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

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>
Cc: stable@vger.kernel.org

diff --git a/arch/avr32/boot/u-boot/head.S b/arch/avr32/boot/u-boot/head.S
index d36d865308df83cf76b2fcfe58bd95fec8799e95..2ffc298f061b3e7704e89dd634ece905ff13dcf4 100644 (file)
--- 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 9899d3cc6f03b109f352faa9ac51387f96497cf7..7301f4806bbede59cf5eaa48649802ec75cddacf 100644 (file)
--- 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: