Re: [Qemu-devel] [PATCH V14 5/7] Add a TPM Passthrough backend driver implementation

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Dec 14, 2011 at 08:43:20AM -0500, Stefan Berger wrote:
> >From Andreas Niederl's original posting with adaptations where necessary:
> 
> This patch is based of off version 9 of Stefan Berger's patch series
>   "Qemu Trusted Platform Module (TPM) integration"
> and adds a new backend driver for it.
> 
> This patch adds a passthrough backend driver for passing commands sent to the
> emulated TPM device directly to a TPM device opened on the host machine.
> 
> Thus it is possible to use a hardware TPM device in a system running on QEMU,
> providing the ability to access a TPM in a special state (e.g. after a Trusted
> Boot).
> 
> This functionality is being used in the acTvSM Trusted Virtualization Platform
> which is available on [1].
> 
> Usage example:
>   qemu-system-x86_64 -tpmdev passthrough,id=tpm0,path=/dev/tpm0 \
>                      -device tpm-tis,tpmdev=tpm0 \
>                      -cdrom test.iso -boot d
> 
> Some notes about the host TPM:
> The TPM needs to be enabled and activated. If that's not the case one
> has to go through the BIOS/UEFI and enable and activate that TPM for TPM
> commands to work as expected.
> It may be necessary to boot the kernel using tpm_tis.force=1 in the boot
> command line or 'modprobe tpm_tis force=1' in case of using it as a module.
> 
> Regards,
> Andreas Niederl, Stefan Berger
> 
> [1] http://trustedjava.sourceforge.net/
> 
> Signed-off-by: Andreas Niederl <andreas.niederl@iaik.tugraz.at>
> Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
> ---
>  Makefile.target      |    1 +
>  configure            |    3 +
>  hw/tpm_passthrough.c |  493 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  qemu-options.hx      |   33 ++++
>  tpm.c                |   16 ++
>  tpm.h                |   33 ++++
>  6 files changed, 579 insertions(+), 0 deletions(-)
>  create mode 100644 hw/tpm_passthrough.c
> 
> diff --git a/Makefile.target b/Makefile.target
> index 0e1c032..2744a5c 100644
> --- a/Makefile.target
> +++ b/Makefile.target
> @@ -207,6 +207,7 @@ obj-$(CONFIG_NO_KVM) += kvm-stub.o
>  obj-y += memory.o
>  obj-y += tpm.o
>  obj-$(CONFIG_TPM) += tpm_tis.o
> +obj-$(CONFIG_TPM_PASSTHROUGH) += tpm_passthrough.o
>  LIBS+=-lz
>  
>  QEMU_CFLAGS += $(VNC_TLS_CFLAGS)
> diff --git a/configure b/configure
> index 385feb4..25995bc 100755
> --- a/configure
> +++ b/configure
> @@ -3721,6 +3721,9 @@ fi
>  
>  if test "$tpm" = "yes"; then
>    if test "$target_softmmu" = "yes" ; then
> +    if test "$linux" = "yes" ; then
> +      echo "CONFIG_TPM_PASSTHROUGH=y" >> $config_target_mak
> +    fi
>      echo "CONFIG_TPM=y" >> $config_host_mak
>    fi
>  fi
> diff --git a/hw/tpm_passthrough.c b/hw/tpm_passthrough.c
> new file mode 100644
> index 0000000..76e4e35
> --- /dev/null
> +++ b/hw/tpm_passthrough.c
> @@ -0,0 +1,493 @@
> +/*
> + *  passthrough TPM driver
> + *
> + *  Copyright (c) 2010, 2011 IBM Corporation
> + *  Authors:
> + *    Stefan Berger <stefanb@us.ibm.com>
> + *
> + *  Copyright (C) 2011 IAIK, Graz University of Technology
> + *    Author: Andreas Niederl
> + *
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2 of the License, or (at your option) any later version.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library; if not, see <http://www.gnu.org/licenses/>
> + */
> +
> +#include "qemu-common.h"
> +#include "qemu-error.h"
> +#include "tpm.h"
> +#include "hw/hw.h"
> +#include "hw/tpm_tis.h"
> +#include "hw/pc.h"
> +
> +/* #define DEBUG_TPM */
> +
> +#ifdef DEBUG_TPM
> +#define dprintf(fmt, ...) \
> +    do { fprintf(stderr, fmt, ## __VA_ARGS__); } while (0)
> +#else
> +#define dprintf(fmt, ...) \
> +    do { } while (0)
> +#endif
> +
> +/* data structures */
> +
> +typedef struct TPMPassthruThreadParams {
> +    TPMState *tpm_state;
> +
> +    TPMRecvDataCB *recv_data_callback;
> +    TPMBackend *tb;
> +} TPMPassthruThreadParams;
> +
> +struct TPMPassthruState {
> +    QemuThread thread;
> +    bool thread_terminate;
> +    bool thread_running;
> +
> +    TPMPassthruThreadParams tpm_thread_params;
> +
> +    char tpm_dev[64];

why not strdup and avoid length limits?


