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kprobes: Support __kprobes and NOKPROBE_SYMBOL in modules

PATCH New Masami Hiramatsu 1 participant 5 messages Mar 26, 2020

Subsystems (2)
Module support kprobes
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Masami Hiramatsu

author maintainer
#0 lore raw

cover kprobes: Support __kprobes and NOKPROBE_SYMBOL in modules

Hi,

Here is a series for adding support of __kprobes attribute and NOKPROBE_SYMBOL() macro in modules. With this series, kprobes user can add its handlers and sub-functions to kprobe blacklist so that other kprobes don't probe it.

Note that user should not use both __kprobes and NOKPROBE_SYMBOL() to same function. In that case, the function will appear twice on the blacklist, and that is a waste of memory.

Thomas, it is easy to add ".noinstr.text" support to this series. as same as __kprobes (.kprobes.text) support in [2/4], we can add mod->noinstr_text_start and mod->noinstr_text_size and register it in add_module_kprobe_blacklist().

Thank you,

---

Masami Hiramatsu (4):
kprobes: Lock kprobe_mutex while showing kprobe_blacklist
kprobes: Support __kprobes blacklist in modules
kprobes: Support NOKPROBE_SYMBOL() in modules samples/kprobes: Add __kprobes and NOKPROBE_SYMBOL() for handlers.

 include/linux/module.h              |    6 +++
 kernel/kprobes.c                    |   67 ++++++++++++++++++++++++++++++++++-
 kernel/module.c                     |    7 ++++
 samples/kprobes/kprobe_example.c    |    6 ++-
 samples/kprobes/kretprobe_example.c |    2 +
 5 files changed, 85 insertions(+), 3 deletions(-)

--
Masami Hiramatsu (Linaro) <[email protected]>

author maintainer
#1 lore raw

PATCH 1/4 kprobes: Lock kprobe_mutex while showing kprobe_blacklist

Lock kprobe_mutex while showing kprobe_blacklist to prevent updating the kprobe_blacklist.

Signed-off-by Masami Hiramatsu <[email protected]>
---
 kernel/kprobes.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)
kernel/kprobes.c +7 -1
index 2625c241ac00..570d60827656 100644
@@ -2420,6 +2420,7 @@ 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_mutex);
 	return seq_list_start(&kprobe_blacklist, *pos);
 }
 

@@ -2446,10 +2447,15 @@ static int kprobe_blacklist_seq_show(struct seq_file *m, void *v)
 	return 0;
 }
 
+static void kprobe_blacklist_seq_stop(struct seq_file *f, void *v)
+{
+	mutex_unlock(&kprobe_mutex);
+}
+
 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,
 };
author maintainer
#2 lore raw

PATCH 2/4 kprobes: Support __kprobes blacklist in modules

In reply to Masami Hiramatsu

Support __kprobes attribute for blacklist functions in modules. The __kprobes attribute functions are stored in .kprobes.text section.

Signed-off-by Masami Hiramatsu <[email protected]>
---
 include/linux/module.h |    4 ++++
 kernel/kprobes.c       |   42 ++++++++++++++++++++++++++++++++++++++++++
 kernel/module.c        |    4 ++++
 3 files changed, 50 insertions(+)
include/linux/module.h +4 -0
index 1ad393e62bef..369c354f9207 100644
@@ -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? */
kernel/kprobes.c +42 -0

66 lines not on this page · raw message

kernel/module.c +4 -0
index 33569a01d6e1..f7712a923d63 100644
@@ -3193,6 +3193,10 @@ static int find_module_sections(struct module *mod, struct load_info *info)
 	mod->ei_funcs = section_objs(info, "_error_injection_whitelist",
 					    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);
author maintainer
#3 lore raw

PATCH 3/4 kprobes: Support NOKPROBE_SYMBOL() in modules

In reply to Masami Hiramatsu

Support NOKPROBE_SYMBOL() in modules. NOKPROBE_SYMBOL() records only symbol address in "_kprobe_blacklist" section in the module.

Signed-off-by Masami Hiramatsu <[email protected]>
---
 include/linux/module.h |    2 ++
 kernel/kprobes.c       |   17 +++++++++++++++++
 kernel/module.c        |    3 +++
 3 files changed, 22 insertions(+)
include/linux/module.h +2 -0
index 369c354f9207..1192097c9a69 100644
@@ -492,6 +492,8 @@ struct module {
 #ifdef CONFIG_KPROBES
 	void *kprobes_text_start;
 	unsigned int kprobes_text_size;
+	unsigned long *kprobe_blacklist;
+	unsigned int num_kprobe_blacklist;
 #endif
 
