Re: [PATCH 2/2] powerpc/kprobes: Replace ppc_optinsn by common optinsn

[Masami Hiramatsu <mhiramat@kernel.org>]

On Wed, 12 May 2021 14:29:27 +0000 (UTC)
Christophe Leroy <christophe.leroy@csgroup.eu> wrote:

> Commit 51c9c0843993 ("powerpc/kprobes: Implement Optprobes")
> implemented a powerpc specific version of optinsn in order
> to workaround the 32Mb limitation for direct branches.
> 
> Instead of implementing a dedicated powerpc version, use the
> common optinsn and override the allocation and freeing functions.
> 
> This also indirectly remove the CLANG warning about
> is_kprobe_ppc_optinsn_slot() not being use, and the powerpc will
> now benefit from commit 5b485629ba0d ("kprobes, extable: Identify
> kprobes trampolines as kernel text area")
> 

This looks good to me.

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>

> Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/powerpc/kernel/optprobes.c | 23 +++++------------------
>  1 file changed, 5 insertions(+), 18 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
> index cdf87086fa33..a370190cd02a 100644
> --- a/arch/powerpc/kernel/optprobes.c
> +++ b/arch/powerpc/kernel/optprobes.c
> @@ -31,11 +31,9 @@
>  #define TMPL_END_IDX		\
>  	(optprobe_template_end - optprobe_template_entry)
>  
> -DEFINE_INSN_CACHE_OPS(ppc_optinsn);
> -
>  static bool insn_page_in_use;
>  
> -static void *__ppc_alloc_insn_page(void)
> +void *alloc_optinsn_page(void)
>  {
>  	if (insn_page_in_use)
>  		return NULL;
> @@ -43,20 +41,11 @@ static void *__ppc_alloc_insn_page(void)
>  	return &optinsn_slot;
>  }
>  
> -static void __ppc_free_insn_page(void *page __maybe_unused)
> +void free_optinsn_page(void *page)
>  {
>  	insn_page_in_use = false;
>  }
>  
> -struct kprobe_insn_cache kprobe_ppc_optinsn_slots = {
> -	.mutex = __MUTEX_INITIALIZER(kprobe_ppc_optinsn_slots.mutex),
> -	.pages = LIST_HEAD_INIT(kprobe_ppc_optinsn_slots.pages),
> -	/* insn_size initialized later */
> -	.alloc = __ppc_alloc_insn_page,
> -	.free = __ppc_free_insn_page,
> -	.nr_garbage = 0,
> -};
> -
>  /*
>   * Check if we can optimize this probe. Returns NIP post-emulation if this can
>   * be optimized and 0 otherwise.
> @@ -136,7 +125,7 @@ NOKPROBE_SYMBOL(optimized_callback);
>  void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
>  {
>  	if (op->optinsn.insn) {
> -		free_ppc_optinsn_slot(op->optinsn.insn, 1);
> +		free_optinsn_slot(op->optinsn.insn, 1);
>  		op->optinsn.insn = NULL;
>  	}
>  }
> @@ -203,14 +192,12 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
>  	unsigned long nip, size;
>  	int rc, i;
>  
> -	kprobe_ppc_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;
> -
>  	nip = can_optimize(p);
>  	if (!nip)
>  		return -EILSEQ;
>  
>  	/* Allocate instruction slot for detour buffer */
> -	buff = get_ppc_optinsn_slot();
> +	buff = get_optinsn_slot();
>  	if (!buff)
>  		return -ENOMEM;
>  
> @@ -297,7 +284,7 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
>  	return 0;
>  
>  error:
> -	free_ppc_optinsn_slot(buff, 0);
> +	free_optinsn_slot(buff, 0);
>  	return -ERANGE;
>  
>  }
> -- 
> 2.25.0
> 


-- 
Masami Hiramatsu <mhiramat@kernel.org>