--- /dev/null
+.. SPDX-License-Identifier: GPL-2.0
+
+===================================================================
+The Definitive SEV Guest API Documentation
+===================================================================
+
+1. General description
+======================
+
+The SEV API is a set of ioctls that are used by the guest or hypervisor
+to get or set a certain aspect of the SEV virtual machine. The ioctls belong
+to the following classes:
+
+ - Hypervisor ioctls: These query and set global attributes which affect the
+ whole SEV firmware. These ioctl are used by platform provisioning tools.
+
+ - Guest ioctls: These query and set attributes of the SEV virtual machine.
+
+2. API description
+==================
+
+This section describes ioctls that is used for querying the SEV guest report
+from the SEV firmware. For each ioctl, the following information is provided
+along with a description:
+
+ Technology:
+ which SEV technology provides this ioctl. SEV, SEV-ES, SEV-SNP or all.
+
+ Type:
+ hypervisor or guest. The ioctl can be used inside the guest or the
+ hypervisor.
+
+ Parameters:
+ what parameters are accepted by the ioctl.
+
+ Returns:
+ the return value. General error numbers (-ENOMEM, -EINVAL)
+ are not detailed, but errors with specific meanings are.
+
+The guest ioctl should be issued on a file descriptor of the /dev/sev-guest device.
+The ioctl accepts struct snp_user_guest_request. The input and output structure is
+specified through the req_data and resp_data field respectively. If the ioctl fails
+to execute due to a firmware error, then fw_err code will be set otherwise the
+fw_err will be set to 0x00000000000000ff.
+
+The firmware checks that the message sequence counter is one greater than
+the guests message sequence counter. If guest driver fails to increment message
+counter (e.g. counter overflow), then -EIO will be returned.
+
+::
+
+ struct snp_guest_request_ioctl {
+ /* Message version number */
+ __u32 msg_version;
+
+ /* Request and response structure address */
+ __u64 req_data;
+ __u64 resp_data;
+
+ /* firmware error code on failure (see psp-sev.h) */
+ __u64 fw_err;
+ };
+
+2.1 SNP_GET_REPORT
+------------------
+
+:Technology: sev-snp
+:Type: guest ioctl
+:Parameters (in): struct snp_report_req
+:Returns (out): struct snp_report_resp on success, -negative on error
+
+The SNP_GET_REPORT ioctl can be used to query the attestation report from the
+SEV-SNP firmware. The ioctl uses the SNP_GUEST_REQUEST (MSG_REPORT_REQ) command
+provided by the SEV-SNP firmware to query the attestation report.
+
+On success, the snp_report_resp.data will contains the report. The report
+contain the format described in the SEV-SNP specification. See the SEV-SNP
+specification for further details.
+
+2.2 SNP_GET_DERIVED_KEY
+-----------------------
+:Technology: sev-snp
+:Type: guest ioctl
+:Parameters (in): struct snp_derived_key_req
+:Returns (out): struct snp_derived_key_resp on success, -negative on error
+
+The SNP_GET_DERIVED_KEY ioctl can be used to get a key derive from a root key.
+The derived key can be used by the guest for any purpose, such as sealing keys
+or communicating with external entities.
+
+The ioctl uses the SNP_GUEST_REQUEST (MSG_KEY_REQ) command provided by the
+SEV-SNP firmware to derive the key. See SEV-SNP specification for further details
+on the various fields passed in the key derivation request.
+
+On success, the snp_derived_key_resp.data contains the derived key value. See
+the SEV-SNP specification for further details.
+
+
+2.3 SNP_GET_EXT_REPORT
+----------------------
+:Technology: sev-snp
+:Type: guest ioctl
+:Parameters (in/out): struct snp_ext_report_req
+:Returns (out): struct snp_report_resp on success, -negative on error
+
+The SNP_GET_EXT_REPORT ioctl is similar to the SNP_GET_REPORT. The difference is
+related to the additional certificate data that is returned with the report.
+The certificate data returned is being provided by the hypervisor through the
+SNP_SET_EXT_CONFIG.
+
+The ioctl uses the SNP_GUEST_REQUEST (MSG_REPORT_REQ) command provided by the SEV-SNP
+firmware to get the attestation report.
+
+On success, the snp_ext_report_resp.data will contain the attestation report
+and snp_ext_report_req.certs_address will contain the certificate blob. If the
+length of the blob is smaller than expected then snp_ext_report_req.certs_len will
+be updated with the expected value.
+
+See GHCB specification for further detail on how to parse the certificate blob.
+
+3. SEV-SNP CPUID Enforcement
+============================
+
+SEV-SNP guests can access a special page that contains a table of CPUID values
+that have been validated by the PSP as part of the SNP_LAUNCH_UPDATE firmware
+command. It provides the following assurances regarding the validity of CPUID
+values:
+
+ - Its address is obtained via bootloader/firmware (via CC blob), and those
+ binaries will be measured as part of the SEV-SNP attestation report.
+ - Its initial state will be encrypted/pvalidated, so attempts to modify
+ it during run-time will result in garbage being written, or #VC exceptions
+ being generated due to changes in validation state if the hypervisor tries
+ to swap the backing page.
+ - Attempts to bypass PSP checks by the hypervisor by using a normal page, or
+ a non-CPUID encrypted page will change the measurement provided by the
+ SEV-SNP attestation report.
+ - The CPUID page contents are *not* measured, but attempts to modify the
+ expected contents of a CPUID page as part of guest initialization will be
+ gated by the PSP CPUID enforcement policy checks performed on the page
+ during SNP_LAUNCH_UPDATE, and noticeable later if the guest owner
+ implements their own checks of the CPUID values.
+
+It is important to note that this last assurance is only useful if the kernel
+has taken care to make use of the SEV-SNP CPUID throughout all stages of boot.
+Otherwise, guest owner attestation provides no assurance that the kernel wasn't
+fed incorrect values at some point during boot.
+
+
+Reference
+---------
+
+SEV-SNP and GHCB specification: developer.amd.com/sev
+
+The driver is based on SEV-SNP firmware spec 0.9 and GHCB spec version 2.0.
+++ /dev/null
-.. SPDX-License-Identifier: GPL-2.0
-
-===================================================================
-The Definitive SEV Guest API Documentation
-===================================================================
-
-1. General description
-======================
-
-The SEV API is a set of ioctls that are used by the guest or hypervisor
-to get or set a certain aspect of the SEV virtual machine. The ioctls belong
-to the following classes:
-
- - Hypervisor ioctls: These query and set global attributes which affect the
- whole SEV firmware. These ioctl are used by platform provisioning tools.
-
- - Guest ioctls: These query and set attributes of the SEV virtual machine.
-
-2. API description
-==================
-
-This section describes ioctls that is used for querying the SEV guest report
-from the SEV firmware. For each ioctl, the following information is provided
-along with a description:
-
- Technology:
- which SEV technology provides this ioctl. SEV, SEV-ES, SEV-SNP or all.
-
- Type:
- hypervisor or guest. The ioctl can be used inside the guest or the
- hypervisor.
-
- Parameters:
- what parameters are accepted by the ioctl.
-
- Returns:
- the return value. General error numbers (-ENOMEM, -EINVAL)
- are not detailed, but errors with specific meanings are.
-
-The guest ioctl should be issued on a file descriptor of the /dev/sev-guest device.
-The ioctl accepts struct snp_user_guest_request. The input and output structure is
-specified through the req_data and resp_data field respectively. If the ioctl fails
-to execute due to a firmware error, then fw_err code will be set otherwise the
-fw_err will be set to 0x00000000000000ff.
-
-The firmware checks that the message sequence counter is one greater than
-the guests message sequence counter. If guest driver fails to increment message
-counter (e.g. counter overflow), then -EIO will be returned.
-
-::
-
- struct snp_guest_request_ioctl {
- /* Message version number */
- __u32 msg_version;
-
- /* Request and response structure address */
- __u64 req_data;
- __u64 resp_data;
-
- /* firmware error code on failure (see psp-sev.h) */
- __u64 fw_err;
- };
-
-2.1 SNP_GET_REPORT
-------------------
-
-:Technology: sev-snp
-:Type: guest ioctl
-:Parameters (in): struct snp_report_req
-:Returns (out): struct snp_report_resp on success, -negative on error
-
-The SNP_GET_REPORT ioctl can be used to query the attestation report from the
-SEV-SNP firmware. The ioctl uses the SNP_GUEST_REQUEST (MSG_REPORT_REQ) command
-provided by the SEV-SNP firmware to query the attestation report.
