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SubjectRe: [PATCH][6/6]Linear/raw format dump file access
Regards, Hari
--
Hariprasad Nellitheertha
Linux Technology Center
India Software Labs
IBM India, Bangalore


This patch contains the code that enables us to access the previous kernel's
memory as /dev/oldmem.

Signed off by Hariprasad Nellitheertha <hari@in.ibm.com>
Signed off by Adam Litke <litke@us.ibm.com>


---
linux-2.6.9-rc1-hari/Documentation/devices.txt | 1
linux-2.6.9-rc1-hari/drivers/char/mem.c | 66 +++++++++++++++++++++++++
2 files changed, 67 insertions(+)
diff -puN Documentation/devices.txt~kd-oldmem-269rc1-mm5 Documentation/devices.txt
--- linux-2.6.9-rc1/Documentation/devices.txt~kd-oldmem-269rc1-mm5 2004-09-15 17:36:57.000000000 +0530
+++ linux-2.6.9-rc1-hari/Documentation/devices.txt 2004-09-15 17:36:57.000000000 +0530
@@ -100,6 +100,7 @@ Your cooperation is appreciated.
9 = /dev/urandom Faster, less secure random number gen.
10 = /dev/aio Asyncronous I/O notification interface
11 = /dev/kmsg Writes to this come out as printk's
+ 12 = /dev/oldmem Access to kexec-ed crash dump
1 block RAM disk
0 = /dev/ram0 First RAM disk
1 = /dev/ram1 Second RAM disk
diff -puN drivers/char/mem.c~kd-oldmem-269rc1-mm5 drivers/char/mem.c
--- linux-2.6.9-rc1/drivers/char/mem.c~kd-oldmem-269rc1-mm5 2004-09-15 17:36:57.000000000 +0530
+++ linux-2.6.9-rc1-hari/drivers/char/mem.c 2004-09-15 17:36:57.000000000 +0530
@@ -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 <asm/uaccess.h>
#include <asm/io.h>
@@ -231,6 +233,60 @@ static int mmap_mem(struct file *file, s
return 0;
}

+/*
+ * 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;
+}
+
extern long vread(char *buf, char *addr, unsigned long count);
extern long vwrite(char *buf, char *addr, unsigned long count);

@@ -535,6 +591,7 @@ static int open_port(struct inode * inod
#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,
@@ -579,6 +636,11 @@ static struct file_operations full_fops
.write = write_full,
};

+static struct file_operations oldmem_fops = {
+ .read = read_oldmem,
+ .open = open_oldmem,
+};
+
static ssize_t kmsg_write(struct file * file, const char __user * buf,
size_t count, loff_t *ppos)
{
@@ -633,6 +695,9 @@ static int memory_open(struct inode * in
case 11:
filp->f_op = &kmsg_fops;
break;
+ case 12:
+ filp->f_op = &oldmem_fops;
+ break;
default:
return -ENXIO;
}
@@ -662,6 +727,7 @@ static const struct {
{8, "random", S_IRUGO | S_IWUSR, &random_fops},
{9, "urandom", S_IRUGO | S_IWUSR, &urandom_fops},
{11,"kmsg", S_IRUGO | S_IWUSR, &kmsg_fops},
+ {12,"oldmem", S_IRUSR | S_IWUSR | S_IRGRP, &oldmem_fops},
};

static struct class_simple *mem_class;
_
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