lkml.org 
[lkml]   [2011]   [Dec]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] hpwd watchdog mark page executable
On 12/20/2011 04:50 PM, Andrew Morton wrote:
> On Mon, 5 Dec 2011 16:25:39 -0800
> Maxim Uvarov<maxim.uvarov@oracle.com> wrote:
>
>> Mark hpwdt watchdog pages executable to prevent failing:
>> BUG: unable to handle kernel paging request at c00f0000
>> IP: [<c00f0000>] 0xc00effff
>> *pdpt = 0000000000b7c001 *pde = 0000000000cf5067 *pte = 80000000000f0163
>> Oops: 0011 [#1] SMP
>>
>> ...
>>
>> --- a/drivers/watchdog/hpwdt.c
>> +++ b/drivers/watchdog/hpwdt.c
>> @@ -335,6 +335,8 @@ static int __devinit detect_cru_service(void)
>> if (p == NULL)
>> return -ENOMEM;
>>
>> + set_memory_x((unsigned long)p& PAGE_MASK, ROM_SIZE>> PAGE_SHIFT);
>> +
>> for (q = p; q< p + ROM_SIZE; q += 16) {
>> rc = bios32_present(q);
>> if (!rc)
>
> Odd. Either nobody else is using this driver, or there's something
> special about your setup. Are you able to explain this?
>

Code drivers/watchdog/hpwdt.c is ifdefed on 2 branches for 32 and 64 bit
accordingly. For 64 bit address for watchdog handler is used from
smbios, for 32 bit - from ioremap(0x000F0000, ). Accordingly 64 kernel
unsets _PAGE_NX flag to pages. I.e. calls set_memory_x(). But 32 bit
did not do so. It worked on 2.6.32 and since 3.0 looks like additional
page protection code was added. I can't find the right commit which
changed it right now.

> Also, do you believe that this fix should be backported into earlier
> stable kernels and if so, why?
>
Andrew, I found this problem in 3.0 than checked that it exist in
linux-next when it was 3.1+. Because it's panic on module loading, yes
this is critical bug and it's needs to be back-ported. (Actually this
driver was not changed so simple cherry-pick one line patch will work.).

Maxim.
> Thanks.



\
 
 \ /
  Last update: 2011-12-21 02:37    [W:0.052 / U:0.152 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site