Subject: [PATCH v2 12/12] kprobes: remove dependcy on CONFIG_MODULES

From: Mike Rapoport <[email-masked]>
Date: Fri, 16 Jun 2023 11:50:38 +0300

From: "Mike Rapoport (IBM)" <[email-masked]>

kprobes depended on CONFIG_MODULES because it has to allocate memory for
code.

Since code allocations are now implemented with execmem, kprobes can be
enabled in non-modular kernels.

Add #ifdef CONFIG_MODULE guards for the code dealing with kprobes inside
modules, make CONFIG_KPROBES select CONFIG_EXECMEM and drop the
dependency of CONFIG_KPROBES on CONFIG_MODULES.

Signed-off-by: Mike Rapoport (IBM) <[email-masked]>
---
 arch/Kconfig                |  2 +-
 kernel/kprobes.c            | 43 +++++++++++++++++++++----------------
 kernel/trace/trace_kprobe.c | 11 ++++++++++
 3 files changed, 37 insertions(+), 19 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 205fd23e0cad..f2e9f82c7d0d 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -39,9 +39,9 @@ config GENERIC_ENTRY
 
 config KPROBES
 	bool "Kprobes"
-	depends on MODULES
 	depends on HAVE_KPROBES
 	select KALLSYMS
+	select EXECMEM
 	select TASKS_RCU if PREEMPTION
 	help
 	  Kprobes allows you to trap at almost any kernel address and
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 37c928d5deaf..2c2ba29d3f9a 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1568,6 +1568,7 @@ static int check_kprobe_address_safe(struct kprobe *p,
 		goto out;
 	}
 
+#ifdef CONFIG_MODULES
 	/* Check if 'p' is probing a module. */
 	*probed_mod = __module_text_address((unsigned long) p->addr);
 	if (*probed_mod) {
@@ -1591,6 +1592,8 @@ static int check_kprobe_address_safe(struct kprobe *p,
 			ret = -ENOENT;
 		}
 	}
+#endif
+
 out:
 	preempt_enable();
 	jump_label_unlock();
@@ -2484,24 +2487,6 @@ int kprobe_add_area_blacklist(unsigned long start, unsigned long end)
 	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);
-	}
-}
-
-static void kprobe_remove_ksym_blacklist(unsigned long entry)
-{
-	kprobe_remove_area_blacklist(entry, entry + 1);
-}
-
 int __weak arch_kprobe_get_kallsym(unsigned int *symnum, unsigned long *value,
 				   char *type, char *sym)
 {
@@ -2566,6 +2551,25 @@ static int __init populate_kprobe_blacklist(unsigned long *start,
 	return ret ? : arch_populate_kprobe_blacklist();
 }
 
+#ifdef CONFIG_MODULES
+/* 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);
+	}
+}
+
+static void kprobe_remove_ksym_blacklist(unsigned long entry)
+{
+	kprobe_remove_area_blacklist(entry, entry + 1);
+}
+
 static void add_module_kprobe_blacklist(struct module *mod)
 {
 	unsigned long start, end;
@@ -2667,6 +2671,7 @@ static struct notifier_block kprobe_module_nb = {
 	.notifier_call = kprobes_module_callback,
 	.priority = 0
 };
+#endif
 
 void kprobe_free_init_mem(void)
 {
@@ -2726,8 +2731,10 @@ static int __init init_kprobes(void)
 	err = arch_init_kprobes();
 	if (!err)
 		err = register_die_notifier(&kprobe_exceptions_nb);
+#ifdef CONFIG_MODULES
 	if (!err)
 		err = register_module_notifier(&kprobe_module_nb);
+#endif
 
 	kprobes_initialized = (err == 0);
 	kprobe_sysctls_init();
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 59cda19a9033..cf804e372554 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -111,6 +111,7 @@ static nokprobe_inline bool trace_kprobe_within_module(struct trace_kprobe *tk,
 	return strncmp(module_name(mod), name, len) == 0 && name[len] == ':';
 }
 
+#ifdef CONFIG_MODULES
 static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk)
 {
 	char *p;
@@ -129,6 +130,12 @@ static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk)
 
 	return ret;
 }
+#else
+static inline bool trace_kprobe_module_exist(struct trace_kprobe *tk)
+{
+	return false;
+}
+#endif
 
 static bool trace_kprobe_is_busy(struct dyn_event *ev)
 {
@@ -670,6 +677,7 @@ static int register_trace_kprobe(struct trace_kprobe *tk)
 	return ret;
 }
 
+#ifdef CONFIG_MODULES
 /* Module notifier call back, checking event on the module */
 static int trace_kprobe_module_callback(struct notifier_block *nb,
 				       unsigned long val, void *data)
@@ -704,6 +712,7 @@ static struct notifier_block trace_kprobe_module_nb = {
 	.notifier_call = trace_kprobe_module_callback,
 	.priority = 1	/* Invoked after kprobe module callback */
 };
+#endif
 
 static int __trace_kprobe_create(int argc, const char *argv[])
 {
@@ -1797,8 +1806,10 @@ static __init int init_kprobe_trace_early(void)
 	if (ret)
 		return ret;
 
+#ifdef CONFIG_MODULES
 	if (register_module_notifier(&trace_kprobe_module_nb))
 		return -EINVAL;
+#endif
 
 	return 0;
 }
-- 
2.35.1