1 #include <linux/highmem.h> 2 #include <linux/bootmem.h> 3 #include <linux/crash_dump.h> 4 #include <asm/uaccess.h> 5 6 static int __init parse_savemaxmem(char *p) 7 { 8 if (p) 9 saved_max_pfn = (memparse(p, &p) >> PAGE_SHIFT) - 1; 10 11 return 1; 12 } 13 __setup("savemaxmem=", parse_savemaxmem); 14 15 16 static void *kdump_buf_page; 17 18 /** 19 * copy_oldmem_page - copy one page from "oldmem" 20 * @pfn: page frame number to be copied 21 * @buf: target memory address for the copy; this can be in kernel address 22 * space or user address space (see @userbuf) 23 * @csize: number of bytes to copy 24 * @offset: offset in bytes into the page (based on pfn) to begin the copy 25 * @userbuf: if set, @buf is in user address space, use copy_to_user(), 26 * otherwise @buf is in kernel address space, use memcpy(). 27 * 28 * Copy a page from "oldmem". For this page, there is no pte mapped 29 * in the current kernel. 30 * 31 * Calling copy_to_user() in atomic context is not desirable. Hence first 32 * copying the data to a pre-allocated kernel page and then copying to user 33 * space in non-atomic context. 34 */ 35 ssize_t copy_oldmem_page(unsigned long pfn, char *buf, 36 size_t csize, unsigned long offset, int userbuf) 37 { 38 void *vaddr; 39 40 if (!csize) 41 return 0; 42 43 vaddr = kmap_atomic_pfn(pfn); 44 45 if (!userbuf) { 46 memcpy(buf, (vaddr + offset), csize); 47 kunmap_atomic(vaddr); 48 } else { 49 if (!kdump_buf_page) { 50 pr_warning("Kdump: Kdump buffer page not allocated\n"); 51 52 return -EFAULT; 53 } 54 copy_page(kdump_buf_page, vaddr); 55 kunmap_atomic(vaddr); 56 if (copy_to_user(buf, (kdump_buf_page + offset), csize)) 57 return -EFAULT; 58 } 59 60 return csize; 61 } 62 63 static int __init kdump_buf_page_init(void) 64 { 65 int ret = 0; 66 67 kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL); 68 if (!kdump_buf_page) { 69 pr_warning("Kdump: Failed to allocate kdump buffer page\n"); 70 ret = -ENOMEM; 71 } 72 73 return ret; 74 } 75 arch_initcall(kdump_buf_page_init); 76