Patchwork [3.5.y.z,extended,stable] Patch "ARM: poison the vectors page" has been added to staging queue

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Submitter Luis Henriques
Date Aug. 4, 2013, 9:49 a.m.
Message ID <1375609770-11584-1-git-send-email-luis.henriques@canonical.com>
Download mbox | patch
Permalink /patch/264491/
State New
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Luis Henriques - Aug. 4, 2013, 9:49 a.m.
This is a note to let you know that I have just added a patch titled

    ARM: poison the vectors page

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

From d8fcd6839813d9c59985160e30a5d17d46622b80 Mon Sep 17 00:00:00 2001
From: Russell King <rmk+kernel@arm.linux.org.uk>
Date: Thu, 4 Jul 2013 11:00:23 +0100
Subject: [PATCH] ARM: poison the vectors page

commit f928d4f2a86f46b030fa0850385b4391fc2b5918 upstream.

Fill the empty regions of the vectors page with an exception generating
instruction.  This ensures that any inappropriate branch to the vector
page is appropriately trapped, rather than just encountering some code
to execute.  (The vectors page was filled with zero before, which
corresponds with the "andeq r0, r0, r0" instruction - a no-op.)

Acked-by Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
 arch/arm/kernel/traps.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

--
1.8.3.2

Patch

diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index eeb7520..eb460ac 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -792,10 +792,20 @@  void __init early_trap_init(void *vectors_base)
 	extern char __vectors_start[], __vectors_end[];
 	extern char __kuser_helper_start[], __kuser_helper_end[];
 	int kuser_sz = __kuser_helper_end - __kuser_helper_start;
+	unsigned i;

 	vectors_page = vectors_base;

 	/*
+	 * Poison the vectors page with an undefined instruction.  This
+	 * instruction is chosen to be undefined for both ARM and Thumb
+	 * ISAs.  The Thumb version is an undefined instruction with a
+	 * branch back to the undefined instruction.
+	 */
+	for (i = 0; i < PAGE_SIZE / sizeof(u32); i++)
+		((u32 *)vectors_base)[i] = 0xe7fddef1;
+
+	/*
 	 * Copy the vectors, stubs and kuser helpers (in entry-armv.S)
 	 * into the vector page, mapped at 0xffff0000, and ensure these
 	 * are visible to the instruction stream.