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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 | // 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) { union acpi_object *obj; obj = wmidev_block_query(to_wmi_device(dev), 0); if (!obj) return -ENODEV; if (obj->type != ACPI_TYPE_INTEGER) { dev_warn(dev, "wmidev_block_query 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 = wmidev_block_set(to_wmi_device(dev), 0, &input); if (ACPI_FAILURE(status)) { dev_err(dev, "wmidev_block_set 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 void intel_wmi_sbl_fw_update_remove(struct wmi_device *wdev) { dev_info(&wdev->dev, "Slim Bootloader signaling driver removed\n"); } 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, .no_singleton = true, }; 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"); |