Re: [PATCH v4 bpf-next 3/7] bpf: Add helpers for trampoline image management

[Daniel Borkmann <daniel@xxxxxxxxxxxxx>]

On 10/18/23 8:03 PM, Song Liu wrote:
[...]
> @@ -1040,6 +1038,38 @@ arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *image
>   	return -ENOTSUPP;
>   }
>   
> +void * __weak arch_alloc_bpf_trampoline(int size)
> +{
> +	void *image;
> +
> +	WARN_ON_ONCE(size > PAGE_SIZE || size <= 0);

non-blocking / can be follow-up, but why not:

if (WARN_ON_ONCE(size > PAGE_SIZE || size <= 0))
	return NULL

size could also be u32, then you don't need size <= 0 check ?

> +	image = bpf_jit_alloc_exec(PAGE_SIZE);
> +	if (image)
> +		set_vm_flush_reset_perms(image);
> +	return image;
> +}
> +
> +void __weak arch_free_bpf_trampoline(void *image, int size)
> +{
> +	/* bpf_jit_free_exec doesn't need "size", but
> +	 * bpf_prog_pack_free() needs it.
> +	 */
> +	bpf_jit_free_exec(image);
> +}
> +
> +void __weak arch_protect_bpf_trampoline(void *image, int size)
> +{
> +	WARN_ON_ONCE(size > PAGE_SIZE || size <= 0);
> +	set_memory_rox((long)image, 1);
> +}
> +
> +void __weak arch_unprotect_bpf_trampoline(void *image, int size)
> +{
> +	WARN_ON_ONCE(size > PAGE_SIZE || size <= 0);
> +	set_memory_nx((long)image, 1);
> +	set_memory_rw((long)image, 1);
> +}
> +
>   static int __init init_trampolines(void)
>   {
>   	int i;