x86: check for and defend against BIOS memory corruption

[linux-2.6-omap-h63xx.git] / arch / x86 / kernel / setup.c

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 362d4e7f2d389b81e345fa27b13db78e80c5980a..ee89ebc5aabc7679e46bff29db43e062176c0a26 100644 (file)
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -578,6 +578,89 @@ static struct x86_quirks default_x86_quirks __initdata;
 
 struct x86_quirks *x86_quirks __initdata = &default_x86_quirks;
 
+/*
+ * 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.
+ */
+#ifdef CONFIG_X86_CHECK_BIOS_CORRUPTION
+#define MAX_SCAN_AREAS 8
+static struct e820entry scan_areas[MAX_SCAN_AREAS];
+static int num_scan_areas;
+
+static void __init setup_bios_corruption_check(void)
+{
+       u64 addr = PAGE_SIZE;   /* assume first page is reserved anyway */
+
+       while(addr < 0x10000 && num_scan_areas < MAX_SCAN_AREAS) {
+               u64 size;
+               addr = find_e820_area_size(addr, &size, PAGE_SIZE);
+
+               if (addr == 0)
+                       break;
+
+               if ((addr + size) > 0x10000)
+                       size = 0x10000 - 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 BIOS corruption\n",
+              num_scan_areas);
+       update_e820();
+}
+
+static int __read_mostly bios_corruption_check = 1;
+
+void check_for_bios_corruption(void)
+{
+       int i;
+       int corruption = 0;
+
+       if (!bios_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;
+               }
+       }
+
+       if (corruption)
+               dump_stack();
+}
+
+static int set_bios_corruption_check(char *arg)
+{
+       char *end;
+
+       bios_corruption_check = simple_strtol(arg, &end, 10);
+
+       return (*end == 0) ? 0 : -EINVAL;
+}
+early_param("bios_corruption_check", set_bios_corruption_check);
+#endif
+
 /*
  * Determine if we were loaded by an EFI loader.  If so, then we have also been
  * passed the efi memmap, systab, etc., so we should use these data structures
@@ -750,6 +833,10 @@ void __init setup_arch(char **cmdline_p)
        high_memory = (void *)__va(max_pfn * PAGE_SIZE - 1) + 1;
 #endif
 
+#ifdef CONFIG_X86_CHECK_BIOS_CORRUPTION
+       setup_bios_corruption_check();
+#endif
+
        /* max_pfn_mapped is updated here */
        max_low_pfn_mapped = init_memory_mapping(0, max_low_pfn<<PAGE_SHIFT);
        max_pfn_mapped = max_low_pfn_mapped;