[linux.git] / drivers / virt / vmgenid.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2022 Jason A. Donenfeld <[email protected]>. All Rights Reserved.
 *
 * The "Virtual Machine Generation ID" is exposed via ACPI and changes when a
 * virtual machine forks or is cloned. This driver exists for shepherding that
 * information to random.c.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/acpi.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 int vmgenid_add(struct acpi_device *device)
{
	struct acpi_buffer parsed = { ACPI_ALLOCATE_BUFFER };
	struct vmgenid_state *state;
	union acpi_object *obj;
	phys_addr_t phys_addr;
	acpi_status status;
	int ret = 0;

	state = devm_kmalloc(&device->dev, sizeof(*state), GFP_KERNEL);
	if (!state)
		return -ENOMEM;

	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);
	state->next_id = devm_memremap(&device->dev, phys_addr, VMGENID_SIZE, MEMREMAP_WB);
	if (IS_ERR(state->next_id)) {
		ret = PTR_ERR(state->next_id);
		goto out;
	}

	memcpy(state->this_id, state->next_id, sizeof(state->this_id));
	add_device_randomness(state->this_id, sizeof(state->this_id));

	device->driver_data = state;

out:
	ACPI_FREE(parsed.pointer);
	return ret;
}

static void vmgenid_notify(struct acpi_device *device, u32 event)
{
	struct vmgenid_state *state = acpi_driver_data(device);
	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 const struct acpi_device_id vmgenid_ids[] = {
	{ "VMGENCTR", 0 },
	{ "VM_GEN_COUNTER", 0 },
	{ }
};

static struct acpi_driver vmgenid_driver = {
	.name = "vmgenid",
	.ids = vmgenid_ids,
	.owner = THIS_MODULE,
	.ops = {
		.add = vmgenid_add,
		.notify = vmgenid_notify
	}
};

module_acpi_driver(vmgenid_driver);

MODULE_DEVICE_TABLE(acpi, vmgenid_ids);
MODULE_DESCRIPTION("Virtual Machine Generation ID");
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Jason A. Donenfeld <[email protected]>");
Commit	Line	Data
af6b54e2 JD	1	// SPDX-License-Identifier: GPL-2.0
	2	/*
	3	* Copyright (C) 2022 Jason A. Donenfeld <[email protected]>. All Rights Reserved.
	4	*
	5	* The "Virtual Machine Generation ID" is exposed via ACPI and changes when a
	6	* virtual machine forks or is cloned. This driver exists for shepherding that
	7	* information to random.c.
	8	*/
	9
	10	#include <linux/kernel.h>
	11	#include <linux/module.h>
	12	#include <linux/acpi.h>
	13	#include <linux/random.h>
	14
	15	ACPI_MODULE_NAME("vmgenid");
	16
	17	enum { VMGENID_SIZE = 16 };
	18
	19	struct vmgenid_state {
	20	u8 *next_id;
	21	u8 this_id[VMGENID_SIZE];
	22	};
	23
	24	static int vmgenid_add(struct acpi_device *device)
	25	{
	26	struct acpi_buffer parsed = { ACPI_ALLOCATE_BUFFER };
	27	struct vmgenid_state *state;
	28	union acpi_object *obj;
	29	phys_addr_t phys_addr;
	30	acpi_status status;
	31	int ret = 0;
	32
	33	state = devm_kmalloc(&device->dev, sizeof(*state), GFP_KERNEL);
	34	if (!state)
	35	return -ENOMEM;
	36
	37	status = acpi_evaluate_object(device->handle, "ADDR", NULL, &parsed);
	38	if (ACPI_FAILURE(status)) {
	39	ACPI_EXCEPTION((AE_INFO, status, "Evaluating ADDR"));
	40	return -ENODEV;
	41	}
	42	obj = parsed.pointer;
	43	if (!obj \|\| obj->type != ACPI_TYPE_PACKAGE \|\| obj->package.count != 2 \|\|
	44	obj->package.elements[0].type != ACPI_TYPE_INTEGER \|\|
	45	obj->package.elements[1].type != ACPI_TYPE_INTEGER) {
	46	ret = -EINVAL;
	47	goto out;
	48	}
	49
	50	phys_addr = (obj->package.elements[0].integer.value << 0) \|
	51	(obj->package.elements[1].integer.value << 32);
	52	state->next_id = devm_memremap(&device->dev, phys_addr, VMGENID_SIZE, MEMREMAP_WB);
	53	if (IS_ERR(state->next_id)) {
	54	ret = PTR_ERR(state->next_id);
	55	goto out;
	56	}
	57
	58	memcpy(state->this_id, state->next_id, sizeof(state->this_id));
	59	add_device_randomness(state->this_id, sizeof(state->this_id));
	60
	61	device->driver_data = state;
	62
	63	out:
	64	ACPI_FREE(parsed.pointer);
65	return ret;
66	}
67
68	static void vmgenid_notify(struct acpi_device *device, u32 event)
69	{
70	struct vmgenid_state *state = acpi_driver_data(device);
71	u8 old_id[VMGENID_SIZE];
72
73	memcpy(old_id, state->this_id, sizeof(old_id));
74	memcpy(state->this_id, state->next_id, sizeof(state->this_id));
75	if (!memcmp(old_id, state->this_id, sizeof(old_id)))
76	return;
77	add_vmfork_randomness(state->this_id, sizeof(state->this_id));
78	}
79
80	static const struct acpi_device_id vmgenid_ids[] = {
0396e46d	81	{ "VMGENCTR", 0 },
af6b54e2 JD	82	{ "VM_GEN_COUNTER", 0 },
	83	{ }
	84	};
	85
	86	static struct acpi_driver vmgenid_driver = {
	87	.name = "vmgenid",
	88	.ids = vmgenid_ids,
	89	.owner = THIS_MODULE,
	90	.ops = {
	91	.add = vmgenid_add,
	92	.notify = vmgenid_notify
	93	}
	94	};
	95
	96	module_acpi_driver(vmgenid_driver);
	97
	98	MODULE_DEVICE_TABLE(acpi, vmgenid_ids);
	99	MODULE_DESCRIPTION("Virtual Machine Generation ID");
	100	MODULE_LICENSE("GPL v2");
	101	MODULE_AUTHOR("Jason A. Donenfeld <[email protected]>");