// SPDX-License-Identifier: GPL-2.0-only
/*
 * AMD Secure Encrypted Virtualization (SEV) guest driver interface
 *
 * Copyright (C) 2021-2024 Advanced Micro Devices, Inc.
 *
 * Author: Brijesh Singh <brijesh.singh@amd.com>
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/mutex.h>
#include <linux/io.h>
#include <linux/platform_device.h>
#include <linux/miscdevice.h>
#include <linux/set_memory.h>
#include <linux/fs.h>
#include <linux/tsm.h>
#include <crypto/gcm.h>
#include <linux/psp-sev.h>
#include <linux/sockptr.h>
#include <linux/cleanup.h>
#include <linux/uuid.h>
#include <linux/configfs.h>
#include <linux/mm.h>
#include <uapi/linux/sev-guest.h>
#include <uapi/linux/psp-sev.h>

#include <asm/svm.h>
#include <asm/sev.h>

#define DEVICE_NAME     "sev-guest"

#define SVSM_MAX_RETRIES                3

struct snp_guest_dev {
        struct device *dev;
        struct miscdevice misc;

        struct snp_msg_desc *msg_desc;
};

/*
 * The VMPCK ID represents the key used by the SNP guest to communicate with the
 * SEV firmware in the AMD Secure Processor (ASP, aka PSP). By default, the key
 * used will be the key associated with the VMPL at which the guest is running.
 * Should the default key be wiped (see snp_disable_vmpck()), this parameter
 * allows for using one of the remaining VMPCKs.
 */
static int vmpck_id = -1;
module_param(vmpck_id, int, 0444);
MODULE_PARM_DESC(vmpck_id, "The VMPCK ID to use when communicating with the PSP.");

static inline struct snp_guest_dev *to_snp_dev(struct file *file)
{
        struct miscdevice *dev = file->private_data;

        return container_of(dev, struct snp_guest_dev, misc);
}

struct snp_req_resp {
        sockptr_t req_data;
        sockptr_t resp_data;
};

static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
{
        struct snp_report_req *report_req __free(kfree) = NULL;
        struct snp_msg_desc *mdesc = snp_dev->msg_desc;
        struct snp_report_resp *report_resp;
        struct snp_guest_req req = {};
        int rc, resp_len;

        if (!arg->req_data || !arg->resp_data)
                return -EINVAL;

        report_req = kzalloc_obj(*report_req, GFP_KERNEL_ACCOUNT);
        if (!report_req)
                return -ENOMEM;

        if (copy_from_user(report_req, (void __user *)arg->req_data, sizeof(*report_req)))
                return -EFAULT;

        /*
         * The intermediate response buffer is used while decrypting the
         * response payload. Make sure that it has enough space to cover the
         * authtag.
         */
        resp_len = sizeof(report_resp->data) + mdesc->ctx->authsize;
        report_resp = kzalloc(resp_len, GFP_KERNEL_ACCOUNT);
        if (!report_resp)
                return -ENOMEM;

        req.msg_version = arg->msg_version;
        req.msg_type = SNP_MSG_REPORT_REQ;
        req.vmpck_id = mdesc->vmpck_id;
        req.req_buf = report_req;
        req.req_sz = sizeof(*report_req);
        req.resp_buf = report_resp->data;
        req.resp_sz = resp_len;
        req.exit_code = SVM_VMGEXIT_GUEST_REQUEST;

        rc = snp_send_guest_request(mdesc, &req);
        arg->exitinfo2 = req.exitinfo2;
        if (rc)
                goto e_free;

        if (copy_to_user((void __user *)arg->resp_data, report_resp, sizeof(*report_resp)))
                rc = -EFAULT;

e_free:
        kfree(report_resp);
        return rc;
}

static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
{
        struct snp_derived_key_resp *derived_key_resp __free(kfree) = NULL;
        struct snp_derived_key_req *derived_key_req __free(kfree) = NULL;
        struct snp_msg_desc *mdesc = snp_dev->msg_desc;
        struct snp_guest_req req = {};
        int rc, resp_len;

        if (!arg->req_data || !arg->resp_data)
                return -EINVAL;

