cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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vmgenid.c (2669B)

      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	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
     80static const struct acpi_device_id vmgenid_ids[] = {
     81	{ "VMGENCTR", 0 },
     82	{ "VM_GEN_COUNTER", 0 },
     83	{ }
     84};
     85
     86static 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
     96module_acpi_driver(vmgenid_driver);
     97
     98MODULE_DEVICE_TABLE(acpi, vmgenid_ids);
     99MODULE_DESCRIPTION("Virtual Machine Generation ID");
    100MODULE_LICENSE("GPL v2");
    101MODULE_AUTHOR("Jason A. Donenfeld <Jason@zx2c4.com>");