-
-On success, the snp_report_resp.data will contains the report. The report
-contain the format described in the SEV-SNP specification. See the SEV-SNP
-specification for further details.
-
-2.2 SNP_GET_DERIVED_KEY
------------------------
-:Technology: sev-snp
-:Type: guest ioctl
-:Parameters (in): struct snp_derived_key_req
-:Returns (out): struct snp_derived_key_resp on success, -negative on error
-
-The SNP_GET_DERIVED_KEY ioctl can be used to get a key derive from a root key.
-The derived key can be used by the guest for any purpose, such as sealing keys
-or communicating with external entities.
-
-The ioctl uses the SNP_GUEST_REQUEST (MSG_KEY_REQ) command provided by the
-SEV-SNP firmware to derive the key. See SEV-SNP specification for further details
-on the various fields passed in the key derivation request.
-
-On success, the snp_derived_key_resp.data contains the derived key value. See
-the SEV-SNP specification for further details.
-
-
-2.3 SNP_GET_EXT_REPORT
-----------------------
-:Technology: sev-snp
-:Type: guest ioctl
-:Parameters (in/out): struct snp_ext_report_req
-:Returns (out): struct snp_report_resp on success, -negative on error
-
-The SNP_GET_EXT_REPORT ioctl is similar to the SNP_GET_REPORT. The difference is
-related to the additional certificate data that is returned with the report.
-The certificate data returned is being provided by the hypervisor through the
-SNP_SET_EXT_CONFIG.
-
-The ioctl uses the SNP_GUEST_REQUEST (MSG_REPORT_REQ) command provided by the SEV-SNP
-firmware to get the attestation report.
-
-On success, the snp_ext_report_resp.data will contain the attestation report
-and snp_ext_report_req.certs_address will contain the certificate blob. If the
-length of the blob is smaller than expected then snp_ext_report_req.certs_len will
-be updated with the expected value.
-
-See GHCB specification for further detail on how to parse the certificate blob.
-
-3. SEV-SNP CPUID Enforcement
-============================
-
-SEV-SNP guests can access a special page that contains a table of CPUID values
-that have been validated by the PSP as part of the SNP_LAUNCH_UPDATE firmware
-command. It provides the following assurances regarding the validity of CPUID
-values:
-
- - Its address is obtained via bootloader/firmware (via CC blob), and those
- binaries will be measured as part of the SEV-SNP attestation report.
- - Its initial state will be encrypted/pvalidated, so attempts to modify
- it during run-time will result in garbage being written, or #VC exceptions
- being generated due to changes in validation state if the hypervisor tries
- to swap the backing page.
- - Attempts to bypass PSP checks by the hypervisor by using a normal page, or
- a non-CPUID encrypted page will change the measurement provided by the
- SEV-SNP attestation report.
- - The CPUID page contents are *not* measured, but attempts to modify the
- expected contents of a CPUID page as part of guest initialization will be
- gated by the PSP CPUID enforcement policy checks performed on the page
- during SNP_LAUNCH_UPDATE, and noticeable later if the guest owner
- implements their own checks of the CPUID values.
-
-It is important to note that this last assurance is only useful if the kernel
-has taken care to make use of the SEV-SNP CPUID throughout all stages of boot.
-Otherwise, guest owner attestation provides no assurance that the kernel wasn't
-fed incorrect values at some point during boot.
-
-
-Reference
----------
-
-SEV-SNP and GHCB specification: developer.amd.com/sev
-
-The driver is based on SEV-SNP firmware spec 0.9 and GHCB spec version 2.0.
guest-halt-polling
ne_overview
acrn/index
- coco/sevguest
+ coco/sev-guest
.. only:: html and subproject
source "drivers/virt/acrn/Kconfig"
-source "drivers/virt/coco/sevguest/Kconfig"
+source "drivers/virt/coco/sev-guest/Kconfig"
endif
obj-$(CONFIG_NITRO_ENCLAVES) += nitro_enclaves/
obj-$(CONFIG_ACRN_HSM) += acrn/
-obj-$(CONFIG_SEV_GUEST) += coco/sevguest/
+obj-$(CONFIG_SEV_GUEST) += coco/sev-guest/
--- /dev/null
+config SEV_GUEST
+ tristate "AMD SEV Guest driver"
+ default m
+ depends on AMD_MEM_ENCRYPT
+ select CRYPTO_AEAD2
+ select CRYPTO_GCM
+ help
+ SEV-SNP firmware provides the guest a mechanism to communicate with
+ the PSP without risk from a malicious hypervisor who wishes to read,
+ alter, drop or replay the messages sent. The driver provides
+ userspace interface to communicate with the PSP to request the
+ attestation report and more.
+
+ If you choose 'M' here, this module will be called sev-guest.
--- /dev/null
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_SEV_GUEST) += sev-guest.o
--- /dev/null
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AMD Secure Encrypted Virtualization (SEV) guest driver interface
+ *
+ * Copyright (C) 2021 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 <crypto/aead.h>
+#include <linux/scatterlist.h>
+#include <linux/psp-sev.h>
+#include <uapi/linux/sev-guest.h>
+#include <uapi/linux/psp-sev.h>
+
+#include <asm/svm.h>
+#include <asm/sev.h>
+
+#include "sev-guest.h"
+
+#define DEVICE_NAME "sev-guest"
+#define AAD_LEN 48
+#define MSG_HDR_VER 1
+
+struct snp_guest_crypto {
+ struct crypto_aead *tfm;
+ u8 *iv, *authtag;
+ int iv_len, a_len;
+};
+
+struct snp_guest_dev {
+ struct device *dev;
+ struct miscdevice misc;
+
+ void *certs_data;
+ struct snp_guest_crypto *crypto;
+ struct snp_guest_msg *request, *response;
+ struct snp_secrets_page_layout *layout;
+ struct snp_req_data input;
+ u32 *os_area_msg_seqno;
+ u8 *vmpck;
+};
+
+static u32 vmpck_id;
+module_param(vmpck_id, uint, 0444);
+MODULE_PARM_DESC(vmpck_id, "The VMPCK ID to use when communicating with the PSP.");
+
+/* Mutex to serialize the shared buffer access and command handling. */
+static DEFINE_MUTEX(snp_cmd_mutex);
+
+static bool is_vmpck_empty(struct snp_guest_dev *snp_dev)
+{
+ char zero_key[VMPCK_KEY_LEN] = {0};
+
+ if (snp_dev->vmpck)
+ return !memcmp(snp_dev->vmpck, zero_key, VMPCK_KEY_LEN);
+
+ return true;
+}
+
+static void snp_disable_vmpck(struct snp_guest_dev *snp_dev)
+{
+ memzero_explicit(snp_dev->vmpck, VMPCK_KEY_LEN);
+ snp_dev->vmpck = NULL;
+}
+
+static inline u64 __snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
+{
+ u64 count;
+
+ lockdep_assert_held(&snp_cmd_mutex);
+
+ /* Read the current message sequence counter from secrets pages */
+ count = *snp_dev->os_area_msg_seqno;
+
+ return count + 1;
+}
+
+/* Return a non-zero on success */
+static u64 snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
+{
+ u64 count = __snp_get_msg_seqno(snp_dev);
+
+ /*
+ * The message sequence counter for the SNP guest request is a 64-bit
+ * value but the version 2 of GHCB specification defines a 32-bit storage
+ * for it. If the counter exceeds the 32-bit value then return zero.
+ * The caller should check the return value, but if the caller happens to
+ * not check the value and use it, then the firmware treats zero as an
+ * invalid number and will fail the message request.
+ */
+ if (count >= UINT_MAX) {
+ dev_err(snp_dev->dev, "request message sequence counter overflow\n");
+ return 0;
+ }
+
+ return count;
+}
+
+static void snp_inc_msg_seqno(struct snp_guest_dev *snp_dev)
+{
+ /*
+ * The counter is also incremented by the PSP, so increment it by 2
+ * and save in secrets page.
