static_call: Add call depth tracking support

When indirect calls are switched to direct calls then it has to be ensured
that the call target is not the function, but the call thunk when call
depth tracking is enabled. But static calls are available before call
thunks have been set up.

Ensure a second run through the static call patching code after call thunks
have been created. When call thunks are not enabled this has no side
effects.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220915111148.306100465@infradead.org

5 files changed, 44 insertions, 5 deletions

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 4c416b21bac8..07ac25793a3f 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -91,11 +91,16 @@ struct callthunk_sites {
 extern void callthunks_patch_builtin_calls(void);
 extern void callthunks_patch_module_calls(struct callthunk_sites *sites,
 					  struct module *mod);
+extern void *callthunks_translate_call_dest(void *dest);
 #else
 static __always_inline void callthunks_patch_builtin_calls(void) {}
 static __always_inline void
 callthunks_patch_module_calls(struct callthunk_sites *sites,
 			      struct module *mod) {}
+static __always_inline void *callthunks_translate_call_dest(void *dest)
+{
+	return dest;
+}
 #endif
 
 #ifdef CONFIG_SMP
diff --git a/arch/x86/kernel/callthunks.c b/arch/x86/kernel/callthunks.c
index dfe7ffff88b9..071003605a86 100644
--- a/arch/x86/kernel/callthunks.c
+++ b/arch/x86/kernel/callthunks.c
@@ -6,6 +6,7 @@
 #include <linux/kallsyms.h>
 #include <linux/memory.h>
 #include <linux/moduleloader.h>
+#include <linux/static_call.h>
 
 #include <asm/alternative.h>
 #include <asm/asm-offsets.h>
@@ -271,10 +272,27 @@ void __init callthunks_patch_builtin_calls(void)
 	pr_info("Setting up call depth tracking\n");
 	mutex_lock(&text_mutex);
 	callthunks_setup(&cs, &builtin_coretext);
+	static_call_force_reinit();
 	thunks_initialized = true;
 	mutex_unlock(&text_mutex);
 }
 
+void *callthunks_translate_call_dest(void *dest)
+{
+	void *target;
+
+	lockdep_assert_held(&text_mutex);
+
+	if (!thunks_initialized || skip_addr(dest))
+		return dest;
+
+	if (!is_coretext(NULL, dest))
+		return dest;
+
+	target = patch_dest(dest, false);
+	return target ? : dest;
+}
+
 #ifdef CONFIG_MODULES
 void noinline callthunks_patch_module_calls(struct callthunk_sites *cs,
 					    struct module *mod)
diff --git a/arch/x86/kernel/static_call.c b/arch/x86/kernel/static_call.c
index 5d3844a98373..2ebc338980bc 100644
--- a/arch/x86/kernel/static_call.c
+++ b/arch/x86/kernel/static_call.c
@@ -34,6 +34,7 @@ static void __ref __static_call_transform(void *insn, enum insn_type type,
 
 	switch (type) {
 	case CALL:
+		func = callthunks_translate_call_dest(func);
 		code = text_gen_insn(CALL_INSN_OPCODE, insn, func);
 		if (func == &__static_call_return0) {
 			emulate = code;
diff --git a/include/linux/static_call.h b/include/linux/static_call.h
index df53bed9d71f..141e6b176a1b 100644
--- a/include/linux/static_call.h
+++ b/include/linux/static_call.h
@@ -162,6 +162,8 @@ extern void arch_static_call_transform(void *site, void *tramp, void *func, bool
 
 extern int __init static_call_init(void);
 
+extern void static_call_force_reinit(void);
+
 struct static_call_mod {
 	struct static_call_mod *next;
 	struct module *mod; /* for vmlinux, mod == NULL */
diff --git a/kernel/static_call_inline.c b/kernel/static_call_inline.c
index dc5665b62814..639397b5491c 100644
--- a/kernel/static_call_inline.c
+++ b/kernel/static_call_inline.c
@@ -15,7 +15,18 @@ extern struct static_call_site __start_static_call_sites[],
 extern struct static_call_tramp_key __start_static_call_tramp_key[],
 				    __stop_static_call_tramp_key[];
 
-static bool static_call_initialized;
+static int static_call_initialized;
+
+/*
+ * Must be called before early_initcall() to be effective.
+ */
+void static_call_force_reinit(void)
+{
+	if (WARN_ON_ONCE(!static_call_initialized))
+		return;
+
+	static_call_initialized++;
+}
 
 /* mutex to protect key modules/sites */
 static DEFINE_MUTEX(static_call_mutex);
@@ -475,7 +486,8 @@ int __init static_call_init(void)
 {
 	int ret;
 
-	if (static_call_initialized)
+	/* See static_call_force_reinit(). */
+	if (static_call_initialized == 1)
 		return 0;
 
 	cpus_read_lock();
@@ -490,11 +502,12 @@ int __init static_call_init(void)
 		BUG();
 	}
 
-	static_call_initialized = true;
-
 #ifdef CONFIG_MODULES
-	register_module_notifier(&static_call_module_nb);
+	if (!static_call_initialized)
+		register_module_notifier(&static_call_module_nb);
 #endif
+
+	static_call_initialized = 1;
 	return 0;
 }
 early_initcall(static_call_init);