> +    int tpm_fd;
> +    bool had_startup_error;
> +};
> +
> +#define TPM_PASSTHROUGH_DEFAULT_DEVICE "/dev/tpm0"
> +
> +/* borrowed from qemu-char.c */
> +static int tpm_passthrough_unix_write(int fd, const uint8_t *buf, uint32_t len)
> +{
> +    int ret, len1;
> +
> +    len1 = len;
> +    while (len1 > 0) {
> +        ret = write(fd, buf, len1);
> +        if (ret < 0) {
> +            if (errno != EINTR && errno != EAGAIN) {
> +                return -1;
> +            }
> +        } else if (ret == 0) {
> +            break;
> +        } else {
> +            buf  += ret;
> +            len1 -= ret;
> +        }
> +    }
> +    return len - len1;
> +}
> +
> +static int tpm_passthrough_unix_read(int fd, uint8_t *buf, uint32_t len)
> +{
> +    int ret, len1;
> +    uint8_t *buf1;
> +
> +    len1 = len;
> +    buf1 = buf;
> +    while ((len1 > 0) && (ret = read(fd, buf1, len1)) != 0) {
> +        if (ret < 0) {
> +            if (errno != EINTR && errno != EAGAIN) {
> +                return -1;
> +            }
> +        } else {
> +            buf1 += ret;
> +            len1 -= ret;
> +        }
> +    }
> +    return len - len1;
> +}
> +
> +static uint32_t tpm_passthrough_get_size_from_buffer(const uint8_t *buf)
> +{
> +    return be32_to_cpu(*(uint32_t *)&buf[2]);
> +}
> +
> +static int tpm_passthrough_unix_tx_bufs(int tpm_fd,
> +                                        const uint8_t *in, uint32_t in_len,
> +                                        uint8_t *out, uint32_t out_len)
> +{
> +    int ret;
> +
> +    ret = tpm_passthrough_unix_write(tpm_fd, in, in_len);
> +    if (ret < 0) {
> +        error_report("tpm_passthrough: error while transmitting data "
> +                     "to TPM: %s (%i)\n",
> +                     strerror(errno), errno);
> +        goto err_exit;
> +    }
> +
> +    ret = tpm_passthrough_unix_read(tpm_fd, out, out_len);
> +    if (ret < 0) {
> +        error_report("tpm_passthrough: error while reading data from "
> +                     "TPM: %s (%i)\n",
> +                     strerror(errno), errno);
> +    } else if (ret < sizeof(struct tpm_resp_hdr) ||
> +               tpm_passthrough_get_size_from_buffer(out) != ret) {
> +        ret = -1;
> +        error_report("tpm_passthrough: received invalid response "
> +                     "packet from TPM\n");
> +    }
> +
> +err_exit:
> +    if (ret < 0) {
> +        tpm_write_fatal_error_response(out, out_len);
> +    }
> +
> +    return ret;
> +}
> +
> +static int tpm_passthrough_unix_transfer(int tpm_fd,
> +                                         const TPMLocality *cmd_locty)
> +{
> +    return tpm_passthrough_unix_tx_bufs(tpm_fd,
> +                                        cmd_locty->w_buffer.buffer,
> +                                        cmd_locty->w_offset,
> +                                        cmd_locty->r_buffer.buffer,
> +                                        cmd_locty->r_buffer.size);
> +}
> +
> +static void *tpm_passthrough_thread(void *d)
> +{
> +    TPMPassthruThreadParams *thr_parms = d;
> +    TPMPassthruState *tpm_pt = thr_parms->tb->s.tpm_pt;
> +    uint32_t in_len;
> +
> +    dprintf("tpm_passthrough: THREAD IS STARTING\n");
> +
> +    /* start command processing */
> +    while (!tpm_pt->thread_terminate) {
> +        /* receive and handle commands */
> +        in_len = 0;
> +        do {
> +            dprintf("tpm_passthrough: waiting for commands...\n");
> +
> +            if (tpm_pt->thread_terminate) {
> +                break;
> +            }
> +
> +            qemu_mutex_lock(&thr_parms->tpm_state->state_lock);
> +
> +            /* in case we were to slow and missed the signal, the



