// SPDX-License-Identifier: GPL-2.0 /* * This code comes from arch/arm64/kernel/crash_dump.c * Created by: AKASHI Takahiro <takahiro.akashi@linaro.org> * Copyright (C) 2017 Linaro Limited */ #include <linux/crash_dump.h> #include <linux/io.h> /** * copy_oldmem_page() - copy one page from old kernel memory * @pfn: page frame number to be copied * @buf: buffer where the copied page is placed * @csize: number of bytes to copy * @offset: offset in bytes into the page * @userbuf: if set, @buf is in a user address space * * This function copies one page from old kernel memory into buffer pointed by * @buf. If @buf is in userspace, set @userbuf to %1. Returns number of bytes * copied or negative error in case of failure. */ 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 = memremap(__pfn_to_phys(pfn), PAGE_SIZE, MEMREMAP_WB); if (!vaddr) return -ENOMEM; if (userbuf) { if (copy_to_user((char __user *)buf, vaddr + offset, csize)) { memunmap(vaddr); return -EFAULT; } } else memcpy(buf, vaddr + offset, csize); memunmap(vaddr); return csize; }