linux-kernel - [PATCH] riscv: kprobes: allow writing to x0

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Message-Id: <20230829182500.61875-1-namcaov@gmail.com>
Date:   Tue, 29 Aug 2023 20:25:00 +0200
From:   Nam Cao <namcaov@...il.com>
To:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     guoren@...nel.org, Nam Cao <namcaov@...il.com>,
        stable@...r.kernel.org
Subject: [PATCH] riscv: kprobes: allow writing to x0

Instructions can write to x0, so we should simulate these instructions
normally.

Currently, the kernel hangs if an instruction who writes to x0 is
simulated.

Fixes: c22b0bcb1dd0 ("riscv: Add kprobes supported")
Cc: stable@...r.kernel.org
Signed-off-by: Nam Cao <namcaov@...il.com>
---
 arch/riscv/kernel/probes/simulate-insn.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/probes/simulate-insn.c b/arch/riscv/kernel/probes/simulate-insn.c
index d3099d67816d..6c166029079c 100644
--- a/arch/riscv/kernel/probes/simulate-insn.c
+++ b/arch/riscv/kernel/probes/simulate-insn.c
@@ -24,7 +24,7 @@ static inline bool rv_insn_reg_set_val(struct pt_regs *regs, u32 index,
 				       unsigned long val)
 {
 	if (index == 0)
-		return false;
+		return true;
 	else if (index <= 31)
 		*((unsigned long *)regs + index) = val;
 	else
-- 
2.34.1