *buf, char *addr, unsigned long count);
extern long vwrite(char *buf, char *addr, unsigned long count);
@@ -721,6 +779,7 @@
#define read_full read_zero
#define open_mem open_port
#define open_kmem open_mem
+#define open_oldmem open_mem
static struct file_operations mem_fops = {
.llseek = memory_lseek,
@@ -770,6 +829,13 @@
.write = write_full,
};
+#ifdef CONFIG_CRASH_DUMP
+static struct file_operations oldmem_fops = {
+ .read = read_oldmem,
+ .open = open_oldmem,
+};
+#endif
+
static ssize_t kmsg_write(struct file * file, const char __user * buf,
size_t count, loff_t *ppos)
{
@@ -825,6 +891,11 @@
case 11:
filp->f_op = &kmsg_fops;
break;
+#ifdef CONFIG_CRASH_DUMP
+ case 12:
+ filp->f_op = &oldmem_fops;
+ break;
+#endif
default:
return -ENXIO;
}
@@ -854,6 +925,9 @@
{8, "random", S_IRUGO | S_IWUSR, &random_fops},
{9, "urandom", S_IRUGO | S_IWUSR, &urandom_fops},
{11,"kmsg", S_IRUGO | S_IWUSR, &kmsg_fops},
+#ifdef CONFIG_CRASH_DUMP
+ {12,"oldmem", S_IRUSR | S_IWUSR | S_IRGRP, &oldmem_fops},
+#endif
};
static struct class *mem_class;