linux-kernel - Re: [PATCH v4 14/15] kprobes: remove dependency on CONFIG

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Date: Sat, 20 Apr 2024 10:33:38 +0300
From: Mike Rapoport <rppt@...nel.org>
To: Christophe Leroy <christophe.leroy@...roup.eu>
Cc: Masami Hiramatsu <masami.hiramatsu@...il.com>,
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Subject: Re: [PATCH v4 14/15] kprobes: remove dependency on CONFIG_MODULES

On Fri, Apr 19, 2024 at 03:59:40PM +0000, Christophe Leroy wrote:
> 
> 
> Le 19/04/2024 à 17:49, Mike Rapoport a écrit :
> > Hi Masami,
> > 
> > On Thu, Apr 18, 2024 at 06:16:15AM +0900, Masami Hiramatsu wrote:
> >> Hi Mike,
> >>
> >> On Thu, 11 Apr 2024 19:00:50 +0300
> >> Mike Rapoport <rppt@...nel.org> wrote:
> >>
> >>> From: "Mike Rapoport (IBM)" <rppt@...nel.org>
> >>>
> >>> kprobes depended on CONFIG_MODULES because it has to allocate memory for
> >>> code.
> >>>
> >>> Since code allocations are now implemented with execmem, kprobes can be
> >>> enabled in non-modular kernels.
> >>>
> >>> Add #ifdef CONFIG_MODULE guards for the code dealing with kprobes inside
> >>> modules, make CONFIG_KPROBES select CONFIG_EXECMEM and drop the
> >>> dependency of CONFIG_KPROBES on CONFIG_MODULES.
> >>
> >> Thanks for this work, but this conflicts with the latest fix in v6.9-rc4.
> >> Also, can you use IS_ENABLED(CONFIG_MODULES) instead of #ifdefs in
> >> function body? We have enough dummy functions for that, so it should
> >> not make a problem.
> > 
> > The code in check_kprobe_address_safe() that gets the module and checks for
> > __init functions does not compile with IS_ENABLED(CONFIG_MODULES).
> > I can pull it out to a helper or leave #ifdef in the function body,
> > whichever you prefer.
> 
> As far as I can see, the only problem is MODULE_STATE_COMING.
> Can we move 'enum module_state' out of #ifdef CONFIG_MODULES in module.h  ?

There's dereference of 'struct module' there:
 
		(*probed_mod)->state != MODULE_STATE_COMING) {
			...
		}

so moving out 'enum module_state' won't be enough.
 
> >   
> >> -- 
> >> Masami Hiramatsu
> > 

-- 
Sincerely yours,
Mike.