2 files changed, 83 insertions, 23 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 1bb52e2ca02e..cbee4199689c 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -201,9 +201,6 @@ config X86_TRAMPOLINE
         depends on X86_SMP || (X86_VOYAGER && SMP) || (64BIT && ACPI_SLEEP)
         default y
 
-config X86_CHECK_BIOS_CORRUPTION
-        def_bool y
-
 config KTIME_SCALAR
         def_bool X86_32
 source "init/Kconfig"
@@ -1062,6 +1059,29 @@ config HIGHPTE
           low memory.  Setting this option will put user-space page table
           entries in high memory.
 
+config X86_CHECK_BIOS_CORRUPTION
+        bool "Check for low memory corruption"
+        default y
+        help
+         Periodically check for memory corruption in low memory, which
+         is suspected to be caused by BIOS.  Even when enabled in the
+         configuration, it is disabled at runtime.  Enable it by
+         setting "memory_corruption_check=1" on the kernel command
+         line.  By default it scans the low 64k of memory every 60
+         seconds; see the memory_corruption_check_size and
+         memory_corruption_check_period parameters in
+         Documentation/kernel-parameters.txt to adjust this.
+
+         When enabled with the default parameters, this option has
+         almost no overhead, as it reserves a relatively small amount
+         of memory and scans it infrequently.  It both detects corruption
+         and prevents it from affecting the running system.
+
+         It is, however, intended as a diagnostic tool; if repeatable
+         BIOS-originated corruption always affects the same memory,
+         you can use memmap= to prevent the kernel from using that
+         memory.
+
 config MATH_EMULATION
         bool
         prompt "Math emulation" if X86_32
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index c239b3780973..27ae91288855 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -586,22 +586,71 @@ struct x86_quirks *x86_quirks __initdata = &default_x86_quirks;
  */
 #ifdef CONFIG_X86_CHECK_BIOS_CORRUPTION
 #define MAX_SCAN_AREAS  8
+
+static int __read_mostly memory_corruption_check = 0;
+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 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 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 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);
+
+
 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) {
+        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) > 0x10000)
-                        size = 0x10000 - addr;
+                if ((addr + size) > corruption_check_size)
+                        size = corruption_check_size - addr;
 
                 if (size == 0)
                         break;
@@ -617,12 +666,11 @@ static void __init setup_bios_corruption_check(void)
                 addr += size;
         }
 
-        printk(KERN_INFO "scanning %d areas for BIOS corruption\n",
+        printk(KERN_INFO "Scanning %d areas for low memory corruption\n",
                num_scan_areas);
         update_e820();
 }
 
-static int __read_mostly bios_corruption_check = 1;
 static struct timer_list periodic_check_timer;
 
 void check_for_bios_corruption(void)
@@ -630,7 +678,7 @@ void check_for_bios_corruption(void)
         int i;
         int corruption = 0;
 
-        if (!bios_corruption_check)
+        if (!memory_corruption_check)
                 return;
 
         for(i = 0; i < num_scan_areas; i++) {
@@ -647,35 +695,27 @@ void check_for_bios_corruption(void)
                 }
         }
 
-        if (corruption)
-                dump_stack();
+        WARN(corruption, KERN_ERR "Memory corruption detected in low memory\n");
 }
 
 static void periodic_check_for_corruption(unsigned long data)
 {
         check_for_bios_corruption();
-        mod_timer(&periodic_check_timer, jiffies + 60*HZ);
+        mod_timer(&periodic_check_timer, jiffies + corruption_check_period*HZ);
 }
 
 void start_periodic_check_for_corruption(void)
 {
-        if (!bios_corruption_check)
+        if (!memory_corruption_check || corruption_check_period == 0)
                 return;
 
+        printk(KERN_INFO "Scanning for low memory corruption every %d seconds\n",
+               corruption_check_period);
+
         init_timer(&periodic_check_timer);
         periodic_check_timer.function = &periodic_check_for_corruption;
         periodic_check_for_corruption(0);
 }
-
-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
 
 /*