linux-kernel - [PATCH V2] riscv: kprobe: Fixup misaligned load text

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Date:   Sat,  4 Feb 2023 01:35:31 -0500
From:   guoren@...nel.org
To:     guoren@...nel.org, palmer@...osinc.com, conor.dooley@...rochip.com,
        liaochang1@...wei.com, bjorn@...nel.org, jrtc27@...c27.com
Cc:     linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org,
        Guo Ren <guoren@...ux.alibaba.com>,
        Bjorn Topel <bjorn.topel@...il.com>
Subject: [PATCH V2] riscv: kprobe: Fixup misaligned load text

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

The current kprobe would cause a misaligned load for the probe point.
This patch fixup it with two half-word loads instead.

Fixes: c22b0bcb1dd0 ("riscv: Add kprobes supported")
Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
Signed-off-by: Guo Ren <guoren@...nel.org>
Link: https://lore.kernel.org/linux-riscv/878rhig9zj.fsf@all.your.base.are.belong.to.us/
Reported-by: Bjorn Topel <bjorn.topel@...il.com>
Cc: Jessica Clarke <jrtc27@...c27.com>
---
Changelog
V2:
 - Optimize coding convention (Thx Bjorn & Jessica)
---
 arch/riscv/kernel/probes/kprobes.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/kernel/probes/kprobes.c b/arch/riscv/kernel/probes/kprobes.c
index c41bd8509032..d3b18e868f30 100644
--- a/arch/riscv/kernel/probes/kprobes.c
+++ b/arch/riscv/kernel/probes/kprobes.c
@@ -71,16 +71,18 @@ static bool __kprobes arch_check_kprobe(struct kprobe *p)
 
 int __kprobes arch_prepare_kprobe(struct kprobe *p)
 {
-	unsigned long probe_addr = (unsigned long)p->addr;
+	u16 *insn = (u16 *)p->addr;
 
-	if (probe_addr & 0x1)
+	if ((unsigned long)insn & 0x1)
 		return -EILSEQ;
 
 	if (!arch_check_kprobe(p))
 		return -EILSEQ;
 
 	/* copy instruction */
-	p->opcode = *p->addr;
+	p->opcode = (kprobe_opcode_t)(*insn++);
+	if (GET_INSN_LENGTH(p->opcode) == 4)
+		p->opcode |= (kprobe_opcode_t)(*insn) << 16;
 
 	/* decode instruction */
 	switch (riscv_probe_decode_insn(p->addr, &p->ainsn.api)) {
-- 
2.36.1