1#include <linux/module.h> 2#include <linux/sched.h> 3#include <linux/kthread.h> 4#include <linux/workqueue.h> 5#include <asm/e820.h> 6#include <asm/proto.h> 7 8/* 9 * Some BIOSes seem to corrupt the low 64k of memory during events 10 * like suspend/resume and unplugging an HDMI cable. Reserve all 11 * remaining free memory in that area and fill it with a distinct 12 * pattern. 13 */ 14#define MAX_SCAN_AREAS 8 15 16static int __read_mostly memory_corruption_check = -1; 17 18static unsigned __read_mostly corruption_check_size = 64*1024; 19static unsigned __read_mostly corruption_check_period = 60; /* seconds */ 20 21static struct e820entry scan_areas[MAX_SCAN_AREAS]; 22static int num_scan_areas; 23 24 25static __init int set_corruption_check(char *arg) 26{ 27 char *end; 28 29 memory_corruption_check = simple_strtol(arg, &end, 10); 30 31 return (*end == 0) ? 0 : -EINVAL; 32} 33early_param("memory_corruption_check", set_corruption_check); 34 35static __init int set_corruption_check_period(char *arg) 36{ 37 char *end; 38 39 corruption_check_period = simple_strtoul(arg, &end, 10); 40 41 return (*end == 0) ? 0 : -EINVAL; 42} 43early_param("memory_corruption_check_period", set_corruption_check_period); 44 45static __init int set_corruption_check_size(char *arg) 46{ 47 char *end; 48 unsigned size; 49 50 size = memparse(arg, &end); 51 52 if (*end == '\0') 53 corruption_check_size = size; 54 55 return (size == corruption_check_size) ? 0 : -EINVAL; 56} 57early_param("memory_corruption_check_size", set_corruption_check_size); 58 59 60void __init setup_bios_corruption_check(void) 61{ 62 u64 addr = PAGE_SIZE; /* assume first page is reserved anyway */ 63 64 if (memory_corruption_check == -1) { 65 memory_corruption_check = 66#ifdef CONFIG_X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK 67 1 68#else 69 0 70#endif 71 ; 72 } 73 74 if (corruption_check_size == 0) 75 memory_corruption_check = 0; 76 77 if (!memory_corruption_check) 78 return; 79 80 corruption_check_size = round_up(corruption_check_size, PAGE_SIZE); 81 82 while (addr < corruption_check_size && num_scan_areas < MAX_SCAN_AREAS) { 83 u64 size; 84 addr = find_e820_area_size(addr, &size, PAGE_SIZE); 85 86 if (!(addr + 1)) 87 break; 88 89 if (addr >= corruption_check_size) 90 break; 91 92 if ((addr + size) > corruption_check_size) 93 size = corruption_check_size - addr; 94 95 e820_update_range(addr, size, E820_RAM, E820_RESERVED); 96 scan_areas[num_scan_areas].addr = addr; 97 scan_areas[num_scan_areas].size = size; 98 num_scan_areas++; 99 100 /* Assume we've already mapped this early memory */ 101 memset(__va(addr), 0, size); 102 103 addr += size; 104 } 105 106 printk(KERN_INFO "Scanning %d areas for low memory corruption\n", 107 num_scan_areas); 108 update_e820(); 109} 110 111 112void check_for_bios_corruption(void) 113{ 114 int i; 115 int corruption = 0; 116 117 if (!memory_corruption_check) 118 return; 119 120 for (i = 0; i < num_scan_areas; i++) { 121 unsigned long *addr = __va(scan_areas[i].addr); 122 unsigned long size = scan_areas[i].size; 123 124 for (; size; addr++, size -= sizeof(unsigned long)) { 125 if (!*addr) 126 continue; 127 printk(KERN_ERR "Corrupted low memory at %p (%lx phys) = %08lx\n", 128 addr, __pa(addr), *addr); 129 corruption = 1; 130 *addr = 0; 131 } 132 } 133 134 WARN_ONCE(corruption, KERN_ERR "Memory corruption detected in low memory\n"); 135} 136 137static void check_corruption(struct work_struct *dummy); 138static DECLARE_DELAYED_WORK(bios_check_work, check_corruption); 139 140static void check_corruption(struct work_struct *dummy) 141{ 142 check_for_bios_corruption(); 143 schedule_delayed_work(&bios_check_work, 144 round_jiffies_relative(corruption_check_period*HZ)); 145} 146 147static int start_periodic_check_for_corruption(void) 148{ 149 if (!memory_corruption_check || corruption_check_period == 0) 150 return 0; 151 152 printk(KERN_INFO "Scanning for low memory corruption every %d seconds\n", 153 corruption_check_period); 154 155 /* First time we run the checks right away */ 156 schedule_delayed_work(&bios_check_work, 0); 157 return 0; 158} 159 160module_init(start_periodic_check_for_corruption); 161