init: add arch_call_rest_init to allow stack switching

With CONFIG_VMAP_STACK=y the kernel stack of all tasks should be allocated in the vmalloc space. The initial stack used for all the early init code is in the init_thread_union. To be able to switch from this early stack to a properly allocated stack from vmalloc the architecture needs a switch-over point. Introduce the arch_call_rest_init() function with a weak definition in init/main.c with the only purpose to call rest_init() from the end of start_kernel(). The architecture override can then do the necessary magic to switch to the new vmalloc'ed stack. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
torvalds · Oct 9, 2018 · 53c99bd · 53c99bd
1 parent 00e9e66
commit 53c99bd
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Showing 2 changed files with 9 additions and 2 deletions.
diff --git a/include/linux/start_kernel.h b/include/linux/start_kernel.h
@@ -9,5 +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);
 
 #endif /* _LINUX_START_KERNEL_H */
diff --git a/init/main.c b/init/main.c
@@ -394,7 +394,7 @@ static void __init setup_command_line(char *command_line)
 
 static __initdata DECLARE_COMPLETION(kthreadd_done);
 
-static noinline void __ref rest_init(void)
+noinline void __ref rest_init(void)
 {
 	struct task_struct *tsk;
 	int pid;
@@ -528,6 +528,11 @@ static void __init mm_init(void)
 	pti_init();
 }
 
+void __init __weak arch_call_rest_init(void)
+{
+	rest_init();
+}
+
 asmlinkage __visible void __init start_kernel(void)
 {
 	char *command_line;
@@ -736,7 +741,7 @@ asmlinkage __visible void __init start_kernel(void)
 	}
 
 	/* Do the rest non-__init'ed, we're now alive */
-	rest_init();
+	arch_call_rest_init();
 }
 
 /* Call all constructor functions linked into the kernel. */