Re: [PATCH 2/3] arm64: use PAGE_KERNEL_ROX directly in alloc_insn_page

[Andrew Morton]

On Thu, 18 Jun 2020 08:43:06 +0200 Christoph Hellwig <hch@xxxxxx> wrote:

> Use PAGE_KERNEL_ROX directly instead of allocating RWX and setting the
> page read-only just after the allocation.
> 
> --- a/arch/arm64/kernel/probes/kprobes.c
> +++ b/arch/arm64/kernel/probes/kprobes.c
> @@ -120,15 +120,9 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
>  
>  void *alloc_insn_page(void)
>  {
> -	void *page;
> -
> -	page = vmalloc_exec(PAGE_SIZE);
> -	if (page) {
> -		set_memory_ro((unsigned long)page, 1);
> -		set_vm_flush_reset_perms(page);
> -	}
> -
> -	return page;
> +	return __vmalloc_node_range(PAGE_SIZE, 1, VMALLOC_START, VMALLOC_END,
> +			GFP_KERNEL, PAGE_KERNEL_ROX, VM_FLUSH_RESET_PERMS,
> +			NUMA_NO_NODE, __func__);
>  }
>  
>  /* arm kprobe: install breakpoint in text */

But why.  I think this is just a cleanup, doesn't address any runtime issue?