--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Slim Bootloader(SBL) firmware update signaling driver
+ *
+ * Slim Bootloader is a small, open-source, non UEFI compliant, boot firmware
+ * optimized for running on certain Intel platforms.
+ *
+ * SBL exposes an ACPI-WMI device via /sys/bus/wmi/devices/<INTEL_WMI_SBL_GUID>.
+ * This driver further adds "firmware_update_request" device attribute.
+ * This attribute normally has a value of 0 and userspace can signal SBL
+ * to update firmware, on next reboot, by writing a value of 1.
+ *
+ * More details of SBL firmware update process is available at:
+ * https://slimbootloader.github.io/security/firmware-update.html
+ */
+
+#include <linux/acpi.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+#include <linux/wmi.h>
+
+#define INTEL_WMI_SBL_GUID "44FADEB1-B204-40F2-8581-394BBDC1B651"
+
+static int get_fwu_request(struct device *dev, u32 *out)
+{
+ struct acpi_buffer result = {ACPI_ALLOCATE_BUFFER, NULL};
+ union acpi_object *obj;
+ acpi_status status;
+
+ status = wmi_query_block(INTEL_WMI_SBL_GUID, 0, &result);
+ if (ACPI_FAILURE(status)) {
+ dev_err(dev, "wmi_query_block failed\n");
+ return -ENODEV;
+ }
+
+ obj = (union acpi_object *)result.pointer;
+ if (!obj || obj->type != ACPI_TYPE_INTEGER) {
+ dev_warn(dev, "wmi_query_block returned invalid value\n");
+ kfree(obj);
+ return -EINVAL;
+ }
+
+ *out = obj->integer.value;
+ kfree(obj);
+
+ return 0;
+}
+
+static int set_fwu_request(struct device *dev, u32 in)
+{
+ struct acpi_buffer input;
+ acpi_status status;
+ u32 value;
+
+ value = in;
+ input.length = sizeof(u32);
+ input.pointer = &value;
+
+ status = wmi_set_block(INTEL_WMI_SBL_GUID, 0, &input);
+ if (ACPI_FAILURE(status)) {
+ dev_err(dev, "wmi_set_block failed\n");
+ return -ENODEV;
+ }
+
+ return 0;
+}
+
+static ssize_t firmware_update_request_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ u32 val;
+ int ret;
+
+ ret = get_fwu_request(dev, &val);
+ if (ret)
+ return ret;
+
+ return sprintf(buf, "%d\n", val);
+}
+
+static ssize_t firmware_update_request_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ unsigned int val;
+ int ret;
+
+ ret = kstrtouint(buf, 0, &val);
+ if (ret)
+ return ret;
+
+ /* May later be extended to support values other than 0 and 1 */
+ if (val > 1)
+ return -ERANGE;
+
+ ret = set_fwu_request(dev, val);
+ if (ret)
+ return ret;
+
+ return count;
+}
+static DEVICE_ATTR_RW(firmware_update_request);
+
+static struct attribute *firmware_update_attrs[] = {
+ &dev_attr_firmware_update_request.attr,
+ NULL
+};
+ATTRIBUTE_GROUPS(firmware_update);
+
+static int intel_wmi_sbl_fw_update_probe(struct wmi_device *wdev,
+ const void *context)
+{
+ dev_info(&wdev->dev, "Slim Bootloader signaling driver attached\n");
+ return 0;
+}
+
+static int intel_wmi_sbl_fw_update_remove(struct wmi_device *wdev)
+{
+ dev_info(&wdev->dev, "Slim Bootloader signaling driver removed\n");
+ return 0;
+}
+
+static const struct wmi_device_id intel_wmi_sbl_id_table[] = {
+ { .guid_string = INTEL_WMI_SBL_GUID },
+ {}
+};
+MODULE_DEVICE_TABLE(wmi, intel_wmi_sbl_id_table);
+
+static struct wmi_driver intel_wmi_sbl_fw_update_driver = {
+ .driver = {
+ .name = "intel-wmi-sbl-fw-update",
+ .dev_groups = firmware_update_groups,
+ },
+ .probe = intel_wmi_sbl_fw_update_probe,
+ .remove = intel_wmi_sbl_fw_update_remove,
+ .id_table = intel_wmi_sbl_id_table,
+};
+module_wmi_driver(intel_wmi_sbl_fw_update_driver);
+
+MODULE_AUTHOR("Jithu Joseph <jithu.joseph@intel.com>");
+MODULE_DESCRIPTION("Slim Bootloader firmware update signaling driver");
+MODULE_LICENSE("GPL v2");
projects / kernel.git / commitdiff