Re: [PATCH 1/2] platform/x86/intel/sdsi: Add ioctl SPDM transport

David E. Box
2024-05-03T16:17:00Z

On Fri, 2024-05-03 at 12:04 +0300, Ilpo Järvinen wrote:
> On Thu, 2 May 2024, David E. Box wrote:
>
> > Intel On Demand adds attestation and firmware measurement retrieval
> > services through use of the protocols defined the Security Protocols and
> > Data Measurement (SPDM) specification. SPDM messages exchanges are used to
> > authenticate On Demand hardware and to retrieve signed measurements of the
> > NVRAM state used to track feature provisioning and the NVRAM state used for
> > metering services. These allow software to verify the authenticity of the
> > On Demand hardware as well as the integrity of the reported silicon
> > configuration.
> >
> > Add an ioctl interface for sending SPDM messages through the On Demand
> > mailbox. Provides commands to get a list of SPDM enabled devices, get the
> > message size limits for SPDM Requesters and Responders, and perform an SPDM
> > message exchange.
> >
> > Signed-off-by: David E. Box <david.e.box@linux.intel.com>
> > Link:
> > https://www.dmtf.org/sites/default/files/standards/documents/DSP0274_1.0.1.pdf
> >  [1]
> > ---
> >  .../userspace-api/ioctl/ioctl-number.rst      |   1 +
> >  MAINTAINERS                                   |   1 +
> >  drivers/platform/x86/intel/sdsi.c             | 210 +++++++++++++++++-
> >  include/uapi/linux/intel_sdsi.h               |  72 ++++++
> >  4 files changed, 283 insertions(+), 1 deletion(-)
> >  create mode 100644 include/uapi/linux/intel_sdsi.h
> >
> > diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst
> > b/Documentation/userspace-api/ioctl/ioctl-number.rst
> > index c472423412bf..20dcc2dbcaf6 100644
> > --- a/Documentation/userspace-api/ioctl/ioctl-number.rst
> > +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
> > @@ -382,6 +382,7 @@ Code  Seq#    Include
> > File                                           Comments
> >
> > <mailto:mathieu.desnoyers@efficios.com>
> >  0xF8  all    arch/x86/include/uapi/asm/amd_hsmp.h                    AMD
> > HSMP EPYC system management interface driver
> >
> > <mailto:nchatrad@amd.com>
> > +0xFC  all    linux/intel_sdsi.h
> >  0xFD  all    linux/dm-ioctl.h
> >  0xFE  all    linux/isst_if.h
> >  ====  =====  =======================================================
> > ================================================================
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 3fb0fa67576d..e3865e61f302 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -11165,6 +11165,7 @@ INTEL SDSI DRIVER
> >  M:     David E. Box <david.e.box@linux.intel.com>
> >  S:     Supported
> >  F:     drivers/platform/x86/intel/sdsi.c
> > +F:     include/uapi/linux/intel_sdsi.h
> >  F:     tools/arch/x86/intel_sdsi/
> >  F:     tools/testing/selftests/drivers/sdsi/
> >
> > diff --git a/drivers/platform/x86/intel/sdsi.c
> > b/drivers/platform/x86/intel/sdsi.c
> > index 277e4f4b20ac..bab6df0521b4 100644
> > --- a/drivers/platform/x86/intel/sdsi.c
> > +++ b/drivers/platform/x86/intel/sdsi.c
> > @@ -11,9 +11,12 @@
> >  #include <linux/auxiliary_bus.h>
> >  #include <linux/bits.h>
> >  #include <linux/bitfield.h>
> > +#include <linux/cleanup.h>
> >  #include <linux/device.h>
> >  #include <linux/iopoll.h>
> > +#include <linux/intel_sdsi.h>
> >  #include <linux/kernel.h>
> > +#include <linux/miscdevice.h>
> >  #include <linux/module.h>
> >  #include <linux/overflow.h>
> >  #include <linux/pci.h>
> > @@ -42,6 +45,7 @@
> >
> >  #define SDSI_ENABLED_FEATURES_OFFSET   16
> >  #define SDSI_FEATURE_SDSI              BIT(3)
