diff options
Diffstat (limited to 'drivers/virt/vmgenid.c')
| -rw-r--r-- | drivers/virt/vmgenid.c | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/drivers/virt/vmgenid.c b/drivers/virt/vmgenid.c new file mode 100644 index 000000000000..66135eac3abf --- /dev/null +++ b/drivers/virt/vmgenid.c @@ -0,0 +1,181 @@ +// 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 or DT and changes when a + * virtual machine forks or is cloned. This driver exists for shepherding that + * information to random.c. + */ + +#include <linux/acpi.h> +#include <linux/interrupt.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/platform_device.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 void vmgenid_notify(struct device *device) +{ + struct vmgenid_state *state = device->driver_data; + 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 void setup_vmgenid_state(struct vmgenid_state *state, void *virt_addr) +{ + state->next_id = virt_addr; + memcpy(state->this_id, state->next_id, sizeof(state->this_id)); + add_device_randomness(state->this_id, sizeof(state->this_id)); +} + +#ifdef CONFIG_ACPI +static void vmgenid_acpi_handler(acpi_handle __always_unused handle, + u32 __always_unused event, void *dev) +{ + vmgenid_notify(dev); +} + +static int vmgenid_add_acpi(struct device *dev, struct vmgenid_state *state) +{ + struct acpi_device *device = ACPI_COMPANION(dev); + struct acpi_buffer parsed = { ACPI_ALLOCATE_BUFFER }; + union acpi_object *obj; + phys_addr_t phys_addr; + acpi_status status; + void *virt_addr; + int ret = 0; + + 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); + + virt_addr = devm_memremap(&device->dev, phys_addr, VMGENID_SIZE, MEMREMAP_WB); + if (IS_ERR(virt_addr)) { + ret = PTR_ERR(virt_addr); + goto out; + } + setup_vmgenid_state(state, virt_addr); + + status = acpi_install_notify_handler(device->handle, ACPI_DEVICE_NOTIFY, + vmgenid_acpi_handler, dev); + if (ACPI_FAILURE(status)) { + ret = -ENODEV; + goto out; + } + + dev->driver_data = state; +out: + ACPI_FREE(parsed.pointer); + return ret; +} +#else +static int vmgenid_add_acpi(struct device *dev, struct vmgenid_state *state) +{ + return -EINVAL; +} +#endif + +static irqreturn_t vmgenid_of_irq_handler(int __always_unused irq, void *dev) +{ + vmgenid_notify(dev); + return IRQ_HANDLED; +} + +static int vmgenid_add_of(struct platform_device *pdev, + struct vmgenid_state *state) +{ + void *virt_addr; + int ret; + + virt_addr = devm_platform_get_and_ioremap_resource(pdev, 0, NULL); + if (IS_ERR(virt_addr)) + return PTR_ERR(virt_addr); + + setup_vmgenid_state(state, virt_addr); + + ret = platform_get_irq(pdev, 0); + if (ret < 0) + return ret; + + ret = devm_request_irq(&pdev->dev, ret, vmgenid_of_irq_handler, + IRQF_SHARED, "vmgenid", &pdev->dev); + if (ret < 0) + return ret; + + pdev->dev.driver_data = state; + return 0; +} + +static int vmgenid_add(struct platform_device *pdev) +{ + struct device *dev = &pdev->dev; + struct vmgenid_state *state; + int ret; + + state = devm_kmalloc(dev, sizeof(*state), GFP_KERNEL); + if (!state) + return -ENOMEM; + + if (dev->of_node) + ret = vmgenid_add_of(pdev, state); + else + ret = vmgenid_add_acpi(dev, state); + + if (ret < 0) + devm_kfree(dev, state); + return ret; +} + +static const struct of_device_id vmgenid_of_ids[] = { + { .compatible = "microsoft,vmgenid", }, + { }, +}; +MODULE_DEVICE_TABLE(of, vmgenid_of_ids); + +static const struct acpi_device_id vmgenid_acpi_ids[] = { + { "VMGENCTR", 0 }, + { "VM_GEN_COUNTER", 0 }, + { } +}; +MODULE_DEVICE_TABLE(acpi, vmgenid_acpi_ids); + +static struct platform_driver vmgenid_plaform_driver = { + .probe = vmgenid_add, + .driver = { + .name = "vmgenid", + .acpi_match_table = vmgenid_acpi_ids, + .of_match_table = vmgenid_of_ids, + }, +}; + +module_platform_driver(vmgenid_plaform_driver) + +MODULE_DESCRIPTION("Virtual Machine Generation ID"); +MODULE_LICENSE("GPL v2"); +MODULE_AUTHOR("Jason A. Donenfeld <Jason@zx2c4.com>"); |