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[PATCH] kdump: Accessing dump file in linear raw format (/dev/oldmem)

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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>
This commit is contained in:
Vivek Goyal 2005-06-25 14:58:23 -07:00 committed by Linus Torvalds
parent 72658e9d50
commit 50b1fdbd81
2 changed files with 75 additions and 0 deletions
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1
Documentation/devices.txt
View file

@ -94,6 +94,7 @@ 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 crash dump from kexec kernel
1 block RAM disk
0 = /dev/ram0 First RAM disk
1 = /dev/ram1 Second RAM disk

74
drivers/char/mem.c
View file

@ -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 @@ static int mmap_kmem(struct file * file, struct vm_area_struct * vma)
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 @@ static int open_port(struct inode * inode, struct file * filp)
#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 @@ static struct file_operations full_fops = {
.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 @@ static int memory_open(struct inode * inode, struct file * filp)
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 @@ 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},
#ifdef CONFIG_CRASH_DUMP
{12,"oldmem", S_IRUSR | S_IWUSR | S_IRGRP, &oldmem_fops},
#endif
};
static struct class *mem_class;