[PATCH v5 14/15] kprobes: remove dependency on CONFIG_MODULES

Mike Rapoport
2024-04-22T09:48:50Z

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) <rppt@kernel.org>
---
arch/Kconfig | 2 +-
include/linux/module.h | 9 ++++++
kernel/kprobes.c | 55 +++++++++++++++++++++++--------------
kernel/trace/trace_kprobe.c | 20 +++++++++++++-
4 files changed, 63 insertions(+), 23 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 7006f71f0110..a48ce6a488b3 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -52,9 +52,9 @@ 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/include/linux/module.h b/include/linux/module.h
index 1153b0d99a80..ffa1c603163c 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -605,6 +605,11 @@ static inline bool module_is_live(struct module *mod)
return mod->state != MODULE_STATE_GOING;
}

+static inline bool module_is_coming(struct module *mod)
+{
+ return mod->state == MODULE_STATE_COMING;
+}
+
struct module *__module_text_address(unsigned long addr);
struct module *__module_address(unsigned long addr);
bool is_module_address(unsigned long addr);
@@ -857,6 +862,10 @@ void *dereference_module_function_descriptor(struct module *mod, void *ptr)
return ptr;
}

+static inline bool module_is_coming(struct module *mod)
+{
+ return false;
+}
#endif /* CONFIG_MODULES */

#ifdef CONFIG_SYSFS
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index ddd7cdc16edf..ca2c6cbd42d2 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1588,7 +1588,7 @@ static int check_kprobe_address_safe(struct kprobe *p,
}

/* Get module refcount and reject __init functions for loaded modules. */
- if (*probed_mod) {
+ if (IS_ENABLED(CONFIG_MODULES) && *probed_mod) {
/*
* We must hold a refcount of the probed module while updating
* its code to prohibit unexpected unloading.
@@ -1603,12 +1603,13 @@ static int check_kprobe_address_safe(struct kprobe *p,
* kprobes in there.
*/
if (within_module_init((unsigned long)p->addr, *probed_mod) &&
- (*probed_mod)->state != MODULE_STATE_COMING) {
+ !module_is_coming(*probed_mod)) {
module_put(*probed_mod);
*probed_mod = NULL;
ret = -ENOENT;
}
}
+
out:
preempt_enable();
jump_label_unlock();
@@ -2488,24 +2489,6 @@ 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)
{
@@ -2570,6 +2553,25 @@ 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;
@@ -2672,6 +2674,17 @@ static struct notifier_block kprobe_module_nb = {
.priority = 0
};

+static int kprobe_register_module_notifier(void)
+{
+ return register_module_notifier(&kprobe_module_nb);
+}
+#else
+static int kprobe_register_module_notifier(void)
+{
+ return 0;
+}
+#endif /* CONFIG_MODULES */
+
void kprobe_free_init_mem(void)
{
void *start = (void *)(&__init_begin);
@@ -2731,7 +2744,7 @@ static int __init init_kprobes(void)
if (!err)
err = register_die_notifier(&kprobe_exceptions_nb);
if (!err)
- err = register_module_notifier(&kprobe_module_nb);
+ err = kprobe_register_module_notifier();

kprobes_initialized = (err == 0);
kprobe_sysctls_init();
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 14099cc17fc9..2cb2a3951b4f 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 +712,16 @@ static struct notifier_block trace_kprobe_module_nb = {
.notifier_call = trace_kprobe_module_callback,
.priority = 1 /* Invoked after kprobe module callback */
};
+static int trace_kprobe_register_module_notifier(void)
+{
+ return register_module_notifier(&trace_kprobe_module_nb);
+}
+#else
+static int trace_kprobe_register_module_notifier(void)
+{
+ return 0;
+}
+#endif /* CONFIG_MODULES */

static int count_symbols(void *data, unsigned long unused)
{
@@ -1933,7 +1951,7 @@ static __init int init_kprobe_trace_early(void)
if (ret)
return ret;

- if (register_module_notifier(&trace_kprobe_module_nb))
+ if (trace_kprobe_register_module_notifier())
return -EINVAL;

return 0;