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Diffstat (limited to 'include/linux/tpm_svsm.h')
| -rw-r--r-- | include/linux/tpm_svsm.h | 149 |
1 files changed, 149 insertions, 0 deletions
diff --git a/include/linux/tpm_svsm.h b/include/linux/tpm_svsm.h new file mode 100644 index 000000000000..38e341f9761a --- /dev/null +++ b/include/linux/tpm_svsm.h @@ -0,0 +1,149 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Copyright (C) 2023 James.Bottomley@HansenPartnership.com + * Copyright (C) 2025 Red Hat, Inc. All Rights Reserved. + * + * Helpers for the SVSM_VTPM_CMD calls used by the vTPM protocol defined by the + * AMD SVSM spec [1]. + * + * The vTPM protocol follows the Official TPM 2.0 Reference Implementation + * (originally by Microsoft, now part of the TCG) simulator protocol. + * + * [1] "Secure VM Service Module for SEV-SNP Guests" + * Publication # 58019 Revision: 1.00 + */ +#ifndef _TPM_SVSM_H_ +#define _TPM_SVSM_H_ + +#include <linux/errno.h> +#include <linux/string.h> +#include <linux/types.h> + +#define SVSM_VTPM_MAX_BUFFER 4096 /* max req/resp buffer size */ + +/** + * struct svsm_vtpm_request - Generic request for single word command + * @cmd: The command to send + * + * Defined by AMD SVSM spec [1] in section "8.2 SVSM_VTPM_CMD Call" - + * Table 15: vTPM Common Request/Response Structure + * Byte Size In/Out Description + * Offset (Bytes) + * 0x000 4 In Platform command + * Out Platform command response size + */ +struct svsm_vtpm_request { + u32 cmd; +}; + +/** + * struct svsm_vtpm_response - Generic response + * @size: The response size (zero if nothing follows) + * + * Defined by AMD SVSM spec [1] in section "8.2 SVSM_VTPM_CMD Call" - + * Table 15: vTPM Common Request/Response Structure + * Byte Size In/Out Description + * Offset (Bytes) + * 0x000 4 In Platform command + * Out Platform command response size + * + * Note: most TCG Simulator commands simply return zero here with no indication + * of success or failure. + */ +struct svsm_vtpm_response { + u32 size; +}; + +/** + * struct svsm_vtpm_cmd_request - Structure for a TPM_SEND_COMMAND request + * @cmd: The command to send (must be TPM_SEND_COMMAND) + * @locality: The locality + * @buf_size: The size of the input buffer following + * @buf: A buffer of size buf_size + * + * Defined by AMD SVSM spec [1] in section "8.2 SVSM_VTPM_CMD Call" - + * Table 16: TPM_SEND_COMMAND Request Structure + * Byte Size Meaning + * Offset (Bytes) + * 0x000 4 Platform command (8) + * 0x004 1 Locality (must-be-0) + * 0x005 4 TPM Command size (in bytes) + * 0x009 Variable TPM Command + * + * Note: the TCG Simulator expects @buf_size to be equal to the size of the + * specific TPM command, otherwise an TPM_RC_COMMAND_SIZE error is returned. + */ +struct svsm_vtpm_cmd_request { + u32 cmd; + u8 locality; + u32 buf_size; + u8 buf[]; +} __packed; + +/** + * struct svsm_vtpm_cmd_response - Structure for a TPM_SEND_COMMAND response + * @buf_size: The size of the output buffer following + * @buf: A buffer of size buf_size + * + * Defined by AMD SVSM spec [1] in section "8.2 SVSM_VTPM_CMD Call" - + * Table 17: TPM_SEND_COMMAND Response Structure + * Byte Size Meaning + * Offset (Bytes) + * 0x000 4 Response size (in bytes) + * 0x004 Variable Response + */ +struct svsm_vtpm_cmd_response { + u32 buf_size; + u8 buf[]; +}; + +/** + * svsm_vtpm_cmd_request_fill() - Fill a TPM_SEND_COMMAND request to be sent to SVSM + * @req: The struct svsm_vtpm_cmd_request to fill + * @locality: The locality + * @buf: The buffer from where to copy the payload of the command + * @len: The size of the buffer + * + * Return: 0 on success, negative error code on failure. + */ +static inline int +svsm_vtpm_cmd_request_fill(struct svsm_vtpm_cmd_request *req, u8 locality, + const u8 *buf, size_t len) +{ + if (len > SVSM_VTPM_MAX_BUFFER - sizeof(*req)) + return -EINVAL; + + req->cmd = 8; /* TPM_SEND_COMMAND */ + req->locality = locality; + req->buf_size = len; + + memcpy(req->buf, buf, len); + + return 0; +} + +/** + * svsm_vtpm_cmd_response_parse() - Parse a TPM_SEND_COMMAND response received from SVSM + * @resp: The struct svsm_vtpm_cmd_response to parse + * @buf: The buffer where to copy the response + * @len: The size of the buffer + * + * Return: buffer size filled with the response on success, negative error + * code on failure. + */ +static inline int +svsm_vtpm_cmd_response_parse(const struct svsm_vtpm_cmd_response *resp, u8 *buf, + size_t len) +{ + if (len < resp->buf_size) + return -E2BIG; + + if (resp->buf_size > SVSM_VTPM_MAX_BUFFER - sizeof(*resp)) + return -EINVAL; // Invalid response from the platform TPM + + memcpy(buf, resp->buf, resp->buf_size); + + return resp->buf_size; +} + +#endif /* _TPM_SVSM_H_ */ |