@@ -0,0 +1,32 @@
+What: /sys/kernel/reboot
+Date: November 2020
+KernelVersion: 5.11
+Contact: Matteo Croce <mcroce@microsoft.com>
+Description: Interface to set the kernel reboot behavior, similarly to
+ what can be done via the reboot= cmdline option.
+ (see Documentation/admin-guide/kernel-parameters.txt)
+
+What: /sys/kernel/reboot/mode
+Date: November 2020
+KernelVersion: 5.11
+Contact: Matteo Croce <mcroce@microsoft.com>
+Description: Reboot mode. Valid values are: cold warm hard soft gpio
+
+What: /sys/kernel/reboot/type
+Date: November 2020
+KernelVersion: 5.11
+Contact: Matteo Croce <mcroce@microsoft.com>
+Description: Reboot type. Valid values are: bios acpi kbd triple efi pci
+
+What: /sys/kernel/reboot/cpu
+Date: November 2020
+KernelVersion: 5.11
+Contact: Matteo Croce <mcroce@microsoft.com>
+Description: CPU number to use to reboot.
+
+What: /sys/kernel/reboot/force
+Date: November 2020
+KernelVersion: 5.11
+Contact: Matteo Croce <mcroce@microsoft.com>
+Description: Don't wait for any other CPUs on reboot and
+ avoid anything that could hang.
@@ -600,3 +600,209 @@ static int __init reboot_setup(char *str
return 1;
}
__setup("reboot=", reboot_setup);
+
+#ifdef CONFIG_SYSFS
+
+#define REBOOT_COLD_STR "cold"
+#define REBOOT_WARM_STR "warm"
+#define REBOOT_HARD_STR "hard"
+#define REBOOT_SOFT_STR "soft"
+#define REBOOT_GPIO_STR "gpio"
+#define REBOOT_UNDEFINED_STR "undefined"
+
+#define BOOT_TRIPLE_STR "triple"
+#define BOOT_KBD_STR "kbd"
+#define BOOT_BIOS_STR "bios"
+#define BOOT_ACPI_STR "acpi"
+#define BOOT_EFI_STR "efi"
+#define BOOT_CF9_FORCE_STR "cf9_force"
+#define BOOT_CF9_SAFE_STR "cf9_safe"
+
+static ssize_t mode_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
+{
+ const char *val;
+
+ switch (reboot_mode) {
+ case REBOOT_COLD:
+ val = REBOOT_COLD_STR;
+ break;
+ case REBOOT_WARM:
+ val = REBOOT_WARM_STR;
+ break;
+ case REBOOT_HARD:
+ val = REBOOT_HARD_STR;
+ break;
+ case REBOOT_SOFT:
+ val = REBOOT_SOFT_STR;
+ break;
+ case REBOOT_GPIO:
+ val = REBOOT_GPIO_STR;
+ break;
+ default:
+ val = REBOOT_UNDEFINED_STR;
+ }
+
+ return sprintf(buf, "%s\n", val);
+}
+static ssize_t mode_store(struct kobject *kobj, struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ if (!capable(CAP_SYS_BOOT))
+ return -EPERM;
+
+ if (!strncmp(buf, REBOOT_COLD_STR, strlen(REBOOT_COLD_STR)))
+ reboot_mode = REBOOT_COLD;
+ else if (!strncmp(buf, REBOOT_WARM_STR, strlen(REBOOT_WARM_STR)))
+ reboot_mode = REBOOT_WARM;
+ else if (!strncmp(buf, REBOOT_HARD_STR, strlen(REBOOT_HARD_STR)))
+ reboot_mode = REBOOT_HARD;
+ else if (!strncmp(buf, REBOOT_SOFT_STR, strlen(REBOOT_SOFT_STR)))
+ reboot_mode = REBOOT_SOFT;
+ else if (!strncmp(buf, REBOOT_GPIO_STR, strlen(REBOOT_GPIO_STR)))
+ reboot_mode = REBOOT_GPIO;
+ else
+ return -EINVAL;
+
+ return count;
+}
+static struct kobj_attribute reboot_mode_attr = __ATTR_RW(mode);
+
+static ssize_t type_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
+{