> > +#define SDSI_FEATURE_ATTESTATION       BIT(12)
> >  #define SDSI_FEATURE_METERING          BIT(26)
> >
> >  #define SDSI_SOCKET_ID_OFFSET          64
> > @@ -91,6 +95,7 @@ enum sdsi_command {
> >         SDSI_CMD_PROVISION_CAP          = 0x0008,
> >         SDSI_CMD_READ_STATE             = 0x0010,
> >         SDSI_CMD_READ_METER             = 0x0014,
> > +       SDSI_CMD_ATTESTATION            = 0x1012,
> >  };
> >
> >  struct sdsi_mbox_info {
> > @@ -109,12 +114,14 @@ struct disc_table {
> >  struct sdsi_priv {
> >         struct mutex            mb_lock;        /* Mailbox access lock */
> >         struct device           *dev;
> > +       struct miscdevice       miscdev;
> >         void __iomem            *control_addr;
> >         void __iomem            *mbox_addr;
> >         void __iomem            *regs_addr;
> >         int                     control_size;
> >         int                     maibox_size;
> >         int                     registers_size;
> > +       int                     id;
> >         u32                     guid;
> >         u32                     features;
> >  };
> > @@ -582,6 +589,94 @@ static const struct attribute_group sdsi_group = {
> >  };
> >  __ATTRIBUTE_GROUPS(sdsi);
> >
> > +/* SPDM transport  */
> > +static int sdsi_spdm_exchange(void *private, const void *request,
> > +                             size_t request_sz, void *response,
> > +                             size_t response_sz)
> > +{
> > +       struct sdsi_priv *priv = private;
> > +       struct sdsi_mbox_info info = {};
> > +       size_t spdm_msg_size, size;
> > +       int ret;
> > +
> > +       /*
> > +        * For the attestation command, the mailbox write size is the sum
> > of:
> > +        *     Size of the SPDM request payload, padded for qword alignment
> > +        *     8 bytes for the mailbox command
> > +        *     8 bytes for the actual (non-padded) size of the SPDM request
> > +        */
> > +       if (request_sz > (SDSI_SIZE_WRITE_MSG - (2 * sizeof(u64))))
>
> This looks way more readable when unnecessary parethesis are eliminated:
>
>         if (request_sz > SDSI_SIZE_WRITE_MSG - 2 * sizeof(u64))
>
> > +               return -EOVERFLOW;
> > +
> > +       info.size = round_up(request_sz, sizeof(u64)) + 2 * sizeof(u64);
> >
> > +       u64 *payload __free(kfree) = kzalloc(info.size, GFP_KERNEL);
> > +       if (!payload)
> > +               return -ENOMEM;
> > +
> > +       memcpy(payload, request, request_sz);
> > +
> > +       /* The non-padded SPDM payload size is the 2nd-to-last qword */
> > +       payload[(info.size / sizeof(u64)) - 2] = request_sz;
> > +
> > +       /* Attestation mailbox command is the last qword of payload buffer
> > */
> > +       payload[(info.size / sizeof(u64)) - 1] = SDSI_CMD_ATTESTATION;
> > +
> > +       info.payload = payload;
> > +       info.buffer = response;
> > +
> > +       ret = mutex_lock_interruptible(&priv->mb_lock);
> > +       if (ret)
> > +               return ret;
> > +       ret = sdsi_mbox_write(priv, &info, &size);
> > +       mutex_unlock(&priv->mb_lock);
> > +       if (ret < 0)
> > +               return ret;
> > +
> > +       /*
> > +        * The read size is the sum of:
> > +        *     Size of the SPDM response payload, padded for qword alignment
> > +        *     8 bytes for the actual (non-padded) size of the SPDM payload
> > +        */
> > +
> > +       if (size < sizeof(u64)) {
> > +               dev_err(priv->dev,
> > +                       "Attestation error: Mailbox reply size, %ld, too
> > small\n",
> > +                       size);
> > +               return -EPROTO;