too slow


> +               to_tpm_execute boolean tells us about a pending command */
> +            if (!thr_parms->tpm_state->to_tpm_execute) {
> +                qemu_cond_wait(&thr_parms->tpm_state->to_tpm_cond,
> +                               &thr_parms->tpm_state->state_lock);
> +            }
> +
> +            thr_parms->tpm_state->to_tpm_execute = false;
> +
> +            qemu_mutex_unlock(&thr_parms->tpm_state->state_lock);
> +
> +            if (tpm_pt->thread_terminate) {
> +                break;
> +            }
> +
> +            in_len = thr_parms->tpm_state->cmd_locty->w_offset;
> +
> +            tpm_passthrough_unix_transfer(tpm_pt->tpm_fd,
> +                                          thr_parms->tpm_state->cmd_locty);
> +
> +            thr_parms->recv_data_callback(thr_parms->tpm_state,
> +                                          thr_parms->tpm_state->command_locty);
> +        } while (in_len > 0);
> +    }
> +
> +    dprintf("tpm_passthrough: THREAD IS ENDING\n");
> +
> +    tpm_pt->thread_running = false;
> +
> +    return NULL;
> +}
> +
> +static void tpm_passthrough_terminate_tpm_thread(TPMBackend *tb)
> +{
> +    TPMPassthruState *tpm_pt = tb->s.tpm_pt;
> +
> +    if (!tpm_pt->thread_running) {
> +        return;
> +    }
> +
> +    dprintf("tpm_passthrough: TERMINATING RUNNING TPM THREAD\n");
> +
> +    if (!tpm_pt->thread_terminate) {
> +        tpm_pt->thread_terminate = true;
> +
> +        qemu_mutex_lock(&tpm_pt->tpm_thread_params.tpm_state->state_lock);
> +        qemu_cond_signal(&tpm_pt->tpm_thread_params.tpm_state->to_tpm_cond);
> +        qemu_mutex_unlock(&tpm_pt->tpm_thread_params.tpm_state->state_lock);

why lock?

> +
> +        if (tpm_pt->thread_running) {
> +            qemu_thread_join(&tpm_pt->thread);
> +        }
> +        memset(&tpm_pt->thread, 0, sizeof(tpm_pt->thread));
> +    }
> +}
> +
> +/**
> + * Start the TPM (thread). If it had been started before, then terminate
> + * and start it again.
> + */
> +static int tpm_passthrough_do_startup_tpm(TPMBackend *tb)
> +{
> +    TPMPassthruState *tpm_pt = tb->s.tpm_pt;
> +
> +    /* terminate a running TPM */
> +    tpm_passthrough_terminate_tpm_thread(tb);
> +
> +    /* reset the flag so the thread keeps on running */
> +    tpm_pt->thread_terminate = false;
> +
> +    qemu_thread_create(&tpm_pt->thread, tpm_passthrough_thread,
> +                       &tpm_pt->tpm_thread_params, 0);
> +
> +    tpm_pt->thread_running = true;
> +
> +    return 0;
> +}
> +
> +static int tpm_passthrough_startup_tpm(TPMBackend *tb)
> +{
> +    TPMPassthruState *tpm_pt = tb->s.tpm_pt;
> +    int rc;
> +
> +    rc = tpm_passthrough_do_startup_tpm(tb);
> +    if (rc) {
> +        tpm_pt->had_startup_error = true;
> +    }
> +    return rc;
> +}
> +
> +static void tpm_passthrough_reset(TPMBackend *tb)
> +{
> +    TPMPassthruState *tpm_pt = tb->s.tpm_pt;
> +
> +    dprintf("tpm_passthrough: CALL TO TPM_RESET!\n");
> +
> +    tpm_passthrough_terminate_tpm_thread(tb);
> +
> +    tpm_pt->had_startup_error = false;
> +}
> +
> +static int tpm_passthrough_init(TPMBackend *tb, TPMState *s,
> +                                TPMRecvDataCB *recv_data_cb)
> +{
> +    TPMPassthruState *tpm_pt = tb->s.tpm_pt;
> +
> +    tpm_pt->tpm_thread_params.tpm_state = s;
> +    tpm_pt->tpm_thread_params.recv_data_callback = recv_data_cb;
> +    tpm_pt->tpm_thread_params.tb = tb;
> +
> +    tpm_pt->thread_running = false;
> +
> +    return 0;
> +}
> +
> +static bool tpm_passthrough_get_tpm_established_flag(TPMBackend *tb)
> +{
> +    return false;
> +}
> +
> +static bool tpm_passthrough_get_startup_error(TPMBackend *tb)
> +{
> +    TPMPassthruState *tpm_pt = tb->s.tpm_pt;
> +
> +    return tpm_pt->had_startup_error;
> +}
> +
> +static size_t tpm_passthrough_realloc_buffer(TPMSizedBuffer *sb)
> +{
> +    size_t wanted_size = 4096; /* Linux tpm.c buffer size */

