From mboxrd@z Thu Jan 1 00:00:00 1970 From: sboyd@codeaurora.org (Stephen Boyd) Date: Thu, 07 Jul 2011 10:44:34 -0700 Subject: [PATCHv2] arm: mm: Poison freed init memory In-Reply-To: <20110707173645.GD20403@n2100.arm.linux.org.uk> References: <20110706210106.GX8286@n2100.arm.linux.org.uk> <1310057247-4933-1-git-send-email-sboyd@codeaurora.org> <20110707173645.GD20403@n2100.arm.linux.org.uk> Message-ID: <4E15F082.7080604@codeaurora.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 07/07/2011 10:36 AM, Russell King - ARM Linux wrote: > On Thu, Jul 07, 2011 at 09:47:27AM -0700, Stephen Boyd wrote: >> Poisoning __init marked memory can be useful when tracking down >> obscure memory corruption bugs. Therefore, poison init memory >> with 0xe7fddef0 to catch bugs earlier. The poison value is an >> undefined instruction in ARM mode and branch to an undefined >> instruction in Thumb mode. >> >> Signed-off-by: Stephen Boyd >> --- >> >> On 7/6/2011 2:01 PM, Russell King - ARM Linux wrote: >>> On Wed, Jul 06, 2011 at 01:55:54PM -0700, Stephen Boyd wrote: >>>> Should it include the initrd too? At least x86 poisons that memory but I >>>> don't know who would be using that incorrectly. >>> It could do - I don't see any harm in not doing so. The only issue >>> is that people may want to disable this stuff if they're after >>> squeezing every last ms out of the boot time. >> I haven't done this. I hope a follow up patch will suffice. >> >>>> How about a free_init_area() function which calls free_area() after >>>> poisoning the memory? >>> I need to go back and look at the Integrator etc situation with regard >>> to reorganizing the vmlinux layout - it may be that the omission of >>> freeing .init memory can now be removed (it was there to stop the >>> memory being used as the first K of memory wasn't DMA-able.) >>> >>> Assuming it has to stay though, we still should arrange for the initrd >>> memory to be poisoned even if it isn't freed. >> Is this is patch what you're saying? I would have liked to do a >> free_init_area() wrapper, but until the Integrator situation can be >> sorted it doesn't look worthwhile. > Yes, thanks. This looks fine for the time being. Have you been able > to test it? If yes, then please put it in the patch system and I'll > see about giving it a test too. Yes it's been tested (which is why there is a PAGE_ALIGN on initrd). 6996/1 -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.