tpm: Probe for connected TPM 1.2 or TPM 2

In the TPM passthrough backend driver, modify the probing code so
that we can check whether a TPM 1.2 or TPM 2 is being used
and adapt the behavior of the TPM TIS accordingly.

Move the code that tested for a TPM 1.2 into tpm_utils.c
and extend it with test for probing for TPM 2. Have the
function return the version of TPM found.

Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 126 insertions, 0 deletions

diff --git a/hw/tpm/tpm_util.c b/hw/tpm/tpm_util.c
new file mode 100644
index 0000000000..4ace5852e0
--- /dev/null
+++ b/hw/tpm/tpm_util.c
@@ -0,0 +1,126 @@
+/*
+ * TPM utility functions
+ *
+ *  Copyright (c) 2010 - 2015 IBM Corporation
+ *  Authors:
+ *    Stefan Berger <stefanb@us.ibm.com>
+ *
+ * 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 "tpm_util.h"
+#include "tpm_int.h"
+
+/*
+ * A basic test of a TPM device. We expect a well formatted response header
+ * (error response is fine) within one second.
+ */
+static int tpm_util_test(int fd,
+                         unsigned char *request,
+                         size_t requestlen,
+                         uint16_t *return_tag)
+{
+    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, request, requestlen);
+    if (n < 0) {
+        return errno;
+    }
+    if (n != requestlen) {
+        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));
+    if (n < sizeof(struct tpm_resp_hdr)) {
+        return EFAULT;
+    }
+
+    resp = (struct tpm_resp_hdr *)buf;
+    /* check the header */
+    if (be32_to_cpu(resp->len) != n) {
+        return EBADMSG;
+    }
+
+    *return_tag = be16_to_cpu(resp->tag);
+
+    return 0;
+}
+
+/*
+ * Probe for the TPM device in the back
+ * Returns 0 on success with the version of the probed TPM set, 1 on failure.
+ */
+int tpm_util_test_tpmdev(int tpm_fd, TPMVersion *tpm_version)
+{
+    /*
+     * Sending a TPM1.2 command to a TPM2 should return a TPM1.2
+     * header (tag = 0xc4) and error code (TPM_BADTAG = 0x1e)
+     *
+     * Sending a TPM2 command to a TPM 2 will give a TPM 2 tag in the
+     * header.
+     * Sending a TPM2 command to a TPM 1.2 will give a TPM 1.2 tag
+     * in the header and an error code.
+     */
+    const struct tpm_req_hdr test_req = {
+        .tag = cpu_to_be16(TPM_TAG_RQU_COMMAND),
+        .len = cpu_to_be32(sizeof(test_req)),
+        .ordinal = cpu_to_be32(TPM_ORD_GetTicks),
+    };
+
+    const struct tpm_req_hdr test_req_tpm2 = {
+        .tag = cpu_to_be16(TPM2_ST_NO_SESSIONS),
+        .len = cpu_to_be32(sizeof(test_req_tpm2)),
+        .ordinal = cpu_to_be32(TPM2_CC_ReadClock),
+    };
+    uint16_t return_tag;
+    int ret;
+
+    /* Send TPM 2 command */
+    ret = tpm_util_test(tpm_fd, (unsigned char *)&test_req_tpm2,
+                        sizeof(test_req_tpm2), &return_tag);
+    /* TPM 2 would respond with a tag of TPM2_ST_NO_SESSIONS */
+    if (!ret && return_tag == TPM2_ST_NO_SESSIONS) {
+        *tpm_version = TPM_VERSION_2_0;
+        return 0;
+    }
+
+    /* Send TPM 1.2 command */
+    ret = tpm_util_test(tpm_fd, (unsigned char *)&test_req,
+                        sizeof(test_req), &return_tag);
+    if (!ret && return_tag == TPM_TAG_RSP_COMMAND) {
+        *tpm_version = TPM_VERSION_1_2;
+        /* this is a TPM 1.2 */
+        return 0;
+    }
+
+    *tpm_version = TPM_VERSION_UNSPEC;
+
+    return 1;
+}