+ */
+ *snp_dev->os_area_msg_seqno += 2;
+}
+
+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);
+}
+
+static struct snp_guest_crypto *init_crypto(struct snp_guest_dev *snp_dev, u8 *key, size_t keylen)
+{
+ struct snp_guest_crypto *crypto;
+
+ crypto = kzalloc(sizeof(*crypto), GFP_KERNEL_ACCOUNT);
+ if (!crypto)
+ return NULL;
+
+ crypto->tfm = crypto_alloc_aead("gcm(aes)", 0, 0);
+ if (IS_ERR(crypto->tfm))
+ goto e_free;
+
+ if (crypto_aead_setkey(crypto->tfm, key, keylen))
+ goto e_free_crypto;
+
+ crypto->iv_len = crypto_aead_ivsize(crypto->tfm);
+ crypto->iv = kmalloc(crypto->iv_len, GFP_KERNEL_ACCOUNT);
+ if (!crypto->iv)
+ goto e_free_crypto;
+
+ if (crypto_aead_authsize(crypto->tfm) > MAX_AUTHTAG_LEN) {
+ if (crypto_aead_setauthsize(crypto->tfm, MAX_AUTHTAG_LEN)) {
+ dev_err(snp_dev->dev, "failed to set authsize to %d\n", MAX_AUTHTAG_LEN);
+ goto e_free_iv;
+ }
+ }
+
+ crypto->a_len = crypto_aead_authsize(crypto->tfm);
+ crypto->authtag = kmalloc(crypto->a_len, GFP_KERNEL_ACCOUNT);
+ if (!crypto->authtag)
+ goto e_free_auth;
+
+ return crypto;
+
+e_free_auth:
+ kfree(crypto->authtag);
+e_free_iv:
+ kfree(crypto->iv);
+e_free_crypto:
+ crypto_free_aead(crypto->tfm);
+e_free:
+ kfree(crypto);
+
+ return NULL;
+}
+
+static void deinit_crypto(struct snp_guest_crypto *crypto)
+{
+ crypto_free_aead(crypto->tfm);
+ kfree(crypto->iv);
+ kfree(crypto->authtag);
+ kfree(crypto);
+}
+
+static int enc_dec_message(struct snp_guest_crypto *crypto, struct snp_guest_msg *msg,
+ u8 *src_buf, u8 *dst_buf, size_t len, bool enc)
+{
+ struct snp_guest_msg_hdr *hdr = &msg->hdr;
+ struct scatterlist src[3], dst[3];
+ DECLARE_CRYPTO_WAIT(wait);
+ struct aead_request *req;
+ int ret;
+
+ req = aead_request_alloc(crypto->tfm, GFP_KERNEL);
+ if (!req)
+ return -ENOMEM;
+
+ /*
+ * AEAD memory operations:
+ * +------ AAD -------+------- DATA -----+---- AUTHTAG----+
+ * | msg header | plaintext | hdr->authtag |
+ * | bytes 30h - 5Fh | or | |
+ * | | cipher | |
+ * +------------------+------------------+----------------+
+ */
+ sg_init_table(src, 3);
+ sg_set_buf(&src[0], &hdr->algo, AAD_LEN);
+ sg_set_buf(&src[1], src_buf, hdr->msg_sz);
+ sg_set_buf(&src[2], hdr->authtag, crypto->a_len);
+
+ sg_init_table(dst, 3);
+ sg_set_buf(&dst[0], &hdr->algo, AAD_LEN);
+ sg_set_buf(&dst[1], dst_buf, hdr->msg_sz);
+ sg_set_buf(&dst[2], hdr->authtag, crypto->a_len);
+
+ aead_request_set_ad(req, AAD_LEN);
+ aead_request_set_tfm(req, crypto->tfm);
+ aead_request_set_callback(req, 0, crypto_req_done, &wait);
+
+ aead_request_set_crypt(req, src, dst, len, crypto->iv);
+ ret = crypto_wait_req(enc ? crypto_aead_encrypt(req) : crypto_aead_decrypt(req), &wait);
+
+ aead_request_free(req);
+ return ret;
+}
+
+static int __enc_payload(struct snp_guest_dev *snp_dev, struct snp_guest_msg *msg,
+ void *plaintext, size_t len)
+{
+ struct snp_guest_crypto *crypto = snp_dev->crypto;
+ struct snp_guest_msg_hdr *hdr = &msg->hdr;
+
+ memset(crypto->iv, 0, crypto->iv_len);
+ memcpy(crypto->iv, &hdr->msg_seqno, sizeof(hdr->msg_seqno));
+
+ return enc_dec_message(crypto, msg, plaintext, msg->payload, len, true);
+}
+
+static int dec_payload(struct snp_guest_dev *snp_dev, struct snp_guest_msg *msg,
+ void *plaintext, size_t len)
+{
+ struct snp_guest_crypto *crypto = snp_dev->crypto;
+ struct snp_guest_msg_hdr *hdr = &msg->hdr;
+
+ /* Build IV with response buffer sequence number */
+ memset(crypto->iv, 0, crypto->iv_len);
+ memcpy(crypto->iv, &hdr->msg_seqno, sizeof(hdr->msg_seqno));
+
+ return enc_dec_message(crypto, msg, msg->payload, plaintext, len, false);
+}
+
+static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, void *payload, u32 sz)
+{
+ struct snp_guest_crypto *crypto = snp_dev->crypto;
+ struct snp_guest_msg *resp = snp_dev->response;
+ struct snp_guest_msg *req = snp_dev->request;
+ struct snp_guest_msg_hdr *req_hdr = &req->hdr;
+ struct snp_guest_msg_hdr *resp_hdr = &resp->hdr;
+
+ dev_dbg(snp_dev->dev, "response [seqno %lld type %d version %d sz %d]\n",
+ resp_hdr->msg_seqno, resp_hdr->msg_type, resp_hdr->msg_version, resp_hdr->msg_sz);
+
+ /* Verify that the sequence counter is incremented by 1 */
+ if (unlikely(resp_hdr->msg_seqno != (req_hdr->msg_seqno + 1)))
+ return -EBADMSG;
+
+ /* Verify response message type and version number. */
+ if (resp_hdr->msg_type != (req_hdr->msg_type + 1) ||
+ resp_hdr->msg_version != req_hdr->msg_version)
+ return -EBADMSG;
+
+ /*
+ * If the message size is greater than our buffer length then return
+ * an error.
+ */
+ if (unlikely((resp_hdr->msg_sz + crypto->a_len) > sz))
+ return -EBADMSG;
+
+ /* Decrypt the payload */
+ return dec_payload(snp_dev, resp, payload, resp_hdr->msg_sz + crypto->a_len);
+}
+
+static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8 type,
+ void *payload, size_t sz)
+{
+ struct snp_guest_msg *req = snp_dev->request;
+ struct snp_guest_msg_hdr *hdr = &req->hdr;
+
+ memset(req, 0, sizeof(*req));
+
+ hdr->algo = SNP_AEAD_AES_256_GCM;
+ hdr->hdr_version = MSG_HDR_VER;
+ hdr->hdr_sz = sizeof(*hdr);
+ hdr->msg_type = type;
+ hdr->msg_version = version;
+ hdr->msg_seqno = seqno;
+ hdr->msg_vmpck = vmpck_id;
+ hdr->msg_sz = sz;
+
+ /* Verify the sequence number is non-zero */
+ if (!hdr->msg_seqno)
+ return -ENOSR;
+
+ dev_dbg(snp_dev->dev, "request [seqno %lld type %d version %d sz %d]\n",
+ hdr->msg_seqno, hdr->msg_type, hdr->msg_version, hdr->msg_sz);
+
+ return __enc_payload(snp_dev, req, payload, sz);
+}
+
+static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, int msg_ver,
+ u8 type, void *req_buf, size_t req_sz, void *resp_buf,
+ u32 resp_sz, __u64 *fw_err)
+{
+ unsigned long err;
+ u64 seqno;
+ int rc;
+
+ /* Get message sequence and verify that its a non-zero */
+ seqno = snp_get_msg_seqno(snp_dev);
+ if (!seqno)
+ return -EIO;
+
+ memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
+
+ /* Encrypt the userspace provided payload */
+ rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz);
+ if (rc)
+ return rc;
+
+ /* Call firmware to process the request */
+ rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err);
+ if (fw_err)
+ *fw_err = err;
+
+ if (rc)
+ return rc;
+
+ /*
+ * The verify_and_dec_payload() will fail only if the hypervisor is
+ * actively modifying the message header or corrupting the encrypted payload.
+ * This hints that hypervisor is acting in a bad faith. Disable the VMPCK so that
+ * the key cannot be used for any communication. The key is disabled to ensure
+ * that AES-GCM does not use the same IV while encrypting the request payload.
