summaryrefslogtreecommitdiffstats
path: root/drivers/virt/vmgenid.c
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/virt/vmgenid.c')
-rw-r--r--drivers/virt/vmgenid.c101
1 files changed, 101 insertions, 0 deletions
diff --git a/drivers/virt/vmgenid.c b/drivers/virt/vmgenid.c
new file mode 100644
index 000000000..a1c467a0e
--- /dev/null
+++ b/drivers/virt/vmgenid.c
@@ -0,0 +1,101 @@
+// 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);
+ 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 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>");