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#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 + 1))
break;
if (addr >= corruption_check_size)
break;
if ((addr + size) > corruption_check_size)
size = corruption_check_size - addr;
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);
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