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// SPDX-License-Identifier: GPL-2.0
/*
* Memory preserving reboot related code.
*
* Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
* 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 <linux/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
}
/**
* copy_oldmem_page - copy one page from "oldmem"
* @pfn: page frame number to be copied
* @buf: target memory address for the copy; this can be in kernel address
* space or user address space (see @userbuf)
* @csize: number of bytes to copy
* @offset: offset in bytes into the page (based on pfn) to begin the copy
* @userbuf: if set, @buf is in user address space, use copy_to_user(),
* otherwise @buf is in kernel address space, use memcpy().
*
* Copy a page from "oldmem". For this page, there is no pte mapped
* in the current kernel. We stitch up a pte, similar to kmap_atomic.
*
* Calling copy_to_user() in atomic context is not desirable. Hence first
* copying the data to a pre-allocated kernel page and then copying to user
* space in non-atomic context.
*/
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);
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