[3.8.y.z extended stable] Patch "avr32: fix out-of-range jump in large kernels" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    avr32: fix out-of-range jump in large kernels

to the linux-3.8.y-queue branch of the 3.8.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-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.14.

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

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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>From cd207368a771da83283a9a64bac21db4dee88fdb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andreas=20Bie=C3=9Fmann?= <andreas at biessmann.de>
Date: Thu, 24 Oct 2013 12:31:04 +0200
Subject: avr32: fix out-of-range jump in large kernels
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

commit d617b338bbfdd77e9cbd8e7dc949cee3dd73d575 upstream.

This patch fixes following error (for big kernels):

---8<---
arch/avr32/boot/u-boot/head.o: In function `no_tag_table':
(.init.text+0x44): relocation truncated to fit: R_AVR32_22H_PCREL against symbol `panic' defined in .text.unlikely section in kernel/built-in.o
arch/avr32/kernel/built-in.o: In function `bad_return':
(.ex.text+0x236): relocation truncated to fit: R_AVR32_22H_PCREL against symbol `panic' defined in .text.unlikely section in kernel/built-in.o
--->8---

It comes up when the kernel increases and 'panic()' is too far away to fit in
the +/- 2MiB range. Which in turn issues from the 21-bit displacement in
'br{cond4}' mnemonic which is one of the two ways to do jumps (rjmp has just
10-bit displacement and therefore a way smaller range). This fact was stated
before in 8d29b7b9f81d6b83d869ff054e6c189d6da73f1f.
One solution to solve this is to add a local storage for the symbol address
and just load the $pc with that value.

Signed-off-by: Andreas Bießmann <andreas at biessmann.de>
Acked-by: Hans-Christian Egtvedt <egtvedt at samfundet.no>
Cc: Haavard Skinnemoen <hskinnemoen at gmail.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/avr32/boot/u-boot/head.S    | 5 ++++-
 arch/avr32/kernel/entry-avr32b.S | 3 ++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/avr32/boot/u-boot/head.S b/arch/avr32/boot/u-boot/head.S
index d36d865..2ffc298 100644
--- a/arch/avr32/boot/u-boot/head.S
+++ b/arch/avr32/boot/u-boot/head.S
@@ -73,8 +73,11 @@ init_sr:
 	.long	0x007f0000	/* Supervisor mode, everything masked */
 stack_addr:
 	.long	init_thread_union
+panic_addr:
+	.long	panic

 no_tag_table:
 	sub	r12, pc, (. - 2f)
-	bral	panic
+	/* branch to panic() which can be far away with that construct */
+	lddpc	pc, panic_addr
 2:	.asciz	"Boot loader didn't provide correct magic number\n"
diff --git a/arch/avr32/kernel/entry-avr32b.S b/arch/avr32/kernel/entry-avr32b.S
index 9899d3c..7301f48 100644
--- a/arch/avr32/kernel/entry-avr32b.S
+++ b/arch/avr32/kernel/entry-avr32b.S
@@ -401,9 +401,10 @@ handle_critical:
 	/* We should never get here... */
 bad_return:
 	sub	r12, pc, (. - 1f)
-	bral	panic
+	lddpc	pc, 2f
 	.align	2
 1:	.asciz	"Return from critical exception!"
+2:	.long	panic

 	.align	1
 do_bus_error_write:
--
1.8.3.2