From 071c44e4278156f18a6a56958617223b6bffa6ab Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Mon, 13 Feb 2023 23:05:58 -0800 Subject: sched/idle: Mark arch_cpu_idle_dead() __noreturn Before commit 076cbf5d2163 ("x86/xen: don't let xen_pv_play_dead() return"), in Xen, when a previously offlined CPU was brought back online, it unexpectedly resumed execution where it left off in the middle of the idle loop. There were some hacks to make that work, but the behavior was surprising as do_idle() doesn't expect an offlined CPU to return from the dead (in arch_cpu_idle_dead()). Now that Xen has been fixed, and the arch-specific implementations of arch_cpu_idle_dead() also don't return, give it a __noreturn attribute. This will cause the compiler to complain if an arch-specific implementation might return. It also improves code generation for both caller and callee. Also fixes the following warning: vmlinux.o: warning: objtool: do_idle+0x25f: unreachable instruction Reported-by: Paul E. McKenney Tested-by: Paul E. McKenney Link: https://lore.kernel.org/r/60d527353da8c99d4cf13b6473131d46719ed16d.1676358308.git.jpoimboe@kernel.org Signed-off-by: Josh Poimboeuf --- arch/s390/kernel/idle.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/s390') diff --git a/arch/s390/kernel/idle.c b/arch/s390/kernel/idle.c index 38e267c7bff7..e7239aaf428b 100644 --- a/arch/s390/kernel/idle.c +++ b/arch/s390/kernel/idle.c @@ -88,7 +88,7 @@ void arch_cpu_idle_exit(void) { } -void arch_cpu_idle_dead(void) +void __noreturn arch_cpu_idle_dead(void) { cpu_die(); } -- cgit v1.2.3-70-g09d2 From 9ea7e6b62c2bd2f7bbfc3f10099df803002dd33b Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Wed, 12 Apr 2023 16:49:31 -0700 Subject: init: Mark [arch_call_]rest_init() __noreturn In preparation for improving objtool's handling of weak noreturn functions, mark start_kernel(), arch_call_rest_init(), and rest_init() __noreturn. Signed-off-by: Josh Poimboeuf Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Nick Desaulniers Link: https://lore.kernel.org/r/7194ed8a989a85b98d92e62df660f4a90435a723.1681342859.git.jpoimboe@kernel.org --- arch/s390/kernel/setup.c | 2 +- include/linux/start_kernel.h | 4 ++-- init/main.c | 4 ++-- tools/objtool/check.c | 2 ++ 4 files changed, 7 insertions(+), 5 deletions(-) (limited to 'arch/s390') diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c index 8ec5cdf9dadc..4259b6c50516 100644 --- a/arch/s390/kernel/setup.c +++ b/arch/s390/kernel/setup.c @@ -396,7 +396,7 @@ int __init arch_early_irq_init(void) return 0; } -void __init arch_call_rest_init(void) +void __init __noreturn arch_call_rest_init(void) { unsigned long stack; diff --git a/include/linux/start_kernel.h b/include/linux/start_kernel.h index 8b369a41c03c..864921e54c92 100644 --- a/include/linux/start_kernel.h +++ b/include/linux/start_kernel.h @@ -9,7 +9,7 @@ up something else. */ extern asmlinkage void __init start_kernel(void); -extern void __init arch_call_rest_init(void); -extern void __ref rest_init(void); +extern void __init __noreturn arch_call_rest_init(void); +extern void __ref __noreturn rest_init(void); #endif /* _LINUX_START_KERNEL_H */ diff --git a/init/main.c b/init/main.c index 4425d1783d5c..161ed956d738 100644 --- a/init/main.c +++ b/init/main.c @@ -683,7 +683,7 @@ static void __init setup_command_line(char *command_line) static __initdata DECLARE_COMPLETION(kthreadd_done); -noinline void __ref rest_init(void) +noinline void __ref __noreturn rest_init(void) { struct task_struct *tsk; int pid; @@ -889,7 +889,7 @@ static int __init early_randomize_kstack_offset(char *buf) early_param("randomize_kstack_offset", early_randomize_kstack_offset); #endif -void __init __weak arch_call_rest_init(void) +void __init __weak __noreturn arch_call_rest_init(void) { rest_init(); } diff --git a/tools/objtool/check.c b/tools/objtool/check.c index df634dafefc4..3d7227f0ea2a 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -202,6 +202,7 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func, "__reiserfs_panic", "__stack_chk_fail", "__ubsan_handle_builtin_unreachable", + "arch_call_rest_init", "arch_cpu_idle_dead", "cpu_bringup_and_idle", "cpu_startup_entry", @@ -217,6 +218,7 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func, "machine_real_restart", "make_task_dead", "panic", + "rest_init", "rewind_stack_and_make_dead", "sev_es_terminate", "snp_abort", -- cgit v1.2.3-70-g09d2