+ */
+ rc = verify_and_dec_payload(snp_dev, resp_buf, resp_sz);
+ if (rc) {
+ dev_alert(snp_dev->dev,
+ "Detected unexpected decode failure, disabling the vmpck_id %d\n",
+ vmpck_id);
+ snp_disable_vmpck(snp_dev);
+ return rc;
+ }
+
+ /* Increment to new message sequence after payload decryption was successful. */
+ snp_inc_msg_seqno(snp_dev);
+
+ return 0;
+}
+
+static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
+{
+ struct snp_guest_crypto *crypto = snp_dev->crypto;
+ struct snp_report_resp *resp;
+ struct snp_report_req req;
+ int rc, resp_len;
+
+ lockdep_assert_held(&snp_cmd_mutex);
+
+ if (!arg->req_data || !arg->resp_data)
+ return -EINVAL;
+
+ if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(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(resp->data) + crypto->a_len;
+ resp = kzalloc(resp_len, GFP_KERNEL_ACCOUNT);
+ if (!resp)
+ return -ENOMEM;
+
+ rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg->msg_version,
+ SNP_MSG_REPORT_REQ, &req, sizeof(req), resp->data,
+ resp_len, &arg->fw_err);
+ if (rc)
+ goto e_free;
+
+ if (copy_to_user((void __user *)arg->resp_data, resp, sizeof(*resp)))
+ rc = -EFAULT;
+
+e_free:
+ kfree(resp);
+ return rc;
+}
+
+static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
+{
+ struct snp_guest_crypto *crypto = snp_dev->crypto;
+ struct snp_derived_key_resp resp = {0};
+ struct snp_derived_key_req req;
+ int rc, resp_len;
+ /* Response data is 64 bytes and max authsize for GCM is 16 bytes. */
+ u8 buf[64 + 16];
+
+ lockdep_assert_held(&snp_cmd_mutex);
+
+ 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(resp.data) + crypto->a_len;
+ if (sizeof(buf) < resp_len)
+ return -ENOMEM;
+
+ if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req)))
+ return -EFAULT;
+
+ rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg->msg_version,
+ SNP_MSG_KEY_REQ, &req, sizeof(req), buf, resp_len,
+ &arg->fw_err);
+ if (rc)
+ return rc;
+
+ memcpy(resp.data, buf, sizeof(resp.data));
+ if (copy_to_user((void __user *)arg->resp_data, &resp, sizeof(resp)))
+ rc = -EFAULT;
+
+ /* The response buffer contains the sensitive data, explicitly clear it. */
+ memzero_explicit(buf, sizeof(buf));
+ memzero_explicit(&resp, sizeof(resp));
+ return rc;
+}
+
+static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
+{
+ struct snp_guest_crypto *crypto = snp_dev->crypto;
+ struct snp_ext_report_req req;
+ struct snp_report_resp *resp;
+ int ret, npages = 0, resp_len;
+
+ lockdep_assert_held(&snp_cmd_mutex);
+
+ if (!arg->req_data || !arg->resp_data)
+ return -EINVAL;
+
+ if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req)))
+ return -EFAULT;
+
+ /* userspace does not want certificate data */
+ if (!req.certs_len || !req.certs_address)
+ goto cmd;
+
+ if (req.certs_len > SEV_FW_BLOB_MAX_SIZE ||
+ !IS_ALIGNED(req.certs_len, PAGE_SIZE))
+ return -EINVAL;
+
+ if (!access_ok((const void __user *)req.certs_address, 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.
+ */
+ memset(snp_dev->certs_data, 0, req.certs_len);
+ npages = req.certs_len >> PAGE_SHIFT;
+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(resp->data) + crypto->a_len;
+ resp = kzalloc(resp_len, GFP_KERNEL_ACCOUNT);
+ if (!resp)
+ return -ENOMEM;
+
+ snp_dev->input.data_npages = npages;
+ ret = handle_guest_request(snp_dev, SVM_VMGEXIT_EXT_GUEST_REQUEST, arg->msg_version,
+ SNP_MSG_REPORT_REQ, &req.data,
+ sizeof(req.data), resp->data, resp_len, &arg->fw_err);
+
+ /* If certs length is invalid then copy the returned length */
+ if (arg->fw_err == SNP_GUEST_REQ_INVALID_LEN) {
+ req.certs_len = snp_dev->input.data_npages << PAGE_SHIFT;
+
+ if (copy_to_user((void __user *)arg->req_data, &req, sizeof(req)))
+ ret = -EFAULT;
+ }
+
+ if (ret)
+ goto e_free;
+
+ if (npages &&
+ copy_to_user((void __user *)req.certs_address, snp_dev->certs_data,
+ req.certs_len)) {
+ ret = -EFAULT;
+ goto e_free;
+ }
+
+ if (copy_to_user((void __user *)arg->resp_data, resp, sizeof(*resp)))
+ ret = -EFAULT;
+
+e_free:
+ kfree(resp);
+ 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;
+ int ret = -ENOTTY;
+
+ if (copy_from_user(&input, argp, sizeof(input)))
+ return -EFAULT;
+
+ input.fw_err = 0xff;
+
+ /* Message version must be non-zero */
+ if (!input.msg_version)
+ return -EINVAL;
+
+ mutex_lock(&snp_cmd_mutex);
+
+ /* Check if the VMPCK is not empty */
+ if (is_vmpck_empty(snp_dev)) {
+ dev_err_ratelimited(snp_dev->dev, "VMPCK is disabled\n");
+ mutex_unlock(&snp_cmd_mutex);
+ return -ENOTTY;
+ }
+
+ 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:
+ ret = get_ext_report(snp_dev, &input);
+ break;
+ default:
+ break;
+ }
+
+ mutex_unlock(&snp_cmd_mutex);
+
+ if (input.fw_err && copy_to_user(argp, &input, sizeof(input)))
+ return -EFAULT;
+
+ return ret;
+}
+
+static void free_shared_pages(void *buf, size_t sz)
+{
+ unsigned int npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
+ int ret;
+
+ if (!buf)
+ return;
+
+ ret = set_memory_encrypted((unsigned long)buf, npages);
+ if (ret) {
+ WARN_ONCE(ret, "failed to restore encryption mask (leak it)\n");
+ return;
+ }
+
+ __free_pages(virt_to_page(buf), get_order(sz));
+}
+
+static void *alloc_shared_pages(struct device *dev, size_t sz)
+{
+ unsigned int npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
+ struct page *page;
+ int ret;
+
+ page = alloc_pages(GFP_KERNEL_ACCOUNT, get_order(sz));
+ if (!page)
+ return NULL;
+
+ ret = set_memory_decrypted((unsigned long)page_address(page), npages);
+ if (ret) {
+ dev_err(dev, "failed to mark page shared, ret=%d\n", ret);
+ __free_pages(page, get_order(sz));
+ return NULL;
+ }
+
+ return page_address(page);
+}
+
+static const struct file_operations snp_guest_fops = {
+ .owner = THIS_MODULE,
+ .unlocked_ioctl = snp_guest_ioctl,
+};
+
+static u8 *get_vmpck(int id, struct snp_secrets_page_layout *layout, u32 **seqno)
+{
+ u8 *key = NULL;
+
+ switch (id) {
+ case 0:
+ *seqno = &layout->os_area.msg_seqno_0;
