A set of objtool fixes:

- Handle __ubsan_handle_builtin_unreachable() correctly and treat it as
     noreturn.
 
   - Allow architectures to select uaccess validation
 
   - Use the non-instrumented bit test for test_cpu_has() to prevent escape
     from non-instrumentable regions.
 
   - Use arch_ prefixed atomics for JUMP_LABEL=n builds to prevent escape
     from non-instrumentable regions.
 
   - Mark a few tiny inline as __always_inline to prevent GCC from bringing
     them out of line and instrumenting them.
 
   - Mark the empty stub context_tracking_enabled() as always inline as GCC
     brings them out of line and instruments the empty shell.
 
   - Annotate ex_handler_msr_mce() as dead end
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Merge tag 'objtool-urgent-2022-06-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull objtool fixes from Thomas Gleixner:

 - Handle __ubsan_handle_builtin_unreachable() correctly and treat it as
   noreturn

 - Allow architectures to select uaccess validation

 - Use the non-instrumented bit test for test_cpu_has() to prevent
   escape from non-instrumentable regions

 - Use arch_ prefixed atomics for JUMP_LABEL=n builds to prevent escape
   from non-instrumentable regions

 - Mark a few tiny inline as __always_inline to prevent GCC from
   bringing them out of line and instrumenting them

 - Mark the empty stub context_tracking_enabled() as always inline as
   GCC brings them out of line and instruments the empty shell

 - Annotate ex_handler_msr_mce() as dead end

* tag 'objtool-urgent-2022-06-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/extable: Annotate ex_handler_msr_mce() as a dead end
  context_tracking: Always inline empty stubs
  x86: Always inline on_thread_stack() and current_top_of_stack()
  jump_label,noinstr: Avoid instrumentation for JUMP_LABEL=n builds
  x86/cpu: Elide KCSAN for cpu_has() and friends
  objtool: Mark __ubsan_handle_builtin_unreachable() as noreturn
  objtool: Add CONFIG_HAVE_UACCESS_VALIDATION

arch/Kconfig

@@ -1048,6 +1048,10 @@ config HAVE_NOINSTR_HACK
 config HAVE_NOINSTR_VALIDATION
 	bool
 
+config HAVE_UACCESS_VALIDATION
+	bool
+	select OBJTOOL
+
 config HAVE_STACK_VALIDATION
 	bool
 	help

arch/x86/Kconfig

@@ -258,6 +258,7 @@ config X86
 	select HAVE_PREEMPT_DYNAMIC_CALL
 	select HAVE_RSEQ
 	select HAVE_SYSCALL_TRACEPOINTS
+	select HAVE_UACCESS_VALIDATION		if HAVE_OBJTOOL
 	select HAVE_UNSTABLE_SCHED_CLOCK
 	select HAVE_USER_RETURN_NOTIFIER
 	select HAVE_GENERIC_VDSO

arch/x86/include/asm/cpufeature.h

@@ -54,7 +54,7 @@ extern const char * const x86_power_flags[32];
 extern const char * const x86_bug_flags[NBUGINTS*32];
 
 #define test_cpu_cap(c, bit)						\
-	 test_bit(bit, (unsigned long *)((c)->x86_capability))
+	 arch_test_bit(bit, (unsigned long *)((c)->x86_capability))
 
 /*
  * There are 32 bits/features in each mask word.  The high bits

arch/x86/include/asm/extable.h

@@ -42,9 +42,13 @@ extern int ex_get_fixup_type(unsigned long ip);
 extern void early_fixup_exception(struct pt_regs *regs, int trapnr);
 
 #ifdef CONFIG_X86_MCE
-extern void ex_handler_msr_mce(struct pt_regs *regs, bool wrmsr);
+extern void __noreturn ex_handler_msr_mce(struct pt_regs *regs, bool wrmsr);
 #else
-static inline void ex_handler_msr_mce(struct pt_regs *regs, bool wrmsr) { }
+static inline void __noreturn ex_handler_msr_mce(struct pt_regs *regs, bool wrmsr)
+{
+	for (;;)
+		cpu_relax();
+}
 #endif
 
 #if defined(CONFIG_BPF_JIT) && defined(CONFIG_X86_64)

arch/x86/include/asm/processor.h

@@ -559,7 +559,7 @@ static __always_inline void native_swapgs(void)
 #endif
 }
 
-static inline unsigned long current_top_of_stack(void)
+static __always_inline unsigned long current_top_of_stack(void)
 {
 	/*
 	 *  We can't read directly from tss.sp0: sp0 on x86_32 is special in
@@ -569,7 +569,7 @@ static inline unsigned long current_top_of_stack(void)
 	return this_cpu_read_stable(cpu_current_top_of_stack);
 }
 
-static inline bool on_thread_stack(void)
+static __always_inline bool on_thread_stack(void)
 {
 	return (unsigned long)(current_top_of_stack() -
 			       current_stack_pointer) < THREAD_SIZE;

include/linux/context_tracking_state.h

@@ -46,10 +46,10 @@ static __always_inline bool context_tracking_in_user(void)
 	return __this_cpu_read(context_tracking.state) == CONTEXT_USER;
 }
 #else
-static inline bool context_tracking_in_user(void) { return false; }
+static __always_inline bool context_tracking_in_user(void) { return false; }
-static inline bool context_tracking_enabled(void) { return false; }
+static __always_inline bool context_tracking_enabled(void) { return false; }
-static inline bool context_tracking_enabled_cpu(int cpu) { return false; }
+static __always_inline bool context_tracking_enabled_cpu(int cpu) { return false; }
-static inline bool context_tracking_enabled_this_cpu(void) { return false; }
+static __always_inline bool context_tracking_enabled_this_cpu(void) { return false; }
 #endif /* CONFIG_CONTEXT_TRACKING */
 
 #endif

include/linux/jump_label.h

@@ -256,9 +256,9 @@ extern void static_key_disable_cpuslocked(struct static_key *key);
 #include <linux/atomic.h>
 #include <linux/bug.h>
 
-static inline int static_key_count(struct static_key *key)
+static __always_inline int static_key_count(struct static_key *key)
 {
-	return atomic_read(&key->enabled);
+	return arch_atomic_read(&key->enabled);
 }
 
 static __always_inline void jump_label_init(void)

scripts/Makefile.lib

@@ -239,7 +239,7 @@ objtool_args =								\
 	$(if $(CONFIG_SLS), --sls)					\
 	$(if $(CONFIG_STACK_VALIDATION), --stackval)			\
 	$(if $(CONFIG_HAVE_STATIC_CALL_INLINE), --static-call)		\
-	--uaccess							\
+	$(if $(CONFIG_HAVE_UACCESS_VALIDATION), --uaccess)		\
 	$(if $(delay-objtool), --link)					\
 	$(if $(part-of-module), --module)				\
 	$(if $(CONFIG_GCOV_KERNEL), --no-unreachable)

tools/objtool/check.c

@@ -186,6 +186,8 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 		"stop_this_cpu",
 		"__invalid_creds",
 		"cpu_startup_entry",
+		"__ubsan_handle_builtin_unreachable",
+		"ex_handler_msr_mce",
 	};
 
 	if (!func)