Re: [patch V4 part 1 16/36] kprobes: Support __kprobes blacklist in modules

Alexandre Chartre
2020-05-06T15:50:01Z

On 5/5/20 3:16 PM, Thomas Gleixner wrote:
> From: Masami Hiramatsu <mhiramat@kernel.org>
>
> Support __kprobes attribute for blacklist functions in modules. The
> __kprobes attribute functions are stored in .kprobes.text section.
>
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Link: https://lkml.kernel.org/r/158523418821.24735.15379873028352411526.stgit@devnote2
>
> ---
> include/linux/module.h | 4 ++++
> kernel/kprobes.c | 42 ++++++++++++++++++++++++++++++++++++++++++
> kernel/module.c | 4 ++++
> 3 files changed, 50 insertions(+)

Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>

alex.

> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -489,6 +489,10 @@ struct module {
> unsigned int num_ftrace_callsites;
> unsigned long *ftrace_callsites;
> #endif
> +#ifdef CONFIG_KPROBES
> + void *kprobes_text_start;
> + unsigned int kprobes_text_size;
> +#endif
>
> #ifdef CONFIG_LIVEPATCH
> bool klp; /* Is this a livepatch module? */
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -2179,6 +2179,19 @@ int kprobe_add_area_blacklist(unsigned l
> return 0;
> }
>
> +/* Remove all symbols in given area from kprobe blacklist */
> +static void kprobe_remove_area_blacklist(unsigned long start, unsigned long end)
> +{
> + struct kprobe_blacklist_entry *ent, *n;
> +
> + list_for_each_entry_safe(ent, n, &kprobe_blacklist, list) {
> + if (ent->start_addr < start || ent->start_addr >= end)
> + continue;
> + list_del(&ent->list);
> + kfree(ent);
> + }
> +}
> +
> int __init __weak arch_populate_kprobe_blacklist(void)
> {
> return 0;
> @@ -2215,6 +2228,28 @@ static int __init populate_kprobe_blackl
> return ret ? : arch_populate_kprobe_blacklist();
> }
>
> +static void add_module_kprobe_blacklist(struct module *mod)
> +{
> + unsigned long start, end;
> +
> + start = (unsigned long)mod->kprobes_text_start;
> + if (start) {
> + end = start + mod->kprobes_text_size;
> + kprobe_add_area_blacklist(start, end);
> + }
> +}
> +
> +static void remove_module_kprobe_blacklist(struct module *mod)
> +{
> + unsigned long start, end;
> +
> + start = (unsigned long)mod->kprobes_text_start;
> + if (start) {
> + end = start + mod->kprobes_text_size;
> + kprobe_remove_area_blacklist(start, end);
> + }
> +}
> +
> /* Module notifier call back, checking kprobes on the module */
> static int kprobes_module_callback(struct notifier_block *nb,
> unsigned long val, void *data)
> @@ -2225,6 +2260,11 @@ static int kprobes_module_callback(struc
> unsigned int i;
> int checkcore = (val == MODULE_STATE_GOING);
>
> + if (val == MODULE_STATE_COMING) {
> + mutex_lock(&kprobe_mutex);
> + add_module_kprobe_blacklist(mod);
> + mutex_unlock(&kprobe_mutex);
> + }
> if (val != MODULE_STATE_GOING && val != MODULE_STATE_LIVE)
> return NOTIFY_DONE;
>
> @@ -2255,6 +2295,8 @@ static int kprobes_module_callback(struc
> kill_kprobe(p);
> }
> }
> + if (val == MODULE_STATE_GOING)
> + remove_module_kprobe_blacklist(mod);
> mutex_unlock(&kprobe_mutex);
> return NOTIFY_DONE;
> }
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -3194,6 +3194,10 @@ static int find_module_sections(struct m
> sizeof(*mod->ei_funcs),
> &mod->num_ei_funcs);
> #endif
> +#ifdef CONFIG_KPROBES
> + mod->kprobes_text_start = section_objs(info, ".kprobes.text", 1,
> + &mod->kprobes_text_size);
> +#endif
> mod->extable = section_objs(info, "__ex_table",
> sizeof(*mod->extable), &mod->num_exentries);
>
>