[tip: sched/core] sched: Harden PREEMPT_DYNAMIC

[tip-bot2 for Peter Zijlstra]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     355b3a57ddba71b73a99aa249a99aed6ed904606
Gitweb:        https://git.kernel.org/tip/355b3a57ddba71b73a99aa249a99aed6ed904606
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Mon, 25 Jan 2021 16:26:50 +01:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 09 Feb 2021 16:31:03 +01:00

sched: Harden PREEMPT_DYNAMIC

Use the new EXPORT_STATIC_CALL_TRAMP() / static_call_mod() to unexport
the static_call_key for the PREEMPT_DYNAMIC calls such that modules
can no longer update these calls.

Having modules change/hi-jack the preemption calls would be horrible.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 arch/x86/include/asm/preempt.h | 4 ++--
 include/linux/kernel.h         | 2 +-
 include/linux/sched.h          | 2 +-
 kernel/sched/core.c            | 8 ++++----
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h
index 9b12dce..0aa96f8 100644
--- a/arch/x86/include/asm/preempt.h
+++ b/arch/x86/include/asm/preempt.h
@@ -114,7 +114,7 @@ DECLARE_STATIC_CALL(preempt_schedule, __preempt_schedule_func);
 
 #define __preempt_schedule() \
 do { \
-	__ADDRESSABLE(STATIC_CALL_KEY(preempt_schedule)); \
+	__STATIC_CALL_MOD_ADDRESSABLE(preempt_schedule); \
 	asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule) : ASM_CALL_CONSTRAINT); \
 } while (0)
 
@@ -127,7 +127,7 @@ DECLARE_STATIC_CALL(preempt_schedule_notrace, __preempt_schedule_notrace_func);
 
 #define __preempt_schedule_notrace() \
 do { \
-	__ADDRESSABLE(STATIC_CALL_KEY(preempt_schedule_notrace)); \
+	__STATIC_CALL_MOD_ADDRESSABLE(preempt_schedule_notrace); \
 	asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule_notrace) : ASM_CALL_CONSTRAINT); \
 } while (0)
 
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index cfd3d34..5b7ed6d 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -93,7 +93,7 @@ DECLARE_STATIC_CALL(might_resched, __cond_resched);
 
 static __always_inline void might_resched(void)
 {
-	static_call(might_resched)();
+	static_call_mod(might_resched)();
 }
 
 #else
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2f35594..4d56828 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1880,7 +1880,7 @@ DECLARE_STATIC_CALL(cond_resched, __cond_resched);
 
 static __always_inline int _cond_resched(void)
 {
-	return static_call(cond_resched)();
+	return static_call_mod(cond_resched)();
 }
 
 #else
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index cb226f7..d93d02b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5253,7 +5253,7 @@ EXPORT_SYMBOL(preempt_schedule);
 
 #ifdef CONFIG_PREEMPT_DYNAMIC
 DEFINE_STATIC_CALL(preempt_schedule, __preempt_schedule_func);
-EXPORT_STATIC_CALL(preempt_schedule);
+EXPORT_STATIC_CALL_TRAMP(preempt_schedule);
 #endif
 
 
@@ -5311,7 +5311,7 @@ EXPORT_SYMBOL_GPL(preempt_schedule_notrace);
 
 #ifdef CONFIG_PREEMPT_DYNAMIC
 DEFINE_STATIC_CALL(preempt_schedule_notrace, __preempt_schedule_notrace_func);
-EXPORT_STATIC_CALL(preempt_schedule_notrace);
+EXPORT_STATIC_CALL_TRAMP(preempt_schedule_notrace);
 #endif
 
 #endif /* CONFIG_PREEMPTION */
@@ -6983,10 +6983,10 @@ EXPORT_SYMBOL(__cond_resched);
 
 #ifdef CONFIG_PREEMPT_DYNAMIC
 DEFINE_STATIC_CALL_RET0(cond_resched, __cond_resched);
-EXPORT_STATIC_CALL(cond_resched);
+EXPORT_STATIC_CALL_TRAMP(cond_resched);
 
 DEFINE_STATIC_CALL_RET0(might_resched, __cond_resched);
-EXPORT_STATIC_CALL(might_resched);
+EXPORT_STATIC_CALL_TRAMP(might_resched);
 #endif
 
 /*