Re: [PATCH] riscv: kprobe: Fixup misaligned load text

[Björn Töpel]

guoren@xxxxxxxxxx writes:

> From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxxxxxx>
> Signed-off-by: Guo Ren <guoren@xxxxxxxxxx>
> Link: https://lore.kernel.org/linux-riscv/878rhig9zj.fsf@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
> Reported-by: Bjorn Topel <bjorn.topel@xxxxxxxxx>
> ---
>  arch/riscv/kernel/probes/kprobes.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kernel/probes/kprobes.c b/arch/riscv/kernel/probes/kprobes.c
> index 41c7481afde3..c1160629cef4 100644
> --- a/arch/riscv/kernel/probes/kprobes.c
> +++ b/arch/riscv/kernel/probes/kprobes.c
> @@ -74,7 +74,9 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
>  		return -EILSEQ;
>  
>  	/* copy instruction */
> -	p->opcode = *p->addr;
> +	p->opcode = (kprobe_opcode_t)(*(u16 *)probe_addr);
> +	if (GET_INSN_LENGTH(p->opcode) == 4)
> +		p->opcode |= (kprobe_opcode_t)(*(u16 *)(probe_addr + 2))
>  	<< 16;

Ugh, those casts. :-( What about the memcpy variant you had in the other
thread?