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1// SPDX-License-Identifier: GPL-2.02/*3 * Copyright (C) 2022 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.4 *5 * The "Virtual Machine Generation ID" is exposed via ACPI or DT and changes when a6 * virtual machine forks or is cloned. This driver exists for shepherding that7 * information to random.c.8 */9 10#include <linux/acpi.h>11#include <linux/interrupt.h>12#include <linux/kernel.h>13#include <linux/module.h>14#include <linux/platform_device.h>15#include <linux/random.h>16 17ACPI_MODULE_NAME("vmgenid");18 19enum { VMGENID_SIZE = 16 };20 21struct vmgenid_state {22 u8 *next_id;23 u8 this_id[VMGENID_SIZE];24};25 26static void vmgenid_notify(struct device *device)27{28 struct vmgenid_state *state = device->driver_data;29 u8 old_id[VMGENID_SIZE];30 31 memcpy(old_id, state->this_id, sizeof(old_id));32 memcpy(state->this_id, state->next_id, sizeof(state->this_id));33 if (!memcmp(old_id, state->this_id, sizeof(old_id)))34 return;35 add_vmfork_randomness(state->this_id, sizeof(state->this_id));36}37 38static void setup_vmgenid_state(struct vmgenid_state *state, void *virt_addr)39{40 state->next_id = virt_addr;41 memcpy(state->this_id, state->next_id, sizeof(state->this_id));42 add_device_randomness(state->this_id, sizeof(state->this_id));43}44 45#ifdef CONFIG_ACPI46static void vmgenid_acpi_handler(acpi_handle __always_unused handle,47 u32 __always_unused event, void *dev)48{49 vmgenid_notify(dev);50}51 52static int vmgenid_add_acpi(struct device *dev, struct vmgenid_state *state)53{54 struct acpi_device *device = ACPI_COMPANION(dev);55 struct acpi_buffer parsed = { ACPI_ALLOCATE_BUFFER };56 union acpi_object *obj;57 phys_addr_t phys_addr;58 acpi_status status;59 void *virt_addr;60 int ret = 0;61 62 status = acpi_evaluate_object(device->handle, "ADDR", NULL, &parsed);63 if (ACPI_FAILURE(status)) {64 ACPI_EXCEPTION((AE_INFO, status, "Evaluating ADDR"));65 return -ENODEV;66 }67 obj = parsed.pointer;68 if (!obj || obj->type != ACPI_TYPE_PACKAGE || obj->package.count != 2 ||69 obj->package.elements[0].type != ACPI_TYPE_INTEGER ||70 obj->package.elements[1].type != ACPI_TYPE_INTEGER) {71 ret = -EINVAL;72 goto out;73 }74 75 phys_addr = (obj->package.elements[0].integer.value << 0) |76 (obj->package.elements[1].integer.value << 32);77 78 virt_addr = devm_memremap(&device->dev, phys_addr, VMGENID_SIZE, MEMREMAP_WB);79 if (IS_ERR(virt_addr)) {80 ret = PTR_ERR(virt_addr);81 goto out;82 }83 setup_vmgenid_state(state, virt_addr);84 85 status = acpi_install_notify_handler(device->handle, ACPI_DEVICE_NOTIFY,86 vmgenid_acpi_handler, dev);87 if (ACPI_FAILURE(status)) {88 ret = -ENODEV;89 goto out;90 }91 92 dev->driver_data = state;93out:94 ACPI_FREE(parsed.pointer);95 return ret;96}97#else98static int vmgenid_add_acpi(struct device *dev, struct vmgenid_state *state)99{100 return -EINVAL;101}102#endif103 104static irqreturn_t vmgenid_of_irq_handler(int __always_unused irq, void *dev)105{106 vmgenid_notify(dev);107 return IRQ_HANDLED;108}109 110static int vmgenid_add_of(struct platform_device *pdev,111 struct vmgenid_state *state)112{113 void *virt_addr;114 int ret;115 116 virt_addr = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);117 if (IS_ERR(virt_addr))118 return PTR_ERR(virt_addr);119 120 setup_vmgenid_state(state, virt_addr);121 122 ret = platform_get_irq(pdev, 0);123 if (ret < 0)124 return ret;125 126 ret = devm_request_irq(&pdev->dev, ret, vmgenid_of_irq_handler,127 IRQF_SHARED, "vmgenid", &pdev->dev);128 if (ret < 0)129 return ret;130 131 pdev->dev.driver_data = state;132 return 0;133}134 135static int vmgenid_add(struct platform_device *pdev)136{137 struct device *dev = &pdev->dev;138 struct vmgenid_state *state;139 int ret;140 141 state = devm_kmalloc(dev, sizeof(*state), GFP_KERNEL);142 if (!state)143 return -ENOMEM;144 145 if (dev->of_node)146 ret = vmgenid_add_of(pdev, state);147 else148 ret = vmgenid_add_acpi(dev, state);149 150 if (ret < 0)151 devm_kfree(dev, state);152 return ret;153}154 155static const struct of_device_id vmgenid_of_ids[] = {156 { .compatible = "microsoft,vmgenid", },157 { },158};159MODULE_DEVICE_TABLE(of, vmgenid_of_ids);160 161static const struct acpi_device_id vmgenid_acpi_ids[] = {162 { "VMGENCTR", 0 },163 { "VM_GEN_COUNTER", 0 },164 { }165};166MODULE_DEVICE_TABLE(acpi, vmgenid_acpi_ids);167 168static struct platform_driver vmgenid_plaform_driver = {169 .probe = vmgenid_add,170 .driver = {171 .name = "vmgenid",172 .acpi_match_table = vmgenid_acpi_ids,173 .of_match_table = vmgenid_of_ids,174 },175};176 177module_platform_driver(vmgenid_plaform_driver)178 179MODULE_DESCRIPTION("Virtual Machine Generation ID");180MODULE_LICENSE("GPL v2");181MODULE_AUTHOR("Jason A. Donenfeld <Jason@zx2c4.com>");182