Re: [PATCH] hpwd watchdog mark page executable
From: Maxim Uvarov
Date: Tue Dec 20 2011 - 20:35:45 EST
On 12/20/2011 04:50 PM, Andrew Morton wrote:
On Mon, 5 Dec 2011 16:25:39 -0800
Maxim Uvarov<maxim.uvarov@xxxxxxxxxx> 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.
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