linux-kernel - [PATCH 4.10 096/129] MIPS: R2-on-R6 MULTU/MADDU/MSUBU emulation bugfix

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Date:   Thu, 11 May 2017 16:12:24 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Leonid Yegoshin <Leonid.Yegoshin@...tec.com>,
        Nikola.Veljkovic@...tec.com, paul.burton@...tec.com,
        yamada.masahiro@...ionext.com, akpm@...ux-foundation.org,
        andrea.gelmini@...ma.net, macro@...tec.com,
        linux-mips@...ux-mips.org, Ralf Baechle <ralf@...ux-mips.org>
Subject: [PATCH 4.10 096/129] MIPS: R2-on-R6 MULTU/MADDU/MSUBU emulation bugfix

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

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

From: Leonid Yegoshin <Leonid.Yegoshin@...tec.com>

commit d65e5677ad5b3a49c43f60ec07644dc1f87bbd2e upstream.

MIPS instructions MULTU, MADDU and MSUBU emulation requires registers HI/LO
to be converted to signed 32bits before 64bit sign extension on MIPS64.

Bug was found on running MIPS32 R2 test application on MIPS64 R6 kernel.

Fixes: b0a668fb2038 ("MIPS: kernel: mips-r2-to-r6-emul: Add R2 emulator for MIPS R6")
Signed-off-by: Leonid Yegoshin <Leonid.Yegoshin@...tec.com>
Reported-by: Nikola.Veljkovic@...tec.com
Cc: paul.burton@...tec.com
Cc: yamada.masahiro@...ionext.com
Cc: akpm@...ux-foundation.org
Cc: andrea.gelmini@...ma.net
Cc: macro@...tec.com
Cc: linux-mips@...ux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14043/
Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/mips/kernel/mips-r2-to-r6-emul.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

--- a/arch/mips/kernel/mips-r2-to-r6-emul.c
+++ b/arch/mips/kernel/mips-r2-to-r6-emul.c
@@ -433,8 +433,8 @@ static int multu_func(struct pt_regs *re
 	rs = regs->regs[MIPSInst_RS(ir)];
 	res = (u64)rt * (u64)rs;
 	rt = res;
-	regs->lo = (s64)rt;
-	regs->hi = (s64)(res >> 32);
+	regs->lo = (s64)(s32)rt;
+	regs->hi = (s64)(s32)(res >> 32);
 
 	MIPS_R2_STATS(muls);
 
@@ -670,9 +670,9 @@ static int maddu_func(struct pt_regs *re
 	res += ((((s64)rt) << 32) | (u32)rs);
 
 	rt = res;
-	regs->lo = (s64)rt;
+	regs->lo = (s64)(s32)rt;
 	rs = res >> 32;
-	regs->hi = (s64)rs;
+	regs->hi = (s64)(s32)rs;
 
 	MIPS_R2_STATS(dsps);
 
@@ -728,9 +728,9 @@ static int msubu_func(struct pt_regs *re
 	res = ((((s64)rt) << 32) | (u32)rs) - res;
 
 	rt = res;
-	regs->lo = (s64)rt;
+	regs->lo = (s64)(s32)rt;
 	rs = res >> 32;
-	regs->hi = (s64)rs;
+	regs->hi = (s64)(s32)rs;
 
 	MIPS_R2_STATS(dsps);