// 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 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); char *envp[] = { "NEW_VMGENID=1", NULL }; 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)); kobject_uevent_env(&device->dev.kobj, KOBJ_CHANGE, envp); } 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 <Jason@zx2c4.com>");