[PATCH 4.9 075/103] MIPS: R2-on-R6 MULTU/MADDU/MSUBU emulation bugfix

[Greg Kroah-Hartman]

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

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

From: Leonid Yegoshin <Leonid.Yegoshin@xxxxxxxxxx>

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@xxxxxxxxxx>
Reported-by: Nikola.Veljkovic@xxxxxxxxxx
Cc: paul.burton@xxxxxxxxxx
Cc: yamada.masahiro@xxxxxxxxxxxxx
Cc: akpm@xxxxxxxxxxxxxxxxxxxx
Cc: andrea.gelmini@xxxxxxxxx
Cc: macro@xxxxxxxxxx
Cc: linux-mips@xxxxxxxxxxxxxx
Patchwork: https://patchwork.linux-mips.org/patch/14043/
Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 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);