objtool: dynamically detect noreturns

index 0e9dfd0a2446c..72ffa71aa19b8 100644
@@ -18,9 +18,6 @@ NORETURN(__x64_sys_exit)
 NORETURN(__x64_sys_exit_group)
 NORETURN(acpi_processor_ffh_play_dead)
 NORETURN(arch_cpu_idle_dead)
-NORETURN(bch2_trans_in_restart_error)
-NORETURN(bch2_trans_restart_error)
-NORETURN(bch2_trans_unlocked_or_in_restart_error)
 NORETURN(cpu_bringup_and_idle)
 NORETURN(cpu_startup_entry)
 NORETURN(do_exit)

@@ -31,7 +28,6 @@ NORETURN(ex_handler_msr_mce)
 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)

@@ -44,7 +40,6 @@ NORETURN(vpanic)
 NORETURN(panic_smp_self_stop)
 NORETURN(rest_init)
 NORETURN(rewind_stack_and_make_dead)
-NORETURN(rust_begin_unwind)
 NORETURN(rust_helper_BUG)
 NORETURN(sev_es_terminate)
 NORETURN(start_kernel)

index 464f6c9d9ff0b..1fe7efa934ebf 100644
@@ -274,30 +274,31 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 		return false;
 
 	/*
-	 * A function can have a sibling call instead of a return.  In that
-	 * case, the function's dead-end status depends on whether the target
-	 * of the sibling call returns.
+	 * A function can have sibling calls instead of a return.  It's only a
+	 * dead end if *all* the sibling call targets are dead ends.
 	 */
 	func_for_each_insn(file, func, insn) {
-		if (is_sibling_call(insn)) {
-			struct instruction *dest = insn->jump_dest;
+		struct symbol *dest;
 
-			if (!dest)
-				/* sibling call to another file */
-				return false;
+		if (!is_sibling_call(insn))
+			continue;
 
-			/* local sibling call */
-			if (recursion == 5) {
-				/*
-				 * Infinite recursion: two functions have
-				 * sibling calls to each other.  This is a very
-				 * rare case.  It means they aren't dead ends.
-				 */
-				return false;
-			}
+		dest = insn_call_dest(insn);
+		if (!dest)
+			/* call to another file */
+			return false;
 
-			return __dead_end_function(file, insn_func(dest), recursion+1);
+		if (recursion == 5) {
+			/*
+			 * Infinite recursion: two functions have sibling
+			 * calls to each other.  This is a very rare case.
+			 * It means they aren't dead ends.
+			 */
+			return false;
 		}
+
+		if (!__dead_end_function(file, dest, recursion+1))
+			return false;
 	}
 
 	return true;

index 1fe7efa934ebf..83b4e748d33ba 100644
@@ -219,94 +219,112 @@ static bool is_rust_noreturn(const struct symbol *func)
 		str_ends_with(func->name, "_fail"));
 }
 
-/*
- * This checks to see if the given function is a "noreturn" function.
- *
- * For global functions which are outside the scope of this object file, we
- * have to keep a manual list of them.
- *
- * For local functions, we have to detect them manually by simply looking for
- * the lack of a return instruction.
- */
-static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
-				int recursion)
+static bool is_listed_noreturn(struct symbol *func)
 {
-	int i;
-	struct instruction *insn;
-	bool empty = true;
-
 #define NORETURN(func) __stringify(func),
 	static const char * const global_noreturns[] = {
 #include "noreturns.h"
 	};
 #undef NORETURN
 
-	if (!func)
+	if (is_local_sym(func))
 		return false;
 
-	if (!is_local_sym(func)) {
-		if (is_rust_noreturn(func))
+	if (is_rust_noreturn(func))
+		return true;
+
+	for (int i = 0; i < ARRAY_SIZE(global_noreturns); i++)
+		if (!strcmp(func->name, global_noreturns[i]))
 			return true;
 
-		for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
-			if (!strcmp(func->name, global_noreturns[i]))
-				return true;
-	}
+	return false;
+}
+
+/*
+ * Use this rather than reading sym->_noreturn directly: the noreturn status
+ * lives on the primary alias, and ANNOTATE_IGNORE_NORETURN() overrides it.
+ */
+static bool is_noreturn(struct symbol *func)
+{
+	func = func->alias->pfunc;
+
+	if (is_listed_noreturn(func))
+		return true;
+
+	return func->_noreturn;
+}
+
+static bool might_return(struct objtool_file *file, struct symbol *func)
+{
+	struct instruction *insn;
+	struct symbol *dest;
 
 	if (is_weak_sym(func))
-		return false;
-
-	if (!func->len)
-		return false;
-
-	insn = find_insn(file, func->sec, func->offset);
-	if (!insn || !insn_func(insn))
-		return false;
+		return true;
 
 	func_for_each_insn(file, func, insn) {
-		empty = false;
-
 		if (insn->type == INSN_RETURN)
-			return false;
-	}
-
-	if (empty)
-		return false;
-
-	/*
-	 * A function can have sibling calls instead of a return.  It's only a
-	 * dead end if *all* the sibling call targets are dead ends.
-	 */
-	func_for_each_insn(file, func, insn) {
-		struct symbol *dest;
+			return true;
 
