linux-kernel - [PATCH 3.16 22/26] MIPS: traps: Fix inline asm ctc1 missing .set hardfloat

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Message-ID: <lsq.1491102264.593686941@decadent.org.uk>
Date:   Sun, 02 Apr 2017 04:04:24 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "James Hogan" <james.hogan@...tec.com>,
        "Ralf Baechle" <ralf@...ux-mips.org>, linux-mips@...ux-mips.org,
        "Paul Burton" <paul.burton@...tec.com>
Subject: [PATCH 3.16 22/26] MIPS: traps: Fix inline asm ctc1 missing .set
 hardfloat

3.16.43-rc2 review patch.  If anyone has any objections, please let me know.

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

From: James Hogan <james.hogan@...tec.com>

commit d76e9b9fc5de7e8fc4fd0e72a94e8c723929ffea upstream.

Commit 842dfc11ea9a ("MIPS: Fix build with binutils 2.24.51+") in v3.18
enabled -msoft-float and sprinkled ".set hardfloat" where necessary to
use FP instructions. However it missed enable_restore_fp_context() which
since v3.17 does a ctc1 with inline assembly, causing the following
assembler errors on Mentor's 2014.05 toolchain:

{standard input}: Assembler messages:
{standard input}:2913: Error: opcode not supported on this processor: mips32r2 (mips32r2) `ctc1 $2,$31'
scripts/Makefile.build:257: recipe for target 'arch/mips/kernel/traps.o' failed

Fix that to use the new write_32bit_cp1_register() macro so that ".set
hardfloat" is automatically added when -msoft-float is in use.

Fixes 842dfc11ea9a ("MIPS: Fix build with binutils 2.24.51+")
Signed-off-by: James Hogan <james.hogan@...tec.com>
Cc: Ralf Baechle <ralf@...ux-mips.org>
Cc: Paul Burton <paul.burton@...tec.com>
Cc: linux-mips@...ux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9173/
Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/mips/kernel/traps.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -1183,7 +1183,8 @@ static int enable_restore_fp_context(int
 
 		/* Restore the scalar FP control & status register */
 		if (!was_fpu_owner)
-			asm volatile("ctc1 %0, $31" : : "r"(current->thread.fpu.fcr31));
+			write_32bit_cp1_register(CP1_STATUS,
+						 current->thread.fpu.fcr31);
 	}
 	return 0;
 }