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

From: "Jarkko Sakkinen" <jarkko@kernel.org>
To: "Masami Hiramatsu" <mhiramat@kernel.org>,
	"Mark Rutland" <mark.rutland@arm.com>
Cc: <linux-kernel@vger.kernel.org>, <agordeev@linux.ibm.com>,
	<anil.s.keshavamurthy@intel.com>, <aou@eecs.berkeley.edu>,
	<bp@alien8.de>, <catalin.marinas@arm.com>,
	<dave.hansen@linux.intel.com>, <davem@davemloft.net>,
	<gor@linux.ibm.com>, <hca@linux.ibm.com>,
	<jcalvinowens@gmail.com>, <linux-arm-kernel@lists.infradead.org>,
	<mingo@redhat.com>, <mpe@ellerman.id.au>,
	<naveen.n.rao@linux.ibm.com>, <palmer@dabbelt.com>,
	<paul.walmsley@sifive.com>, <tglx@linutronix.de>,
	<will@kernel.org>
Subject: Re: [PATCH 4/4] kprobes: Remove core dependency on modules
Date: Wed, 27 Mar 2024 19:46:50 +0200	[thread overview]
Message-ID: <D04PYD185FIK.WABP6RZDCC06@kernel.org> (raw)
In-Reply-To: <20240327090155.873f1ed32700dbdb75f8eada@kernel.org>

On Wed Mar 27, 2024 at 2:01 AM EET, Masami Hiramatsu (Google) wrote:
> On Tue, 26 Mar 2024 17:38:18 +0000
> Mark Rutland <mark.rutland@arm.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!

As for RISC-V:

Tested-by: Jarkko Sakkinen <jarkko@kernel.org> # arch/riscv

I'm fine with adding to all patches because it would be hard
to place tested-by to any specific patch (e.g. if this was a
syscall I would give tested-by just for that patch).

Just adding disclaimer because depending on subsystem people
are more or less strict with this tag :-)

BR, Jarkko