 		if (!is_sibling_call(insn))
 			continue;
 
 		dest = insn_call_dest(insn);
-		if (!dest)
-			/* call to another file */
-			return false;
-
-		if (recursion == 5) {
-			/*
-			 * Infinite recursion: two functions have sibling
-			 * calls to each other.  This is a very rare case.
-			 * It means they aren't dead ends.
-			 */
-			return false;
-		}
-
-		if (!__dead_end_function(file, dest, recursion+1))
-			return false;
+		if (!dest || !is_noreturn(dest))
+			return true;
 	}
 
-	return true;
+	return false;
 }
 
-static bool dead_end_function(struct objtool_file *file, struct symbol *func)
+static void detect_noreturns(struct objtool_file *file)
 {
-	return __dead_end_function(file, func, 0);
+	struct symbol *func, *dest;
+	struct instruction *insn;
+	bool changed;
+
+	/* Mark all functions guilty until proven innocent */
+	for_each_sym(file->elf, func) {
+
+		/* Aliases and cold subfunctions inherit the parent's verdict */
+		if (!is_func_sym(func) || is_undef_sym(func) ||
+		    is_prefix_func(func) || func->embedded_insn ||
+		    func != func->alias->pfunc)
+			continue;
+
+		insn = find_insn(file, func->sec, func->offset);
+		if (!insn || insn_func(insn) != func)
+			continue;
+
+		func->_noreturn = 1;
+	}
+
+	/*
+	 * A function's noreturn status depends on those of its sibling call
+	 * destinations, which may not be settled yet.  Keep clearing the
+	 * noreturn bit for known cases until it stops spreading.
+	 */
+	do {
+		changed = false;
+
+		for_each_sym(file->elf, func) {
+			if (!func->_noreturn || !might_return(file, func))
+				continue;
+
+			func->_noreturn = 0;
+			changed = true;
+		}
+	} while (changed);
+
+	/* Now mark the dead end call sites */
+	for_each_insn(file, insn) {
+		if (insn->type != INSN_CALL)
+			continue;
+
+		dest = insn_call_dest(insn);
+		if (dest && is_noreturn(dest))
+			insn->dead_end = true;
+	}
 }
 
 static void init_cfi_state(struct cfi_state *cfi)

@@ -1422,9 +1440,6 @@ static int annotate_call_site(struct objtool_file *file,
 	    !insn->_call_dest->embedded_insn)
 		list_add_tail(&insn->call_node, &file->call_list);
 
-	if (!sibling && dead_end_function(file, sym))
-		insn->dead_end = true;
-
 	return 0;
 }
 

@@ -2669,6 +2684,17 @@ int decode_file(struct objtool_file *file)
 	if (add_jump_table_alts(file))
 		return -1;
 
+	/*
+	 * Must be after add_jump_table_alts(), which affects sibling call
+	 * detection (jump table branches vs indirect sibling calls).
+	 *
+	 * The dead end marks are read by validate_branch() -- reached from
+	 * both validate_functions() and validate_noinstr_sections() -- and by
+	 * validate_unret().
+	 */
+	if (validate_branch_enabled() || opts.noinstr || opts.unret)
+		detect_noreturns(file);
+
 	if (read_unwind_hints(file))
 		return -1;
 

@@ -2676,8 +2702,7 @@ int decode_file(struct objtool_file *file)
 	mark_holes(file);
 
 	/*
-	 * Must be after add_call_destinations() such that it can override
-	 * dead_end_function() marks.
+	 * Must be after detect_noreturns() so it can override dead_end marks.
 	 */
 	if (read_annotate(file, __annotate_late))
 		return -1;

index a82517a76a0f6..46fb2230ca743 100644
@@ -98,6 +98,7 @@ struct symbol {
 	u8 klp		     : 1;
 	u8 dont_correlate    : 1;
 	u8 fake		     : 1;
+	u8 _noreturn         : 1;
 	struct list_head pv_target;
 	struct reloc *relocs;
 	struct section *group_sec;

index 83b4e748d33ba..f65b1b01b4fe9 100644
@@ -4271,12 +4271,6 @@ static bool ignore_unreachable_insn(struct objtool_file *file, struct instructio
 	    !strcmp(insn->sec->name, ".altinstr_aux"))
 		return true;
 
-	if (!func)
-		return false;
-
-	if (func->static_call_tramp)
-		return true;
-
 	/*
 	 * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
 	 * __builtin_unreachable().  The BUG() macro has an unreachable() after

@@ -4292,6 +4286,12 @@ static bool ignore_unreachable_insn(struct objtool_file *file, struct instructio
 	      insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
 		return true;
 
+	if (!func)
+		return false;
+
+	if (func->static_call_tramp)
+		return true;
+
 	/*
 	 * Check if this (or a subsequent) instruction is related to
 	 * CONFIG_UBSAN or CONFIG_KASAN.

