Re: [PATCH v4 2/8] riscv/kprobe: Allocate detour buffer from module area

[Steven Rostedt]

On Sun,  6 Nov 2022 18:03:10 +0800
Chen Guokai <chenguokai17@xxxxxxxxxxxxxxxx> wrote:

> @@ -84,6 +85,30 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
>  }
>  
>  #ifdef CONFIG_MMU
> +#if defined(CONFIG_OPTPROBES) && defined(CONFIG_64BIT)
> +void *alloc_optinsn_page(void)
> +{
> +	void *page;
> +
> +	page = __vmalloc_node_range(PAGE_SIZE, 1, MODULES_VADDR,
> +				    MODULES_END, GFP_KERNEL,
> +				    PAGE_KERNEL, 0, NUMA_NO_NODE,
> +				    __builtin_return_address(0));
> +	if (!page)
> +		return NULL;
> +
> +	set_vm_flush_reset_perms(page);
> +	/*
> +	 * First make the page read-only, and only then make it executable to
> +	 * prevent it from being W+X in between.
> +	 */
> +	set_memory_ro((unsigned long)page, 1);
> +	set_memory_x((unsigned long)page, 1);

FYI, the above combination is going to be going away:

  https://lore.kernel.org/all/Y10OyLCLAAS6rsZv@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/

-- Steve


> +
> +	return page;
> +}
> +#endif
> +