crash_dump_32.c

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/*
 *  Memory preserving reboot related code.
 *
 *  Created by: Hariprasad Nellitheertha ([email protected])
 *  Copyright (C) IBM Corporation, 2004. All rights reserved
 */

#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/highmem.h>
#include <linux/crash_dump.h>

#include <asm/uaccess.h>

static void *kdump_buf_page;

static inline bool is_crashed_pfn_valid(unsigned long pfn)
{
#ifndef CONFIG_X86_PAE
    /*
     * non-PAE kdump kernel executed from a PAE one will crop high pte
     * bits and poke unwanted space counting again from address 0, we
     * don't want that. pte must fit into unsigned long. In fact the
     * test checks high 12 bits for being zero (pfn will be shifted left
     * by PAGE_SHIFT).
     */
    return pte_pfn(pfn_pte(pfn, __pgprot(0))) == pfn;
#else
    return true;
#endif
}

ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
                               size_t csize, unsigned long offset, int userbuf)
{
    void  *vaddr;

    if (!csize)
        return 0;

    if (!is_crashed_pfn_valid(pfn))
        return -EFAULT;

    vaddr = kmap_atomic_pfn(pfn);

    if (!userbuf) {
        memcpy(buf, (vaddr + offset), csize);
        kunmap_atomic(vaddr);
    } else {
        if (!kdump_buf_page) {
            printk(KERN_WARNING "Kdump: Kdump buffer page not"
                " allocated\n");
            kunmap_atomic(vaddr);
            return -EFAULT;
        }
        copy_page(kdump_buf_page, vaddr);
        kunmap_atomic(vaddr);
        if (copy_to_user(buf, (kdump_buf_page + offset), csize))
            return -EFAULT;
    }

    return csize;
}

static int __init kdump_buf_page_init(void)
{
    int ret = 0;

    kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
    if (!kdump_buf_page) {
        printk(KERN_WARNING "Kdump: Failed to allocate kdump buffer"
             " page\n");
        ret = -ENOMEM;
    }

    return ret;
}
arch_initcall(kdump_buf_page_init);