1 /* 2 * Memory preserving reboot related code. 3 * 4 * Created by: Hariprasad Nellitheertha (hari@in.ibm.com) 5 * Copyright (C) IBM Corporation, 2004. All rights reserved 6 */ 7 8 #include <linux/errno.h> 9 #include <linux/highmem.h> 10 #include <linux/crash_dump.h> 11 12 #include <asm/uaccess.h> 13 14 static void *kdump_buf_page; 15 16 /* Stores the physical address of elf header of crash image. */ 17 unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX; 18 19 /** 20 * copy_oldmem_page - copy one page from "oldmem" 21 * @pfn: page frame number to be copied 22 * @buf: target memory address for the copy; this can be in kernel address 23 * space or user address space (see @userbuf) 24 * @csize: number of bytes to copy 25 * @offset: offset in bytes into the page (based on pfn) to begin the copy 26 * @userbuf: if set, @buf is in user address space, use copy_to_user(), 27 * otherwise @buf is in kernel address space, use memcpy(). 28 * 29 * Copy a page from "oldmem". For this page, there is no pte mapped 30 * in the current kernel. We stitch up a pte, similar to kmap_atomic. 31 * 32 * Calling copy_to_user() in atomic context is not desirable. Hence first 33 * copying the data to a pre-allocated kernel page and then copying to user 34 * space in non-atomic context. 35 */ 36 ssize_t copy_oldmem_page(unsigned long pfn, char *buf, 37 size_t csize, unsigned long offset, int userbuf) 38 { 39 void *vaddr; 40 41 if (!csize) 42 return 0; 43 44 vaddr = kmap_atomic_pfn(pfn, KM_PTE0); 45 46 if (!userbuf) { 47 memcpy(buf, (vaddr + offset), csize); 48 kunmap_atomic(vaddr, KM_PTE0); 49 } else { 50 if (!kdump_buf_page) { 51 printk(KERN_WARNING "Kdump: Kdump buffer page not" 52 " allocated\n"); 53 kunmap_atomic(vaddr, KM_PTE0); 54 return -EFAULT; 55 } 56 copy_page(kdump_buf_page, vaddr); 57 kunmap_atomic(vaddr, KM_PTE0); 58 if (copy_to_user(buf, (kdump_buf_page + offset), csize)) 59 return -EFAULT; 60 } 61 62 return csize; 63 } 64 65 static int __init kdump_buf_page_init(void) 66 { 67 int ret = 0; 68 69 kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL); 70 if (!kdump_buf_page) { 71 printk(KERN_WARNING "Kdump: Failed to allocate kdump buffer" 72 " page\n"); 73 ret = -ENOMEM; 74 } 75 76 return ret; 77 } 78 arch_initcall(kdump_buf_page_init); 79