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101 lines
2.6 KiB
101 lines
2.6 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Copyright (C) 2022 Jason A. Donenfeld <[email protected]>. All Rights Reserved. |
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* |
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* The "Virtual Machine Generation ID" is exposed via ACPI and changes when a |
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* virtual machine forks or is cloned. This driver exists for shepherding that |
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* information to random.c. |
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*/ |
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#include <linux/kernel.h> |
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#include <linux/module.h> |
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#include <linux/acpi.h> |
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#include <linux/random.h> |
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ACPI_MODULE_NAME("vmgenid"); |
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enum { VMGENID_SIZE = 16 }; |
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struct vmgenid_state { |
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u8 *next_id; |
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u8 this_id[VMGENID_SIZE]; |
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}; |
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static int vmgenid_add(struct acpi_device *device) |
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{ |
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struct acpi_buffer parsed = { ACPI_ALLOCATE_BUFFER }; |
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struct vmgenid_state *state; |
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union acpi_object *obj; |
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phys_addr_t phys_addr; |
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acpi_status status; |
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int ret = 0; |
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state = devm_kmalloc(&device->dev, sizeof(*state), GFP_KERNEL); |
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if (!state) |
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return -ENOMEM; |
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status = acpi_evaluate_object(device->handle, "ADDR", NULL, &parsed); |
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if (ACPI_FAILURE(status)) { |
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ACPI_EXCEPTION((AE_INFO, status, "Evaluating ADDR")); |
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return -ENODEV; |
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} |
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obj = parsed.pointer; |
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if (!obj || obj->type != ACPI_TYPE_PACKAGE || obj->package.count != 2 || |
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obj->package.elements[0].type != ACPI_TYPE_INTEGER || |
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obj->package.elements[1].type != ACPI_TYPE_INTEGER) { |
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ret = -EINVAL; |
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goto out; |
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} |
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phys_addr = (obj->package.elements[0].integer.value << 0) | |
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(obj->package.elements[1].integer.value << 32); |
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state->next_id = devm_memremap(&device->dev, phys_addr, VMGENID_SIZE, MEMREMAP_WB); |
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if (IS_ERR(state->next_id)) { |
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ret = PTR_ERR(state->next_id); |
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goto out; |
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} |
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memcpy(state->this_id, state->next_id, sizeof(state->this_id)); |
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add_device_randomness(state->this_id, sizeof(state->this_id)); |
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device->driver_data = state; |
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out: |
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ACPI_FREE(parsed.pointer); |
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return ret; |
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} |
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static void vmgenid_notify(struct acpi_device *device, u32 event) |
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{ |
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struct vmgenid_state *state = acpi_driver_data(device); |
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u8 old_id[VMGENID_SIZE]; |
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memcpy(old_id, state->this_id, sizeof(old_id)); |
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memcpy(state->this_id, state->next_id, sizeof(state->this_id)); |
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if (!memcmp(old_id, state->this_id, sizeof(old_id))) |
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return; |
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add_vmfork_randomness(state->this_id, sizeof(state->this_id)); |
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} |
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static const struct acpi_device_id vmgenid_ids[] = { |
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{ "VMGENCTR", 0 }, |
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{ "VM_GEN_COUNTER", 0 }, |
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{ } |
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}; |
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static struct acpi_driver vmgenid_driver = { |
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.name = "vmgenid", |
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.ids = vmgenid_ids, |
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.owner = THIS_MODULE, |
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.ops = { |
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.add = vmgenid_add, |
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.notify = vmgenid_notify |
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} |
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}; |
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module_acpi_driver(vmgenid_driver); |
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MODULE_DEVICE_TABLE(acpi, vmgenid_ids); |
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MODULE_DESCRIPTION("Virtual Machine Generation ID"); |
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MODULE_LICENSE("GPL v2"); |
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MODULE_AUTHOR("Jason A. Donenfeld <[email protected]>");
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