[PATCH 5.10 016/103] csky: Fixup regs.sr broken in ptrace

Greg Kroah-Hartman
2021-10-18T13:39:27Z

From: Guo Ren <guoren@linux.alibaba.com>

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@linux.alibaba.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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
@@ -98,7 +98,8 @@ 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