what does the comment mean?


> +
> +    if (sb->size != wanted_size) {
> +        sb->buffer = g_realloc(sb->buffer, wanted_size);
> +        if (sb->buffer != NULL) {
> +            sb->size = wanted_size;
> +        } else {
> +            sb->size = 0;
> +        }
> +    }
> +    return sb->size;
> +}
> +
> +static const char *tpm_passthrough_create_desc(void)
> +{
> +    return "Passthrough TPM backend driver";
> +}
> +
> +/* A basic test of a TPM device. We expect a well formatted response header
> + * (error response is fine) within one second.
> + */
> +static int tpm_passthrough_test_tpmdev(int fd)
> +{
> +    struct tpm_req_hdr req = {
> +        .tag = cpu_to_be16(TPM_TAG_RQU_COMMAND),
> +        .len = cpu_to_be32(sizeof(req)),
> +        .ordinal = cpu_to_be32(TPM_ORD_GetTicks),
> +    };
> +    struct tpm_resp_hdr *resp;
> +    fd_set readfds;
> +    int n;
> +    struct timeval tv = {
> +        .tv_sec = 1,
> +        .tv_usec = 0,
> +    };
> +    unsigned char buf[1024];
> +
> +    n = write(fd, &req, sizeof(req));
> +    if (n < 0) {
> +        return errno;
> +    }
> +    if (n != sizeof(req)) {
> +        return EFAULT;
> +    }
> +
> +    FD_ZERO(&readfds);
> +    FD_SET(fd, &readfds);
> +
> +    /* wait for a second */
> +    n = select(fd + 1, &readfds, NULL, NULL, &tv);
> +    if (n != 1) {
> +        return errno;
> +    }
> +
> +    n = read(fd, &buf, sizeof(buf));

so why read the whole buf? hoiw do we know 1024 is enough?
read the heade then discard the rest
until empty.