index af2e68e496e5d..e9c78e026c7a3 100644
@@ -4,6 +4,7 @@
 
 #include <linux/objtool_types.h>
 #include <linux/annotate.h>
+#include <linux/compiler.h>
 
 #ifdef CONFIG_OBJTOOL
 

@@ -30,9 +31,11 @@
  *
  * For more information, see tools/objtool/Documentation/objtool.txt.
  */
-#define STACK_FRAME_NON_STANDARD(func) \
-	static void __used __section(".discard.func_stack_frame_non_standard") \
-		*__func_stack_frame_non_standard_##func = func
+#define STACK_FRAME_NON_STANDARD(func)					\
+	__ADDRESSABLE(func);						\
+	asm(".pushsection .discard.func_stack_frame_non_standard\n\t"	\
+	    ".long " #func " - .\n\t"					\
+	    ".popsection")
 
 /*
  * STACK_FRAME_NON_STANDARD_FP() is a frame-pointer-specific function ignore

@@ -91,8 +94,8 @@
 .endm
 
 .macro STACK_FRAME_NON_STANDARD func:req
-	.pushsection .discard.func_stack_frame_non_standard, "aw"
-	.quad \func
+	.pushsection .discard.func_stack_frame_non_standard, ""
+	.long \func - .
 	.popsection
 .endm
 

index 2b0c87dc99088..737de9afd6a40 100644
@@ -5,6 +5,7 @@
  * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
  */
 
+#include <linux/objtool.h>
 #include <asm/efi.h>
 #include <asm/addrspace.h>
 #include "efistub.h"

@@ -103,3 +104,10 @@ efi_status_t efi_boot_kernel(void *handle, efi_loaded_image_t *image,
 	real_kernel_entry(true, (unsigned long)cmdline_ptr,
 			  (unsigned long)efi_system_table);
 }
+
+/*
+ * Objtool has no way of knowing the real_kernel_entry() indirect call is
+ * noreturn. Just tell it to ignore this function: it's boot code anyway, so
+ * ORC coverage isn't needed.
+ */
+STACK_FRAME_NON_STANDARD(efi_boot_kernel);

index 2f1599c9e5732..a81ca04b4c501 100644
@@ -3,6 +3,7 @@
 #define _LINUX_ANNOTATE_H
 
 #include <linux/objtool_types.h>
+#include <linux/stringify.h>
 
 #ifdef CONFIG_OBJTOOL
 

@@ -105,6 +106,12 @@
  */
 #define ANNOTATE_NOCFI_SYM(sym)		asm(ASM_ANNOTATE_LABEL(sym, ANNOTYPE_NOCFI))
 
+/*
+ * Treat a function as returnable by its callers despite objtool classifying it
+ * as noreturn.
+ */
+#define ANNOTATE_IGNORE_NORETURN(sym)	asm(ASM_ANNOTATE_LABEL(sym, ANNOTYPE_IGNORE_NORETURN))
+
 /*
  * Annotate a special section entry.  This emables livepatch module generation
  * to find and extract individual special section entries as needed.

index c24e9ea392696..ce08ecc808c67 100644
@@ -66,6 +66,7 @@ struct unwind_hint {
 #define ANNOTYPE_INTRA_FUNCTION_CALL	7
 #define ANNOTYPE_REACHABLE		8
 #define ANNOTYPE_NOCFI			9
+#define ANNOTYPE_IGNORE_NORETURN	10
 
 #define ANNOTYPE_DATA_SPECIAL		1
 

index c24e9ea392696..ce08ecc808c67 100644
@@ -66,6 +66,7 @@ struct unwind_hint {
 #define ANNOTYPE_INTRA_FUNCTION_CALL	7
 #define ANNOTYPE_REACHABLE		8
 #define ANNOTYPE_NOCFI			9
+#define ANNOTYPE_IGNORE_NORETURN	10
 
 #define ANNOTYPE_DATA_SPECIAL		1
 

index f65b1b01b4fe9..d3b5c372cba4a 100644
@@ -248,6 +248,9 @@ static bool is_noreturn(struct symbol *func)
 {
 	func = func->alias->pfunc;
 
+	if (func->ignore_noreturn)
+		return false;
+
 	if (is_listed_noreturn(func))
 		return true;
 

@@ -2391,6 +2394,18 @@ static int __annotate_early(struct objtool_file *file, int type, struct instruct
 		insn->noendbr = 1;
 		break;
 
+	/* Must be before detect_noreturns() */
+	case ANNOTYPE_IGNORE_NORETURN: {
+		struct symbol *sym = insn_sym(insn);
+
+		if (!sym) {
+			ERROR_INSN(insn, "dodgy IGNORE_NORETURN annotation");
+			return -1;
+		}
+		sym->ignore_noreturn = 1;
+		break;
+	}
+
 	default:
 		break;
 	}

@@ -2437,6 +2452,10 @@ static int __annotate_late(struct objtool_file *file, int type, struct instructi
 		/* early */
 		break;
 
