1 #include <linux/module.h> 2 #include <linux/sched.h> 3 #include <linux/kthread.h> 4 #include <linux/workqueue.h> 5 #include <linux/memblock.h> 6 7 #include <asm/proto.h> 8 9 /* 10 * Some BIOSes seem to corrupt the low 64k of memory during events 11 * like suspend/resume and unplugging an HDMI cable. Reserve all 12 * remaining free memory in that area and fill it with a distinct 13 * pattern. 14 */ 15 #define MAX_SCAN_AREAS 8 16 17 static int __read_mostly memory_corruption_check = -1; 18 19 static unsigned __read_mostly corruption_check_size = 64*1024; 20 static unsigned __read_mostly corruption_check_period = 60; /* seconds */ 21 22 static struct scan_area { 23 u64 addr; 24 u64 size; 25 } scan_areas[MAX_SCAN_AREAS]; 26 static int num_scan_areas; 27 28 static __init int set_corruption_check(char *arg) 29 { 30 ssize_t ret; 31 unsigned long val; 32 33 ret = kstrtoul(arg, 10, &val); 34 if (ret) 35 return ret; 36 37 memory_corruption_check = val; 38 return 0; 39 } 40 early_param("memory_corruption_check", set_corruption_check); 41 42 static __init int set_corruption_check_period(char *arg) 43 { 44 ssize_t ret; 45 unsigned long val; 46 47 ret = kstrtoul(arg, 10, &val); 48 if (ret) 49 return ret; 50 51 corruption_check_period = val; 52 return 0; 53 } 54 early_param("memory_corruption_check_period", set_corruption_check_period); 55 56 static __init int set_corruption_check_size(char *arg) 57 { 58 char *end; 59 unsigned size; 60 61 size = memparse(arg, &end); 62 63 if (*end == '\0') 64 corruption_check_size = size; 65 66 return (size == corruption_check_size) ? 0 : -EINVAL; 67 } 68 early_param("memory_corruption_check_size", set_corruption_check_size); 69 70 71 void __init setup_bios_corruption_check(void) 72 { 73 phys_addr_t start, end; 74 u64 i; 75 76 if (memory_corruption_check == -1) { 77 memory_corruption_check = 78 #ifdef CONFIG_X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK 79 1 80 #else 81 0 82 #endif 83 ; 84 } 85 86 if (corruption_check_size == 0) 87 memory_corruption_check = 0; 88 89 if (!memory_corruption_check) 90 return; 91 92 corruption_check_size = round_up(corruption_check_size, PAGE_SIZE); 93 94 for_each_free_mem_range(i, MAX_NUMNODES, &start, &end, NULL) { 95 start = clamp_t(phys_addr_t, round_up(start, PAGE_SIZE), 96 PAGE_SIZE, corruption_check_size); 97 end = clamp_t(phys_addr_t, round_down(end, PAGE_SIZE), 98 PAGE_SIZE, corruption_check_size); 99 if (start >= end) 100 continue; 101 102 memblock_reserve(start, end - start); 103 scan_areas[num_scan_areas].addr = start; 104 scan_areas[num_scan_areas].size = end - start; 105 106 /* Assume we've already mapped this early memory */ 107 memset(__va(start), 0, end - start); 108 109 if (++num_scan_areas >= MAX_SCAN_AREAS) 110 break; 111 } 112 113 if (num_scan_areas) 114 printk(KERN_INFO "Scanning %d areas for low memory corruption\n", num_scan_areas); 115 } 116 117 118 void check_for_bios_corruption(void) 119 { 120 int i; 121 int corruption = 0; 122 123 if (!memory_corruption_check) 124 return; 125 126 for (i = 0; i < num_scan_areas; i++) { 127 unsigned long *addr = __va(scan_areas[i].addr); 128 unsigned long size = scan_areas[i].size; 129 130 for (; size; addr++, size -= sizeof(unsigned long)) { 131 if (!*addr) 132 continue; 133 printk(KERN_ERR "Corrupted low memory at %p (%lx phys) = %08lx\n", 134 addr, __pa(addr), *addr); 135 corruption = 1; 136 *addr = 0; 137 } 138 } 139 140 WARN_ONCE(corruption, KERN_ERR "Memory corruption detected in low memory\n"); 141 } 142 143 static void check_corruption(struct work_struct *dummy); 144 static DECLARE_DELAYED_WORK(bios_check_work, check_corruption); 145 146 static void check_corruption(struct work_struct *dummy) 147 { 148 check_for_bios_corruption(); 149 schedule_delayed_work(&bios_check_work, 150 round_jiffies_relative(corruption_check_period*HZ)); 151 } 152 153 static int start_periodic_check_for_corruption(void) 154 { 155 if (!num_scan_areas || !memory_corruption_check || corruption_check_period == 0) 156 return 0; 157 158 printk(KERN_INFO "Scanning for low memory corruption every %d seconds\n", 159 corruption_check_period); 160 161 /* First time we run the checks right away */ 162 schedule_delayed_work(&bios_check_work, 0); 163 return 0; 164 } 165 166 module_init(start_periodic_check_for_corruption); 167 168