+ key = layout->vmpck0;
+ break;
+ case 1:
+ *seqno = &layout->os_area.msg_seqno_1;
+ key = layout->vmpck1;
+ break;
+ case 2:
+ *seqno = &layout->os_area.msg_seqno_2;
+ key = layout->vmpck2;
+ break;
+ case 3:
+ *seqno = &layout->os_area.msg_seqno_3;
+ key = layout->vmpck3;
+ break;
+ default:
+ break;
+ }
+
+ return key;
+}
+
+static int __init sev_guest_probe(struct platform_device *pdev)
+{
+ struct snp_secrets_page_layout *layout;
+ struct sev_guest_platform_data *data;
+ struct device *dev = &pdev->dev;
+ struct snp_guest_dev *snp_dev;
+ struct miscdevice *misc;
+ int ret;
+
+ if (!dev->platform_data)
+ return -ENODEV;
+
+ data = (struct sev_guest_platform_data *)dev->platform_data;
+ layout = (__force void *)ioremap_encrypted(data->secrets_gpa, PAGE_SIZE);
+ if (!layout)
+ return -ENODEV;
+
+ ret = -ENOMEM;
+ snp_dev = devm_kzalloc(&pdev->dev, sizeof(struct snp_guest_dev), GFP_KERNEL);
+ if (!snp_dev)
+ goto e_unmap;
+
+ ret = -EINVAL;
+ snp_dev->vmpck = get_vmpck(vmpck_id, layout, &snp_dev->os_area_msg_seqno);
+ if (!snp_dev->vmpck) {
+ dev_err(dev, "invalid vmpck id %d\n", vmpck_id);
+ goto e_unmap;
+ }
+
+ /* Verify that VMPCK is not zero. */
+ if (is_vmpck_empty(snp_dev)) {
+ dev_err(dev, "vmpck id %d is null\n", vmpck_id);
+ goto e_unmap;
+ }
+
+ platform_set_drvdata(pdev, snp_dev);
+ snp_dev->dev = dev;
+ snp_dev->layout = layout;
+
+ /* Allocate the shared page used for the request and response message. */
+ snp_dev->request = alloc_shared_pages(dev, sizeof(struct snp_guest_msg));
+ if (!snp_dev->request)
+ goto e_unmap;
+
+ snp_dev->response = alloc_shared_pages(dev, sizeof(struct snp_guest_msg));
+ if (!snp_dev->response)
+ goto e_free_request;
+
+ snp_dev->certs_data = alloc_shared_pages(dev, SEV_FW_BLOB_MAX_SIZE);
+ if (!snp_dev->certs_data)
+ goto e_free_response;
+
+ ret = -EIO;
+ snp_dev->crypto = init_crypto(snp_dev, snp_dev->vmpck, VMPCK_KEY_LEN);
+ if (!snp_dev->crypto)
+ goto e_free_cert_data;
+
+ misc = &snp_dev->misc;
+ misc->minor = MISC_DYNAMIC_MINOR;
+ misc->name = DEVICE_NAME;
+ misc->fops = &snp_guest_fops;
+
+ /* initial the input address for guest request */
+ snp_dev->input.req_gpa = __pa(snp_dev->request);
+ snp_dev->input.resp_gpa = __pa(snp_dev->response);
+ snp_dev->input.data_gpa = __pa(snp_dev->certs_data);
+
+ ret = misc_register(misc);
+ if (ret)
+ goto e_free_cert_data;
+
+ dev_info(dev, "Initialized SEV guest driver (using vmpck_id %d)\n", vmpck_id);
+ return 0;
+
+e_free_cert_data:
+ free_shared_pages(snp_dev->certs_data, SEV_FW_BLOB_MAX_SIZE);
+e_free_response:
+ free_shared_pages(snp_dev->response, sizeof(struct snp_guest_msg));
+e_free_request:
+ free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg));
+e_unmap:
+ iounmap(layout);
+ return ret;
+}
+
+static int __exit sev_guest_remove(struct platform_device *pdev)
+{
+ struct snp_guest_dev *snp_dev = platform_get_drvdata(pdev);
+
+ free_shared_pages(snp_dev->certs_data, SEV_FW_BLOB_MAX_SIZE);
+ free_shared_pages(snp_dev->response, sizeof(struct snp_guest_msg));
+ free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg));
+ deinit_crypto(snp_dev->crypto);
+ misc_deregister(&snp_dev->misc);
+
+ return 0;
+}
+
+/*
+ * 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".
+ */
+static struct platform_driver sev_guest_driver = {
+ .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");
--- /dev/null
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2021 Advanced Micro Devices, Inc.
+ *
+ * Author: Brijesh Singh <brijesh.singh@amd.com>
+ *
+ * SEV-SNP API spec is available at https://developer.amd.com/sev
+ */
+
+#ifndef __VIRT_SEVGUEST_H__
+#define __VIRT_SEVGUEST_H__
+
+#include <linux/types.h>
+
+#define MAX_AUTHTAG_LEN 32
+
+/* See SNP spec SNP_GUEST_REQUEST section for the structure */
+enum msg_type {
+ SNP_MSG_TYPE_INVALID = 0,
+ SNP_MSG_CPUID_REQ,
+ SNP_MSG_CPUID_RSP,
+ SNP_MSG_KEY_REQ,
+ SNP_MSG_KEY_RSP,
+ SNP_MSG_REPORT_REQ,
+ SNP_MSG_REPORT_RSP,
+ SNP_MSG_EXPORT_REQ,
+ SNP_MSG_EXPORT_RSP,
+ SNP_MSG_IMPORT_REQ,
+ SNP_MSG_IMPORT_RSP,
+ SNP_MSG_ABSORB_REQ,
+ SNP_MSG_ABSORB_RSP,
+ SNP_MSG_VMRK_REQ,
+ SNP_MSG_VMRK_RSP,
+
+ SNP_MSG_TYPE_MAX
+};
+
+enum aead_algo {
+ SNP_AEAD_INVALID,
+ SNP_AEAD_AES_256_GCM,
+};
+
+struct snp_guest_msg_hdr {
+ u8 authtag[MAX_AUTHTAG_LEN];
+ u64 msg_seqno;
+ u8 rsvd1[8];
+ u8 algo;
+ u8 hdr_version;
+ u16 hdr_sz;
+ u8 msg_type;
+ u8 msg_version;
+ u16 msg_sz;
+ u32 rsvd2;
+ u8 msg_vmpck;
+ u8 rsvd3[35];
+} __packed;
+
+struct snp_guest_msg {
+ struct snp_guest_msg_hdr hdr;
+ u8 payload[4000];
+} __packed;
+
+/*
+ * The secrets page contains 96-bytes of reserved field that can be used by
+ * the guest OS. The guest OS uses the area to save the message sequence
+ * number for each VMPCK.
+ *
+ * See the GHCB spec section Secret page layout for the format for this area.
+ */
+struct secrets_os_area {
+ u32 msg_seqno_0;
+ u32 msg_seqno_1;
+ u32 msg_seqno_2;
+ u32 msg_seqno_3;
+ u64 ap_jump_table_pa;
+ u8 rsvd[40];
+ u8 guest_usage[32];
+} __packed;
+
+#define VMPCK_KEY_LEN 32
+
+/* See the SNP spec version 0.9 for secrets page format */
+struct snp_secrets_page_layout {
+ u32 version;
+ u32 imien : 1,
+ rsvd1 : 31;
+ u32 fms;
+ u32 rsvd2;
+ u8 gosvw[16];
+ u8 vmpck0[VMPCK_KEY_LEN];
+ u8 vmpck1[VMPCK_KEY_LEN];
+ u8 vmpck2[VMPCK_KEY_LEN];
+ u8 vmpck3[VMPCK_KEY_LEN];
+ struct secrets_os_area os_area;
+ u8 rsvd3[3840];
+} __packed;
+
+#endif /* __VIRT_SEVGUEST_H__ */
+++ /dev/null
-config SEV_GUEST
- tristate "AMD SEV Guest driver"
- default m
- depends on AMD_MEM_ENCRYPT
- select CRYPTO_AEAD2
- select CRYPTO_GCM
- help
- SEV-SNP firmware provides the guest a mechanism to communicate with
- the PSP without risk from a malicious hypervisor who wishes to read,
- alter, drop or replay the messages sent. The driver provides
- userspace interface to communicate with the PSP to request the
- attestation report and more.
-
- If you choose 'M' here, this module will be called sevguest.
