On Tue, Mar 11, 2025 at 10:42:23AM +0100, Stefano Garzarella wrote: > 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 > > Co-developed-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> > Signed-off-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> > Co-developed-by: Claudio Carvalho <cclaudio@xxxxxxxxxxxxx> > Signed-off-by: Claudio Carvalho <cclaudio@xxxxxxxxxxxxx> > Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx> > --- > v3: > - renamed header and prefix to make clear it's related to the SVSM vTPM > protocol > - renamed fill/parse functions [Tom] > - removed link to the spec because those URLs are unstable [Borislav] > --- > include/linux/svsm_vtpm.h | 141 ++++++++++++++++++++++++++++++++++++++ > 1 file changed, 141 insertions(+) > create mode 100644 include/linux/svsm_vtpm.h > > diff --git a/include/linux/svsm_vtpm.h b/include/linux/svsm_vtpm.h > new file mode 100644 > index 000000000000..2ce9b1cb827e > --- /dev/null > +++ b/include/linux/svsm_vtpm.h > @@ -0,0 +1,141 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +/* > + * Copyright (C) 2023 James.Bottomley@xxxxxxxxxxxxxxxxxxxxx > + * 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 _SVSM_VTPM_H_ > +#define _SVSM_VTPM_H_ > + > +#include <linux/errno.h> > +#include <linux/string.h> > +#include <linux/types.h> > + > +/* > + * The current TCG Simulator TPM commands we support. The complete list is > + * in the TcpTpmProtocol header: > + * > + * https://github.com/TrustedComputingGroup/TPM/blob/main/TPMCmd/Simulator/include/TpmTcpProtocol.h > + */ > + > +#define TPM_SEND_COMMAND 8 > +#define TPM_SIGNAL_CANCEL_ON 9 > +#define TPM_SIGNAL_CANCEL_OFF 10 > +/* > + * Any platform specific commands should be placed here and should start > + * at 0x8000 to avoid clashes with the TCG Simulator protocol. They should > + * follow the same self describing buffer format below. > + */ > + > +#define SVSM_VTPM_MAX_BUFFER 4096 /* max req/resp buffer size */ > + Across the board below data structures: I'd svsm_vtpm_ prefix them. The rational is quite practical: it would easier to grep them later on. > +/** > + * struct tpm_req - generic request header for single word command > + * > + * @cmd: The command to send > + */ > +struct tpm_req { > + u32 cmd; > +} __packed; __packed is useless here. > + > +/** > + * struct tpm_resp - generic response header > + * > + * @size: The response size (zero if nothing follows) > + * > + * Note: most TCG Simulator commands simply return zero here with no indication > + * of success or failure. > + */ > +struct tpm_resp { > + u32 size; > +} __packed; Ditto. > + > +/** > + * struct tpm_send_cmd_req - Structure for a TPM_SEND_COMMAND request > + * > + * @hdr: The request header whit the command (must be TPM_SEND_COMMAND) > + * @locality: The locality > + * @inbuf_size: The size of the input buffer following > + * @inbuf: A buffer of size inbuf_size > + * > + * Note that TCG Simulator expects @inbuf_size to be equal to the size of the > + * specific TPM command, otherwise an TPM_RC_COMMAND_SIZE error is > + * returned. > + */ > +struct tpm_send_cmd_req { > + struct tpm_req hdr; Useless nesting that makes this obfuscated: you can just as well put that single field here, i.e. u32 cmd; > + u8 locality; > + u32 inbuf_size; > + u8 inbuf[]; Why not just buf? > +} __packed; Since we don't care about TCG Simulator compatibility I'd expect that these are ordered in a way that they align nicely. E.g., struct svsm_vtpm_request { u32 command; u16 locality; u16 buffer_size; u8 buffer[]; }; 64k should enough for any possible TPM command. > + > +/** > + * struct tpm_send_cmd_req - Structure for a TPM_SEND_COMMAND response > + * > + * @hdr: The response header whit the following size > + * @outbuf: A buffer of size hdr.size > + */ > +struct tpm_send_cmd_resp { > + struct tpm_resp hdr; > + u8 outbuf[]; > +} __packed; Why this does not have size? Here also __packed is useless even with the pre-existing layout, and something like svsm_tpm_response would be a factor more reasonable name. > + > +/** > + * svsm_vtpm_fill_cmd_req() - fill a struct tpm_send_cmd_req to be sent to SVSM > + * @req: The struct tpm_send_cmd_req 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_fill_cmd_req(struct tpm_send_cmd_req *req, u8 locality, > + const u8 *buf, size_t len) svsm_vtpm_fill_request() > +{ > + if (len > SVSM_VTPM_MAX_BUFFER - sizeof(*req)) > + return -EINVAL; > + > + req->hdr.cmd = TPM_SEND_COMMAND; > + req->locality = locality; > + req->inbuf_size = len; > + > + memcpy(req->inbuf, buf, len); > + > + return 0; > +} > + > +/** > + * svsm_vtpm_parse_cmd_resp() - Parse a struct tpm_send_cmd_resp received from > + * SVSM > + * @resp: The struct tpm_send_cmd_resp 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_parse_cmd_resp(const struct tpm_send_cmd_resp *resp, u8 *buf, > + size_t len) svsm_vtpm_parse_response() > +{ > + if (len < resp->hdr.size) > + return -E2BIG; > + > + if (resp->hdr.size > SVSM_VTPM_MAX_BUFFER - sizeof(*resp)) > + return -EINVAL; // Invalid response from the platform TPM > + > + memcpy(buf, resp->outbuf, resp->hdr.size); > + > + return resp->hdr.size; > +} > + > +#endif /* _SVSM_VTPM_H_ */ > -- > 2.48.1 > BR, Jarkko
