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

Luis Henriques luis.henriques at canonical.com
Fri Nov 29 14:03:42 UTC 2013


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-3.5.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

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>From 3cc8b8e159f2f0fb71e432375dbe98e4cc5e98d2 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
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Content-Type: text/plain; charset=UTF-8
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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 BieƟmann <andreas at biessmann.de>
Acked-by: Hans-Christian Egtvedt <egtvedt at samfundet.no>
Cc: Haavard Skinnemoen <hskinnemoen at gmail.com>
Signed-off-by: Luis Henriques <luis.henriques 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 df28841..55da272 100644
--- a/arch/avr32/kernel/entry-avr32b.S
+++ b/arch/avr32/kernel/entry-avr32b.S
@@ -399,9 +399,10 @@ 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





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