+	case ANNOTYPE_IGNORE_NORETURN:
+		/* early */
+		break;
+
 	case ANNOTYPE_RETPOLINE_SAFE:
 		if (insn->type != INSN_JUMP_DYNAMIC &&
 		    insn->type != INSN_CALL_DYNAMIC &&

index 46fb2230ca743..0e3593d993ac8 100644
@@ -99,6 +99,7 @@ struct symbol {
 	u8 dont_correlate    : 1;
 	u8 fake		     : 1;
 	u8 _noreturn         : 1;
+	u8 ignore_noreturn   : 1;
 	struct list_head pv_target;
 	struct reloc *relocs;
 	struct section *group_sec;

index 1883cae93bc31..e40b6767df24e 100644
@@ -16,6 +16,7 @@
 #include <linux/reboot.h>
 #include <linux/sched.h>
 #include <linux/sched/task_stack.h>
+#include <linux/annotate.h>
 
 #include <asm/bootinfo.h>
 #include <asm/cacheflush.h>

@@ -296,3 +297,4 @@ void machine_kexec(struct kimage *image)
 
 	kexec_reboot();
 }
+ANNOTATE_IGNORE_NORETURN(machine_kexec);

index de8fa5a8a825c..89ee0edcf58d2 100644
@@ -11,6 +11,7 @@
 #include <linux/reboot.h>
 #include <linux/delay.h>
 #include <linux/console.h>
+#include <linux/annotate.h>
 
 #include <acpi/reboot.h>
 #include <asm/idle.h>

@@ -36,6 +37,7 @@ void machine_halt(void)
 		__asm__ __volatile__("idle 0" : : : "memory");
 	}
 }
+ANNOTATE_IGNORE_NORETURN(machine_halt);
 
 void machine_power_off(void)
 {

@@ -56,6 +58,7 @@ void machine_power_off(void)
 		__asm__ __volatile__("idle 0" : : : "memory");
 	}
 }
+ANNOTATE_IGNORE_NORETURN(machine_power_off);
 
 void machine_restart(char *command)
 {

@@ -77,3 +80,4 @@ void machine_restart(char *command)
 		__asm__ __volatile__("idle 0" : : : "memory");
 	}
 }
+ANNOTATE_IGNORE_NORETURN(machine_restart);

index 72ffa71aa19b8..cd41f580ccb72 100644
@@ -7,45 +7,21 @@
  * Yes, this is unfortunate.  A better solution is in the works.
  */
 NORETURN(__fortify_panic)
-NORETURN(__ia32_sys_exit)
-NORETURN(__ia32_sys_exit_group)
 NORETURN(__kunit_abort)
 NORETURN(__module_put_and_kthread_exit)
 NORETURN(__stack_chk_fail)
-NORETURN(__tdx_hypercall_failed)
 NORETURN(__ubsan_handle_builtin_unreachable)
-NORETURN(__x64_sys_exit)
-NORETURN(__x64_sys_exit_group)
 NORETURN(acpi_processor_ffh_play_dead)
-NORETURN(arch_cpu_idle_dead)
-NORETURN(cpu_bringup_and_idle)
-NORETURN(cpu_startup_entry)
 NORETURN(do_exit)
-NORETURN(do_group_exit)
-NORETURN(do_task_dead)
-NORETURN(efi_rts_park_worker)
-NORETURN(ex_handler_msr_mce)
-NORETURN(hlt_play_dead)
-NORETURN(hv_ghcb_terminate)
 NORETURN(kthread_complete_and_exit)
 NORETURN(kunit_try_catch_throw)
-NORETURN(machine_real_restart)
-NORETURN(make_task_dead)
 NORETURN(mpt_halt_firmware)
-NORETURN(mwait_play_dead)
-NORETURN(native_play_dead)
 NORETURN(nmi_panic_self_stop)
 NORETURN(panic)
 NORETURN(vpanic)
 NORETURN(panic_smp_self_stop)
-NORETURN(rest_init)
 NORETURN(rewind_stack_and_make_dead)
 NORETURN(rust_helper_BUG)
 NORETURN(sev_es_terminate)
-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)

index 8d2ea2cbd98b0..803c131c6aa78 100644
@@ -153,7 +153,9 @@ void do_insterror_or_kprobe(unsigned long address, struct pt_regs *regs)
 /*
  * abort() call generated by older gcc for __builtin_trap()
  */
-void abort(void)
+void __noreturn abort(void)
 {
 	__asm__ __volatile__("trap_s  5\n");
+
+	unreachable();
 }

index afbd2ebe5c39d..a3bd26d41612f 100644
@@ -777,7 +777,7 @@ asmlinkage void __div0(void)
 }
 EXPORT_SYMBOL(__div0);
 
-void abort(void)
+void __noreturn abort(void)
 {
 	BUG();
 

index f1dd417e54b29..da8778360dadf 100644
@@ -33,7 +33,7 @@ extern int sysctl_panic_on_stackoverflow;
 extern bool crash_kexec_post_notifiers;
 
 extern void __stack_chk_fail(void);
-void abort(void);
+void abort(void) __noreturn;
 
