Patch "entry: Fix noinstr warning in __enter_from_user_mode()" has been added to the 6.2-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    entry: Fix noinstr warning in __enter_from_user_mode()

to the 6.2-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     entry-fix-noinstr-warning-in-__enter_from_user_mode.patch
and it can be found in the queue-6.2 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 2895d155feb7bfa517e4558f918950880b63e3aa
Author: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Date:   Sat Feb 25 16:01:36 2023 -0800

    entry: Fix noinstr warning in __enter_from_user_mode()
    
    [ Upstream commit f87d28673b71b35b248231a2086f9404afbb7f28 ]
    
    __enter_from_user_mode() is triggering noinstr warnings with
    CONFIG_DEBUG_PREEMPT due to its call of preempt_count_add() via
    ct_state().
    
    The preemption disable isn't needed as interrupts are already disabled.
    And the context_tracking_enabled() check in ct_state() also isn't needed
    as that's already being done by the CT_WARN_ON().
    
    Just use __ct_state() instead.
    
    Fixes the following warnings:
    
      vmlinux.o: warning: objtool: enter_from_user_mode+0xba: call to preempt_count_add() leaves .noinstr.text section
      vmlinux.o: warning: objtool: syscall_enter_from_user_mode+0xf9: call to preempt_count_add() leaves .noinstr.text section
      vmlinux.o: warning: objtool: syscall_enter_from_user_mode_prepare+0xc7: call to preempt_count_add() leaves .noinstr.text section
      vmlinux.o: warning: objtool: irqentry_enter_from_user_mode+0xba: call to preempt_count_add() leaves .noinstr.text section
    
    Fixes: 171476775d32 ("context_tracking: Convert state to atomic_t")
    Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
    Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/d8955fa6d68dc955dda19baf13ae014ae27926f5.1677369694.git.jpoimboe@xxxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index d4afa8508a806..3a7909ed54980 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -96,6 +96,7 @@ static inline void user_exit_irqoff(void) { }
 static inline int exception_enter(void) { return 0; }
 static inline void exception_exit(enum ctx_state prev_ctx) { }
 static inline int ct_state(void) { return -1; }
+static inline int __ct_state(void) { return -1; }
 static __always_inline bool context_tracking_guest_enter(void) { return false; }
 static inline void context_tracking_guest_exit(void) { }
 #define CT_WARN_ON(cond) do { } while (0)
diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
index 4a4d56f771802..fdd537ea513ff 100644
--- a/include/linux/context_tracking_state.h
+++ b/include/linux/context_tracking_state.h
@@ -46,7 +46,9 @@ struct context_tracking {
 
 #ifdef CONFIG_CONTEXT_TRACKING
 DECLARE_PER_CPU(struct context_tracking, context_tracking);
+#endif
 
+#ifdef CONFIG_CONTEXT_TRACKING_USER
 static __always_inline int __ct_state(void)
 {
 	return arch_atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_STATE_MASK;
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index 846add8394c41..1314894d2efad 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -21,7 +21,7 @@ static __always_inline void __enter_from_user_mode(struct pt_regs *regs)
 	arch_enter_from_user_mode(regs);
 	lockdep_hardirqs_off(CALLER_ADDR0);
 
-	CT_WARN_ON(ct_state() != CONTEXT_USER);
+	CT_WARN_ON(__ct_state() != CONTEXT_USER);
 	user_exit_irqoff();
 
 	instrumentation_begin();