linux-kernel - [PATCH 3/3] arm: vfp: Bounce undefined instructions in vectored mode

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Date:	Thu, 18 Sep 2014 14:43:12 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Stepan Moskovchenko <stepanm@...eaurora.org>,
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Will Deacon <will.deacon@....com>
Subject: [PATCH 3/3] arm: vfp: Bounce undefined instructions in vectored mode

From: Stepan Moskovchenko <stepanm@...eaurora.org>

Certain ARM CPU implementations (e.g. Cortex-A15) may not raise a
floating- point exception whenever deprecated short-vector VFP
instructions are executed. Instead these instructions are treated
as UNALLOCATED. Change the VFP exception handling code to emulate
short-vector instructions even if FPEXC exception bits are not
set.

Tested-by: Will Deacon <will.deacon@....com>
Signed-off-by: Stepan Moskovchenko <stepanm@...eaurora.org>
Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
---
 arch/arm/vfp/vfphw.S | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S
index be807625ed8c..c041579a8d82 100644
--- a/arch/arm/vfp/vfphw.S
+++ b/arch/arm/vfp/vfphw.S
@@ -197,6 +197,12 @@ look_for_VFP_exceptions:
 	tst	r5, #FPSCR_IXE
 	bne	process_exception
 
+	tst	r5, #FPSCR_LENGTH_MASK
+	beq	skip
+	orr	r1, r1, #FPEXC_DEX
+	b process_exception
+skip:
+
 	@ Fall into hand on to next handler - appropriate coproc instr
 	@ not recognised by VFP
 
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