        /*
         * The intermediate response buffer is used while decrypting the
         * response payload. Make sure that it has enough space to cover the
         * authtag.
         */
        resp_len = sizeof(derived_key_resp->data) + mdesc->ctx->authsize;
        derived_key_resp = kzalloc(resp_len, GFP_KERNEL_ACCOUNT);
        if (!derived_key_resp)
                return -ENOMEM;

        derived_key_req = kzalloc_obj(*derived_key_req, GFP_KERNEL_ACCOUNT);
        if (!derived_key_req)
                return -ENOMEM;

        if (copy_from_user(derived_key_req, (void __user *)arg->req_data,
                           sizeof(*derived_key_req)))
                return -EFAULT;

        req.msg_version = arg->msg_version;
        req.msg_type = SNP_MSG_KEY_REQ;
        req.vmpck_id = mdesc->vmpck_id;
        req.req_buf = derived_key_req;
        req.req_sz = sizeof(*derived_key_req);
        req.resp_buf = derived_key_resp;
        req.resp_sz = resp_len;
        req.exit_code = SVM_VMGEXIT_GUEST_REQUEST;

        rc = snp_send_guest_request(mdesc, &req);
        arg->exitinfo2 = req.exitinfo2;
        if (!rc) {
                if (copy_to_user((void __user *)arg->resp_data, derived_key_resp,
                                 sizeof(derived_key_resp->data)))
                        rc = -EFAULT;
        }

        /* The response buffer contains the sensitive data, explicitly clear it. */
        memzero_explicit(derived_key_resp, sizeof(*derived_key_resp));

        return rc;
}

static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg,
                          struct snp_req_resp *io)

{
        struct snp_ext_report_req *report_req __free(kfree) = NULL;
        struct snp_msg_desc *mdesc = snp_dev->msg_desc;
        struct snp_report_resp *report_resp;
        struct snp_guest_req req = {};
        int ret, npages = 0, resp_len;
        sockptr_t certs_address;
        struct page *page;

        if (sockptr_is_null(io->req_data) || sockptr_is_null(io->resp_data))
                return -EINVAL;

        report_req = kzalloc_obj(*report_req, GFP_KERNEL_ACCOUNT);
        if (!report_req)
                return -ENOMEM;

        if (copy_from_sockptr(report_req, io->req_data, sizeof(*report_req)))
                return -EFAULT;

        /* caller does not want certificate data */
        if (!report_req->certs_len || !report_req->certs_address)
                goto cmd;

        if (report_req->certs_len > SEV_FW_BLOB_MAX_SIZE ||
            !IS_ALIGNED(report_req->certs_len, PAGE_SIZE))
                return -EINVAL;

        if (sockptr_is_kernel(io->resp_data)) {
                certs_address = KERNEL_SOCKPTR((void *)report_req->certs_address);
        } else {
                certs_address = USER_SOCKPTR((void __user *)report_req->certs_address);
                if (!access_ok(certs_address.user, report_req->certs_len))
                        return -EFAULT;
        }

        /*
         * Initialize the intermediate buffer with all zeros. This buffer
         * is used in the guest request message to get the certs blob from
         * the host. If host does not supply any certs in it, then copy
         * zeros to indicate that certificate data was not provided.
         */
        npages = report_req->certs_len >> PAGE_SHIFT;
        page = alloc_pages(GFP_KERNEL_ACCOUNT | __GFP_ZERO,
                           get_order(report_req->certs_len));
        if (!page)
                return -ENOMEM;

        req.certs_data = page_address(page);
        ret = set_memory_decrypted((unsigned long)req.certs_data, npages);
        if (ret) {
                pr_err("failed to mark page shared, ret=%d\n", ret);
                __free_pages(page, get_order(report_req->certs_len));
                return -EFAULT;
        }

