[PATCH -tip v9 20/26] kprobes: Support blacklist functions in module

Masami Hiramatsu
2014-04-17T08:19:12Z

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.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Rob Landley <rob@landley.net>
Cc: Rusty Russell <rusty@rustcorp.com.au>
---
Documentation/kprobes.txt | 8 ++++++
include/linux/module.h | 5 ++++
kernel/kprobes.c | 63 ++++++++++++++++++++++++++++++++++++++-------
kernel/module.c | 6 ++++
4 files changed, 72 insertions(+), 10 deletions(-)

diff --git a/Documentation/kprobes.txt b/Documentation/kprobes.txt
index 4bbeca8..2845956 100644
--- a/Documentation/kprobes.txt
+++ b/Documentation/kprobes.txt
@@ -512,6 +512,14 @@ 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 f520a76..2fdb673 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -16,6 +16,7 @@
#include <linux/kobject.h>
#include <linux/moduleparam.h>
#include <linux/jump_label.h>
+#include <linux/kprobes.h>
#include <linux/export.h>

#include <linux/percpu.h>
@@ -357,6 +358,10 @@ struct module {
unsigned int num_ftrace_callsites;
unsigned long *ftrace_callsites;
#endif
+#ifdef CONFIG_KPROBES
+ unsigned int num_kprobe_blacklist;
+ unsigned long *kprobe_blacklist;
+#endif

#ifdef CONFIG_MODULE_UNLOAD
/* What modules depend on me? */
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 3214289..8319048 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
/*
@@ -1331,22 +1332,27 @@ 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);
}

/*
@@ -1432,6 +1438,7 @@ static int check_kprobe_address_safe(struct kprobe *p,
#endif
}

+ mutex_lock(&kprobe_blacklist_mutex);
jump_label_lock();
preempt_disable();

@@ -1469,6 +1476,7 @@ static int check_kprobe_address_safe(struct kprobe *p,
out:
preempt_enable();
jump_label_unlock();
+ mutex_unlock(&kprobe_blacklist_mutex);

return ret;
}
@@ -2032,13 +2040,13 @@ 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 offset = 0, size = 0;

+ mutex_lock(&kprobe_blacklist_mutex);
for (iter = start; iter < end; iter++) {
if (!kallsyms_lookup_size_offset(*iter, &size, &offset)) {
pr_err("Failed to find blacklist %p\n", (void *)*iter);
@@ -2053,9 +2061,28 @@ 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)
@@ -2066,6 +2093,16 @@ 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;

@@ -2252,6 +2289,7 @@ 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);
}

@@ -2260,6 +2298,11 @@ 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 =
@@ -2273,7 +2316,7 @@ 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 1186940..895c635 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -58,6 +58,7 @@
#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 <linux/fips.h>
@@ -2772,6 +2773,11 @@ 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);