[rtems commit] bsps/powerpc: Fix potential relocation truncation

[Sebastian Huber]

Module:    rtems
Branch:    master
Commit:    d9ff8b3e687a0ec56cac6463ba01ba7775eccd41
Changeset: http://git.rtems.org/rtems/commit/?id=d9ff8b3e687a0ec56cac6463ba01ba7775eccd41

Author:    Sebastian Huber <sebastian.huber at embedded-brains.de>
Date:      Fri Jun  6 13:35:56 2014 +0200

bsps/powerpc: Fix potential relocation truncation

See also

https://sourceware.org/ml/binutils/2014-06/msg00059.html

On Fri, Jun 06, 2014 at 11:01:10AM +0200, Sebastian Huber wrote:
> I performed a git bisect and found this:
>
> 93d1b056cb396d6468781fe0e40dd769891bed32 is the first bad commit
> commit 93d1b056cb396d6468781fe0e40dd769891bed32
> Author: Alan Modra <amodra at gmail.com>
> Date:   Tue May 20 11:42:42 2014 +0930
>
>     Rewrite ppc32 backend .sdata and .sdata2 handling

Hmm, I'm surprised that your git bisect found this patch.  Was
_SDA_BASE_ set differently before this?

>                 0x00000000000dfc00                _SDA_BASE_
>                 0x00000000000d7f78                ppc_exc_lock_std

>      4b8:       28 05 00 00     cmplwi  r5,0
>                         4ba: R_PPC_SDAREL16     ppc_exc_lock_std

ppc_exc_lock_std at sdarel will be calculating 0xd7f78 - 0xdfc00
which is 0xf...fff8378, and that falls foul of

commit 86c9573369616e7437481b6e5533aef3a435cdcf
Author: Alan Modra <amodra at gmail.com>
Date:   Sat Mar 8 13:05:06 2014 +1030

    Better overflow checking for powerpc32 relocations

cmplwi has an *unsigned* 16-bit field, and we now check the overflow
properly.

I wonder how many more of these we'll hit, and whether the uproar will
be enough that I'll be forced to relax the checks?

---

 .../new-exceptions/bspsupport/ppc_exc_asm_macros.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/c/src/lib/libcpu/powerpc/new-exceptions/bspsupport/ppc_exc_asm_macros.h b/c/src/lib/libcpu/powerpc/new-exceptions/bspsupport/ppc_exc_asm_macros.h
index 0e3bc96..9a303f7 100644
--- a/c/src/lib/libcpu/powerpc/new-exceptions/bspsupport/ppc_exc_asm_macros.h
+++ b/c/src/lib/libcpu/powerpc/new-exceptions/bspsupport/ppc_exc_asm_macros.h
@@ -168,7 +168,7 @@ ppc_exc_min_prolog_sync_\_NAME:
 	 * if what's left compares against the 'ppc_exc_lock_std at sdarel'
 	 * address offset then we have a match...
 	 */
-	cmplwi	cr0, \_REG, ppc_exc_lock_std at sdarel
+	cmplwi	cr0, \_REG, ppc_exc_lock_std at sdarel@l
 
 	.endm