 #ifdef CONFIG_LIVEPATCH
kernel/kprobes.c +17 -0
index b7549992b9bd..9eb5acf0a9f3 100644
@@ -2192,6 +2192,11 @@ static void kprobe_remove_area_blacklist(unsigned long start, unsigned long end)
 	}
 }
 
+static void kprobe_remove_ksym_blacklist(unsigned long entry)
+{
+	kprobe_remove_area_blacklist(entry, entry + 1);
+}
+
 int __init __weak arch_populate_kprobe_blacklist(void)
 {
 	return 0;

@@ -2231,6 +2236,12 @@ static int __init populate_kprobe_blacklist(unsigned long *start,
 static void add_module_kprobe_blacklist(struct module *mod)
 {
 	unsigned long start, end;
+	int i;
+
+	if (mod->kprobe_blacklist) {
+		for (i = 0; i < mod->num_kprobe_blacklist; i++)
+			kprobe_add_ksym_blacklist(mod->kprobe_blacklist[i]);
+	}
 
 	start = (unsigned long)mod->kprobes_text_start;
 	if (start) {

@@ -2242,6 +2253,12 @@ static void add_module_kprobe_blacklist(struct module *mod)
 static void remove_module_kprobe_blacklist(struct module *mod)
 {
 	unsigned long start, end;
+	int i;
+
+	if (mod->kprobe_blacklist) {
+		for (i = 0; i < mod->num_kprobe_blacklist; i++)
+			kprobe_remove_ksym_blacklist(mod->kprobe_blacklist[i]);
+	}
 
 	start = (unsigned long)mod->kprobes_text_start;
 	if (start) {
kernel/module.c +3 -0
index f7712a923d63..7be011dacd8a 100644
@@ -3197,6 +3197,9 @@ static int find_module_sections(struct module *mod, struct load_info *info)
 #ifdef CONFIG_KPROBES
 	mod->kprobes_text_start = section_objs(info, ".kprobes.text", 1,
 						&mod->kprobes_text_size);
+	mod->kprobe_blacklist = section_objs(info, "_kprobe_blacklist",
+						sizeof(unsigned long),
+						&mod->num_kprobe_blacklist);
 #endif
 	mod->extable = section_objs(info, "__ex_table",
 				    sizeof(*mod->extable), &mod->num_exentries);
author maintainer
#4 lore raw

PATCH 4/4 samples/kprobes: Add __kprobes and NOKPROBE_SYMBOL() for handlers.

In reply to Masami Hiramatsu

Add __kprobes and NOKPROBE_SYMBOL() for sample
kprobe handlers.

Signed-off-by Masami Hiramatsu <[email protected]>
---
 samples/kprobes/kprobe_example.c    |    6 ++++--
 samples/kprobes/kretprobe_example.c |    2 ++
 2 files changed, 6 insertions(+), 2 deletions(-)
samples/kprobes/kprobe_example.c +4 -2
index d693c23a85e8..501911d1b327 100644
@@ -25,7 +25,7 @@ static struct kprobe kp = {
 };
 
 /* kprobe pre_handler: called just before the probed instruction is executed */
-static int handler_pre(struct kprobe *p, struct pt_regs *regs)
+static int __kprobes handler_pre(struct kprobe *p, struct pt_regs *regs)
 {
 #ifdef CONFIG_X86
 	pr_info("<%s> pre_handler: p->addr = 0x%p, ip = %lx, flags = 0x%lx\n",

@@ -54,7 +54,7 @@ static int handler_pre(struct kprobe *p, struct pt_regs *regs)
 }
 
 /* kprobe post_handler: called after the probed instruction is executed */
-static void handler_post(struct kprobe *p, struct pt_regs *regs,
+static void __kprobes handler_post(struct kprobe *p, struct pt_regs *regs,
 				unsigned long flags)
 {
 #ifdef CONFIG_X86

@@ -90,6 +90,8 @@ static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
 	/* Return 0 because we don't handle the fault. */
 	return 0;
 }
+/* NOKPROBE_SYMBOL() is also available */
+NOKPROBE_SYMBOL(handler_fault);
 
 static int __init kprobe_init(void)
 {
samples/kprobes/kretprobe_example.c +2 -0
index 186315ca88b3..013e8e6ebae9 100644
@@ -48,6 +48,7 @@ static int entry_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
 	data->entry_stamp = ktime_get();
 	return 0;
 }
+NOKPROBE_SYMBOL(entry_handler);
 
 /*
  * Return-probe handler: Log the return value and duration. Duration may turn

@@ -67,6 +68,7 @@ static int ret_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
 			func_name, retval, (long long)delta);
 	return 0;
 }
+NOKPROBE_SYMBOL(ret_handler);
 
 static struct kretprobe my_kretprobe = {
 	.handler		= ret_handler,