6 files changed, 110 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 1150444a21ab..df48af505d15 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -360,6 +360,11 @@ and is between 256 and 4096 characters. It is defined in the file
                         Format: <io>,<irq>,<mode>
                         See header of drivers/net/hamradio/baycom_ser_hdx.c.
 
+        bios_corruption_check=0/1 [X86]
+                        Some BIOSes seem to corrupt the first 64k of memory
+                        when doing things like suspend/resume.  Setting this
+                        option will scan the memory looking for corruption.
+
         boot_delay=     Milliseconds to delay each printk during boot.
                         Values larger than 10 seconds (10000) are changed to
                         no delay (0).
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index ed92864d1325..1bb52e2ca02e 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -201,6 +201,9 @@ 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"
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 362d4e7f2d38..ee89ebc5aabc 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -579,6 +579,89 @@ 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
  * for initialization.  Note, the efi init code path is determined by the
@@ -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;
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 455f3fe67b42..5140bdf03020 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -848,6 +848,8 @@ no_context:
  * Oops. The kernel tried to access some bad page. We'll have to
  * terminate things with extreme prejudice.
  */
+        check_for_bios_corruption();
+
 #ifdef CONFIG_X86_32
         bust_spinlocks(1);
 #else
diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 273a944d4040..bf6d3554e506 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -254,6 +254,7 @@ static char *pm_verb(int event)
 
 static void pm_dev_dbg(struct device *dev, pm_message_t state, char *info)
 {
+        check_for_bios_corruption();
         dev_dbg(dev, "%s%s%s\n", info, pm_verb(state.event),
                 ((state.event & PM_EVENT_SLEEP) && device_may_wakeup(dev)) ?
                 ", may wakeup" : "");
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 2651f805ba6d..8017129e6b63 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -240,6 +240,18 @@ extern const char *print_tainted(void);
 extern void add_taint(unsigned);
 extern int root_mountflags;
 
+#ifdef CONFIG_X86_CHECK_BIOS_CORRUPTION
+/*
+ * This is obviously not a great place for this, but we want to be
+ * able to scatter it around anywhere in the kernel.
+ */
+void check_for_bios_corruption(void);
+#else
+static inline void check_for_bios_corruption(void)
+{
+}
+#endif
+
 /* Values used for system_state */
 extern enum system_states {
         SYSTEM_BOOTING,