cmd:
        /*
         * The intermediate response buffer is used while decrypting the
         * response payload. Make sure that it has enough space to cover the
         * authtag.
         */
        resp_len = sizeof(report_resp->data) + mdesc->ctx->authsize;
        report_resp = kzalloc(resp_len, GFP_KERNEL_ACCOUNT);
        if (!report_resp) {
                ret = -ENOMEM;
                goto e_free_data;
        }

        req.input.data_npages = npages;

        req.msg_version = arg->msg_version;
        req.msg_type = SNP_MSG_REPORT_REQ;
        req.vmpck_id = mdesc->vmpck_id;
        req.req_buf = &report_req->data;
        req.req_sz = sizeof(report_req->data);
        req.resp_buf = report_resp->data;
        req.resp_sz = resp_len;
        req.exit_code = SVM_VMGEXIT_EXT_GUEST_REQUEST;

        ret = snp_send_guest_request(mdesc, &req);
        arg->exitinfo2 = req.exitinfo2;

        /* If certs length is invalid then copy the returned length */
        if (arg->vmm_error == SNP_GUEST_VMM_ERR_INVALID_LEN) {
                report_req->certs_len = req.input.data_npages << PAGE_SHIFT;

                if (copy_to_sockptr(io->req_data, report_req, sizeof(*report_req)))
                        ret = -EFAULT;
        }

        if (ret)
                goto e_free;

        if (npages && copy_to_sockptr(certs_address, req.certs_data, report_req->certs_len)) {
                ret = -EFAULT;
                goto e_free;
        }

        if (copy_to_sockptr(io->resp_data, report_resp, sizeof(*report_resp)))
                ret = -EFAULT;

e_free:
        kfree(report_resp);
e_free_data:
        if (npages) {
                if (set_memory_encrypted((unsigned long)req.certs_data, npages))
                        WARN_ONCE(ret, "failed to restore encryption mask (leak it)\n");
                else
                        __free_pages(page, get_order(report_req->certs_len));
        }
        return ret;
}

static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long arg)
{
        struct snp_guest_dev *snp_dev = to_snp_dev(file);
        void __user *argp = (void __user *)arg;
        struct snp_guest_request_ioctl input;
        struct snp_req_resp io;
        int ret = -ENOTTY;

        if (copy_from_user(&input, argp, sizeof(input)))
                return -EFAULT;

        input.exitinfo2 = 0xff;

        /* Message version must be non-zero */
        if (!input.msg_version)
                return -EINVAL;

        switch (ioctl) {
        case SNP_GET_REPORT:
                ret = get_report(snp_dev, &input);
                break;
        case SNP_GET_DERIVED_KEY:
                ret = get_derived_key(snp_dev, &input);
                break;
        case SNP_GET_EXT_REPORT:
                /*
                 * As get_ext_report() may be called from the ioctl() path and a
                 * kernel internal path (configfs-tsm), decorate the passed
                 * buffers as user pointers.
                 */
                io.req_data = USER_SOCKPTR((void __user *)input.req_data);
                io.resp_data = USER_SOCKPTR((void __user *)input.resp_data);
                ret = get_ext_report(snp_dev, &input, &io);
                break;
        default:
                break;
        }

        if (input.exitinfo2 && copy_to_user(argp, &input, sizeof(input)))
                return -EFAULT;

        return ret;
}

static const struct file_operations snp_guest_fops = {
        .owner  = THIS_MODULE,
        .unlocked_ioctl = snp_guest_ioctl,
};

struct snp_msg_report_resp_hdr {
        u32 status;
        u32 report_size;
        u8 rsvd[24];
};

struct snp_msg_cert_entry {
        guid_t guid;
        u32 offset;
        u32 length;
};

static int sev_svsm_report_new(struct tsm_report *report, void *data)
{
        unsigned int rep_len, man_len, certs_len;
        struct tsm_report_desc *desc = &report->desc;
        struct svsm_attest_call ac = {};
        unsigned int retry_count;
        void *rep, *man, *certs;
        struct svsm_call call;
        unsigned int size;
        bool try_again;
        void *buffer;
        u64 call_id;
        int ret;

