Subject: Re: [PATCH bpf-next 2/7] set_memory: introduce set_memory_[ro|x]_noalias

From: Peter Zijlstra <[email-masked]>
Date: Thu, 18 Nov 2021 08:54:47 +0100

On Wed, Nov 17, 2021 at 11:57:12PM +0000, Song Liu wrote:

> I would agree that __text_poke() is a safer option. But in this case, we 
> will need the temporary hole to be 2MB in size. Also, we will probably 
> hold the temporary mapping for longer time (the whole JITing process). 
> Does this sound reasonable?

No :-)

Jit to a buffer, then copy the buffer into the 2M page using 4k aliases.
IIRC each program is still smaller than a single page, right? So at no
point do you need more than 2 pages mapped anyway.