Subject: [V2 PATCH 1/3] powerpc: Enable emulate_step In Little Endian Mode

From: Tom <[email-masked]>
Date: Thu, 31 Oct 2013 13:38:56 -0500

From: Tom Musta <[email-masked]>

This patch modifies the endian chicken switch in the single step
emulation code (emulate_step()).  The old (big endian) code bailed
early if a load or store instruction was to be emulated in little
endian mode.

The new code modifies the check and only bails in a cross-endian
situation (LE mode in a kernel compiled for BE and vice verse).

V2: fixed bug in MSR[LE] check identified by Andreas Schwab and
Geert Uytterhoeven.

Signed-off-by: Tom Musta <[email-masked]>
---
 arch/powerpc/lib/sstep.c |   12 +++++++++---
 1 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index b1faa15..7bfaa9d 100644
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -1222,12 +1222,18 @@ int __kprobes emulate_step(struct pt_regs *regs, unsigned int instr)
 	}
 
 	/*
-	 * Following cases are for loads and stores, so bail out
-	 * if we're in little-endian mode.
+	 * Following cases are for loads and stores and this
+	 * implementation does not support cross-endian.  So
+	 * bail out if this is the case.
 	 */
+#ifdef __BIG_ENDIAN__
 	if (regs->msr & MSR_LE)
 		return 0;
-
+#endif
+#ifdef __LITTLE_ENDIAN__
+	if (!(regs->msr & MSR_LE))
+		return 0;
+#endif
 	/*
 	 * Save register RA in case it's an update form load or store
 	 * and the access faults.
-- 
1.7.1