* [PATCH] powerpc/sstep: mullw should calculate a 64 bit signed result
@ 2017-09-19 23:32 Anton Blanchard
2017-09-21 1:46 ` Michael Ellerman
0 siblings, 1 reply; 2+ messages in thread
From: Anton Blanchard @ 2017-09-19 23:32 UTC (permalink / raw)
To: benh, paulus, mpe; +Cc: linuxppc-dev
From: Anton Blanchard <anton@samba.org>
mullw should do a 32 bit signed multiply and create a 64 bit signed
result. It currently truncates the result to 32 bits.
Signed-off-by: Anton Blanchard <anton@samba.org>
---
arch/powerpc/lib/sstep.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index c4cda1afb49d..5e8418c28bd8 100644
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -1651,8 +1651,9 @@ int analyse_instr(struct instruction_op *op, const struct pt_regs *regs,
goto arith_done;
case 235: /* mullw */
- op->val = (unsigned int) regs->gpr[ra] *
- (unsigned int) regs->gpr[rb];
+ op->val = (long)(int) regs->gpr[ra] *
+ (int) regs->gpr[rb];
+
goto arith_done;
case 266: /* add */
--
2.11.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: powerpc/sstep: mullw should calculate a 64 bit signed result
2017-09-19 23:32 [PATCH] powerpc/sstep: mullw should calculate a 64 bit signed result Anton Blanchard
@ 2017-09-21 1:46 ` Michael Ellerman
0 siblings, 0 replies; 2+ messages in thread
From: Michael Ellerman @ 2017-09-21 1:46 UTC (permalink / raw)
To: Anton Blanchard, benh, paulus; +Cc: linuxppc-dev
On Tue, 2017-09-19 at 23:32:19 UTC, Anton Blanchard wrote:
> From: Anton Blanchard <anton@samba.org>
>
> mullw should do a 32 bit signed multiply and create a 64 bit signed
> result. It currently truncates the result to 32 bits.
>
> Signed-off-by: Anton Blanchard <anton@samba.org>
Applied to powerpc fixes, thanks.
https://git.kernel.org/powerpc/c/1575fe06f6b1d156ed31fb22c8631d
cheers
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