 /*
  * panic_cpu is used for synchronizing panic() and crash_kexec() execution. It

index 97686af895013..e541e61945f9a 100644
@@ -2027,7 +2027,7 @@ COMPAT_SYSCALL_DEFINE5(waitid,
  *
  * See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88345#c11
  */
-__weak __function_aligned void abort(void)
+__weak __function_aligned void __noreturn abort(void)
 {
 	BUG();
 

index f2053cbe9b0ce..9f227f06cbaf5 100644
@@ -37,6 +37,7 @@ void __init __weak mem_map_via_hcall(struct boot_params *ptr __maybe_unused)
 	xen_raw_printk("Error: Could not find memory map\n");
 	BUG();
 }
+ANNOTATE_IGNORE_NORETURN(mem_map_via_hcall);
 
 static void __init init_pvh_bootparams(bool xen_guest)
 {

index d3b5c372cba4a..35e24151f5785 100644
@@ -262,9 +262,6 @@ static bool might_return(struct objtool_file *file, struct symbol *func)
 	struct instruction *insn;
 	struct symbol *dest;
 
-	if (is_weak_sym(func))
-		return true;
-
 	func_for_each_insn(file, func, insn) {
 		if (insn->type == INSN_RETURN)
 			return true;

index cd41f580ccb72..26f62f98bc8ef 100644
@@ -11,15 +11,14 @@ NORETURN(__kunit_abort)
 NORETURN(__module_put_and_kthread_exit)
 NORETURN(__stack_chk_fail)
 NORETURN(__ubsan_handle_builtin_unreachable)
+NORETURN(abort)
 NORETURN(acpi_processor_ffh_play_dead)
 NORETURN(do_exit)
 NORETURN(kthread_complete_and_exit)
 NORETURN(kunit_try_catch_throw)
 NORETURN(mpt_halt_firmware)
-NORETURN(nmi_panic_self_stop)
 NORETURN(panic)
 NORETURN(vpanic)
-NORETURN(panic_smp_self_stop)
 NORETURN(rewind_stack_and_make_dead)
 NORETURN(rust_helper_BUG)
 NORETURN(sev_es_terminate)

index 26f62f98bc8ef..ff93e94ee09a0 100644
@@ -19,7 +19,6 @@ NORETURN(kunit_try_catch_throw)
 NORETURN(mpt_halt_firmware)
 NORETURN(panic)
 NORETURN(vpanic)
-NORETURN(rewind_stack_and_make_dead)
 NORETURN(rust_helper_BUG)
 NORETURN(sev_es_terminate)
 NORETURN(xen_cpu_bringup_again)

index ff93e94ee09a0..01c94f20d1818 100644
@@ -21,5 +21,4 @@ NORETURN(panic)
 NORETURN(vpanic)
 NORETURN(rust_helper_BUG)
 NORETURN(sev_es_terminate)
-NORETURN(xen_cpu_bringup_again)
 NORETURN(xen_start_kernel)

index 2c64b388f6164..8ec78df9d1d5b 100644
@@ -1325,15 +1325,12 @@ static void __init xen_domu_set_legacy_features(void)
 extern void early_xen_iret_patch(void);
 
 /* First C function to be called on Xen boot */
-asmlinkage __visible void __init xen_start_kernel(struct start_info *si)
+asmlinkage __visible void __init __noreturn xen_start_kernel(struct start_info *si)
 {
 	struct physdev_set_iopl set_iopl;
 	unsigned long initrd_start = 0;
 	int rc;
 
-	if (!si)
-		return;
-
 	clear_bss();
 
 	xen_start_info = si;

index 47eebbb3684ab..d830807cfffca 100644
@@ -73,7 +73,7 @@ void xen_force_evtchn_callback(void);
 
 void xen_pv_pre_suspend(void);
 void xen_pv_post_suspend(int suspend_cancelled);
-void xen_start_kernel(struct start_info *si);
+void __noreturn xen_start_kernel(struct start_info *si);
 
 void set_pte_mfn(unsigned long vaddr, unsigned long pfn, pgprot_t flags);
 void xen_init_mmu_ops(void);

index 01c94f20d1818..c4b93fc6e6299 100644
@@ -21,4 +21,3 @@ NORETURN(panic)
 NORETURN(vpanic)
 NORETURN(rust_helper_BUG)
 NORETURN(sev_es_terminate)
-NORETURN(xen_start_kernel)

