MIPS: R2-on-R6 MULTU/MADDU/MSUBU emulation bugfix

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@imgtec.com>
Reported-by: Nikola.Veljkovic@imgtec.com
Cc: paul.burton@imgtec.com
Cc: yamada.masahiro@socionext.com
Cc: akpm@linux-foundation.org
Cc: andrea.gelmini@gelma.net
Cc: macro@imgtec.com
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14043/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/kernel/mips-r2-to-r6-emul.c b/arch/mips/kernel/mips-r2-to-r6-emul.c
index ef2ca28a028b04b4913d56d1f3a98f75718fd0f4..d8f1cf1ec3703ad56fcea2ac96a0c5c487ccdd67 100644 (file)
--- 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 *regs, u32 ir)
        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 *regs, u32 ir)
        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 *regs, u32 ir)
        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);