[PATCH] csky: Fixup regs.sr broken in ptrace

From: guoren
Date: Fri Sep 24 2021 - 03:36:54 EST


From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>

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>
---
arch/csky/kernel/ptrace.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/csky/kernel/ptrace.c b/arch/csky/kernel/ptrace.c
index 0105ac81b432..1a5f54e0d272 100644
--- a/arch/csky/kernel/ptrace.c
+++ b/arch/csky/kernel/ptrace.c
@@ -99,7 +99,8 @@ static int gpr_set(struct task_struct *target,
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
--
2.25.1