deleted file mode 100644
index 01d2363dc445f..0000000000000
@@ -1,14 +0,0 @@
-
-/*
- * The symbols below are functions that are implemented by the startup code,
- * but called at runtime by the SEV code residing in the core kernel.
- */
-PROVIDE(early_set_pages_state		= __pi_early_set_pages_state);
-PROVIDE(early_snp_set_memory_private	= __pi_early_snp_set_memory_private);
-PROVIDE(early_snp_set_memory_shared	= __pi_early_snp_set_memory_shared);
-PROVIDE(get_hv_features			= __pi_get_hv_features);
-PROVIDE(sev_es_terminate		= __pi_sev_es_terminate);
-PROVIDE(snp_cpuid			= __pi_snp_cpuid);
-PROVIDE(snp_cpuid_get_table		= __pi_snp_cpuid_get_table);
-PROVIDE(svsm_issue_call			= __pi_svsm_issue_call);
-PROVIDE(svsm_process_result_codes	= __pi_svsm_process_result_codes);

index c4b93fc6e6299..2dce56030b980 100644
@@ -20,4 +20,3 @@ NORETURN(mpt_halt_firmware)
 NORETURN(panic)
 NORETURN(vpanic)
 NORETURN(rust_helper_BUG)
-NORETURN(sev_es_terminate)

index 35e24151f5785..41df5f608535f 100644
@@ -266,8 +266,22 @@ static bool might_return(struct objtool_file *file, struct symbol *func)
 		if (insn->type == INSN_RETURN)
 			return true;
 
-		if (!is_sibling_call(insn))
+		if (!is_sibling_call(insn)) {
+			/*
+			 * Assume a jump into a non-function eventually returns
+			 * to the original caller one way or another, e.g., the
+			 * jump in srso_alias_untrain_ret().
+			 *
+			 * .altinstr_aux is an exception, cpu_feature_enabled()
+			 * jumps there and then right back.
+			 */
+			if (is_static_jump(insn) && insn->jump_dest &&
+			    !insn_func(insn->jump_dest) &&
+			    strcmp(insn->jump_dest->sec->name, ".altinstr_aux"))
+				return true;
+
 			continue;
+		}
 
 		dest = insn_call_dest(insn);
 		if (!dest || !is_noreturn(dest))

index 75b11dc85010e..c4c4210f84662 100644
@@ -101,6 +101,8 @@ static const struct option check_options[] = {
 	OPT_BOOLEAN(0,		 "module", &opts.module, "object is part of a kernel module"),
 	OPT_BOOLEAN(0,		 "mnop", &opts.mnop, "nop out mcount call sites"),
 	OPT_BOOLEAN(0,		 "no-unreachable", &opts.no_unreachable, "skip 'unreachable instruction' warnings"),
+	OPT_STRING(0,		 "noreturns-read", &opts.noreturns_read, "file", "read exported noreturns from a file"),
+	OPT_STRING(0,		 "noreturns-write", &opts.noreturns_write, "file", "write exported noreturns to a file"),
 	OPT_STRING('o',		 "output", &opts.output, "file", "output file name"),
 	OPT_BOOLEAN(0,		 "sec-address", &opts.sec_address, "print section addresses in warnings"),
 	OPT_BOOLEAN(0,		 "stats", &opts.stats, "print statistics"),

@@ -180,6 +182,16 @@ static bool opts_valid(void)
 		return false;
 	}
 
+	if (opts.noreturns_write && !opts.link) {
+		ERROR("--noreturns-write requires --link");
+		return false;
+	}
+
+	if (opts.noreturns_write && !opts.stackval && !opts.orc && !opts.uaccess) {
+		ERROR("--noreturns-write requires --stackval, --orc, or --uaccess");
+		return false;
+	}
+
 	if (opts.disas			||
 	    opts.hack_jump_label	||
 	    opts.hack_noinstr		||

179 lines not on this page · raw message

index 349690bb1c50e..fb33d57a54c95 100644
@@ -41,6 +41,8 @@ struct opts {
 	bool mnop;
 	bool module;
 	bool no_unreachable;
+	const char *noreturns_read;
+	const char *noreturns_write;
 	const char *output;
 	bool sec_address;
 	bool stats;

index 0e3593d993ac8..adf6e1322c6df 100644
@@ -100,6 +100,7 @@ struct symbol {
 	u8 fake		     : 1;
 	u8 _noreturn         : 1;
 	u8 ignore_noreturn   : 1;
+	u8 exported          : 1;
 	struct list_head pv_target;
 	struct reloc *relocs;
 	struct section *group_sec;

58 lines not on this page · raw message

index 2dce56030b980..4e8007a8c2584 100644
@@ -1,22 +1,9 @@
 /* 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.
+ * This is a list of noreturn functions which are exported *by modules*.
+ * No other noreturns need to be listed here.
  */
-NORETURN(__fortify_panic)
 NORETURN(__kunit_abort)
-NORETURN(__module_put_and_kthread_exit)
-NORETURN(__stack_chk_fail)
-NORETURN(__ubsan_handle_builtin_unreachable)
-NORETURN(abort)
-NORETURN(acpi_processor_ffh_play_dead)
-NORETURN(do_exit)
-NORETURN(kthread_complete_and_exit)
 NORETURN(kunit_try_catch_throw)
 NORETURN(mpt_halt_firmware)
-NORETURN(panic)
-NORETURN(vpanic)
-NORETURN(rust_helper_BUG)

index a81ca04b4c501..70450eeec3186 100644
@@ -25,6 +25,15 @@
 	"912: "								\
 	__stringify(__ASM_ANNOTATE(.discard.annotate_data, 912b, type))
 
