Re: [PATCH v7 15/28] powerpc/kprobes: Use patch_instruction()

[Alistair Popple <alistair@popple.id.au>]

Without CONFIG_STRICT_KERNEL_RWX this boils down to doing the same thing 
(although with a few more safety checks along the way), and with 
CONFIG_STRICT_KERNEL_RWX this should make it actually work (although perhaps 
there was some other mechanism that made it work anyway).

Reviewed-by: Alistair Popple <alistair@popple.id.au>

On Friday, 1 May 2020 1:42:07 PM AEST Jordan Niethe wrote:
> Instead of using memcpy() and flush_icache_range() use
> patch_instruction() which not only accomplishes both of these steps but
> will also make it easier to add support for prefixed instructions.
> 
> Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
> ---
> v6: New to series.
> ---
>  arch/powerpc/kernel/kprobes.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
> index f64312dca84f..a72c8e1a42ad 100644
> --- a/arch/powerpc/kernel/kprobes.c
> +++ b/arch/powerpc/kernel/kprobes.c
> @@ -125,11 +125,8 @@ int arch_prepare_kprobe(struct kprobe *p)
>  	}
> 
>  	if (!ret) {
> -		memcpy(p->ainsn.insn, p->addr,
> -				MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
> +		patch_instruction((struct ppc_inst *)p->ainsn.insn, insn);
>  		p->opcode = ppc_inst_val(insn);
> -		flush_icache_range((unsigned long)p->ainsn.insn,
> -			(unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
>  	}
> 
>  	p->ainsn.boostable = 0;