* [PATCH] powerpc: handle unaligned ldbrx/stdbrx
@ 2013-07-31 5:05 Anton Blanchard
2013-07-31 8:19 ` Stephen Rothwell
0 siblings, 1 reply; 2+ messages in thread
From: Anton Blanchard @ 2013-07-31 5:05 UTC (permalink / raw)
To: benh, paulus, mikey; +Cc: linuxppc-dev
Normally when we haven't implemented an alignment handler for
a load or store instruction the process will be terminated.
The alignment handler uses the DSISR (or a pseudo one) to locate
the right handler. Unfortunately ldbrx and stdbrx overlap lfs and
stfs so we incorrectly think ldbrx is an lfs and stdbrx is an
stfs.
This bug is particularly nasty - instead of terminating the
process we apply an incorrect fixup and continue on.
With more and more overlapping instructions we should stop
creating a pseudo DSISR and index using the instruction directly,
but for now add a special case to catch ldbrx/stdbrx.
Signed-off-by: Anton Blanchard <anton@samba.org>
Cc: <stable@kernel.org>
---
Index: b/arch/powerpc/kernel/align.c
===================================================================
--- a/arch/powerpc/kernel/align.c
+++ b/arch/powerpc/kernel/align.c
@@ -764,6 +764,16 @@ int fix_alignment(struct pt_regs *regs)
nb = aligninfo[instr].len;
flags = aligninfo[instr].flags;
+ /* ldbrx/stdbrx overlap lfs/stfs in the DSISR unfortunately */
+ if (IS_XFORM(instruction) && ((instruction >> 1) & 0x3ff) == 532) {
+ nb = 8;
+ flags = LD+SW;
+ } else if (IS_XFORM(instruction) &&
+ ((instruction >> 1) & 0x3ff) == 660) {
+ nb = 8;
+ flags = ST+SW;
+ }
+
/* Byteswap little endian loads and stores */
swiz = 0;
if (regs->msr & MSR_LE) {
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] powerpc: handle unaligned ldbrx/stdbrx
2013-07-31 5:05 [PATCH] powerpc: handle unaligned ldbrx/stdbrx Anton Blanchard
@ 2013-07-31 8:19 ` Stephen Rothwell
0 siblings, 0 replies; 2+ messages in thread
From: Stephen Rothwell @ 2013-07-31 8:19 UTC (permalink / raw)
To: Anton Blanchard; +Cc: mikey, paulus, linuxppc-dev
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Hi Anton,
On Wed, 31 Jul 2013 15:05:21 +1000 Anton Blanchard <anton@samba.org> wrote:
>
> +++ b/arch/powerpc/kernel/align.c
> @@ -764,6 +764,16 @@ int fix_alignment(struct pt_regs *regs)
> nb = aligninfo[instr].len;
> flags = aligninfo[instr].flags;
>
> + /* ldbrx/stdbrx overlap lfs/stfs in the DSISR unfortunately */
> + if (IS_XFORM(instruction) && ((instruction >> 1) & 0x3ff) == 532) {
We have get_xop() in asm/disassemble.h (which is unfortunately not
included by this file) ...
> + nb = 8;
> + flags = LD+SW;
> + } else if (IS_XFORM(instruction) &&
> + ((instruction >> 1) & 0x3ff) == 660) {
ditto
/me points at a bike shed :-)
--
Cheers,
Stephen Rothwell sfr@canb.auug.org.au
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