objtool: Move noreturn function list to separate file

This makes it a little cleaner and easier to maintain.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lore.kernel.org/r/cecacf07a69a244c74474c18b7652627de67a528.1681853186.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

tools/objtool/Documentation/objtool.txt

@@ -306,9 +306,8 @@ the objtool maintainers.
 3. file.o: warning: objtool: foo+0x48c: bar() is missing a __noreturn annotation
 
    The call from foo() to bar() doesn't return, but bar() is missing the
-   __noreturn annotation.  NOTE: In addition to adding the __noreturn
-   annotation, the function name also needs to be added to
-   'global_noreturns' in tools/objtool/check.c.
+   __noreturn annotation.  NOTE: In addition to annotating the function
+   with __noreturn, please also add it to tools/objtool/noreturns.h.
 
 4. file.o: warning: objtool: func(): can't find starting instruction
    or

tools/objtool/check.c

@@ -192,49 +192,11 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 	struct instruction *insn;
 	bool empty = true;
 
-	/*
-	 * Unfortunately these have to be hard coded because the noreturn
-	 * attribute isn't provided in ELF data. Keep 'em sorted.
-	 */
+#define NORETURN(func) __stringify(func),
 	static const char * const global_noreturns[] = {
-		"__invalid_creds",
-		"__module_put_and_kthread_exit",
-		"__reiserfs_panic",
-		"__stack_chk_fail",
-		"__ubsan_handle_builtin_unreachable",
-		"arch_call_rest_init",
-		"arch_cpu_idle_dead",
-		"btrfs_assertfail",
-		"cpu_bringup_and_idle",
-		"cpu_startup_entry",
-		"do_exit",
-		"do_group_exit",
-		"do_task_dead",
-		"ex_handler_msr_mce",
-		"fortify_panic",
-		"hlt_play_dead",
-		"hv_ghcb_terminate",
-		"kthread_complete_and_exit",
-		"kthread_exit",
-		"kunit_try_catch_throw",
-		"machine_real_restart",
-		"make_task_dead",
-		"mpt_halt_firmware",
-		"nmi_panic_self_stop",
-		"panic",
-		"panic_smp_self_stop",
-		"rest_init",
-		"rewind_stack_and_make_dead",
-		"sev_es_terminate",
-		"snp_abort",
-		"start_kernel",
-		"stop_this_cpu",
-		"usercopy_abort",
-		"x86_64_start_kernel",
-		"x86_64_start_reservations",
-		"xen_cpu_bringup_again",
-		"xen_start_kernel",
+#include "noreturns.h"
 	};
+#undef NORETURN
 
 	if (!func)
 		return false;

tools/objtool/noreturns.h

@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * This is a (sorted!) list of all known __noreturn functions in the kernel.
+ * It's needed for objtool to properly reverse-engineer the control flow graph.
+ *
+ * Yes, this is unfortunate.  A better solution is in the works.
+ */
+NORETURN(__invalid_creds)
+NORETURN(__module_put_and_kthread_exit)
+NORETURN(__reiserfs_panic)
+NORETURN(__stack_chk_fail)
+NORETURN(__ubsan_handle_builtin_unreachable)
+NORETURN(arch_call_rest_init)
+NORETURN(arch_cpu_idle_dead)
+NORETURN(btrfs_assertfail)
+NORETURN(cpu_bringup_and_idle)
+NORETURN(cpu_startup_entry)
+NORETURN(do_exit)
+NORETURN(do_group_exit)
+NORETURN(do_task_dead)
+NORETURN(ex_handler_msr_mce)
+NORETURN(fortify_panic)
+NORETURN(hlt_play_dead)
+NORETURN(hv_ghcb_terminate)
+NORETURN(kthread_complete_and_exit)
+NORETURN(kthread_exit)
+NORETURN(kunit_try_catch_throw)
+NORETURN(machine_real_restart)
+NORETURN(make_task_dead)
+NORETURN(mpt_halt_firmware)
+NORETURN(nmi_panic_self_stop)
+NORETURN(panic)
+NORETURN(panic_smp_self_stop)
+NORETURN(rest_init)
+NORETURN(rewind_stack_and_make_dead)
+NORETURN(sev_es_terminate)
+NORETURN(snp_abort)
+NORETURN(start_kernel)
+NORETURN(stop_this_cpu)
+NORETURN(usercopy_abort)
+NORETURN(x86_64_start_kernel)
+NORETURN(x86_64_start_reservations)
+NORETURN(xen_cpu_bringup_again)
+NORETURN(xen_start_kernel)