+/*
+ * Annotate a symbol by name rather than by relocation, so it can optionally be
+ * used in a header file.
+ */
+#define ASM_ANNOTATE_NAME(section, sym)					\
+	".pushsection " section ", \"MS\", @progbits, 1\n\t"		\
+	".asciz \"" __stringify(sym) "\"\n\t"				\
+	".popsection"
+
 #else /* __ASSEMBLY__ */
 
 .macro ANNOTATE type

@@ -44,6 +53,7 @@
 #define ASM_ANNOTATE_LABEL(label, type) ""
 #define ASM_ANNOTATE(type)
 #define ASM_ANNOTATE_DATA(type)
+#define ASM_ANNOTATE_NAME(section, sym) ""
 #else /* __ASSEMBLY__ */
 .macro ANNOTATE type
 .endm

@@ -112,6 +122,13 @@
  */
 #define ANNOTATE_IGNORE_NORETURN(sym)	asm(ASM_ANNOTATE_LABEL(sym, ANNOTYPE_IGNORE_NORETURN))
 
+/*
+ * Tell objtool running on a module that a function exported by another module
+ * is __noreturn.  Objtool has no way of communicating that between modules due
+ * to the parallel nature of module linking in kbuild.
+ */
+#define ANNOTATE_EXPORTED_NORETURN(sym)	asm(ASM_ANNOTATE_NAME(".discard.annotate_noreturn", sym))
+
 /*
  * Annotate a special section entry.  This emables livepatch module generation
  * to find and extract individual special section entries as needed.

index 52630519bdbf2..94beedcdb49bb 100644
@@ -409,6 +409,31 @@ static int read_noreturns(struct objtool_file *file)
 	return 0;
 }
 
+static void read_annotate_noreturn(struct objtool_file *file)
+{
+	struct section *sec;
+	struct symbol *func;
+	unsigned long off;
+	const char *name;
+
+	sec = find_section_by_name(file->elf, ".discard.annotate_noreturn");
+	if (!sec || !sec->data)
+		return;
+
+	for (off = 0; off < sec_size(sec); off += strlen(name) + 1) {
+		name = sec->data->d_buf + off;
+		if (!*name)
+			continue;
+
+		func = find_global_symbol_by_name(file->elf, name);
+		if (!func)
+			continue;
+
+		if (is_undef_sym(func))
+			func->_noreturn = 1;
+	}
+}
+
 static void init_cfi_state(struct cfi_state *cfi)
 {
 	int i;

@@ -4983,6 +5008,8 @@ int check(struct objtool_file *file)
 			goto out;
 	}
 
+	read_annotate_noreturn(file);
+
 	ret = decode_file(file);
 	if (ret)
 		goto out;

index 34da55e456097..8a30bf7d1eaf9 100644
@@ -360,6 +360,7 @@ static bool is_special_section(struct section *sec)
 
 	static const char * const non_special_discards[] = {
 		".discard.addressable",
+		".discard.annotate_noreturn",
 		".discard.sym_checksum",
 	};
 

@@ -2216,6 +2217,34 @@ static int copy_import_ns(struct elfs *e)
 	return 0;
 }
 
+/*
+ * ANNOTATE_EXPORTED_NORETURN() annotations reference their functions by name
+ * rather than by relocation, so individual entries can't be extracted.  Copy
+ * the (tiny) section as-is.
+ */
+static int copy_annotate_noreturn(struct elfs *e)
+{
+	struct section *patched_sec, *out_sec;
+
+	patched_sec = find_section_by_name(e->patched, ".discard.annotate_noreturn");
+	if (!patched_sec || !patched_sec->data || !sec_size(patched_sec))
+		return 0;
+
+	out_sec = elf_create_section(e->out, patched_sec->name, 0,
+				     patched_sec->sh.sh_entsize,
+				     patched_sec->sh.sh_type,
+				     patched_sec->sh.sh_addralign,
+				     patched_sec->sh.sh_flags);
+	if (!out_sec)
+		return -1;
+
+	if (!elf_add_data(e->out, out_sec, patched_sec->data->d_buf,
+			  sec_size(patched_sec)))
+		return -1;
+
+	return 0;
+}
+
 int cmd_klp_diff(int argc, const char **argv)
 {
 	struct elfs e = {0};

@@ -2287,6 +2316,9 @@ int cmd_klp_diff(int argc, const char **argv)
 	if (copy_import_ns(&e))
 		return -1;
 
+	if (copy_annotate_noreturn(&e))
+		return -1;
+
 	if  (elf_write(e.out))
 		return -1;
 

index b406fd676da09..387b707a66742 100644
@@ -49,6 +49,7 @@
 #define MPTBASE_H_INCLUDED
 /*{-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=*/
 
+#include <linux/annotate.h>
 #include <linux/kernel.h>
 #include <linux/pci.h>
 #include <linux/mutex.h>