+++ /dev/null
-# SPDX-License-Identifier: GPL-2.0-only
-obj-$(CONFIG_SEV_GUEST) += sevguest.o
+++ /dev/null
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * AMD Secure Encrypted Virtualization (SEV) guest driver interface
- *
- * Copyright (C) 2021 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 <crypto/aead.h>
-#include <linux/scatterlist.h>
-#include <linux/psp-sev.h>
-#include <uapi/linux/sev-guest.h>
-#include <uapi/linux/psp-sev.h>
-
-#include <asm/svm.h>
-#include <asm/sev.h>
-
-#include "sevguest.h"
-
-#define DEVICE_NAME "sev-guest"
-#define AAD_LEN 48
-#define MSG_HDR_VER 1
-
-struct snp_guest_crypto {
- struct crypto_aead *tfm;
- u8 *iv, *authtag;
- int iv_len, a_len;
-};
-
-struct snp_guest_dev {
- struct device *dev;
- struct miscdevice misc;
-
- void *certs_data;
- struct snp_guest_crypto *crypto;
- struct snp_guest_msg *request, *response;
- struct snp_secrets_page_layout *layout;
- struct snp_req_data input;
- u32 *os_area_msg_seqno;
- u8 *vmpck;
-};
-
-static u32 vmpck_id;
-module_param(vmpck_id, uint, 0444);
-MODULE_PARM_DESC(vmpck_id, "The VMPCK ID to use when communicating with the PSP.");
-
-/* Mutex to serialize the shared buffer access and command handling. */
-static DEFINE_MUTEX(snp_cmd_mutex);
-
-static bool is_vmpck_empty(struct snp_guest_dev *snp_dev)
-{
- char zero_key[VMPCK_KEY_LEN] = {0};
-
- if (snp_dev->vmpck)
- return !memcmp(snp_dev->vmpck, zero_key, VMPCK_KEY_LEN);
-
- return true;
-}
-
-static void snp_disable_vmpck(struct snp_guest_dev *snp_dev)
-{
- memzero_explicit(snp_dev->vmpck, VMPCK_KEY_LEN);
- snp_dev->vmpck = NULL;
-}
-
-static inline u64 __snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
-{
- u64 count;
-
- lockdep_assert_held(&snp_cmd_mutex);
-
- /* Read the current message sequence counter from secrets pages */
- count = *snp_dev->os_area_msg_seqno;
-
- return count + 1;
-}
-
-/* Return a non-zero on success */
-static u64 snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
-{
- u64 count = __snp_get_msg_seqno(snp_dev);
-
- /*
- * The message sequence counter for the SNP guest request is a 64-bit
- * value but the version 2 of GHCB specification defines a 32-bit storage
- * for it. If the counter exceeds the 32-bit value then return zero.
- * The caller should check the return value, but if the caller happens to
- * not check the value and use it, then the firmware treats zero as an
- * invalid number and will fail the message request.
- */
- if (count >= UINT_MAX) {
- dev_err(snp_dev->dev, "request message sequence counter overflow\n");
- return 0;
- }
-
- return count;
-}
-
-static void snp_inc_msg_seqno(struct snp_guest_dev *snp_dev)
-{
- /*
- * The counter is also incremented by the PSP, so increment it by 2
- * and save in secrets page.
- */
- *snp_dev->os_area_msg_seqno += 2;
-}
-
-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);
-}
-
-static struct snp_guest_crypto *init_crypto(struct snp_guest_dev *snp_dev, u8 *key, size_t keylen)
-{
- struct snp_guest_crypto *crypto;
-
- crypto = kzalloc(sizeof(*crypto), GFP_KERNEL_ACCOUNT);
- if (!crypto)
- return NULL;
-
- crypto->tfm = crypto_alloc_aead("gcm(aes)", 0, 0);
- if (IS_ERR(crypto->tfm))
- goto e_free;
-
- if (crypto_aead_setkey(crypto->tfm, key, keylen))
- goto e_free_crypto;
-
- crypto->iv_len = crypto_aead_ivsize(crypto->tfm);
- crypto->iv = kmalloc(crypto->iv_len, GFP_KERNEL_ACCOUNT);
- if (!crypto->iv)
- goto e_free_crypto;
-
- if (crypto_aead_authsize(crypto->tfm) > MAX_AUTHTAG_LEN) {
- if (crypto_aead_setauthsize(crypto->tfm, MAX_AUTHTAG_LEN)) {
- dev_err(snp_dev->dev, "failed to set authsize to %d\n", MAX_AUTHTAG_LEN);
- goto e_free_iv;
- }
- }
-
- crypto->a_len = crypto_aead_authsize(crypto->tfm);
- crypto->authtag = kmalloc(crypto->a_len, GFP_KERNEL_ACCOUNT);
- if (!crypto->authtag)
- goto e_free_auth;
-
- return crypto;
-
-e_free_auth:
- kfree(crypto->authtag);
-e_free_iv:
- kfree(crypto->iv);
-e_free_crypto:
- crypto_free_aead(crypto->tfm);
-e_free:
- kfree(crypto);
-
- return NULL;
-}
-
-static void deinit_crypto(struct snp_guest_crypto *crypto)
-{
- crypto_free_aead(crypto->tfm);
- kfree(crypto->iv);
- kfree(crypto->authtag);
- kfree(crypto);
-}
-
-static int enc_dec_message(struct snp_guest_crypto *crypto, struct snp_guest_msg *msg,
- u8 *src_buf, u8 *dst_buf, size_t len, bool enc)
-{
- struct snp_guest_msg_hdr *hdr = &msg->hdr;
- struct scatterlist src[3], dst[3];
- DECLARE_CRYPTO_WAIT(wait);
- struct aead_request *req;
- int ret;
-
- req = aead_request_alloc(crypto->tfm, GFP_KERNEL);
- if (!req)
- return -ENOMEM;
-
- /*
- * AEAD memory operations:
- * +------ AAD -------+------- DATA -----+---- AUTHTAG----+
- * | msg header | plaintext | hdr->authtag |
- * | bytes 30h - 5Fh | or | |
- * | | cipher | |
- * +------------------+------------------+----------------+
- */
- sg_init_table(src, 3);
- sg_set_buf(&src[0], &hdr->algo, AAD_LEN);
- sg_set_buf(&src[1], src_buf, hdr->msg_sz);
- sg_set_buf(&src[2], hdr->authtag, crypto->a_len);
-
- sg_init_table(dst, 3);
- sg_set_buf(&dst[0], &hdr->algo, AAD_LEN);
- sg_set_buf(&dst[1], dst_buf, hdr->msg_sz);
- sg_set_buf(&dst[2], hdr->authtag, crypto->a_len);
-
- aead_request_set_ad(req, AAD_LEN);
- aead_request_set_tfm(req, crypto->tfm);
- aead_request_set_callback(req, 0, crypto_req_done, &wait);
-
- aead_request_set_crypt(req, src, dst, len, crypto->iv);
- ret = crypto_wait_req(enc ? crypto_aead_encrypt(req) : crypto_aead_decrypt(req), &wait);
-
- aead_request_free(req);
- return ret;
-}
-
-static int __enc_payload(struct snp_guest_dev *snp_dev, struct snp_guest_msg *msg,
- void *plaintext, size_t len)
-{
- struct snp_guest_crypto *crypto = snp_dev->crypto;
- struct snp_guest_msg_hdr *hdr = &msg->hdr;
-
- memset(crypto->iv, 0, crypto->iv_len);
- memcpy(crypto->iv, &hdr->msg_seqno, sizeof(hdr->msg_seqno));
-
- return enc_dec_message(crypto, msg, plaintext, msg->payload, len, true);
-}
-
-static int dec_payload(struct snp_guest_dev *snp_dev, struct snp_guest_msg *msg,
- void *plaintext, size_t len)
-{
- struct snp_guest_crypto *crypto = snp_dev->crypto;
- struct snp_guest_msg_hdr *hdr = &msg->hdr;
-
- /* Build IV with response buffer sequence number */
- memset(crypto->iv, 0, crypto->iv_len);
- memcpy(crypto->iv, &hdr->msg_seqno, sizeof(hdr->msg_seqno));
-
- return enc_dec_message(crypto, msg, msg->payload, plaintext, len, false);
-}
-
-static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, void *payload, u32 sz)
-{
- struct snp_guest_crypto *crypto = snp_dev->crypto;
- struct snp_guest_msg *resp = snp_dev->response;
- struct snp_guest_msg *req = snp_dev->request;
- struct snp_guest_msg_hdr *req_hdr = &req->hdr;
- struct snp_guest_msg_hdr *resp_hdr = &resp->hdr;
-
- dev_dbg(snp_dev->dev, "response [seqno %lld type %d version %d sz %d]\n",
- resp_hdr->msg_seqno, resp_hdr->msg_type, resp_hdr->msg_version, resp_hdr->msg_sz);
-
- /* Verify that the sequence counter is incremented by 1 */
- if (unlikely(resp_hdr->msg_seqno != (req_hdr->msg_seqno + 1)))
- return -EBADMSG;
-
- /* Verify response message type and version number. */
- if (resp_hdr->msg_type != (req_hdr->msg_type + 1) ||
- resp_hdr->msg_version != req_hdr->msg_version)
- return -EBADMSG;
-
- /*
- * If the message size is greater than our buffer length then return
- * an error.