        /*
         * Allocate pages for the request:
         * - Report blob (4K)
         * - Manifest blob (4K)
         * - Certificate blob (16K)
         *
         * Above addresses must be 4K aligned
         */
        rep_len = SZ_4K;
        man_len = SZ_4K;
        certs_len = SEV_FW_BLOB_MAX_SIZE;

        if (guid_is_null(&desc->service_guid)) {
                call_id = SVSM_ATTEST_CALL(SVSM_ATTEST_SERVICES);
        } else {
                export_guid(ac.service_guid, &desc->service_guid);
                ac.service_manifest_ver = desc->service_manifest_version;

                call_id = SVSM_ATTEST_CALL(SVSM_ATTEST_SINGLE_SERVICE);
        }

        retry_count = 0;

retry:
        memset(&call, 0, sizeof(call));

        size = rep_len + man_len + certs_len;
        buffer = alloc_pages_exact(size, __GFP_ZERO);
        if (!buffer)
                return -ENOMEM;

        rep = buffer;
        ac.report_buf.pa = __pa(rep);
        ac.report_buf.len = rep_len;

        man = rep + rep_len;
        ac.manifest_buf.pa = __pa(man);
        ac.manifest_buf.len = man_len;

        certs = man + man_len;
        ac.certificates_buf.pa = __pa(certs);
        ac.certificates_buf.len = certs_len;

        ac.nonce.pa = __pa(desc->inblob);
        ac.nonce.len = desc->inblob_len;

        ret = snp_issue_svsm_attest_req(call_id, &call, &ac);
        if (ret) {
                free_pages_exact(buffer, size);

                switch (call.rax_out) {
                case SVSM_ERR_INVALID_PARAMETER:
                        try_again = false;

                        if (ac.report_buf.len > rep_len) {
                                rep_len = PAGE_ALIGN(ac.report_buf.len);
                                try_again = true;
                        }

                        if (ac.manifest_buf.len > man_len) {
                                man_len = PAGE_ALIGN(ac.manifest_buf.len);
                                try_again = true;
                        }

                        if (ac.certificates_buf.len > certs_len) {
                                certs_len = PAGE_ALIGN(ac.certificates_buf.len);
                                try_again = true;
                        }

                        /* If one of the buffers wasn't large enough, retry the request */
                        if (try_again && retry_count < SVSM_MAX_RETRIES) {
                                retry_count++;
                                goto retry;
                        }

                        return -EINVAL;
                default:
                        pr_err_ratelimited("SVSM attestation request failed (%d / 0x%llx)\n",
                                           ret, call.rax_out);
                        return -EINVAL;
                }
        }

        /*
         * Allocate all the blob memory buffers at once so that the cleanup is
         * done for errors that occur after the first allocation (i.e. before
         * using no_free_ptr()).
         */
        rep_len = ac.report_buf.len;
        void *rbuf __free(kvfree) = kvzalloc(rep_len, GFP_KERNEL);

        man_len = ac.manifest_buf.len;
        void *mbuf __free(kvfree) = kvzalloc(man_len, GFP_KERNEL);

        certs_len = ac.certificates_buf.len;
        void *cbuf __free(kvfree) = certs_len ? kvzalloc(certs_len, GFP_KERNEL) : NULL;

        if (!rbuf || !mbuf || (certs_len && !cbuf)) {
                free_pages_exact(buffer, size);
                return -ENOMEM;
        }

        memcpy(rbuf, rep, rep_len);
        report->outblob = no_free_ptr(rbuf);
        report->outblob_len = rep_len;

        memcpy(mbuf, man, man_len);
        report->manifestblob = no_free_ptr(mbuf);
        report->manifestblob_len = man_len;

        if (certs_len) {
                memcpy(cbuf, certs, certs_len);
                report->auxblob = no_free_ptr(cbuf);
                report->auxblob_len = certs_len;
        }