+ const char *val;
+
+ switch (reboot_type) {
+ case BOOT_TRIPLE:
+ val = BOOT_TRIPLE_STR;
+ break;
+ case BOOT_KBD:
+ val = BOOT_KBD_STR;
+ break;
+ case BOOT_BIOS:
+ val = BOOT_BIOS_STR;
+ break;
+ case BOOT_ACPI:
+ val = BOOT_ACPI_STR;
+ break;
+ case BOOT_EFI:
+ val = BOOT_EFI_STR;
+ break;
+ case BOOT_CF9_FORCE:
+ val = BOOT_CF9_FORCE_STR;
+ break;
+ case BOOT_CF9_SAFE:
+ val = BOOT_CF9_SAFE_STR;
+ break;
+ default:
+ val = REBOOT_UNDEFINED_STR;
+ }
+
+ return sprintf(buf, "%s\n", val);
+}
+static ssize_t type_store(struct kobject *kobj, struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ if (!capable(CAP_SYS_BOOT))
+ return -EPERM;
+
+ if (!strncmp(buf, BOOT_TRIPLE_STR, strlen(BOOT_TRIPLE_STR)))
+ reboot_type = BOOT_TRIPLE;
+ else if (!strncmp(buf, BOOT_KBD_STR, strlen(BOOT_KBD_STR)))
+ reboot_type = BOOT_KBD;
+ else if (!strncmp(buf, BOOT_BIOS_STR, strlen(BOOT_BIOS_STR)))
+ reboot_type = BOOT_BIOS;
+ else if (!strncmp(buf, BOOT_ACPI_STR, strlen(BOOT_ACPI_STR)))
+ reboot_type = BOOT_ACPI;
+ else if (!strncmp(buf, BOOT_EFI_STR, strlen(BOOT_EFI_STR)))
+ reboot_type = BOOT_EFI;
+ else if (!strncmp(buf, BOOT_CF9_FORCE_STR, strlen(BOOT_CF9_FORCE_STR)))
+ reboot_type = BOOT_CF9_FORCE;
+ else if (!strncmp(buf, BOOT_CF9_SAFE_STR, strlen(BOOT_CF9_SAFE_STR)))
+ reboot_type = BOOT_CF9_SAFE;
+ else
+ return -EINVAL;
+
+ return count;
+}
+static struct kobj_attribute reboot_type_attr = __ATTR_RW(type);
+
+static ssize_t cpu_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%d\n", reboot_cpu);
+}
+static ssize_t cpu_store(struct kobject *kobj, struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ unsigned int cpunum;
+ int rc;
+
+ if (!capable(CAP_SYS_BOOT))
+ return -EPERM;
+
+ rc = kstrtouint(buf, 0, &cpunum);
+
+ if (rc)
+ return rc;
+
+ if (cpunum >= num_possible_cpus())
+ return -ERANGE;
+
+ reboot_cpu = cpunum;
+
+ return count;
+}
+static struct kobj_attribute reboot_cpu_attr = __ATTR_RW(cpu);
+
+static ssize_t force_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%d\n", reboot_force);
+}
+static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ bool res;
+
+ if (!capable(CAP_SYS_BOOT))
+ return -EPERM;
+
+ if (kstrtobool(buf, &res))
+ return -EINVAL;
+
+ reboot_force = res;
+
+ return count;
+}
+static struct kobj_attribute reboot_force_attr = __ATTR_RW(force);
+
+static struct attribute *reboot_attrs[] = {
+ &reboot_mode_attr.attr,
+ &reboot_type_attr.attr,
+ &reboot_cpu_attr.attr,
+ &reboot_force_attr.attr,
+ NULL,
+};
+
+static const struct attribute_group reboot_attr_group = {
+ .attrs = reboot_attrs,
+};
+
+static int __init reboot_ksysfs_init(void)
+{
+ struct kobject *reboot_kobj;
+ int ret;
+
+ reboot_kobj = kobject_create_and_add("reboot", kernel_kobj);
+ if (!reboot_kobj)
+ return -ENOMEM;
+
+ ret = sysfs_create_group(reboot_kobj, &reboot_attr_group);
+ if (ret) {
+ kobject_put(reboot_kobj);
+ return ret;
+ }
+
+ return 0;
+}
+late_initcall(reboot_ksysfs_init);
+
+#endif