From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx> commit af89ebaa64de726ca0a39bbb0bf0c81a1f43ad50 upstream. gpr_get() return the entire pt_regs (include sr) to userspace, if we don't restore the C bit in gpr_set, it may break the ALU result in that context. So the C flag bit is part of gpr context, that's why riscv totally remove the C bit in the ISA. That makes sr reg clear from userspace to supervisor privilege. Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/csky/kernel/ptrace.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/arch/csky/kernel/ptrace.c +++ b/arch/csky/kernel/ptrace.c @@ -96,7 +96,8 @@ static int gpr_set(struct task_struct *t if (ret) return ret; - regs.sr = task_pt_regs(target)->sr; + /* BIT(0) of regs.sr is Condition Code/Carry bit */ + regs.sr = (regs.sr & BIT(0)) | (task_pt_regs(target)->sr & ~BIT(0)); #ifdef CONFIG_CPU_HAS_HILO regs.dcsr = task_pt_regs(target)->dcsr; #endif