- */
- if (unlikely((resp_hdr->msg_sz + crypto->a_len) > sz))
- return -EBADMSG;
-
- /* Decrypt the payload */
- return dec_payload(snp_dev, resp, payload, resp_hdr->msg_sz + crypto->a_len);
-}
-
-static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8 type,
- void *payload, size_t sz)
-{
- struct snp_guest_msg *req = snp_dev->request;
- struct snp_guest_msg_hdr *hdr = &req->hdr;
-
- memset(req, 0, sizeof(*req));
-
- hdr->algo = SNP_AEAD_AES_256_GCM;
- hdr->hdr_version = MSG_HDR_VER;
- hdr->hdr_sz = sizeof(*hdr);
- hdr->msg_type = type;
- hdr->msg_version = version;
- hdr->msg_seqno = seqno;
- hdr->msg_vmpck = vmpck_id;
- hdr->msg_sz = sz;
-
- /* Verify the sequence number is non-zero */
- if (!hdr->msg_seqno)
- return -ENOSR;
-
- dev_dbg(snp_dev->dev, "request [seqno %lld type %d version %d sz %d]\n",
- hdr->msg_seqno, hdr->msg_type, hdr->msg_version, hdr->msg_sz);
-
- return __enc_payload(snp_dev, req, payload, sz);
-}
-
-static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, int msg_ver,
- u8 type, void *req_buf, size_t req_sz, void *resp_buf,
- u32 resp_sz, __u64 *fw_err)
-{
- unsigned long err;
- u64 seqno;
- int rc;
-
- /* Get message sequence and verify that its a non-zero */
- seqno = snp_get_msg_seqno(snp_dev);
- if (!seqno)
- return -EIO;
-
- memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
-
- /* Encrypt the userspace provided payload */
- rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz);
- if (rc)
- return rc;
-
- /* Call firmware to process the request */
- rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err);
- if (fw_err)
- *fw_err = err;
-
- if (rc)
- return rc;
-
- /*
- * The verify_and_dec_payload() will fail only if the hypervisor is
- * actively modifying the message header or corrupting the encrypted payload.
- * This hints that hypervisor is acting in a bad faith. Disable the VMPCK so that
- * the key cannot be used for any communication. The key is disabled to ensure
- * that AES-GCM does not use the same IV while encrypting the request payload.
- */
- rc = verify_and_dec_payload(snp_dev, resp_buf, resp_sz);
- if (rc) {
- dev_alert(snp_dev->dev,
- "Detected unexpected decode failure, disabling the vmpck_id %d\n",
- vmpck_id);
- snp_disable_vmpck(snp_dev);
- return rc;
- }
-
- /* Increment to new message sequence after payload decryption was successful. */
- snp_inc_msg_seqno(snp_dev);
-
- return 0;
-}
-
-static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
-{
- struct snp_guest_crypto *crypto = snp_dev->crypto;
- struct snp_report_resp *resp;
- struct snp_report_req req;
- int rc, resp_len;
-
- lockdep_assert_held(&snp_cmd_mutex);
-
- if (!arg->req_data || !arg->resp_data)
- return -EINVAL;
-
- if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(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(resp->data) + crypto->a_len;
- resp = kzalloc(resp_len, GFP_KERNEL_ACCOUNT);
- if (!resp)
- return -ENOMEM;
-
- rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg->msg_version,
- SNP_MSG_REPORT_REQ, &req, sizeof(req), resp->data,
- resp_len, &arg->fw_err);
- if (rc)
- goto e_free;
-
- if (copy_to_user((void __user *)arg->resp_data, resp, sizeof(*resp)))
- rc = -EFAULT;
-
-e_free:
- kfree(resp);
- return rc;
-}
-
-static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
-{
- struct snp_guest_crypto *crypto = snp_dev->crypto;
- struct snp_derived_key_resp resp = {0};
- struct snp_derived_key_req req;
- int rc, resp_len;
- /* Response data is 64 bytes and max authsize for GCM is 16 bytes. */
- u8 buf[64 + 16];
-
- lockdep_assert_held(&snp_cmd_mutex);
-
- 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(resp.data) + crypto->a_len;
- if (sizeof(buf) < resp_len)
- return -ENOMEM;
-
- if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req)))
- return -EFAULT;
-
- rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg->msg_version,
- SNP_MSG_KEY_REQ, &req, sizeof(req), buf, resp_len,
- &arg->fw_err);
- if (rc)
- return rc;
-
- memcpy(resp.data, buf, sizeof(resp.data));
- if (copy_to_user((void __user *)arg->resp_data, &resp, sizeof(resp)))
- rc = -EFAULT;
-
- /* The response buffer contains the sensitive data, explicitly clear it. */
- memzero_explicit(buf, sizeof(buf));
- memzero_explicit(&resp, sizeof(resp));
- return rc;
-}
-
-static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
-{
- struct snp_guest_crypto *crypto = snp_dev->crypto;
- struct snp_ext_report_req req;
- struct snp_report_resp *resp;
- int ret, npages = 0, resp_len;
-
- lockdep_assert_held(&snp_cmd_mutex);
-
- if (!arg->req_data || !arg->resp_data)
- return -EINVAL;
-
- if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req)))
- return -EFAULT;
-
- /* userspace does not want certificate data */
- if (!req.certs_len || !req.certs_address)
- goto cmd;
-
- if (req.certs_len > SEV_FW_BLOB_MAX_SIZE ||
- !IS_ALIGNED(req.certs_len, PAGE_SIZE))
- return -EINVAL;
-
- if (!access_ok((const void __user *)req.certs_address, 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.
- */
- memset(snp_dev->certs_data, 0, req.certs_len);
- npages = req.certs_len >> PAGE_SHIFT;
-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(resp->data) + crypto->a_len;
- resp = kzalloc(resp_len, GFP_KERNEL_ACCOUNT);
- if (!resp)
- return -ENOMEM;
-
- snp_dev->input.data_npages = npages;
- ret = handle_guest_request(snp_dev, SVM_VMGEXIT_EXT_GUEST_REQUEST, arg->msg_version,
- SNP_MSG_REPORT_REQ, &req.data,
- sizeof(req.data), resp->data, resp_len, &arg->fw_err);
-
- /* If certs length is invalid then copy the returned length */
- if (arg->fw_err == SNP_GUEST_REQ_INVALID_LEN) {
- req.certs_len = snp_dev->input.data_npages << PAGE_SHIFT;
-
- if (copy_to_user((void __user *)arg->req_data, &req, sizeof(req)))
- ret = -EFAULT;
- }
-
- if (ret)
- goto e_free;
-
- if (npages &&
- copy_to_user((void __user *)req.certs_address, snp_dev->certs_data,
- req.certs_len)) {
- ret = -EFAULT;
- goto e_free;
- }
-
- if (copy_to_user((void __user *)arg->resp_data, resp, sizeof(*resp)))
- ret = -EFAULT;
-
-e_free:
- kfree(resp);
- 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;
- int ret = -ENOTTY;
-
- if (copy_from_user(&input, argp, sizeof(input)))
- return -EFAULT;
-
- input.fw_err = 0xff;
-
- /* Message version must be non-zero */
- if (!input.msg_version)
- return -EINVAL;
-
- mutex_lock(&snp_cmd_mutex);
-
- /* Check if the VMPCK is not empty */
- if (is_vmpck_empty(snp_dev)) {
- dev_err_ratelimited(snp_dev->dev, "VMPCK is disabled\n");
- mutex_unlock(&snp_cmd_mutex);
- return -ENOTTY;
- }
-
- 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:
- ret = get_ext_report(snp_dev, &input);
- break;
- default:
- break;
- }
-
- mutex_unlock(&snp_cmd_mutex);
-
- if (input.fw_err && copy_to_user(argp, &input, sizeof(input)))
- return -EFAULT;
-
