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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2022 Jason A. Donenfeld <Jason@zx2c4.com>. 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
15ACPI_MODULE_NAME("vmgenid");
16
17enum { VMGENID_SIZE = 16 };
18
19struct vmgenid_state {
20 u8 *next_id;
21 u8 this_id[VMGENID_SIZE];
22};
23
24static 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
63out:
64 ACPI_FREE(parsed.pointer);
65 return ret;
66}
67
68static void vmgenid_notify(struct acpi_device *device, u32 event)
69{
70 struct vmgenid_state *state = acpi_driver_data(device);
71 char *envp[] = { "NEW_VMGENID=1", NULL };
72 u8 old_id[VMGENID_SIZE];
73
74 memcpy(old_id, state->this_id, sizeof(old_id));
75 memcpy(state->this_id, state->next_id, sizeof(state->this_id));
76 if (!memcmp(old_id, state->this_id, sizeof(old_id)))
77 return;
78 add_vmfork_randomness(state->this_id, sizeof(state->this_id));
79 kobject_uevent_env(&device->dev.kobj, KOBJ_CHANGE, envp);
80}
81
82static const struct acpi_device_id vmgenid_ids[] = {
83 { "VMGENCTR", 0 },
84 { "VM_GEN_COUNTER", 0 },
85 { }
86};
87
88static struct acpi_driver vmgenid_driver = {
89 .name = "vmgenid",
90 .ids = vmgenid_ids,
91 .owner = THIS_MODULE,
92 .ops = {
93 .add = vmgenid_add,
94 .notify = vmgenid_notify
95 }
96};
97
98module_acpi_driver(vmgenid_driver);
99
100MODULE_DEVICE_TABLE(acpi, vmgenid_ids);
101MODULE_DESCRIPTION("Virtual Machine Generation ID");
102MODULE_LICENSE("GPL v2");
103MODULE_AUTHOR("Jason A. Donenfeld <Jason@zx2c4.com>");
1// SPDX-License-Identifier: GPL-2.0
2/*
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 a
6 * virtual machine forks or is cloned. This driver exists for shepherding that
7 * 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_ACPI
46static 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#else
98static int vmgenid_add_acpi(struct device *dev, struct vmgenid_state *state)
99{
100 return -EINVAL;
101}
102#endif
103
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 else
148 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>");