[PATCH v2] riscv: misaligned: Restore epc in error path

[Zishun Yi]

In handle_scalar_misaligned_store/load, regs->epc is temporarily set to
0. And be restored in the first error path.  But it not restore for the
rest of the error path. This cause the epc corrupted.

Fix this by restore epc in fp error and copy_from_user error.

Fixes: 7c586a555a48 ("riscv: add floating point insn support to misaligned access emulation")
Fixes: 441381506ba7 ("riscv: misaligned: remove CONFIG_RISCV_M_MODE specific code")
Assisted-by: Gemini:gemini-3.1-pro
Signed-off-by: Zishun Yi <vulab at iscas.ac.cn>
---
Changes in v2:
- Added 'Assisted-by' tag.

 arch/riscv/kernel/traps_misaligned.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
index 2a27d3ff4ac6..24f898853bba 100644
--- a/arch/riscv/kernel/traps_misaligned.c
+++ b/arch/riscv/kernel/traps_misaligned.c
@@ -307,13 +307,17 @@ static int handle_scalar_misaligned_load(struct pt_regs *regs)
 		return -1;
 	}
 
-	if (!IS_ENABLED(CONFIG_FPU) && fp)
+	if (!IS_ENABLED(CONFIG_FPU) && fp) {
+		regs->epc = epc;
 		return -EOPNOTSUPP;
+	}
 
 	val.data_u64 = 0;
 	if (user_mode(regs)) {
-		if (copy_from_user(&val, (u8 __user *)addr, len))
+		if (copy_from_user(&val, (u8 __user *)addr, len)) {
+			regs->epc = epc;
 			return -1;
+		}
 	} else {
 		memcpy(&val, (u8 *)addr, len);
 	}
@@ -409,12 +413,16 @@ static int handle_scalar_misaligned_store(struct pt_regs *regs)
 		return -1;
 	}
 
-	if (!IS_ENABLED(CONFIG_FPU) && fp)
+	if (!IS_ENABLED(CONFIG_FPU) && fp) {
+		regs->epc = epc;
 		return -EOPNOTSUPP;
+	}
 
 	if (user_mode(regs)) {
-		if (copy_to_user((u8 __user *)addr, &val, len))
+		if (copy_to_user((u8 __user *)addr, &val, len)) {
+			regs->epc = epc;
 			return -1;
+		}
 	} else {
 		memcpy((u8 *)addr, &val, len);
 	}
-- 
2.51.2