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Message-ID: <87k2u0mj3u.fsf@rustcorp.com.au>
Date: Thu, 16 Jul 2015 21:04:29 +0930
From: Rusty Russell <rusty@...tcorp.com.au>
To: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
Ingo Molnar <mingo@...nel.org>
Cc: Pratyush Anand <panand@...hat.com>,
Ananth N Mavinakayanahalli <ananth@...ibm.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...hat.com>, Rob Landley <rob@...dley.net>,
"H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH tip/master 1/3] kprobes: Support blacklist functions in module
Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> writes:
> To blacklist the functions in a module (e.g. user-defined
> kprobe handler and the functions invoked from it), expand
> blacklist support for modules.
> With this change, users can use NOKPROBE_SYMBOL() macro in
> their own modules.
Looks great, thanks!
Acked-by: Rusty Russell <rusty@...tcorp.com.au>
> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Cc: Ananth N Mavinakayanahalli <ananth@...ibm.com>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Rob Landley <rob@...dley.net>
> Cc: Rusty Russell <rusty@...tcorp.com.au>
> ---
> Documentation/kprobes.txt | 8 ++++++
> include/linux/module.h | 4 +++
> kernel/kprobes.c | 64 ++++++++++++++++++++++++++++++++++++++-------
> kernel/module.c | 6 ++++
> 4 files changed, 72 insertions(+), 10 deletions(-)
>
> diff --git a/Documentation/kprobes.txt b/Documentation/kprobes.txt
> index 1f9b3e2..b5a698f 100644
> --- a/Documentation/kprobes.txt
> +++ b/Documentation/kprobes.txt
> @@ -513,6 +513,14 @@ int enable_jprobe(struct jprobe *jp);
> Enables *probe which has been disabled by disable_*probe(). You must specify
> the probe which has been registered.
>
> +4.9 NOKPROBE_SYMBOL()
> +
> +#include <linux/kprobes.h>
> +NOKPROBE_SYMBOL(FUNCTION);
> +
> +Protects given FUNCTION from other kprobes. This is useful for handler
> +functions and functions called from the handlers.
> +
> 5. Kprobes Features and Limitations
>
> Kprobes allows multiple probes at the same address. Currently,
> diff --git a/include/linux/module.h b/include/linux/module.h
> index d67b193..0827e34 100644
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -352,6 +352,10 @@ struct module {
> void __percpu *percpu;
> unsigned int percpu_size;
> #endif
> +#ifdef CONFIG_KPROBES
> + unsigned int num_kprobe_blacklist;
> + unsigned long *kprobe_blacklist;
> +#endif
>
> #ifdef CONFIG_TRACEPOINTS
> unsigned int num_tracepoints;
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index c90e417..53951c3 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -88,6 +88,7 @@ static raw_spinlock_t *kretprobe_table_lock_ptr(unsigned long hash)
>
> /* Blacklist -- list of struct kprobe_blacklist_entry */
> static LIST_HEAD(kprobe_blacklist);
> +static DEFINE_MUTEX(kprobe_blacklist_mutex);
>
> #ifdef __ARCH_WANT_KPROBES_INSN_SLOT
> /*
> @@ -1332,22 +1333,27 @@ bool __weak arch_within_kprobe_blacklist(unsigned long addr)
> addr < (unsigned long)__kprobes_text_end;
> }
>
> -static bool within_kprobe_blacklist(unsigned long addr)
> +static struct kprobe_blacklist_entry *find_blacklist_entry(unsigned long addr)
> {
> struct kprobe_blacklist_entry *ent;
>
> + list_for_each_entry(ent, &kprobe_blacklist, list) {
> + if (addr >= ent->start_addr && addr < ent->end_addr)
> + return ent;
> + }
> +
> + return NULL;
> +}
> +
> +static bool within_kprobe_blacklist(unsigned long addr)
> +{
> if (arch_within_kprobe_blacklist(addr))
> return true;
> /*
> * If there exists a kprobe_blacklist, verify and
> * fail any probe registration in the prohibited area
> */
> - list_for_each_entry(ent, &kprobe_blacklist, list) {
> - if (addr >= ent->start_addr && addr < ent->end_addr)
> - return true;
> - }
> -
> - return false;
> + return !!find_blacklist_entry(addr);
> }
>
> /*
> @@ -1437,6 +1443,8 @@ static int check_kprobe_address_safe(struct kprobe *p,
> ret = arch_check_ftrace_location(p);
> if (ret)
> return ret;
> +
> + mutex_lock(&kprobe_blacklist_mutex);
> jump_label_lock();
> preempt_disable();
>
> @@ -1474,6 +1482,7 @@ static int check_kprobe_address_safe(struct kprobe *p,
> out:
> preempt_enable();
> jump_label_unlock();
> + mutex_unlock(&kprobe_blacklist_mutex);
>
> return ret;
> }
> @@ -2054,13 +2063,13 @@ NOKPROBE_SYMBOL(dump_kprobe);
> * since a kprobe need not necessarily be at the beginning
> * of a function.