        free_pages_exact(buffer, size);

        return 0;
}

static int sev_report_new(struct tsm_report *report, void *data)
{
        struct snp_msg_cert_entry *cert_table;
        struct tsm_report_desc *desc = &report->desc;
        struct snp_guest_dev *snp_dev = data;
        struct snp_msg_report_resp_hdr hdr;
        const u32 report_size = SZ_4K;
        const u32 ext_size = SEV_FW_BLOB_MAX_SIZE;
        u32 certs_size, i, size = report_size + ext_size;
        int ret;

        if (desc->inblob_len != SNP_REPORT_USER_DATA_SIZE)
                return -EINVAL;

        if (desc->service_provider) {
                if (strcmp(desc->service_provider, "svsm"))
                        return -EINVAL;

                return sev_svsm_report_new(report, data);
        }

        void *buf __free(kvfree) = kvzalloc(size, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;

        cert_table = buf + report_size;
        struct snp_ext_report_req ext_req = {
                .data = { .vmpl = desc->privlevel },
                .certs_address = (__u64)cert_table,
                .certs_len = ext_size,
        };
        memcpy(&ext_req.data.user_data, desc->inblob, desc->inblob_len);

        struct snp_guest_request_ioctl input = {
                .msg_version = 1,
                .req_data = (__u64)&ext_req,
                .resp_data = (__u64)buf,
                .exitinfo2 = 0xff,
        };
        struct snp_req_resp io = {
                .req_data = KERNEL_SOCKPTR(&ext_req),
                .resp_data = KERNEL_SOCKPTR(buf),
        };

        ret = get_ext_report(snp_dev, &input, &io);
        if (ret)
                return ret;

        memcpy(&hdr, buf, sizeof(hdr));
        if (hdr.status == SEV_RET_INVALID_PARAM)
                return -EINVAL;
        if (hdr.status == SEV_RET_INVALID_KEY)
                return -EINVAL;
        if (hdr.status)
                return -ENXIO;
        if ((hdr.report_size + sizeof(hdr)) > report_size)
                return -ENOMEM;

        void *rbuf __free(kvfree) = kvzalloc(hdr.report_size, GFP_KERNEL);
        if (!rbuf)
                return -ENOMEM;

        memcpy(rbuf, buf + sizeof(hdr), hdr.report_size);
        report->outblob = no_free_ptr(rbuf);
        report->outblob_len = hdr.report_size;

        certs_size = 0;
        for (i = 0; i < ext_size / sizeof(struct snp_msg_cert_entry); i++) {
                struct snp_msg_cert_entry *ent = &cert_table[i];

                if (guid_is_null(&ent->guid) && !ent->offset && !ent->length)
                        break;
                certs_size = max(certs_size, ent->offset + ent->length);
        }

        /* Suspicious that the response populated entries without populating size */
        if (!certs_size && i)
                dev_warn_ratelimited(snp_dev->dev, "certificate slots conveyed without size\n");

        /* No certs to report */
        if (!certs_size)
                return 0;

        /* Suspicious that the certificate blob size contract was violated
         */
        if (certs_size > ext_size) {
                dev_warn_ratelimited(snp_dev->dev, "certificate data truncated\n");
                certs_size = ext_size;
        }

        void *cbuf __free(kvfree) = kvzalloc(certs_size, GFP_KERNEL);
        if (!cbuf)
                return -ENOMEM;

        memcpy(cbuf, cert_table, certs_size);
        report->auxblob = no_free_ptr(cbuf);
        report->auxblob_len = certs_size;

        return 0;
}

static bool sev_report_attr_visible(int n)
{
        switch (n) {
        case TSM_REPORT_GENERATION:
        case TSM_REPORT_PROVIDER:
        case TSM_REPORT_PRIVLEVEL:
        case TSM_REPORT_PRIVLEVEL_FLOOR:
                return true;
        case TSM_REPORT_SERVICE_PROVIDER:
        case TSM_REPORT_SERVICE_GUID:
        case TSM_REPORT_SERVICE_MANIFEST_VER:
                return snp_vmpl;
        }

