[v2,12/12] kprobes: remove dependcy on CONFIG_MODULES

Commit Message

Mike Rapoport June 16, 2023, 8:50 a.m. UTC

From: "Mike Rapoport (IBM)" <[e-mail]>

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) <[e-mail]>
---
 arch/Kconfig                |  2 +-
 kernel/kprobes.c            | 43 +++++++++++++++++++++----------------
 kernel/trace/trace_kprobe.c | 11 ++++++++++
 3 files changed, 37 insertions(+), 19 deletions(-)

Comments

Björn Töpel June 16, 2023, 11:44 a.m. UTC | #1

Mike Rapoport <[e-mail]> writes:

> From: "Mike Rapoport (IBM)" <[e-mail]>
>
> kprobes depended on CONFIG_MODULES because it has to allocate memory for
> code.

I think you can remove the MODULES dependency from BPF_JIT as well:

--8<--
diff --git a/kernel/bpf/Kconfig b/kernel/bpf/Kconfig
index 2dfe1079f772..fa4587027f8b 100644
--- a/kernel/bpf/Kconfig
+++ b/kernel/bpf/Kconfig
@@ -41,7 +41,6 @@ config BPF_JIT
        bool "Enable BPF Just In Time compiler"
        depends on BPF
        depends on HAVE_CBPF_JIT || HAVE_EBPF_JIT
-       depends on MODULES
        help
          BPF programs are normally handled by a BPF interpreter. This option
          allows the kernel to generate native code when a program is loaded
--8<--


Björn

Mike Rapoport June 17, 2023, 6:52 a.m. UTC | #2

On Fri, Jun 16, 2023 at 01:44:55PM +0200, Björn Töpel wrote:
> Mike Rapoport <[e-mail]> writes:
> 
> > From: "Mike Rapoport (IBM)" <[e-mail]>
> >
> > kprobes depended on CONFIG_MODULES because it has to allocate memory for
> > code.
> 
> I think you can remove the MODULES dependency from BPF_JIT as well:

Yeah, I think so. Thanks!
 
> --8<--
> diff --git a/kernel/bpf/Kconfig b/kernel/bpf/Kconfig
> index 2dfe1079f772..fa4587027f8b 100644
> --- a/kernel/bpf/Kconfig
> +++ b/kernel/bpf/Kconfig
> @@ -41,7 +41,6 @@ config BPF_JIT
>         bool "Enable BPF Just In Time compiler"
>         depends on BPF
>         depends on HAVE_CBPF_JIT || HAVE_EBPF_JIT
> -       depends on MODULES
>         help
>           BPF programs are normally handled by a BPF interpreter. This option
>           allows the kernel to generate native code when a program is loaded
> --8<--
> 
> 
> Björn

Patch

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;
 }