linux-kernel - Re: [PATCH 4/4] kprobes: Remove core dependency on modules

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Date: Wed, 27 Mar 2024 15:23:24 +0200
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Masami Hiramatsu <mhiramat@...nel.org>, Mark Rutland
 <mark.rutland@....com>
Cc: linux-kernel@...r.kernel.org, agordeev@...ux.ibm.com, 
 anil.s.keshavamurthy@...el.com, aou@...s.berkeley.edu, bp@...en8.de, 
 catalin.marinas@....com, dave.hansen@...ux.intel.com, davem@...emloft.net, 
 gor@...ux.ibm.com, hca@...ux.ibm.com, jcalvinowens@...il.com, 
 linux-arm-kernel@...ts.infradead.org, mingo@...hat.com, mpe@...erman.id.au,
  naveen.n.rao@...ux.ibm.com, palmer@...belt.com, paul.walmsley@...ive.com, 
 tglx@...utronix.de, will@...nel.org
Subject: Re: [PATCH 4/4] kprobes: Remove core dependency on modules

On Wed, 2024-03-27 at 09:01 +0900, Masami Hiramatsu wrote:
> On Tue, 26 Mar 2024 17:38:18 +0000
> Mark Rutland <mark.rutland@....com> wrote:
> 
> > On Tue, Mar 26, 2024 at 07:13:51PM +0200, Jarkko Sakkinen wrote:
> > > On Tue Mar 26, 2024 at 6:36 PM EET, Mark Rutland wrote:
> > 
> > > > +#ifdef CONFIG_MODULES
> > > >  	/* Check if 'p' is probing a module. */
> > > >  	*probed_mod = __module_text_address((unsigned long) p-
> > > > >addr);
> > > >  	if (*probed_mod) {
> > > > @@ -1605,6 +1606,8 @@ static int
> > > > check_kprobe_address_safe(struct kprobe *p,
> > > >  			ret = -ENOENT;
> > > >  		}
> > > >  	}
> > > > +#endif
> > > 
> > > This can be scoped a bit more (see v7 of my patch set).
> > 
> > > > +#ifdef CONFIG_MODULES
> > > >  static nokprobe_inline bool trace_kprobe_module_exist(struct
> > > > trace_kprobe *tk)
> > > >  {
> > > >  	char *p;
> > > > @@ -129,6 +130,9 @@ static nokprobe_inline bool
> > > > trace_kprobe_module_exist(struct trace_kprobe *tk)
> > > >  
> > > >  	return ret;
> > > >  }
> > > > +#else
> > > > +#define trace_kprobe_module_exist(tk) false /* aka a module
> > > > never exists */
> > > > +#endif /* CONFIG_MODULES */
> > > >  
> > > >  static bool trace_kprobe_is_busy(struct dyn_event *ev)
> > > >  {
> > > > @@ -670,6 +674,7 @@ static int register_trace_kprobe(struct
> > > > trace_kprobe *tk)
> > > >  	return ret;
> > > >  }
> > > >  
> > > > +#ifdef CONFIG_MODULES
> > > >  /* Module notifier call back, checking event on the module */
> > > >  static int trace_kprobe_module_callback(struct notifier_block
> > > > *nb,
> > > >  				       unsigned long val, void
> > > > *data)
> > > > @@ -699,6 +704,9 @@ static int
> > > > trace_kprobe_module_callback(struct notifier_block *nb,
> > > >  
> > > >  	return NOTIFY_DONE;
> > > >  }
> > > > +#else
> > > > +#define trace_kprobe_module_callback (NULL)
> > > > +#endif /* CONFIG_MODULES */
> > > 
> > > The last two CONFIG_MODULES sections could be combined. This was
> > > also in
> > > v7.
> > 
> > > Other than lgtm.
> > 
> > Great! I've folded your v7 changes in, and pushed that out to:
> > 
> >  
> > https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/log/?h=kprobes/without-modules
> > 
> > I'll hold off sending that out to the list until other folk have
> > had a chance
> > to comment.
> 
> Yeah, the updated one looks good to me too.
> 
> Thanks!

Yeah, I'm also planning to test this with x86 instrumenting sgx_* calls
as I need to test the cgroups support for it so can help with the
coverage both RISC-V and x86 (as I find a good time slot).

BR, Jarkko