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// SPDX-License-Identifier: GPL-2.0
/*
* kernel/crash_dump.c - Memory preserving reboot related code.
*
* Created by: Simon Horman <horms@verge.net.au>
* Original code moved from kernel/crash.c
* Original code comment copied from the i386 version of this file
*/
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/crash_dump.h>
#include <asm/page.h>
#include <linux/uaccess.h>
/**
* 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;
vaddr = __va(pfn<<PAGE_SHIFT);
if (userbuf) {
if (copy_to_user(buf, (vaddr + offset), csize)) {
return -EFAULT;
}
} else
memcpy(buf, (vaddr + offset), csize);
return csize;
}
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