@@ -942,6 +943,7 @@ extern int	mpt_raid_phys_disk_get_num_paths(MPT_ADAPTER *ioc,
 extern int	 mpt_set_taskmgmt_in_progress_flag(MPT_ADAPTER *ioc);
 extern void	 mpt_clear_taskmgmt_in_progress_flag(MPT_ADAPTER *ioc);
 extern void __noreturn mpt_halt_firmware(MPT_ADAPTER *ioc);
+ANNOTATE_EXPORTED_NORETURN(mpt_halt_firmware);
 
 
 /*

index da5312e0dfa57..9aa4c1d3a9821 100644
@@ -723,6 +723,7 @@ void __printf(2, 3) kunit_log_append(struct string_stream *log, const char *fmt,
 #define KUNIT_SUCCEED(test) _KUNIT_SAVE_LOC(test)
 
 void __noreturn __kunit_abort(struct kunit *test);
+ANNOTATE_EXPORTED_NORETURN(__kunit_abort);
 
 void __printf(6, 7) __kunit_do_failed_assertion(struct kunit *test,
 						const struct kunit_loc *loc,

index d4e1a5b98ed67..f3c0af4650080 100644
@@ -10,6 +10,7 @@
 #ifndef _KUNIT_TRY_CATCH_H
 #define _KUNIT_TRY_CATCH_H
 
+#include <linux/annotate.h>
 #include <linux/types.h>
 
 typedef void (*kunit_try_catch_func_t)(void *);

@@ -54,6 +55,7 @@ struct kunit_try_catch {
 void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context);
 
 void __noreturn kunit_try_catch_throw(struct kunit_try_catch *try_catch);
+ANNOTATE_EXPORTED_NORETURN(kunit_try_catch_throw);
 
 static inline int kunit_try_catch_get_result(struct kunit_try_catch *try_catch)
 {

index 8ec0ebfaef04f..a0e1bf99407b7 100644
@@ -21,6 +21,7 @@
 #ifndef _LINUX_RTC_DS1685_H_
 #define _LINUX_RTC_DS1685_H_
 
+#include <linux/annotate.h>
 #include <linux/rtc.h>
 #include <linux/platform_device.h>
 #include <linux/workqueue.h>

@@ -362,5 +363,6 @@ struct ds1685_rtc_platform_data {
  */
 extern void __noreturn
 ds1685_rtc_poweroff(struct platform_device *pdev);
+ANNOTATE_EXPORTED_NORETURN(ds1685_rtc_poweroff);
 
 #endif /* _LINUX_RTC_DS1685_H_ */

index 94beedcdb49bb..e6d33e57b7b33 100644
@@ -176,24 +176,6 @@ static bool is_sibling_call(struct instruction *insn)
 	return (is_static_jump(insn) && insn_call_dest(insn));
 }
 
-static bool is_listed_noreturn(struct symbol *func)
-{
-#define NORETURN(func) __stringify(func),
-	static const char * const global_noreturns[] = {
-#include "noreturns.h"
-	};
-#undef NORETURN
-
-	if (is_local_sym(func))
-		return false;
-
-	for (int i = 0; i < ARRAY_SIZE(global_noreturns); i++)
-		if (!strcmp(func->name, global_noreturns[i]))
-			return true;
-
-	return false;
-}
-
 /*
  * Use this rather than reading sym->_noreturn directly: the noreturn status
  * lives on the primary alias, and ANNOTATE_IGNORE_NORETURN() overrides it.

@@ -205,9 +187,6 @@ static bool is_noreturn(struct symbol *func)
 	if (func->ignore_noreturn)
 		return false;
 
-	if (is_listed_noreturn(func))
-		return true;
-
 	return func->_noreturn;
 }
 

@@ -4890,7 +4869,7 @@ static int validate_reachable_instructions(struct objtool_file *file)
 		if (prev_insn && prev_insn->dead_end) {
 			call_dest = insn_call_dest(prev_insn);
 			if (call_dest) {
-				WARN_INSN(insn, "%s() missing __noreturn in .c/.h or NORETURN() in noreturns.h",
+				WARN_INSN(insn, "%s() is missing __noreturn in .c/.h",
 					  call_dest->name);
 				warnings++;
 				continue;

deleted file mode 100644
index 4e8007a8c2584..0000000000000
@@ -1,9 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-
-/*
- * This is a list of noreturn functions which are exported *by modules*.
- * No other noreturns need to be listed here.
- */
-NORETURN(__kunit_abort)
-NORETURN(kunit_try_catch_throw)
-NORETURN(mpt_halt_firmware)

87 lines not on this page · raw message

index adf6e1322c6df..e79cdabf09c26 100644
@@ -100,6 +100,7 @@ struct symbol {
 	u8 fake		     : 1;
 	u8 _noreturn         : 1;
 	u8 ignore_noreturn   : 1;
+	u8 annotate_noreturn : 1;
 	u8 exported          : 1;
 	struct list_head pv_target;
 	struct reloc *relocs;