PM / hibernate: introduce "nohibernate" boot parameter

To support using kernel features that are not compatible with hibernation,
this creates the "nohibernate" kernel boot parameter to disable both
hibernation and resume. This allows hibernation support to be a boot-time
choice instead of only a compile-time choice.
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation/kernel-parameters.txt

@@ -2184,6 +2184,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			in certain environments such as networked servers or
 			real-time systems.
 
+	nohibernate	[HIBERNATION] Disable hibernation and resume.
+
 	nohz=		[KNL] Boottime enable/disable dynamic ticks
 			Valid arguments: on, off
 			Default: on
@@ -2980,6 +2982,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 		noresume	Don't check if there's a hibernation image
 				present during boot.
 		nocompress	Don't compress/decompress hibernation images.
+		no		Disable hibernation and resume.
 
 	retain_initrd	[RAM] Keep initrd memory after extraction
 

include/linux/suspend.h

@@ -327,6 +327,7 @@ extern unsigned long get_safe_page(gfp_t gfp_mask);
 extern void hibernation_set_ops(const struct platform_hibernation_ops *ops);
 extern int hibernate(void);
 extern bool system_entering_hibernation(void);
+extern bool hibernation_available(void);
 asmlinkage int swsusp_save(void);
 extern struct pbe *restore_pblist;
 #else /* CONFIG_HIBERNATION */
@@ -339,6 +340,7 @@ static inline void swsusp_unset_page_free(struct page *p) {}
 static inline void hibernation_set_ops(const struct platform_hibernation_ops *ops) {}
 static inline int hibernate(void) { return -ENOSYS; }
 static inline bool system_entering_hibernation(void) { return false; }
+static inline bool hibernation_available(void) { return false; }
 #endif /* CONFIG_HIBERNATION */
 
 /* Hibernation and suspend events */

kernel/power/hibernate.c

@@ -35,6 +35,7 @@
 
 static int nocompress;
 static int noresume;
+static int nohibernate;
 static int resume_wait;
 static unsigned int resume_delay;
 static char resume_file[256] = CONFIG_PM_STD_PARTITION;
@@ -62,6 +63,11 @@ bool freezer_test_done;
 
 static const struct platform_hibernation_ops *hibernation_ops;
 
+bool hibernation_available(void)
+{
+	return (nohibernate == 0);
+}
+
 /**
  * hibernation_set_ops - Set the global hibernate operations.
  * @ops: Hibernation operations to use in subsequent hibernation transitions.
@@ -642,6 +648,11 @@ int hibernate(void)
 {
 	int error;
 
+	if (!hibernation_available()) {
+		pr_debug("PM: Hibernation not available.\n");
+		return -EPERM;
+	}
+
 	lock_system_sleep();
 	/* The snapshot device should not be opened while we're running */
 	if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {
@@ -734,7 +745,7 @@ static int software_resume(void)
 	/*
 	 * If the user said "noresume".. bail out early.
 	 */
-	if (noresume)
+	if (noresume || !hibernation_available())
 		return 0;
 
 	/*
@@ -900,6 +911,9 @@ static ssize_t disk_show(struct kobject *kobj, struct kobj_attribute *attr,
 	int i;
 	char *start = buf;
 
+	if (!hibernation_available())
+		return sprintf(buf, "[disabled]\n");
+
 	for (i = HIBERNATION_FIRST; i <= HIBERNATION_MAX; i++) {
 		if (!hibernation_modes[i])
 			continue;
@@ -934,6 +948,9 @@ static ssize_t disk_store(struct kobject *kobj, struct kobj_attribute *attr,
 	char *p;
 	int mode = HIBERNATION_INVALID;
 
+	if (!hibernation_available())
+		return -EPERM;
+
 	p = memchr(buf, '\n', n);
 	len = p ? p - buf : n;
 
@@ -1101,6 +1118,10 @@ static int __init hibernate_setup(char *str)
 		noresume = 1;
 	else if (!strncmp(str, "nocompress", 10))
 		nocompress = 1;
+	else if (!strncmp(str, "no", 2)) {
+		noresume = 1;
+		nohibernate = 1;
+	}
 	return 1;
 }
 
@@ -1125,9 +1146,17 @@ static int __init resumedelay_setup(char *str)
 	return 1;
 }
 
+static int __init nohibernate_setup(char *str)
+{
+	noresume = 1;
+	nohibernate = 1;
+	return 1;
+}
+
 __setup("noresume", noresume_setup);
 __setup("resume_offset=", resume_offset_setup);
 __setup("resume=", resume_setup);
 __setup("hibernate=", hibernate_setup);
 __setup("resumewait", resumewait_setup);
 __setup("resumedelay=", resumedelay_setup);
+__setup("nohibernate", nohibernate_setup);

kernel/power/main.c

@@ -300,13 +300,11 @@ static ssize_t state_show(struct kobject *kobj, struct kobj_attribute *attr,
 			s += sprintf(s,"%s ", pm_states[i].label);
 
 #endif
-#ifdef CONFIG_HIBERNATION
-	s += sprintf(s, "%s\n", "disk");
-#else
+	if (hibernation_available())
+		s += sprintf(s, "disk ");
 	if (s != buf)
 		/* convert the last space to a newline */
 		*(s-1) = '\n';
-#endif
 	return (s - buf);
 }
 

kernel/power/user.c

@@ -49,6 +49,9 @@ static int snapshot_open(struct inode *inode, struct file *filp)
 	struct snapshot_data *data;
 	int error;
 
+	if (!hibernation_available())
+		return -EPERM;
+
 	lock_system_sleep();
 
 	if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {