[PATCH 057/104] powerpc: Handle unaligned ldbrx/stdbrx

Luis Henriques luis.henriques at canonical.com
Mon Sep 30 10:10:34 UTC 2013


3.5.7.22 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Anton Blanchard <anton at samba.org>

commit 230aef7a6a23b6166bd4003bfff5af23c9bd381f upstream.

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 at samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 arch/powerpc/kernel/align.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/powerpc/kernel/align.c b/arch/powerpc/kernel/align.c
index ee5b690..52e5758 100644
--- 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) {
-- 
1.8.3.2





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