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Date: Thu, 16 Jul 2020 20:36:28 +0300
From: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To: Masami Hiramatsu <mhiramat@...nel.org>
Cc: linux-kernel@...r.kernel.org, x86@...r.kernel.org,
Andi Kleen <ak@...ux.intel.com>, Jessica Yu <jeyu@...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>,
Steven Rostedt <rostedt@...dmis.org>,
Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH v3 3/3] kprobes: Flag out CONFIG_MODULES dependent code
On Wed, Jul 15, 2020 at 05:35:24PM +0900, Masami Hiramatsu wrote:
> Hi Jarkko,
>
> On Wed, 15 Jul 2020 01:32:29 +0300
> Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com> wrote:
>
> > Remove CONFIG_MODULES dependency by flagging out the dependent code. This
> > allows to use kprobes in a kernel without support for loadable modules,
> > which could be useful for a test kernel or perhaps an embedded kernel.
> >
>
> OK, looks good, I just have 2 comments below.
>
> > Cc: Andi Kleen <ak@...ux.intel.com>
> > Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> > ---
> > include/linux/module.h | 14 +++++++-------
> > kernel/kprobes.c | 7 +++++++
> > kernel/trace/trace_kprobe.c | 16 +++++++++++++++-
> > 3 files changed, 29 insertions(+), 8 deletions(-)
> >
> > diff --git a/include/linux/module.h b/include/linux/module.h
> > index 857b84bf9e90..eaa8ad02f75c 100644
> > --- a/include/linux/module.h
> > +++ b/include/linux/module.h
> > @@ -290,6 +290,13 @@ extern typeof(name) __mod_##type##__##name##_device_table \
> >
> > struct notifier_block;
> >
> > +enum module_state {
> > + MODULE_STATE_LIVE, /* Normal state. */
> > + MODULE_STATE_COMING, /* Full formed, running module_init. */
> > + MODULE_STATE_GOING, /* Going away. */
> > + MODULE_STATE_UNFORMED, /* Still setting it up. */
> > +};
> > +
> > #ifdef CONFIG_MODULES
> >
> > extern int modules_disabled; /* for sysctl */
> > @@ -305,13 +312,6 @@ struct module_use {
> > struct module *source, *target;
> > };
> >
> > -enum module_state {
> > - MODULE_STATE_LIVE, /* Normal state. */
> > - MODULE_STATE_COMING, /* Full formed, running module_init. */
> > - MODULE_STATE_GOING, /* Going away. */
> > - MODULE_STATE_UNFORMED, /* Still setting it up. */
> > -};
> > -
> > struct mod_tree_node {
> > struct module *mod;
> > struct latch_tree_node node;
> > diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> > index b4f3c24cd2ef..3039df13d34e 100644
> > --- a/kernel/kprobes.c
> > +++ b/kernel/kprobes.c
> > @@ -2225,6 +2225,7 @@ int kprobe_add_area_blacklist(unsigned long start, unsigned long end)
> > return 0;
> > }
> >
> > +#ifdef CONFIG_MODULES
> > /* Remove all symbols in given area from kprobe blacklist */
> > static void kprobe_remove_area_blacklist(unsigned long start, unsigned long end)
> > {
> > @@ -2242,6 +2243,7 @@ static void kprobe_remove_ksym_blacklist(unsigned long entry)
> > {
> > kprobe_remove_area_blacklist(entry, entry + 1);
> > }
> > +#endif
> >
> > int __init __weak arch_populate_kprobe_blacklist(void)
> > {
> > @@ -2285,6 +2287,7 @@ static int __init populate_kprobe_blacklist(unsigned long *start,
> > return ret ? : arch_populate_kprobe_blacklist();
> > }
> >
> > +#ifdef CONFIG_MODULES
> > static void add_module_kprobe_blacklist(struct module *mod)
> > {
> > unsigned long start, end;
> > @@ -2330,6 +2333,10 @@ static void remove_module_kprobe_blacklist(struct module *mod)
> > kprobe_remove_area_blacklist(start, end);
> > }
> > }
> > +#else
> > +static void add_module_kprobe_blacklist(struct module *mod) {}
> > +static void remove_module_kprobe_blacklist(struct module *mod) {}
> > +#endif /* CONFIG_MODULES */
>
> Please feel free to move the function. I would like to see;
>
> #ifdef CONFIG_MODULES
> /* Remove all symbols in given area from kprobe blacklist */
> static void kprobe_remove_area_blacklist(unsigned long start, unsigned long end)
> {
> ...
> }
> static void add_module_kprobe_blacklist(struct module *mod)
> {
> ...
> }
> #else
> static void add_module_kprobe_blacklist(struct module *mod) {}
> static void remove_module_kprobe_blacklist(struct module *mod) {}
> #endif /* CONFIG_MODULES */
>
> Rather than split #ifdefs.
>
> >
> > /* Module notifier call back, checking kprobes on the module */
> > static int kprobes_module_callback(struct notifier_block *nb,
> > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> > index 710ec6a6aa8f..7fcd1bf2d96e 100644
> > --- a/kernel/trace/trace_kprobe.c
> > +++ b/kernel/trace/trace_kprobe.c
> > @@ -103,8 +103,9 @@ static nokprobe_inline bool trace_kprobe_has_gone(struct trace_kprobe *tk)
> > return !!(kprobe_gone(&tk->rp.kp));
> > }
> >
> > +#ifdef CONFIG_MODULES
> > static nokprobe_inline bool trace_kprobe_within_module(struct trace_kprobe *tk,
> > - struct module *mod)
> > + struct module *mod)
> > {
> > int len = strlen(mod->name);
> > const char *name = trace_kprobe_symbol(tk);
> > @@ -129,6 +130,17 @@ static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk)
> >
> > return ret;
> > }
> > +#else
> > +static nokprobe_inline bool trace_kprobe_within_module(struct trace_kprobe *tk,
> > + struct module *mod)
> > +{
> > + return false;
> > +}
> > +static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk)
> > +{
> > + return false;
> > +}
> > +#endif
> >
> > static bool trace_kprobe_is_busy(struct dyn_event *ev)
> > {
> > @@ -685,10 +697,12 @@ static int trace_kprobe_module_callback(struct notifier_block *nb,
> > /* Don't need to check busy - this should have gone. */
> > __unregister_trace_kprobe(tk);
> > ret = __register_trace_kprobe(tk);
> > +#ifdef CONFIG_MODULES
> > if (ret)
> > pr_warn("Failed to re-register probe %s on %s: %d\n",
> > trace_probe_name(&tk->tp),
> > mod->name, ret);
> > +#endif
>
> I guess this CONFIG_MODULES is for avoiding build error according to mod->name,
> if so, please use module_name(mod) macro instead of this #ifdef.
>
> > }
> > }
> > mutex_unlock(&event_mutex);
> > --
> > 2.25.1
> >
>
>
> --
> Masami Hiramatsu <mhiramat@...nel.org>
Thanks, agree with the remarks.
/Jarkko
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