[PATCH 3.10 091/173] avr32: fix out-of-range jump in large kernels

Greg Kroah-Hartman
2013-12-02T19:11:14Z

From: Andreas Bießmann <andreas@biessmann.de>

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@biessmann.de>
Acked-by: Hans-Christian Egtvedt <egtvedt@samfundet.no>
Cc: Haavard Skinnemoen <hskinnemoen@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/avr32/boot/u-boot/head.S | 5 ++++-
arch/avr32/kernel/entry-avr32b.S | 3 ++-
2 files changed, 6 insertions(+), 2 deletions(-)

--- 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"
--- 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