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/slab.h> 9 #include <linux/errno.h> 10 #include <linux/highmem.h> 11 #include <linux/crash_dump.h> 12 13 #include <asm/uaccess.h> 14 15 static void *kdump_buf_page; 16 17 static inline bool is_crashed_pfn_valid(unsigned long pfn) 18 { 19 #ifndef CONFIG_X86_PAE 20 /* 21 * non-PAE kdump kernel executed from a PAE one will crop high pte 22 * bits and poke unwanted space counting again from address 0, we 23 * don't want that. pte must fit into unsigned long. In fact the 24 * test checks high 12 bits for being zero (pfn will be shifted left 25 * by PAGE_SHIFT). 26 */ 27 return pte_pfn(pfn_pte(pfn, __pgprot(0))) == pfn; 28 #else 29 return true; 30 #endif 31 } 32 33 /** 34 * copy_oldmem_page - copy one page from "oldmem" 35 * @pfn: page frame number to be copied 36 * @buf: target memory address for the copy; this can be in kernel address 37 * space or user address space (see @userbuf) 38 * @csize: number of bytes to copy 39 * @offset: offset in bytes into the page (based on pfn) to begin the copy 40 * @userbuf: if set, @buf is in user address space, use copy_to_user(), 41 * otherwise @buf is in kernel address space, use memcpy(). 42 * 43 * Copy a page from "oldmem". For this page, there is no pte mapped 44 * in the current kernel. We stitch up a pte, similar to kmap_atomic. 45 * 46 * Calling copy_to_user() in atomic context is not desirable. Hence first 47 * copying the data to a pre-allocated kernel page and then copying to user 48 * space in non-atomic context. 49 */ 50 ssize_t copy_oldmem_page(unsigned long pfn, char *buf, 51 size_t csize, unsigned long offset, int userbuf) 52 { 53 void *vaddr; 54 55 if (!csize) 56 return 0; 57 58 if (!is_crashed_pfn_valid(pfn)) 59 return -EFAULT; 60 61 vaddr = kmap_atomic_pfn(pfn); 62 63 if (!userbuf) { 64 memcpy(buf, (vaddr + offset), csize); 65 kunmap_atomic(vaddr); 66 } else { 67 if (!kdump_buf_page) { 68 printk(KERN_WARNING "Kdump: Kdump buffer page not" 69 " allocated\n"); 70 kunmap_atomic(vaddr); 71 return -EFAULT; 72 } 73 copy_page(kdump_buf_page, vaddr); 74 kunmap_atomic(vaddr); 75 if (copy_to_user(buf, (kdump_buf_page + offset), csize)) 76 return -EFAULT; 77 } 78 79 return csize; 80 } 81 82 static int __init kdump_buf_page_init(void) 83 { 84 int ret = 0; 85 86 kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL); 87 if (!kdump_buf_page) { 88 printk(KERN_WARNING "Kdump: Failed to allocate kdump buffer" 89 " page\n"); 90 ret = -ENOMEM; 91 } 92 93 return ret; 94 } 95 arch_initcall(kdump_buf_page_init); 96