> +    if (n < sizeof(struct tpm_resp_hdr)) {
> +        return EFAULT;
> +    }
> +
> +    resp = (struct tpm_resp_hdr *)buf;
> +    /* check the header */
> +    if (be16_to_cpu(resp->tag) != TPM_TAG_RSP_COMMAND ||
> +        be32_to_cpu(resp->len) != n) {
> +        return EBADMSG;
> +    }
> +
> +    return 0;
> +}
> +
> +static int tpm_passthrough_handle_device_opts(QemuOpts *opts, TPMBackend *tb)
> +{
> +    const char *value;
> +    char buf[64];
> +    int n;
> +
> +    value = qemu_opt_get(opts, "path");
> +    if (!value) {
> +        value = TPM_PASSTHROUGH_DEFAULT_DEVICE;
> +    }
> +
> +    n = snprintf(tb->s.tpm_pt->tpm_dev, sizeof(tb->s.tpm_pt->tpm_dev),
> +                 "%s", value);
> +
> +    if (n >= sizeof(tb->s.tpm_pt->tpm_dev)) {
> +        error_report("TPM device path is too long.\n");
> +        goto err_exit;
> +    }
> +
> +    snprintf(buf, sizeof(buf), "path=%s", tb->s.tpm_pt->tpm_dev);
> +
> +    tb->parameters = g_strdup(buf);
> +
> +    if (tb->parameters == NULL) {
> +        return 1;
> +    }
> +
> +    tb->s.tpm_pt->tpm_fd = open(tb->s.tpm_pt->tpm_dev, O_RDWR);
> +    if (tb->s.tpm_pt->tpm_fd < 0) {
> +        error_report("Cannot access TPM device using '%s'.\n",
> +                     tb->s.tpm_pt->tpm_dev);
> +        goto err_exit;
> +    }
> +
> +    if (tpm_passthrough_test_tpmdev(tb->s.tpm_pt->tpm_fd)) {
> +        error_report("'%s' is not a TPM device.\n",
> +                     tb->s.tpm_pt->tpm_dev);
> +        goto err_close_tpmdev;
> +    }
> +
> +    return 0;
> +
> + err_close_tpmdev:
> +    close(tb->s.tpm_pt->tpm_fd);
> +    tb->s.tpm_pt->tpm_fd = -1;
> +
> + err_exit:
> +    g_free(tb->parameters);
> +    tb->parameters = NULL;
> +
> +    return 1;
> +}
> +
> +
> +static TPMBackend *tpm_passthrough_create(QemuOpts *opts, const char *id)
> +{
> +    TPMBackend *tb;
> +
> +    tb = g_malloc0(sizeof(TPMBackend));
> +    if (tb == NULL) {
> +        error_report("tpm_passthrough: Could not allocate memory.\n");
> +        return NULL;
> +    }
> +
> +    tb->s.tpm_pt = g_malloc0(sizeof(TPMPassthruState));
> +    if (tb->s.tpm_pt == NULL) {
> +        error_report("tpm_passthrough: Could not allocate memory.\n");
> +        g_free(tb);
> +        return NULL;
> +    }
> +
> +    tb->id = g_strdup(id);
> +    if (tb->id == NULL) {
> +        error_report("tpm_passthrough: Could not allocate memory.\n");
> +        goto err_exit;
> +    }
> +
> +    tb->ops = &tpm_passthrough_driver;
> +
> +    if (tpm_passthrough_handle_device_opts(opts, tb)) {
> +        goto err_exit;
> +    }
> +
> +    return tb;
> +
> +err_exit:
> +    g_free(tb->id);
> +    g_free(tb->s.tpm_pt);
> +    g_free(tb);
> +
> +    return NULL;
> +}
> +
> +static void tpm_passthrough_destroy(TPMBackend *tb)
> +{
> +    TPMPassthruState *tpm_pt = tb->s.tpm_pt;
> +
> +    tpm_passthrough_terminate_tpm_thread(tb);
> +
> +    close(tpm_pt->tpm_fd);
> +
> +    g_free(tb->id);
> +    g_free(tb->parameters);
> +    g_free(tb->s.tpm_pt);
> +    g_free(tb);
> +}
> +
> +const TPMDriverOps tpm_passthrough_driver = {
> +    .id                       = "passthrough",
> +    .desc                     = tpm_passthrough_create_desc,
> +    .create                   = tpm_passthrough_create,
> +    .destroy                  = tpm_passthrough_destroy,
> +    .init                     = tpm_passthrough_init,
> +    .startup_tpm              = tpm_passthrough_startup_tpm,
> +    .realloc_buffer           = tpm_passthrough_realloc_buffer,
> +    .reset                    = tpm_passthrough_reset,
> +    .had_startup_error        = tpm_passthrough_get_startup_error,
> +    .get_tpm_established_flag = tpm_passthrough_get_tpm_established_flag,
> +};
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 40a63b1..10ae499 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -1916,6 +1916,7 @@ The general form of a TPM device option is:
>  @item -tpmdev @var{backend} ,id=@var{id} [,@var{options}]
>  @findex -tpmdev
>  Backend type must be:
> +@option{passthrough}.
>  
>  The specific backend type will determine the applicable options.
>  The @code{-tpmdev} options requires a @code{-device} option.
