linux-kernel - Re: [PATCH] hpwd watchdog mark page executable

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Date:	Thu, 22 Dec 2011 08:57:34 +0100
From:	Wim Van Sebroeck <wim@...ana.be>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Maxim Uvarov <maxim.uvarov@...cle.com>,
	linux-kernel@...r.kernel.org, linux-watchdog@...r.kernel.org,
	wim@...ana.be
Subject: Re: [PATCH] hpwd watchdog mark page executable

Hi All,

> > 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?  
> 
> Also, do you believe that this fix should be backported into earlier
> stable kernels and if so, why?

See attached the patch that the driver author has sent in and which is in linux-next since 2 days.
This is a reworked version (due to nmi changes) but the original comment from Thomas Mingarelli was:
> This is needed for SLES11 SP2 and the latest upstream kernel as it appears the
> NX Execute Disable has grown in its control.
> I have tested this against the SLES11 SP2 kernel, the 3.0.4 upstream stable
> kernel, and the latest upstream kernel in development (which this patch is
> created against).

Kind regards,
Wim.
-------------------------------------------------------------------------------------------------
From: Mingarelli, Thomas
Sent: Monday, November 07, 2011 10:59 AM
To: Wim Van Sebroeck
Cc: Mingarelli, Thomas
Subject: [hpwdt patch] Changes to handle NX secure bit in 32bit path

This patch makes use of the set_memory_x() kernel API in order
to make necessary BIOS calls to source NMIs.
Signed-off by: Thomas Mingarelli <thomas.mingarelli@...com>

diff -up ./drivers/watchdog/hpwdt.c.ORIG ./drivers/watchdog/hpwdt.c
--- ./drivers/watchdog/hpwdt.c.ORIG	2011-11-07 10:46:37.000000000 -0600
+++ ./drivers/watchdog/hpwdt.c	2011-11-07 10:50:59.000000000 -0600
@@ -230,6 +230,7 @@ static int __devinit cru_detect(unsigned
 
 	cmn_regs.u1.reax = CRU_BIOS_SIGNATURE_VALUE;
 
+	set_memory_x((unsigned long)bios32_entrypoint, (2 * PAGE_SIZE));
 	asminline_call(&cmn_regs, bios32_entrypoint);
 
 	if (cmn_regs.u1.ral != 0) {
@@ -247,8 +248,10 @@ static int __devinit cru_detect(unsigned
 		if ((physical_bios_base + physical_bios_offset)) {
 			cru_rom_addr =
 				ioremap(cru_physical_address, cru_length);
-			if (cru_rom_addr)
+			if (cru_rom_addr) {
+				set_memory_x((unsigned long)cru_rom_addr, cru_length);
 				retval = 0;
+			}
 		}
 
 		printk(KERN_DEBUG "hpwdt: CRU Base Address:   0x%lx\n",


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