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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright IBM Corp. 2022
* Author(s): Steffen Eiden <seiden@linux.ibm.com>
*
* This file provides a Linux misc device to give userspace access to some
* Ultravisor (UV) functions. The device only accepts IOCTLs and will only
* be present if the Ultravisor facility (158) is present.
*
* When userspace sends a valid IOCTL uvdevice will copy the input data to
* kernel space, do some basic validity checks to avoid kernel/system
* corruption. Any other check that the Ultravisor does will not be done by
* the uvdevice to keep changes minimal when adding new functionalities
* to existing UV-calls.
* After the checks uvdevice builds a corresponding
* Ultravisor Call Control Block, and sends the request to the Ultravisor.
* Then, it copies the response, including the return codes, back to userspace.
* It is the responsibility of the userspace to check for any error issued
* by UV and to interpret the UV response. The uvdevice acts as a communication
* channel for userspace to the Ultravisor.
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/miscdevice.h>
#include <linux/types.h>
#include <linux/stddef.h>
#include <linux/vmalloc.h>
#include <linux/slab.h>
#include <linux/cpufeature.h>
#include <asm/uvdevice.h>
#include <asm/uv.h>
static int uvio_build_uvcb_attest(struct uv_cb_attest *uvcb_attest, u8 *arcb,
u8 *meas, u8 *add_data, struct uvio_attest *uvio_attest)
{
void __user *user_buf_arcb = (void __user *)uvio_attest->arcb_addr;
if (copy_from_user(arcb, user_buf_arcb, uvio_attest->arcb_len))
return -EFAULT;
uvcb_attest->header.len = sizeof(*uvcb_attest);
uvcb_attest->header.cmd = UVC_CMD_RETR_ATTEST;
uvcb_attest->arcb_addr = (u64)arcb;
uvcb_attest->cont_token = 0;
uvcb_attest->user_data_len = uvio_attest->user_data_len;
memcpy(uvcb_attest->user_data, uvio_attest->user_data, sizeof(uvcb_attest->user_data));
uvcb_attest->meas_len = uvio_attest->meas_len;
uvcb_attest->meas_addr = (u64)meas;
uvcb_attest->add_data_len = uvio_attest->add_data_len;
uvcb_attest->add_data_addr = (u64)add_data;
return 0;
}
static int uvio_copy_attest_result_to_user(struct uv_cb_attest *uvcb_attest,
struct uvio_ioctl_cb *uv_ioctl,
u8 *measurement, u8 *add_data,
struct uvio_attest *uvio_attest)
{
struct uvio_attest __user *user_uvio_attest = (void __user *)uv_ioctl->argument_addr;
void __user *user_buf_add = (void __user *)uvio_attest->add_data_addr;
void __user *user_buf_meas = (void __user *)uvio_attest->meas_addr;
void __user *user_buf_uid = &user_uvio_attest->config_uid;
if (copy_to_user(user_buf_meas, measurement, uvio_attest->meas_len))
return -EFAULT;
if (add_data && copy_to_user(user_buf_add, add_data, uvio_attest->add_data_len))
return -EFAULT;
if (copy_to_user(user_buf_uid, uvcb_attest->config_uid, sizeof(uvcb_attest->config_uid)))
return -EFAULT;
return 0;
}
static int get_uvio_attest(struct uvio_ioctl_cb *uv_ioctl, struct uvio_attest *uvio_attest)
{
u8 __user *user_arg_buf = (u8 __user *)uv_ioctl->argument_addr;
if (copy_from_user(uvio_attest, user_arg_buf, sizeof(*uvio_attest)))
return -EFAULT;
if (uvio_attest->arcb_len > UVIO_ATT_ARCB_MAX_LEN)
return -EINVAL;
if (uvio_attest->arcb_len == 0)
return -EINVAL;
if (uvio_attest->meas_len > UVIO_ATT_MEASUREMENT_MAX_LEN)
return -EINVAL;
if (uvio_attest->meas_len == 0)
return -EINVAL;
if (uvio_attest->add_data_len > UVIO_ATT_ADDITIONAL_MAX_LEN)
return -EINVAL;
if (uvio_attest->reserved136)
return -EINVAL;
return 0;
}
/**
* uvio_attestation() - Perform a Retrieve Attestation Measurement UVC.
*
* @uv_ioctl: ioctl control block
*
* uvio_attestation() does a Retrieve Attestation Measurement Ultravisor Call.
* It verifies that the given userspace addresses are valid and request sizes
* are sane. Every other check is made by the Ultravisor (UV) and won't result
* in a negative return value. It copies the input to kernelspace, builds the
* request, sends the UV-call, and copies the result to userspace.
