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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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