4 files changed, 248 insertions, 2 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 44d4f2130d01..25e2f7a20d66 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1061,6 +1061,56 @@ 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"
+        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 X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
+        bool "Set the default setting of memory_corruption_check"
+        depends on X86_CHECK_BIOS_CORRUPTION
+        default y
+        help
+         Set whether the default state of memory_corruption_check is
+         on or off.
+
+config X86_RESERVE_LOW_64K
+        bool "Reserve low 64K of RAM on AMI/Phoenix BIOSen"
+        default y
+        help
+         Reserve the first 64K of physical RAM on BIOSes that are known
+         to potentially corrupt that memory range. A numbers of BIOSes are
+         known to utilize this area during suspend/resume, so it must not
+         be used by the kernel.
+
+         Set this to N if you are absolutely sure that you trust the BIOS
+         to get all its memory reservations and usages right.
+
+         If you have doubts about the BIOS (e.g. suspend/resume does not
+         work or there's kernel crashes after certain hardware hotplug
+         events) and it's not AMI or Phoenix, then you might want to enable
+         X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check typical
+         corruption patterns.
+
+         Say Y if unsure.
+
 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 46c98efbbf8d..21b8e0a59780 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -582,6 +582,190 @@ 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 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 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 */
+
+        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();
+}
+
+static struct timer_list periodic_check_timer;
+
+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(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, round_jiffies(jiffies + corruption_check_period*HZ));
+}
+
+void start_periodic_check_for_corruption(void)
+{
+        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);
+}
+#endif
+
+static int __init dmi_low_memory_corruption(const struct dmi_system_id *d)
+{
+        printk(KERN_NOTICE
+                "%s detected: BIOS may corrupt low RAM, working it around.\n",
+                d->ident);
+
+        e820_update_range(0, 0x10000, E820_RAM, E820_RESERVED);
+        sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
+
+        return 0;
+}
+
+/* List of systems that have known low memory corruption BIOS problems */
+static struct dmi_system_id __initdata bad_bios_dmi_table[] = {
+#ifdef CONFIG_X86_RESERVE_LOW_64K
+        {
+                .callback = dmi_low_memory_corruption,
+                .ident = "AMI BIOS",
+                .matches = {
+                        DMI_MATCH(DMI_BIOS_VENDOR, "American Megatrends Inc."),
+                },
+        },
+        {
+                .callback = dmi_low_memory_corruption,
+                .ident = "Phoenix BIOS",
+                .matches = {
+                        DMI_MATCH(DMI_BIOS_VENDOR, "Phoenix Technologies, LTD"),
+                },
+        },
+#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
@@ -715,6 +899,10 @@ void __init setup_arch(char **cmdline_p)
 
         finish_e820_parsing();
 
+        dmi_scan_machine();
+
+        dmi_check_system(bad_bios_dmi_table);
+
 #ifdef CONFIG_X86_32
         probe_roms();
 #endif
@@ -771,6 +959,10 @@ 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;
@@ -799,8 +991,6 @@ void __init setup_arch(char **cmdline_p)
         vsmp_init();
 #endif
 
-        dmi_scan_machine();
-
         io_delay_init();
 
         /*
@@ -903,3 +1093,5 @@ void __init setup_arch(char **cmdline_p)
 #endif
 #endif
 }
+
+
diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index c3789bb19308..7e05462ffb11 100644
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -969,6 +969,8 @@ void __init mem_init(void)
         int codesize, reservedpages, datasize, initsize;
         int tmp;
 
+        start_periodic_check_for_corruption();
+
 #ifdef CONFIG_FLATMEM
         BUG_ON(!mem_map);
 #endif
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 83e13f2d53d2..d84d3e91d348 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -881,6 +881,8 @@ void __init mem_init(void)
 {
         long codesize, reservedpages, datasize, initsize;
 
+        start_periodic_check_for_corruption();
+
         pci_iommu_alloc();
 
         /* clear_bss() already clear the empty_zero_page */