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Linux/arch/x86/kernel/crash_dump_32.c

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  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 

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