1 files changed, 161 insertions, 0 deletions

diff --git a/arch/x86/kernel/check.c b/arch/x86/kernel/check.c
new file mode 100644
index 000000000000..2ac0ab71412a
--- /dev/null
+++ b/arch/x86/kernel/check.c
@@ -0,0 +1,161 @@
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/kthread.h>
+#include <linux/workqueue.h>
+#include <asm/e820.h>
+#include <asm/proto.h>
+
+/*
+ * Some BIOSes seem to corrupt the low 64k of memory during events
+ * like suspend/resume and unplugging an HDMI cable.  Reserve all
+ * remaining free memory in that area and fill it with a distinct
+ * pattern.
+ */
+#define MAX_SCAN_AREAS  8
+
+static int __read_mostly memory_corruption_check = -1;
+
+static unsigned __read_mostly corruption_check_size = 64*1024;
+static unsigned __read_mostly corruption_check_period = 60; /* seconds */
+
+static struct e820entry scan_areas[MAX_SCAN_AREAS];
+static int num_scan_areas;
+
+
+static __init int set_corruption_check(char *arg)
+{
+        char *end;
+
+        memory_corruption_check = simple_strtol(arg, &end, 10);
+
+        return (*end == 0) ? 0 : -EINVAL;
+}
+early_param("memory_corruption_check", set_corruption_check);
+
+static __init int set_corruption_check_period(char *arg)
+{
+        char *end;
+
+        corruption_check_period = simple_strtoul(arg, &end, 10);
+
+        return (*end == 0) ? 0 : -EINVAL;
+}
+early_param("memory_corruption_check_period", set_corruption_check_period);
+
+static __init int set_corruption_check_size(char *arg)
+{
+        char *end;
+        unsigned size;
+
+        size = memparse(arg, &end);
+
+        if (*end == '\0')
+                corruption_check_size = size;
+
+        return (size == corruption_check_size) ? 0 : -EINVAL;
+}
+early_param("memory_corruption_check_size", set_corruption_check_size);
+
+
+void __init setup_bios_corruption_check(void)
+{
+        u64 addr = PAGE_SIZE;   /* assume first page is reserved anyway */
+
+        if (memory_corruption_check == -1) {
+                memory_corruption_check =
+#ifdef CONFIG_X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
+                        1
+#else
+                        0
+#endif
+                        ;
+        }
+
+        if (corruption_check_size == 0)
+                memory_corruption_check = 0;
+
+        if (!memory_corruption_check)
+                return;
+
+        corruption_check_size = round_up(corruption_check_size, PAGE_SIZE);
+
+        while (addr < corruption_check_size && num_scan_areas < MAX_SCAN_AREAS) {
+                u64 size;
+                addr = find_e820_area_size(addr, &size, PAGE_SIZE);
+
+                if (addr == 0)
+                        break;
+
+                if ((addr + size) > corruption_check_size)
+                        size = corruption_check_size - addr;
+
+                if (size == 0)
+                        break;
+
+                e820_update_range(addr, size, E820_RAM, E820_RESERVED);
+                scan_areas[num_scan_areas].addr = addr;
+                scan_areas[num_scan_areas].size = size;
+                num_scan_areas++;
+
+                /* Assume we've already mapped this early memory */
+                memset(__va(addr), 0, size);
+
+                addr += size;
+        }
+
+        printk(KERN_INFO "Scanning %d areas for low memory corruption\n",
+               num_scan_areas);
+        update_e820();
+}
+
+
+void check_for_bios_corruption(void)
+{
+        int i;
+        int corruption = 0;
+
+        if (!memory_corruption_check)
+                return;
+
+        for (i = 0; i < num_scan_areas; i++) {
+                unsigned long *addr = __va(scan_areas[i].addr);
+                unsigned long size = scan_areas[i].size;
+
+                for (; size; addr++, size -= sizeof(unsigned long)) {
+                        if (!*addr)
+                                continue;
+                        printk(KERN_ERR "Corrupted low memory at %p (%lx phys) = %08lx\n",
+                               addr, __pa(addr), *addr);
+                        corruption = 1;
+                        *addr = 0;
+                }
+        }
+
+        WARN_ONCE(corruption, KERN_ERR "Memory corruption detected in low memory\n");
+}
+
+static void check_corruption(struct work_struct *dummy);
+static DECLARE_DELAYED_WORK(bios_check_work, check_corruption);
+
+static void check_corruption(struct work_struct *dummy)
+{
+        check_for_bios_corruption();
+        schedule_delayed_work(&bios_check_work,
+                round_jiffies_relative(corruption_check_period*HZ)); 
+}
+
+static int start_periodic_check_for_corruption(void)
+{
+        if (!memory_corruption_check || corruption_check_period == 0)
+                return 0;
+
+        printk(KERN_INFO "Scanning for low memory corruption every %d seconds\n",
+               corruption_check_period);
+
+        /* First time we run the checks right away */
+        schedule_delayed_work(&bios_check_work, 0);
+        return 0;
+}
+
+module_init(start_periodic_check_for_corruption);
+