        return false;
}

static bool sev_report_bin_attr_visible(int n)
{
        switch (n) {
        case TSM_REPORT_INBLOB:
        case TSM_REPORT_OUTBLOB:
        case TSM_REPORT_AUXBLOB:
                return true;
        case TSM_REPORT_MANIFESTBLOB:
                return snp_vmpl;
        }

        return false;
}

static struct tsm_report_ops sev_tsm_report_ops = {
        .name = KBUILD_MODNAME,
        .report_new = sev_report_new,
        .report_attr_visible = sev_report_attr_visible,
        .report_bin_attr_visible = sev_report_bin_attr_visible,
};

static void unregister_sev_tsm(void *data)
{
        tsm_report_unregister(&sev_tsm_report_ops);
}

static int __init sev_guest_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct snp_guest_dev *snp_dev;
        struct snp_msg_desc *mdesc;
        struct miscdevice *misc;
        int ret;

        BUILD_BUG_ON(sizeof(struct snp_guest_msg) > PAGE_SIZE);

        if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
                return -ENODEV;

        snp_dev = devm_kzalloc(&pdev->dev, sizeof(struct snp_guest_dev), GFP_KERNEL);
        if (!snp_dev)
                return -ENOMEM;

        mdesc = snp_msg_alloc();
        if (IS_ERR_OR_NULL(mdesc))
                return -ENOMEM;

        ret = snp_msg_init(mdesc, vmpck_id);
        if (ret)
                goto e_msg_init;

        platform_set_drvdata(pdev, snp_dev);
        snp_dev->dev = dev;

        misc = &snp_dev->misc;
        misc->minor = MISC_DYNAMIC_MINOR;
        misc->name = DEVICE_NAME;
        misc->fops = &snp_guest_fops;

        /* Set the privlevel_floor attribute based on the vmpck_id */
        sev_tsm_report_ops.privlevel_floor = mdesc->vmpck_id;

        ret = tsm_report_register(&sev_tsm_report_ops, snp_dev);
        if (ret)
                goto e_msg_init;

        ret = devm_add_action_or_reset(&pdev->dev, unregister_sev_tsm, NULL);
        if (ret)
                goto e_msg_init;

        ret =  misc_register(misc);
        if (ret)
                goto e_msg_init;

        snp_dev->msg_desc = mdesc;
        dev_info(dev, "Initialized SEV guest driver (using VMPCK%d communication key)\n",
                 mdesc->vmpck_id);
        return 0;

e_msg_init:
        snp_msg_free(mdesc);

        return ret;
}

static void __exit sev_guest_remove(struct platform_device *pdev)
{
        struct snp_guest_dev *snp_dev = platform_get_drvdata(pdev);

        snp_msg_free(snp_dev->msg_desc);
        misc_deregister(&snp_dev->misc);
}

/*
 * This driver is meant to be a common SEV guest interface driver and to
 * support any SEV guest API. As such, even though it has been introduced
 * with the SEV-SNP support, it is named "sev-guest".
 *
 * sev_guest_remove() lives in .exit.text. For drivers registered via
 * module_platform_driver_probe() this is ok because they cannot get unbound
 * at runtime. So mark the driver struct with __refdata to prevent modpost
 * triggering a section mismatch warning.
 */
static struct platform_driver sev_guest_driver __refdata = {
        .remove         = __exit_p(sev_guest_remove),
        .driver         = {
                .name = "sev-guest",
        },
};

module_platform_driver_probe(sev_guest_driver, sev_guest_probe);

MODULE_AUTHOR("Brijesh Singh <brijesh.singh@amd.com>");
MODULE_LICENSE("GPL");
MODULE_VERSION("1.0.0");
MODULE_DESCRIPTION("AMD SEV Guest Driver");
MODULE_ALIAS("platform:sev-guest");