x86/head: Mark *_start_kernel() __noreturn

Now that start_kernel() is __noreturn, mark its chain of callers
__noreturn.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/c2525f96b88be98ee027ee0291d58003036d4120.1681342859.git.jpoimboe@kernel.org

arch/x86/include/asm/setup.h

@@ -125,11 +125,11 @@ void clear_bss(void);
 
 #ifdef __i386__
 
-asmlinkage void __init i386_start_kernel(void);
+asmlinkage void __init __noreturn i386_start_kernel(void);
 
 #else
-asmlinkage void __init x86_64_start_kernel(char *real_mode);
-asmlinkage void __init x86_64_start_reservations(char *real_mode_data);
+asmlinkage void __init __noreturn x86_64_start_kernel(char *real_mode);
+asmlinkage void __init __noreturn x86_64_start_reservations(char *real_mode_data);
 
 #endif /* __i386__ */
 #endif /* _SETUP */

arch/x86/kernel/head32.c

@@ -29,7 +29,7 @@ static void __init i386_default_early_setup(void)
 	x86_init.mpparse.setup_ioapic_ids = setup_ioapic_ids_from_mpc;
 }
 
-asmlinkage __visible void __init i386_start_kernel(void)
+asmlinkage __visible void __init __noreturn i386_start_kernel(void)
 {
 	/* Make sure IDT is set up before any exception happens */
 	idt_setup_early_handler();

arch/x86/kernel/head64.c

@@ -471,7 +471,7 @@ static void __init copy_bootdata(char *real_mode_data)
 	sme_unmap_bootdata(real_mode_data);
 }
 
-asmlinkage __visible void __init x86_64_start_kernel(char * real_mode_data)
+asmlinkage __visible void __init __noreturn x86_64_start_kernel(char * real_mode_data)
 {
 	/*
 	 * Build-time sanity checks on the kernel image and module
@@ -537,7 +537,7 @@ asmlinkage __visible void __init x86_64_start_kernel(char * real_mode_data)
 	x86_64_start_reservations(real_mode_data);
 }
 
-void __init x86_64_start_reservations(char *real_mode_data)
+void __init __noreturn x86_64_start_reservations(char *real_mode_data)
 {
 	/* version is always not zero if it is copied */
 	if (!boot_params.hdr.version)

tools/objtool/check.c

@@ -225,6 +225,8 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 		"start_kernel",
 		"stop_this_cpu",
 		"usercopy_abort",
+		"x86_64_start_kernel",
+		"x86_64_start_reservations",
 		"xen_cpu_bringup_again",
 		"xen_start_kernel",
 	};