- return ret;
-}
-
-static void free_shared_pages(void *buf, size_t sz)
-{
- unsigned int npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
- int ret;
-
- if (!buf)
- return;
-
- ret = set_memory_encrypted((unsigned long)buf, npages);
- if (ret) {
- WARN_ONCE(ret, "failed to restore encryption mask (leak it)\n");
- return;
- }
-
- __free_pages(virt_to_page(buf), get_order(sz));
-}
-
-static void *alloc_shared_pages(struct device *dev, size_t sz)
-{
- unsigned int npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
- struct page *page;
- int ret;
-
- page = alloc_pages(GFP_KERNEL_ACCOUNT, get_order(sz));
- if (!page)
- return NULL;
-
- ret = set_memory_decrypted((unsigned long)page_address(page), npages);
- if (ret) {
- dev_err(dev, "failed to mark page shared, ret=%d\n", ret);
- __free_pages(page, get_order(sz));
- return NULL;
- }
-
- return page_address(page);
-}
-
-static const struct file_operations snp_guest_fops = {
- .owner = THIS_MODULE,
- .unlocked_ioctl = snp_guest_ioctl,
-};
-
-static u8 *get_vmpck(int id, struct snp_secrets_page_layout *layout, u32 **seqno)
-{
- u8 *key = NULL;
-
- switch (id) {
- case 0:
- *seqno = &layout->os_area.msg_seqno_0;
- key = layout->vmpck0;
- break;
- case 1:
- *seqno = &layout->os_area.msg_seqno_1;
- key = layout->vmpck1;
- break;
- case 2:
- *seqno = &layout->os_area.msg_seqno_2;
- key = layout->vmpck2;
- break;
- case 3:
- *seqno = &layout->os_area.msg_seqno_3;
- key = layout->vmpck3;
- break;
- default:
- break;
- }
-
- return key;
-}
-
-static int __init sev_guest_probe(struct platform_device *pdev)
-{
- struct snp_secrets_page_layout *layout;
- struct sev_guest_platform_data *data;
- struct device *dev = &pdev->dev;
- struct snp_guest_dev *snp_dev;
- struct miscdevice *misc;
- int ret;
-
- if (!dev->platform_data)
- return -ENODEV;
-
- data = (struct sev_guest_platform_data *)dev->platform_data;
- layout = (__force void *)ioremap_encrypted(data->secrets_gpa, PAGE_SIZE);
- if (!layout)
- return -ENODEV;
-
- ret = -ENOMEM;
- snp_dev = devm_kzalloc(&pdev->dev, sizeof(struct snp_guest_dev), GFP_KERNEL);
- if (!snp_dev)
- goto e_unmap;
-
- ret = -EINVAL;
- snp_dev->vmpck = get_vmpck(vmpck_id, layout, &snp_dev->os_area_msg_seqno);
- if (!snp_dev->vmpck) {
- dev_err(dev, "invalid vmpck id %d\n", vmpck_id);
- goto e_unmap;
- }
-
- /* Verify that VMPCK is not zero. */
- if (is_vmpck_empty(snp_dev)) {
- dev_err(dev, "vmpck id %d is null\n", vmpck_id);
- goto e_unmap;
- }
-
- platform_set_drvdata(pdev, snp_dev);
- snp_dev->dev = dev;
- snp_dev->layout = layout;
-
- /* Allocate the shared page used for the request and response message. */
- snp_dev->request = alloc_shared_pages(dev, sizeof(struct snp_guest_msg));
- if (!snp_dev->request)
- goto e_unmap;
-
- snp_dev->response = alloc_shared_pages(dev, sizeof(struct snp_guest_msg));
- if (!snp_dev->response)
- goto e_free_request;
-
- snp_dev->certs_data = alloc_shared_pages(dev, SEV_FW_BLOB_MAX_SIZE);
- if (!snp_dev->certs_data)
- goto e_free_response;
-
- ret = -EIO;
- snp_dev->crypto = init_crypto(snp_dev, snp_dev->vmpck, VMPCK_KEY_LEN);
- if (!snp_dev->crypto)
- goto e_free_cert_data;
-
- misc = &snp_dev->misc;
- misc->minor = MISC_DYNAMIC_MINOR;
- misc->name = DEVICE_NAME;
- misc->fops = &snp_guest_fops;
-
- /* initial the input address for guest request */
- snp_dev->input.req_gpa = __pa(snp_dev->request);
- snp_dev->input.resp_gpa = __pa(snp_dev->response);
- snp_dev->input.data_gpa = __pa(snp_dev->certs_data);
-
- ret = misc_register(misc);
- if (ret)
- goto e_free_cert_data;
-
- dev_info(dev, "Initialized SEV guest driver (using vmpck_id %d)\n", vmpck_id);
- return 0;
-
-e_free_cert_data:
- free_shared_pages(snp_dev->certs_data, SEV_FW_BLOB_MAX_SIZE);
-e_free_response:
- free_shared_pages(snp_dev->response, sizeof(struct snp_guest_msg));
-e_free_request:
- free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg));
-e_unmap:
- iounmap(layout);
- return ret;
-}
-
-static int __exit sev_guest_remove(struct platform_device *pdev)
-{
- struct snp_guest_dev *snp_dev = platform_get_drvdata(pdev);
-
- free_shared_pages(snp_dev->certs_data, SEV_FW_BLOB_MAX_SIZE);
- free_shared_pages(snp_dev->response, sizeof(struct snp_guest_msg));
- free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg));
- deinit_crypto(snp_dev->crypto);
- misc_deregister(&snp_dev->misc);
-
- return 0;
-}
-
-/*
- * This driver is a common SEV guest interface driver and meant to support
- * any SEV guest API. As such, even though it has been introduced along with
- * the SEV-SNP support, it is named "sev-guest".
- */
-static struct platform_driver sev_guest_driver = {
- .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");
+++ /dev/null
-/* SPDX-License-Identifier: GPL-2.0-only */
-/*
- * Copyright (C) 2021 Advanced Micro Devices, Inc.
- *
- * Author: Brijesh Singh <brijesh.singh@amd.com>
- *
- * SEV-SNP API spec is available at https://developer.amd.com/sev
- */
-
-#ifndef __VIRT_SEVGUEST_H__
-#define __VIRT_SEVGUEST_H__
-
-#include <linux/types.h>
-
-#define MAX_AUTHTAG_LEN 32
-
-/* See SNP spec SNP_GUEST_REQUEST section for the structure */
-enum msg_type {
- SNP_MSG_TYPE_INVALID = 0,
- SNP_MSG_CPUID_REQ,
- SNP_MSG_CPUID_RSP,
- SNP_MSG_KEY_REQ,
- SNP_MSG_KEY_RSP,
- SNP_MSG_REPORT_REQ,
- SNP_MSG_REPORT_RSP,
- SNP_MSG_EXPORT_REQ,
- SNP_MSG_EXPORT_RSP,
- SNP_MSG_IMPORT_REQ,
- SNP_MSG_IMPORT_RSP,
- SNP_MSG_ABSORB_REQ,
- SNP_MSG_ABSORB_RSP,
- SNP_MSG_VMRK_REQ,
- SNP_MSG_VMRK_RSP,
-
- SNP_MSG_TYPE_MAX
-};
-
-enum aead_algo {
- SNP_AEAD_INVALID,
- SNP_AEAD_AES_256_GCM,
-};
-
-struct snp_guest_msg_hdr {
- u8 authtag[MAX_AUTHTAG_LEN];
- u64 msg_seqno;
- u8 rsvd1[8];
- u8 algo;
- u8 hdr_version;
- u16 hdr_sz;
- u8 msg_type;
- u8 msg_version;
- u16 msg_sz;
- u32 rsvd2;
- u8 msg_vmpck;
- u8 rsvd3[35];
-} __packed;
-
-struct snp_guest_msg {
- struct snp_guest_msg_hdr hdr;
- u8 payload[4000];
-} __packed;
-
-/*
- * The secrets page contains 96-bytes of reserved field that can be used by
- * the guest OS. The guest OS uses the area to save the message sequence
- * number for each VMPCK.
- *
- * See the GHCB spec section Secret page layout for the format for this area.
- */
-struct secrets_os_area {
- u32 msg_seqno_0;
- u32 msg_seqno_1;
- u32 msg_seqno_2;
- u32 msg_seqno_3;
- u64 ap_jump_table_pa;
- u8 rsvd[40];
- u8 guest_usage[32];
-} __packed;
-
-#define VMPCK_KEY_LEN 32
-
-/* See the SNP spec version 0.9 for secrets page format */
-struct snp_secrets_page_layout {
- u32 version;
- u32 imien : 1,
- rsvd1 : 31;
- u32 fms;
- u32 rsvd2;
- u8 gosvw[16];
- u8 vmpck0[VMPCK_KEY_LEN];
- u8 vmpck1[VMPCK_KEY_LEN];
- u8 vmpck2[VMPCK_KEY_LEN];
- u8 vmpck3[VMPCK_KEY_LEN];
- struct secrets_os_area os_area;
- u8 rsvd3[3840];
-} __packed;
-
-#endif /* __VIRT_SEVGUEST_H__ */
projects / linux.git / commitdiff