Re: [PATCH RFC] x86: check for and defend against BIOS memory corruption

[Yinghai Lu]

On Thu, Aug 28, 2008 at 12:52 PM, Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:
> Some BIOSes have been observed to corrupt memory in the low 64k.  This
> patch does two things:
>  - Reserves all memory which does not have to be in that area, to
>   prevent it from being used as general memory by the kernel.  Things
>   like the SMP trampoline are still in the memory, however.
>  - Clears the reserved memory so we can observe changes to it.
>  - Adds a function check_for_bios_corruption() which checks and reports on
>   memory becoming unexpectedly non-zero.  Currently it's called in the
>   x86 fault handler, and the powermanagement debug output.
>
> RFC: What other places should we check for corruption in?
>
> [ Alan, Rafał: could you check you see:
>   1: corruption messages
>   2: no crashes
>  Thanks -J
> ]
>
> Signed-off-by: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
> Cc: Alan Jenkins <alan-jenkins@xxxxxxxxxxxxxx>
> Cc: Hugh Dickens <hugh@xxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxx>
> Cc: Rafael J. Wysocki <rjw@xxxxxxx>
> Cc: Rafał Miłecki <zajec5@xxxxxxxxx>
> Cc: H. Peter Anvin <hpa@xxxxxxxxx>
> ---
>  Documentation/kernel-parameters.txt |    5 ++
>  arch/x86/Kconfig                    |    3 +
>  arch/x86/kernel/setup.c             |   86 +++++++++++++++++++++++++++++++++++
>  arch/x86/mm/fault.c                 |    2
>  drivers/base/power/main.c           |    1
>  include/linux/kernel.h              |   12 ++++
>  6 files changed, 109 insertions(+)
>
> ===================================================================
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -359,6 +359,11 @@
>                        BayCom Serial Port AX.25 Modem (Half Duplex Mode)
>                        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
> ===================================================================
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -203,6 +203,9 @@
>        bool
>        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
> ===================================================================
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -582,6 +582,88 @@
>  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 */
> +

can you please not punish systems without this bios problem?

if (!bios_corruption_check)
   return;

> +       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;

move earlier and
bios_corruption_check = 0;

BTW: SMI evil damaged that area?

YH
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