> @@ -1927,6 +1928,38 @@ Use ? to print all available TPM backend types.
>  qemu -tpmdev ?
>  @end example
>  
> +@item -tpmdev passthrough, id=@var{id}, path=@var{path}
> +
> +(Linux-host only) Enable access to the host's TPM using the passthrough
> +driver.
> +
> +@option{path} specifies the path to the host's TPM device, i.e., on
> +a Linux host this would be @code{/dev/tpm0}.
> +@option{path} is optional and by default @code{/dev/tpm0} is used.
> +
> +Some notes about using the host's TPM with the passthrough driver:
> +
> +The TPM device accessed by the passthrough driver must not be
> +used by any other application on the host.
> +
> +Since the host's firmware (BIOS/UEFI) has already initialized the TPM,
> +the VM's firmware (BIOS/UEFI) will not be able to initialize the
> +TPM again and may therefore not show a TPM-specific menu that would
> +otherwise allow the user to configure the TPM, e.g., allow the user to
> +enable/disable or activate/deactivate the TPM.
> +Further, if TPM ownership is released from within a VM then the host's TPM
> +will get disabled and deactivated. To enable and activate the
> +TPM again afterwards, the host has to be rebooted and the user is
> +required to enter the firmware's menu to enable and activate the TPM.
> +If the TPM is left disabled and/or deactivated most TPM commands will fail.
> +
> +To create a passthrough TPM use the following two options:
> +@example
> +-tpmdev passthrough,id=tpm0 -device tpm-tis,tpmdev=tpm0
> +@end example
> +Note that the @code{-tpmdev} id is @code{tpm0} and is referenced by
> +@code{tpmdev=tpm0} in the device option.
> +
>  @end table
>  
>  ETEXI
> diff --git a/tpm.c b/tpm.c
> index 408d319..ee38107 100644
> --- a/tpm.c
> +++ b/tpm.c
> @@ -24,9 +24,25 @@ static QLIST_HEAD(, TPMBackend) tpm_backends =
>  #ifdef CONFIG_TPM
>  
>  static const TPMDriverOps *bes[] = {
> +#ifdef CONFIG_TPM_PASSTHROUGH
> +    &tpm_passthrough_driver,
> +#endif
>      NULL,
>  };
>  
> +/* Write an error message in the given output buffer.
> + */
> +void tpm_write_fatal_error_response(uint8_t *out, uint32_t out_len)
> +{
> +    if (out_len >= sizeof(struct tpm_resp_hdr)) {
> +        struct tpm_resp_hdr *resp = (struct tpm_resp_hdr *)out;
> +
> +        resp->tag = cpu_to_be16(TPM_TAG_RSP_COMMAND);
> +        resp->len = cpu_to_be32(sizeof(struct tpm_resp_hdr));
> +        resp->errcode = cpu_to_be32(TPM_FAIL);
> +    }
> +}
> +
>  const TPMDriverOps *tpm_get_backend_driver(const char *id)
>  {
>      int i;
> diff --git a/tpm.h b/tpm.h
> index 075de3f..1b278cc 100644
> --- a/tpm.h
> +++ b/tpm.h
> @@ -18,12 +18,18 @@
>  struct TPMDriverOps;
>  typedef struct TPMDriverOps TPMDriverOps;
>  
> +typedef struct TPMPassthruState TPMPassthruState;
> +
>  typedef struct TPMBackend {
>      char *id;
>      const char *fe_model;
>      char *parameters;
>      const TPMDriverOps *ops;
>  
> +    union {
> +        TPMPassthruState *tpm_pt;
> +    } s;
> +
>      QLIST_ENTRY(TPMBackend) list;
>  } TPMBackend;
>  
> @@ -76,11 +82,38 @@ struct TPMDriverOps {
>  
>  #define TPM_DEFAULT_DEVICE_MODEL "tpm-tis"
>  
> +struct tpm_req_hdr {
> +    uint16_t tag;
> +    uint32_t len;
> +    uint32_t ordinal;
> +} __attribute__((packed));
> +
> +struct tpm_resp_hdr {
> +    uint16_t tag;
> +    uint32_t len;
> +    uint32_t errcode;
> +} __attribute__((packed));
> +
> +#define TPM_TAG_RQU_COMMAND       0xc1
> +#define TPM_TAG_RQU_AUTH1_COMMAND 0xc2
> +#define TPM_TAG_RQU_AUTH2_COMMAND 0xc3
> +
> +#define TPM_TAG_RSP_COMMAND       0xc4
> +#define TPM_TAG_RSP_AUTH1_COMMAND 0xc5
> +#define TPM_TAG_RSP_AUTH2_COMMAND 0xc6
> +
> +#define TPM_FAIL                  9
> +
> +#define TPM_ORD_GetTicks          0xf1
> +
>  int tpm_config_parse(QemuOptsList *opts_list, const char *optarg);
>  int tpm_init(void);
>  void tpm_cleanup(void);
>  TPMBackend *qemu_find_tpm(const char *id);
>  void tpm_display_backend_drivers(void);
>  const TPMDriverOps *tpm_get_backend_driver(const char *id);
> +void tpm_write_fatal_error_response(uint8_t *out, uint32_t out_len);
> +
> +extern const TPMDriverOps tpm_passthrough_driver;
>  
>  #endif /* QEMU_TPM_H */
> -- 
> 1.7.6.4
>