// SPDX-License-Identifier: GPL-2.0
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/*
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* Memory preserving reboot related code.
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*
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* Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
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* Copyright (C) IBM Corporation, 2004. All rights reserved
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*/
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#include <linux/slab.h>
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#include <linux/errno.h>
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#include <linux/highmem.h>
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#include <linux/crash_dump.h>
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#include <linux/uaccess.h>
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static void *kdump_buf_page;
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static inline bool is_crashed_pfn_valid(unsigned long pfn)
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{
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#ifndef CONFIG_X86_PAE
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/*
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* non-PAE kdump kernel executed from a PAE one will crop high pte
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* bits and poke unwanted space counting again from address 0, we
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* don't want that. pte must fit into unsigned long. In fact the
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* test checks high 12 bits for being zero (pfn will be shifted left
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* by PAGE_SHIFT).
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*/
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return pte_pfn(pfn_pte(pfn, __pgprot(0))) == pfn;
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#else
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return true;
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#endif
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}
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/**
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* copy_oldmem_page - copy one page from "oldmem"
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* @pfn: page frame number to be copied
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* @buf: target memory address for the copy; this can be in kernel address
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* space or user address space (see @userbuf)
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* @csize: number of bytes to copy
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* @offset: offset in bytes into the page (based on pfn) to begin the copy
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* @userbuf: if set, @buf is in user address space, use copy_to_user(),
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* otherwise @buf is in kernel address space, use memcpy().
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*
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* Copy a page from "oldmem". For this page, there is no pte mapped
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* in the current kernel. We stitch up a pte, similar to kmap_atomic.
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*
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* Calling copy_to_user() in atomic context is not desirable. Hence first
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* copying the data to a pre-allocated kernel page and then copying to user
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* space in non-atomic context.
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*/
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ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
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size_t csize, unsigned long offset, int userbuf)
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{
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void *vaddr;
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if (!csize)
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return 0;
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if (!is_crashed_pfn_valid(pfn))
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return -EFAULT;
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vaddr = kmap_atomic_pfn(pfn);
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if (!userbuf) {
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memcpy(buf, (vaddr + offset), csize);
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kunmap_atomic(vaddr);
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} else {
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if (!kdump_buf_page) {
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printk(KERN_WARNING "Kdump: Kdump buffer page not"
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" allocated\n");
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kunmap_atomic(vaddr);
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return -EFAULT;
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}
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copy_page(kdump_buf_page, vaddr);
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kunmap_atomic(vaddr);
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if (copy_to_user(buf, (kdump_buf_page + offset), csize))
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return -EFAULT;
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}
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return csize;
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}
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static int __init kdump_buf_page_init(void)
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{
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int ret = 0;
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kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
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if (!kdump_buf_page) {
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printk(KERN_WARNING "Kdump: Failed to allocate kdump buffer"
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" page\n");
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ret = -ENOMEM;
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}
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return ret;
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}
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arch_initcall(kdump_buf_page_init);
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