// SPDX-License-Identifier: GPL-2.0/* * Copyright (C) 2022 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. * * The "Virtual Machine Generation ID" is exposed via ACPI or DT and changes when a * virtual machine forks or is cloned. This driver exists for shepherding that * information to random.c. */ #include <linux/acpi.h>#include <linux/interrupt.h>#include <linux/kernel.h>#include <linux/module.h>#include <linux/platform_device.h>#include <linux/random.h> ACPI_MODULE_NAME("vmgenid"); enum { VMGENID_SIZE = 16 }; struct vmgenid_state {	u8 *next_id;	u8 this_id[VMGENID_SIZE];}; static void vmgenid_notify(struct device *device){	struct vmgenid_state *state = device->driver_data;	u8 old_id[VMGENID_SIZE]; 	memcpy(old_id, state->this_id, sizeof(old_id));	memcpy(state->this_id, state->next_id, sizeof(state->this_id));	if (!memcmp(old_id, state->this_id, sizeof(old_id)))		return;	add_vmfork_randomness(state->this_id, sizeof(state->this_id));} static void setup_vmgenid_state(struct vmgenid_state *state, void *virt_addr){	state->next_id = virt_addr;	memcpy(state->this_id, state->next_id, sizeof(state->this_id));	add_device_randomness(state->this_id, sizeof(state->this_id));} #ifdef CONFIG_ACPIstatic void vmgenid_acpi_handler(acpi_handle __always_unused handle,				 u32 __always_unused event, void *dev){	vmgenid_notify(dev);} static int vmgenid_add_acpi(struct device *dev, struct vmgenid_state *state){	struct acpi_device *device = ACPI_COMPANION(dev);	struct acpi_buffer parsed = { ACPI_ALLOCATE_BUFFER };	union acpi_object *obj;	phys_addr_t phys_addr;	acpi_status status;	void *virt_addr;	int ret = 0; 	status = acpi_evaluate_object(device->handle, "ADDR", NULL, &parsed);	if (ACPI_FAILURE(status)) {		ACPI_EXCEPTION((AE_INFO, status, "Evaluating ADDR"));		return -ENODEV;	}	obj = parsed.pointer;	if (!obj || obj->type != ACPI_TYPE_PACKAGE || obj->package.count != 2 ||	    obj->package.elements[0].type != ACPI_TYPE_INTEGER ||	    obj->package.elements[1].type != ACPI_TYPE_INTEGER) {		ret = -EINVAL;		goto out;	} 	phys_addr = (obj->package.elements[0].integer.value << 0) |		    (obj->package.elements[1].integer.value << 32); 	virt_addr = devm_memremap(&device->dev, phys_addr, VMGENID_SIZE, MEMREMAP_WB);	if (IS_ERR(virt_addr)) {		ret = PTR_ERR(virt_addr);		goto out;	}	setup_vmgenid_state(state, virt_addr); 	status = acpi_install_notify_handler(device->handle, ACPI_DEVICE_NOTIFY,					     vmgenid_acpi_handler, dev);	if (ACPI_FAILURE(status)) {		ret = -ENODEV;		goto out;	} 	dev->driver_data = state;out:	ACPI_FREE(parsed.pointer);	return ret;}#elsestatic int vmgenid_add_acpi(struct device *dev, struct vmgenid_state *state){	return -EINVAL;}#endif static irqreturn_t vmgenid_of_irq_handler(int __always_unused irq, void *dev){	vmgenid_notify(dev);	return IRQ_HANDLED;} static int vmgenid_add_of(struct platform_device *pdev,			  struct vmgenid_state *state){	void *virt_addr;	int ret; 	virt_addr = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);	if (IS_ERR(virt_addr))		return PTR_ERR(virt_addr); 	setup_vmgenid_state(state, virt_addr); 	ret = platform_get_irq(pdev, 0);	if (ret < 0)		return ret; 	ret = devm_request_irq(&pdev->dev, ret, vmgenid_of_irq_handler,			       IRQF_SHARED, "vmgenid", &pdev->dev);	if (ret < 0)		return ret; 	pdev->dev.driver_data = state;	return 0;} static int vmgenid_add(struct platform_device *pdev){	struct device *dev = &pdev->dev;	struct vmgenid_state *state;	int ret; 	state = devm_kmalloc(dev, sizeof(*state), GFP_KERNEL);	if (!state)		return -ENOMEM; 	if (dev->of_node)		ret = vmgenid_add_of(pdev, state);	else		ret = vmgenid_add_acpi(dev, state); 	if (ret < 0)		devm_kfree(dev, state);	return ret;} static const struct of_device_id vmgenid_of_ids[] = {	{ .compatible = "microsoft,vmgenid", },	{ },};MODULE_DEVICE_TABLE(of, vmgenid_of_ids); static const struct acpi_device_id vmgenid_acpi_ids[] = {	{ "VMGENCTR", 0 },	{ "VM_GEN_COUNTER", 0 },	{ }};MODULE_DEVICE_TABLE(acpi, vmgenid_acpi_ids); static struct platform_driver vmgenid_plaform_driver = {	.probe      = vmgenid_add,	.driver     = {		.name   = "vmgenid",		.acpi_match_table = vmgenid_acpi_ids,		.of_match_table = vmgenid_of_ids,	},}; module_platform_driver(vmgenid_plaform_driver) MODULE_DESCRIPTION("Virtual Machine Generation ID");MODULE_LICENSE("GPL v2");MODULE_AUTHOR("Jason A. Donenfeld <Jason@zx2c4.com>");