Re: [PATCH 2/2] ARM: mm: keep rodata non-executable

From: Laura Abbott
Date: Tue Apr 01 2014 - 18:55:04 EST

On 4/1/2014 3:34 PM, Kees Cook wrote:
> On Mon, Mar 24, 2014 at 3:47 AM, Jon Medhurst (Tixy) <tixy@xxxxxxxxxx> wrote:
>> On Sun, 2014-03-23 at 16:21 -0600, Kees Cook wrote:
>>> For this stage, how about I make this "depends on KEXEC=n &&
>>> KPROBES=n"?
>> There's also ftrace (CONFIG_DYNAMIC_FTRACE I believe) which modifies
>> kernel code with a call to probe_kernel_write(), which GDB uses as well.
>> And grepping for the patch_text() function also shows
>> __arch_jump_label_transform() modifies kernel code. Not sure how and
>> when that gets used.
> Right, so, I'm trying to fix ftrace now, and I've hit a wall. It is as
> if changes to the kernel text PMD aren't being noticed after the
> kernel is running. Does anyone know why this might be happening?
> Code and details here:
> -Kees

We had a flush_tlb_kernel_page after the pmd_flush in our out of tree code
which makes the text writeable in __patch_text.


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