riscv: kprobe: Fixup misaligned load text

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

Fixes: c22b0bcb ("riscv: Add kprobes supported")
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Link: https://lore.kernel.org/linux-riscv/878rhig9zj.fsf@all.your.base.are.belong.to.us/Reported-by: Bjorn Topel <bjorn.topel@gmail.com>
Reviewed-by: Björn Töpel <bjorn@kernel.org>
Link: https://lore.kernel.org/r/20230204063531.740220-1-guoren@kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/kernel/probes/kprobes.c

@@ -65,16 +65,18 @@ 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)) {