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Linux/arch/mips/kernel/crash_dump.c

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  1 #include <linux/highmem.h>
  2 #include <linux/bootmem.h>
  3 #include <linux/crash_dump.h>
  4 #include <asm/uaccess.h>
  5 #include <linux/slab.h>
  6 
  7 static void *kdump_buf_page;
  8 
  9 /**
 10  * copy_oldmem_page - copy one page from "oldmem"
 11  * @pfn: page frame number to be copied
 12  * @buf: target memory address for the copy; this can be in kernel address
 13  *      space or user address space (see @userbuf)
 14  * @csize: number of bytes to copy
 15  * @offset: offset in bytes into the page (based on pfn) to begin the copy
 16  * @userbuf: if set, @buf is in user address space, use copy_to_user(),
 17  *      otherwise @buf is in kernel address space, use memcpy().
 18  *
 19  * Copy a page from "oldmem". For this page, there is no pte mapped
 20  * in the current kernel.
 21  *
 22  * Calling copy_to_user() in atomic context is not desirable. Hence first
 23  * copying the data to a pre-allocated kernel page and then copying to user
 24  * space in non-atomic context.
 25  */
 26 ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
 27                          size_t csize, unsigned long offset, int userbuf)
 28 {
 29         void  *vaddr;
 30 
 31         if (!csize)
 32                 return 0;
 33 
 34         vaddr = kmap_atomic_pfn(pfn);
 35 
 36         if (!userbuf) {
 37                 memcpy(buf, (vaddr + offset), csize);
 38                 kunmap_atomic(vaddr);
 39         } else {
 40                 if (!kdump_buf_page) {
 41                         pr_warn("Kdump: Kdump buffer page not allocated\n");
 42 
 43                         return -EFAULT;
 44                 }
 45                 copy_page(kdump_buf_page, vaddr);
 46                 kunmap_atomic(vaddr);
 47                 if (copy_to_user(buf, (kdump_buf_page + offset), csize))
 48                         return -EFAULT;
 49         }
 50 
 51         return csize;
 52 }
 53 
 54 static int __init kdump_buf_page_init(void)
 55 {
 56         int ret = 0;
 57 
 58         kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
 59         if (!kdump_buf_page) {
 60                 pr_warn("Kdump: Failed to allocate kdump buffer page\n");
 61                 ret = -ENOMEM;
 62         }
 63 
 64         return ret;
 65 }
 66 arch_initcall(kdump_buf_page_init);
 67 

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