> > +       }
> > +
> > +       if (!IS_ALIGNED(size, sizeof(u64))) {
> > +               dev_err(priv->dev,
> > +                       "Attestation error: Mailbox reply size, %ld, is not
> > aligned\n",
> > +                       size);
> > +               return -EPROTO;
> > +       }
> > +
> > +       /*
> > +        * Get the SPDM response size from the last QWORD and check it fits
> > +        * with no more than 7 bytes of padding
> > +        */
> > +       spdm_msg_size = ((u64 *)info.buffer)[(size - sizeof(u64)) /
> > sizeof(u64)];
> > +       if (!in_range(size - spdm_msg_size - sizeof(u64), 0, 8)) {
> > +               dev_err(priv->dev,
> > +                       "Attestation error: Invalid SPDM response size,
> > %ld\n",
> > +                       spdm_msg_size);
> > +               return -EPROTO;
> > +       }
> > +
> > +       if (spdm_msg_size > response_sz) {
> > +               dev_err(priv->dev, "Attestation error: Expected response
> > size %ld, got %ld\n",
> > +                        response_sz, spdm_msg_size);
> > +               return -EOVERFLOW;
> > +       }
> > +
> > +       memcpy(response, info.buffer, spdm_msg_size);
> > +
> > +       return spdm_msg_size;
> > +}
> > +
> >  static int sdsi_get_layout(struct sdsi_priv *priv, struct disc_table
> > *table)
> >  {
> >         switch (table->guid) {
> > @@ -649,6 +744,92 @@ static int sdsi_map_mbox_registers(struct sdsi_priv
> > *priv, struct pci_dev *paren
> >         return 0;
> >  }
> >
> > +#define SDSI_SPDM_DRIVER_VERSION       1
> > +
> > +static int sdsi_spdm_get_info(struct sdsi_priv *priv,
> > +                             struct sdsi_spdm_info __user *argp)
> > +{
> > +       struct sdsi_spdm_info info;
> > +
> > +       info.driver_version = SDSI_SPDM_DRIVER_VERSION;
> > +       info.api_version = priv->guid;
> > +       info.dev_no = priv->id;
> > +       info.max_request_size = SDSI_SIZE_WRITE_MSG - (2 * sizeof(u64));
> > +       info.max_response_size = SDSI_SIZE_READ_MSG - (sizeof(u64));
>
> Unnecessary parenthesis on both lines.
>
> > +
> > +       if (copy_to_user(argp, &info, sizeof(info)))
> > +               return -EFAULT;
> > +
> > +       return 0;
> > +}
> > +
> > +static int sdsi_spdm_do_command(struct sdsi_priv *priv,
> > +                               struct sdsi_spdm_command __user *argp)
> > +{
> > +       u32 req_size, rsp_size;
> > +
> > +       if (get_user(req_size, &argp->size))
> > +               return -EFAULT;
> > +
> > +       if (req_size < 4 || req_size > sizeof(struct sdsi_spdm_message))
> > +               return -EINVAL;
> > +
> > +       struct sdsi_spdm_message *request __free(kfree) =
> > +               kmalloc(req_size, GFP_KERNEL);
> > +       if (!request)
> > +               return -ENOMEM;
> > +
> > +       struct sdsi_spdm_command *response __free(kfree) =
> > +               kmalloc(SDSI_SIZE_READ_MSG, GFP_KERNEL);
> > +       if (!response)
> > +               return -ENOMEM;
> > +
> > +       if (copy_from_user(request, &argp->message, req_size))
> > +               return -EFAULT;
> > +
> > +       rsp_size = sdsi_spdm_exchange(priv, request, req_size, response,
> > +                                     SDSI_SIZE_READ_MSG);
> > +       if (rsp_size < 4)
> > +               return rsp_size;
>
> Hmm, what the return value of this function actually means? Here it can
> returns -inf..3 but in the end you return 0. So clearly the return value
> isn't size. Is it something "work remaining to do" or what? Consider
> adding function comment about the return value because it looks a bit
> odd from the code alone.

