Commit 50b1fdbd authored by Vivek Goyal's avatar Vivek Goyal Committed by Linus Torvalds
Browse files

[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: default avatarEric Biederman <ebiederm@xmission.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 72658e9d

Documentation/devices.txt

+1 −0
Original line number Diff line number Diff line
@@ -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

drivers/char/mem.c

+74 −0
Original line number Diff line number Diff line
@@ -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;