> */
> -static int __init populate_kprobe_blacklist(unsigned long *start,
> - unsigned long *end)
> +static int populate_kprobe_blacklist(unsigned long *start, unsigned long *end)
> {
> unsigned long *iter;
> struct kprobe_blacklist_entry *ent;
> unsigned long entry, offset = 0, size = 0;
>
> + mutex_lock(&kprobe_blacklist_mutex);
> for (iter = start; iter < end; iter++) {
> entry = arch_deref_entry_point((void *)*iter);
>
> @@ -2079,9 +2088,28 @@ static int __init populate_kprobe_blacklist(unsigned long *start,
> INIT_LIST_HEAD(&ent->list);
> list_add_tail(&ent->list, &kprobe_blacklist);
> }
> + mutex_unlock(&kprobe_blacklist_mutex);
> +
> return 0;
> }
>
> +/* Shrink the blacklist */
> +static void shrink_kprobe_blacklist(unsigned long *start, unsigned long *end)
> +{
> + struct kprobe_blacklist_entry *ent;
> + unsigned long *iter;
> +
> + mutex_lock(&kprobe_blacklist_mutex);
> + for (iter = start; iter < end; iter++) {
> + ent = find_blacklist_entry(*iter);
> + if (!ent)
> + continue;
> + list_del(&ent->list);
> + kfree(ent);
> + }
> + mutex_unlock(&kprobe_blacklist_mutex);
> +}
> +
> /* Module notifier call back, checking kprobes on the module */
> static int kprobes_module_callback(struct notifier_block *nb,
> unsigned long val, void *data)
> @@ -2092,6 +2120,16 @@ static int kprobes_module_callback(struct notifier_block *nb,
> unsigned int i;
> int checkcore = (val == MODULE_STATE_GOING);
>
> + /* Add/remove module blacklist */
> + if (val == MODULE_STATE_COMING)
> + populate_kprobe_blacklist(mod->kprobe_blacklist,
> + mod->kprobe_blacklist +
> + mod->num_kprobe_blacklist);
> + else if (val == MODULE_STATE_GOING)
> + shrink_kprobe_blacklist(mod->kprobe_blacklist,
> + mod->kprobe_blacklist +
> + mod->num_kprobe_blacklist);
> +
> if (val != MODULE_STATE_GOING && val != MODULE_STATE_LIVE)
> return NOTIFY_DONE;
>
> @@ -2278,6 +2316,7 @@ static const struct file_operations debugfs_kprobes_operations = {
> /* kprobes/blacklist -- shows which functions can not be probed */
> static void *kprobe_blacklist_seq_start(struct seq_file *m, loff_t *pos)
> {
> + mutex_lock(&kprobe_blacklist_mutex);
> return seq_list_start(&kprobe_blacklist, *pos);
> }
>
> @@ -2286,6 +2325,11 @@ static void *kprobe_blacklist_seq_next(struct seq_file *m, void *v, loff_t *pos)
> return seq_list_next(v, &kprobe_blacklist, pos);
> }
>
> +static void kprobe_blacklist_seq_stop(struct seq_file *m, void *v)
> +{
> + mutex_unlock(&kprobe_blacklist_mutex);
> +}
> +
> static int kprobe_blacklist_seq_show(struct seq_file *m, void *v)
> {
> struct kprobe_blacklist_entry *ent =
> @@ -2299,7 +2343,7 @@ static int kprobe_blacklist_seq_show(struct seq_file *m, void *v)
> static const struct seq_operations kprobe_blacklist_seq_ops = {
> .start = kprobe_blacklist_seq_start,
> .next = kprobe_blacklist_seq_next,
> - .stop = kprobe_seq_stop, /* Reuse void function */
> + .stop = kprobe_blacklist_seq_stop,
> .show = kprobe_blacklist_seq_show,
> };
>
> diff --git a/kernel/module.c b/kernel/module.c
> index 4d2b82e..c3a593c 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -57,6 +57,7 @@
> #include <linux/percpu.h>
> #include <linux/kmemleak.h>
> #include <linux/jump_label.h>
> +#include <linux/kprobes.h>
> #include <linux/pfn.h>
> #include <linux/bsearch.h>
> #include <uapi/linux/module.h>
> @@ -2937,6 +2938,11 @@ static int find_module_sections(struct module *mod, struct load_info *info)
> sizeof(*mod->ftrace_callsites),
> &mod->num_ftrace_callsites);
> #endif
> +#ifdef CONFIG_KPROBES
> + mod->kprobe_blacklist = section_objs(info, "_kprobe_blacklist",
> + sizeof(*mod->kprobe_blacklist),
> + &mod->num_kprobe_blacklist);
> +#endif
>
> mod->extable = section_objs(info, "__ex_table",
> sizeof(*mod->extable), &mod->num_exentries);
>
> --
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