*
* The Attestation Request has two input and two outputs.
* ARCB and User Data are inputs for the UV generated by userspace.
* Measurement and Additional Data are outputs for userspace generated by UV.
*
* The Attestation Request Control Block (ARCB) is a cryptographically verified
* and secured request to UV and User Data is some plaintext data which is
* going to be included in the Attestation Measurement calculation.
*
* Measurement is a cryptographic measurement of the callers properties,
* optional data configured by the ARCB and the user data. If specified by the
* ARCB, UV will add some Additional Data to the measurement calculation.
* This Additional Data is then returned as well.
*
* If the Retrieve Attestation Measurement UV facility is not present,
* UV will return invalid command rc. This won't be fenced in the driver
* and does not result in a negative return value.
*
* Context: might sleep
*
* Return: 0 on success or a negative error code on error.
*/
static int uvio_attestation(struct uvio_ioctl_cb *uv_ioctl)
{
struct uv_cb_attest *uvcb_attest = NULL;
struct uvio_attest *uvio_attest = NULL;
u8 *measurement = NULL;
u8 *add_data = NULL;
u8 *arcb = NULL;
int ret;
ret = -EINVAL;
if (uv_ioctl->argument_len != sizeof(*uvio_attest))
goto out;
ret = -ENOMEM;
uvio_attest = kzalloc(sizeof(*uvio_attest), GFP_KERNEL);
if (!uvio_attest)
goto out;
ret = get_uvio_attest(uv_ioctl, uvio_attest);
if (ret)
goto out;
ret = -ENOMEM;
arcb = kvzalloc(uvio_attest->arcb_len, GFP_KERNEL);
measurement = kvzalloc(uvio_attest->meas_len, GFP_KERNEL);
if (!arcb || !measurement)
goto out;
if (uvio_attest->add_data_len) {
add_data = kvzalloc(uvio_attest->add_data_len, GFP_KERNEL);
if (!add_data)
goto out;
}
uvcb_attest = kzalloc(sizeof(*uvcb_attest), GFP_KERNEL);
if (!uvcb_attest)
goto out;
ret = uvio_build_uvcb_attest(uvcb_attest, arcb, measurement, add_data, uvio_attest);
if (ret)
goto out;
uv_call_sched(0, (u64)uvcb_attest);
uv_ioctl->uv_rc = uvcb_attest->header.rc;
uv_ioctl->uv_rrc = uvcb_attest->header.rrc;
ret = uvio_copy_attest_result_to_user(uvcb_attest, uv_ioctl, measurement, add_data,
uvio_attest);
out:
kvfree(arcb);
kvfree(measurement);
kvfree(add_data);
kfree(uvio_attest);
kfree(uvcb_attest);
return ret;
}
static int uvio_copy_and_check_ioctl(struct uvio_ioctl_cb *ioctl, void __user *argp)
{
if (copy_from_user(ioctl, argp, sizeof(*ioctl)))
return -EFAULT;
if (ioctl->flags != 0)
return -EINVAL;
if (memchr_inv(ioctl->reserved14, 0, sizeof(ioctl->reserved14)))
return -EINVAL;
return 0;
}
/*
* IOCTL entry point for the Ultravisor device.
*/
static long uvio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
void __user *argp = (void __user *)arg;
struct uvio_ioctl_cb uv_ioctl = { };
long ret;
switch (cmd) {
case UVIO_IOCTL_ATT:
ret = uvio_copy_and_check_ioctl(&uv_ioctl, argp);
if (ret)
return ret;
ret = uvio_attestation(&uv_ioctl);
break;
default:
ret = -ENOIOCTLCMD;
break;
}
if (ret)
return ret;
if (copy_to_user(argp, &uv_ioctl, sizeof(uv_ioctl)))
ret = -EFAULT;
return ret;
}
static const struct file_operations uvio_dev_fops = {
.owner = THIS_MODULE,
.unlocked_ioctl = uvio_ioctl,
.llseek = no_llseek,
};
static struct miscdevice uvio_dev_miscdev = {
.minor = MISC_DYNAMIC_MINOR,
.name = UVIO_DEVICE_NAME,
.fops = &uvio_dev_fops,
};
static void __exit uvio_dev_exit(void)
{
misc_deregister(&uvio_dev_miscdev);
}
static int __init uvio_dev_init(void)
{
return misc_register(&uvio_dev_miscdev);
}
module_cpu_feature_match(S390_CPU_FEATURE_UV, uvio_dev_init);
module_exit(uvio_dev_exit);
MODULE_AUTHOR("IBM Corporation");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Ultravisor UAPI driver");
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