linux-kernel - Re: [RFC][PATCH 0/4] Make bpf_jit and kprobes work with CONFIG

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Date: Fri, 8 Mar 2024 12:27:50 -0800
From: Calvin Owens <jcalvinowens@...il.com>
To: Luis Chamberlain <mcgrof@...nel.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, Song Liu <song@...nel.org>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Mike Rapoport <rppt@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Naveen N Rao <naveen.n.rao@...ux.ibm.com>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	David S Miller <davem@...emloft.net>,
	Thomas Gleixner <tglx@...utronix.de>, bpf@...r.kernel.org,
	linux-modules@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 0/4] Make bpf_jit and kprobes work with
 CONFIG_MODULES=n

On Thursday 03/07 at 18:55 -0800, Luis Chamberlain wrote:
> On Thu, Mar 7, 2024 at 6:50 PM Masami Hiramatsu <mhiramat@...nel.org> wrote:
> >
> > On Wed, 6 Mar 2024 17:58:14 -0800
> > Song Liu <song@...nel.org> wrote:
> >
> > > Hi Calvin,
> > >
> > > It is great to hear from you! :)
> > >
> > > On Wed, Mar 6, 2024 at 3:23 PM Calvin Owens <jcalvinowens@...il.com> wrote:
> > > >
> > > > On Wednesday 03/06 at 13:34 -0800, Luis Chamberlain wrote:
> > > > > On Wed, Mar 06, 2024 at 12:05:07PM -0800, Calvin Owens wrote:
> > > > > > Hello all,
> > > > > >
> > > > > > This patchset makes it possible to use bpftrace with kprobes on kernels
> > > > > > built without loadable module support.
> > > > >
> > > > > This is a step in the right direction for another reason: clearly the
> > > > > module_alloc() is not about modules, and we have special reasons for it
> > > > > now beyond modules. The effort to share a generalize a huge page for
> > > > > these things is also another reason for some of this but that is more
> > > > > long term.
> > > > >
> > > > > I'm all for minor changes here so to avoid regressions but it seems a
> > > > > rename is in order -- if we're going to all this might as well do it
> > > > > now. And for that I'd just like to ask you paint the bikeshed with
> > > > > Song Liu as he's been the one slowly making way to help us get there
> > > > > with the "module: replace module_layout with module_memory",
> > > > > and Mike Rapoport as he's had some follow up attempts [0]. As I see it,
> > > > > the EXECMEM stuff would be what we use instead then. Mike kept the
> > > > > module_alloc() and the execmem was just a wrapper but your move of the
> > > > > arch stuff makes sense as well and I think would complement his series
> > > > > nicely.
> > > >
> > > > I apologize for missing that. I think these are the four most recent
> > > > versions of the different series referenced from that LWN link:
> > > >
> > > >   a) https://lore.kernel.org/all/20230918072955.2507221-1-rppt@kernel.org/
> > > >   b) https://lore.kernel.org/all/20230526051529.3387103-1-song@kernel.org/
> > > >   c) https://lore.kernel.org/all/20221107223921.3451913-1-song@kernel.org/
> > > >   d) https://lore.kernel.org/all/20201120202426.18009-1-rick.p.edgecombe@intel.com/
> > > >
> > > > Song and Mike, please correct me if I'm wrong, but I think what I've
> > > > done here (see [1], sorry for not adding you initially) is compatible
> > > > with everything both of you have recently proposed above. How do you
> > > > feel about this as a first step?
> > >
> > > I agree that the work here is compatible with other efforts. I have no
> > > objection to making this the first step.
> > >
> > > >
> > > > For naming, execmem_alloc() seems reasonable to me? I have no strong
> > > > feelings at all, I'll just use that going forward unless somebody else
> > > > expresses an opinion.
> > >
> > > I am not good at naming things. No objection from me to "execmem_alloc".
> >
> > Hm, it sounds good to me too. I think we should add a patch which just
> > rename the module_alloc/module_memfree with execmem_alloc/free first.
> 
> I think that would be cleaner, yes. Leaving the possible move to a
> secondary patch and placing the testing more on the later part.

Makes sense to me.