You're right. The function returns size or an error code. But size less than 4
also indicates a bad message which is better to check for in
sdsi_spdm_exchange(). Will make that change.

>
> > +
> > +       if (put_user(rsp_size, &argp->size))
> > +               return -EFAULT;
> > +
> > +       if (copy_to_user(&argp->message, response, rsp_size))
> > +               return -EFAULT;
> > +
> > +       return 0;
> > +}
> > +
> > +static long sdsi_spdm_ioctl(struct file *file, unsigned int cmd,
> > +                           unsigned long arg)
> > +{
> > +       struct sdsi_priv *priv;
> > +       long ret = -ENOTTY;
> > +
> > +       priv = container_of(file->private_data, struct sdsi_priv, miscdev);
> > +
> > +       switch (cmd) {
> > +       case SDSI_IF_SPDM_INFO:
> > +               ret = sdsi_spdm_get_info(priv,
> > +                               (struct sdsi_spdm_info __user *)arg);
> > +               break;
> > +       case SDSI_IF_SPDM_COMMAND:
> > +               ret = sdsi_spdm_do_command(priv,
> > +                               (struct sdsi_spdm_command __user *)arg);
> > +               break;
> > +       default:
> > +               break;
> > +       }
> > +
> > +       return ret;
> > +}
> > +
> > +static const struct file_operations sdsi_spdm_ops = {
> > +       .owner = THIS_MODULE,
> > +       .unlocked_ioctl = sdsi_spdm_ioctl,
> > +};
> > +
> >  static int sdsi_probe(struct auxiliary_device *auxdev, const struct
> > auxiliary_device_id *id)
> >  {
> >         struct intel_vsec_device *intel_cap_dev = auxdev_to_ivdev(auxdev);
> > @@ -663,6 +844,7 @@ static int sdsi_probe(struct auxiliary_device *auxdev,
> > const struct auxiliary_de
> >                 return -ENOMEM;
> >
> >         priv->dev = &auxdev->dev;
> > +       priv->id = auxdev->id;
> >         mutex_init(&priv->mb_lock);
> >         auxiliary_set_drvdata(auxdev, priv);
> >
> > @@ -686,9 +868,35 @@ static int sdsi_probe(struct auxiliary_device *auxdev,
> > const struct auxiliary_de
> >         if (ret)
> >                 return ret;
> >
> > +       /* Attestation miscdevice */
> > +       if (priv->features & SDSI_FEATURE_ATTESTATION) {
> > +               priv->miscdev.name = kasprintf(GFP_KERNEL, "isdsi%d", priv-
> > >id);
>
> devm_kasprintf() ?
>
> > +               if (!priv->miscdev.name)
> > +                       return -ENOMEM;
> > +
> > +               priv->miscdev.minor = MISC_DYNAMIC_MINOR;
> > +               priv->miscdev.fops = &sdsi_spdm_ops;
> > +
> > +               ret = misc_register(&priv->miscdev);
> > +               if (!ret) {
> > +                       kfree_const(priv->miscdev.name);
> > +                       return ret;
> > +               }
> > +       }
> > +
> >         return 0;
> >  }
> >
> > +static void sdsi_remove(struct auxiliary_device *auxdev)
> > +{
> > +       struct sdsi_priv *priv = auxiliary_get_drvdata(auxdev);
> > +
> > +       if (priv->features & SDSI_FEATURE_ATTESTATION) {
> > +               misc_deregister(&priv->miscdev);
> > +               kfree_const(priv->miscdev.name);
> > +       }
> > +}
> > +
> >  static const struct auxiliary_device_id sdsi_aux_id_table[] = {
> >         { .name = "intel_vsec.sdsi" },
> >         {}
> > @@ -701,7 +909,7 @@ static struct auxiliary_driver sdsi_aux_driver = {
> >         },
> >         .id_table       = sdsi_aux_id_table,
> >         .probe          = sdsi_probe,
> > -       /* No remove. All resources are handled under devm */
> > +       .remove         = sdsi_remove,
> >  };
> >  module_auxiliary_driver(sdsi_aux_driver);
> >
> > diff --git a/include/uapi/linux/intel_sdsi.h
> > b/include/uapi/linux/intel_sdsi.h
> > new file mode 100644
> > index 000000000000..de9e7f6c44c5
> > --- /dev/null
> > +++ b/include/uapi/linux/intel_sdsi.h
> > @@ -0,0 +1,72 @@
> > +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> > +/*
> > + * Intel On Demand (SDSi) Interface for SPDM based attestation.
> > + * Copyright (c) 2019, Intel Corporation.
> > + * All rights reserved.
> > + *
> > + * Author: David E. Box <david.e.box@linux.intel.com>
> > + */
> > +
> > +#ifndef __SDSI_H
> > +#define __SDSI_H
> > +
> > +#include <linux/types.h>
> > +
> > +/**
> > + * struct sdsi_spdm_info - Define platform information
> > + * @api_version:       Version of the firmware document, which this driver
> > + *                     can communicate
> > + * @driver_version:    Driver version, which will help user to send right
> > + *                     commands. Even if the firmware is capable, driver
> > may
> > + *                     not be ready
> > + * @dev_no:            Returns the auxiliary device number the
> > corresponding
> > + *                     sdsi instance
> > + * @max_request_size:  Returns the maximum allowed size for SPDM request
> > + *                     messages
> > + * @max_response_size: Returns the maximum size of an SPDM response message
> > + *
> > + * Used to return output of IOCTL SDSI_SPDM_INFO. This
> > + * information can be used by the user space, to get the driver, firmware
> > + * support and also number of commands to send in a single IOCTL request.
> > + */
> > +struct sdsi_spdm_info {
> > +       __u32 api_version;
> > +       __u16 driver_version;
> > +       __u16 dev_no;
> > +       __u16 max_request_size;
> > +       __u16 max_response_size;
> > +};
> > +
> > +/**
> > + * struct sdsi_spdm_message - The SPDM message sent and received from the
> > device
> > + * @spdm_version:              Supported SPDM version
> > + * @request_response_code:     The SPDM message code for requests and
> > responses
> > + * @param1:                    Parameter 1
> > + * @param2:                    Parameter 2
> > + * @buffer:                    SDPM message specific buffer
> > + *
> > + */
> > +struct sdsi_spdm_message {
> > +       __u8 spdm_version;
> > +       __u8 request_response_code;
> > +       __u8 param1;
> > +       __u8 param2;
> > +       __u8 buffer[4092];
>
> How about SZ_4K - 4 * sizeof(__u8) ?
>
> Or move those header/metadata fields into another struct which is
> anonymously embedded into this one so you could do SZ_4K - sizeof(struct
> sdsi_spdm_message_header).

That's even better, thanks. Ack on all other requests.

David

>
> Remember to add #include for SZ_4K.
>