Re: [PATCH] objtool,x86: Verify poke_int3_handler() is self contained

From: peterz
Date: Tue Jul 28 2020 - 04:34:40 EST

On Mon, Jul 27, 2020 at 10:56:03PM +0200, Thomas Gleixner wrote:
> peterz@xxxxxxxxxxxxx writes:
> > Abuse the SMAP rules to ensure poke_int3_handler() doesn't call out to
> > anything.
> Yuck. Isn't that what noinstr is for or am I missing something?

Well, we don't want poke_int3_handler() to call out to noinstr either.

So noinstr only allows calling noinstr, The above hack only allows it
calling uaccess-safe functions, and the group of functions that is both
noinstr and uaccess-safe is 'small'.

But like I said yesterday, perhaps this wants it own annotation. Then we
can also verify the lack of any dynamic code.

So yes, yuck and a bad idea, ignore this ;-)