tpm: Abstract crypto agile event size calculations

We need to calculate the size of crypto agile events in multiple
locations, including in the EFI boot stub. The easiest way to do this is
to put it in a header file as an inline and leave a wrapper to ensure we
don't end up with multiple copies of it embedded in the existing code.

Signed-off-by: Matthew Garrett <mjg59@google.com>
Reviewed-by: Bartosz Szczepanek <bsz@semihalf.com>
Tested-by: Bartosz Szczepanek <bsz@semihalf.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

diff --git a/drivers/char/tpm/eventlog/tpm2.c b/drivers/char/tpm/eventlog/tpm2.c
index d506362e046fc66cadcce1709261d72f8c5d6652..22b3346b9946e30c24436c0792a4d9bdf730523e 100644 (file)
--- a/drivers/char/tpm/eventlog/tpm2.c
+++ b/drivers/char/tpm/eventlog/tpm2.c
@@ -36,52 +36,7 @@
 static size_t calc_tpm2_event_size(struct tcg_pcr_event2_head *event,
                                   struct tcg_pcr_event *event_header)
 {
-       struct tcg_efi_specid_event_head *efispecid;
-       struct tcg_event_field *event_field;
-       void *marker;
-       void *marker_start;
-       u32 halg_size;
-       size_t size;
-       u16 halg;
-       int i;
-       int j;
-
-       marker = event;
-       marker_start = marker;
-       marker = marker + sizeof(event->pcr_idx) + sizeof(event->event_type)
-               + sizeof(event->count);
-
-       efispecid = (struct tcg_efi_specid_event_head *)event_header->event;
-
-       /* Check if event is malformed. */
-       if (event->count > efispecid->num_algs)
-               return 0;
-
-       for (i = 0; i < event->count; i++) {
-               halg_size = sizeof(event->digests[i].alg_id);
-               memcpy(&halg, marker, halg_size);
-               marker = marker + halg_size;
-               for (j = 0; j < efispecid->num_algs; j++) {
-                       if (halg == efispecid->digest_sizes[j].alg_id) {
-                               marker +=
-                                       efispecid->digest_sizes[j].digest_size;
-                               break;
-                       }
-               }
-               /* Algorithm without known length. Such event is unparseable. */
-               if (j == efispecid->num_algs)
-                       return 0;
-       }
-
-       event_field = (struct tcg_event_field *)marker;
-       marker = marker + sizeof(event_field->event_size)
-               + event_field->event_size;
-       size = marker - marker_start;
-
-       if ((event->event_type == 0) && (event_field->event_size == 0))
-               return 0;
-
-       return size;
+       return __calc_tpm2_event_size(event, event_header);
 }
 
 static void *tpm2_bios_measurements_start(struct seq_file *m, loff_t *pos)

diff --git a/include/linux/tpm_eventlog.h b/include/linux/tpm_eventlog.h
index 81519f1632111ec1d26862322738e5aa5adf7c74..6a86144e13f14b484d1e6450e7feaa11ecb5236a 100644 (file)
--- a/include/linux/tpm_eventlog.h
+++ b/include/linux/tpm_eventlog.h
@@ -112,4 +112,72 @@ struct tcg_pcr_event2_head {
        struct tpm_digest digests[];
 } __packed;
 
+/**
+ * __calc_tpm2_event_size - calculate the size of a TPM2 event log entry
+ * @event:        Pointer to the event whose size should be calculated
+ * @event_header: Pointer to the initial event containing the digest lengths
+ *
+ * The TPM2 event log format can contain multiple digests corresponding to
+ * separate PCR banks, and also contains a variable length of the data that
+ * was measured. This requires knowledge of how long each digest type is,
+ * and this information is contained within the first event in the log.
+ *
+ * We calculate the length by examining the number of events, and then looking
+ * at each event in turn to determine how much space is used for events in
+ * total. Once we've done this we know the offset of the data length field,
+ * and can calculate the total size of the event.
+ *
+ * Return: size of the event on success, <0 on failure
+ */
+
+static inline int __calc_tpm2_event_size(struct tcg_pcr_event2_head *event,
+                                        struct tcg_pcr_event *event_header)
+{
+       struct tcg_efi_specid_event_head *efispecid;
+       struct tcg_event_field *event_field;
+       void *marker;
+       void *marker_start;
+       u32 halg_size;
+       size_t size;
+       u16 halg;
+       int i;
+       int j;
+
+       marker = event;
+       marker_start = marker;
+       marker = marker + sizeof(event->pcr_idx) + sizeof(event->event_type)
+               + sizeof(event->count);
+
+       efispecid = (struct tcg_efi_specid_event_head *)event_header->event;
+
+       /* Check if event is malformed. */
+       if (event->count > efispecid->num_algs)
+               return 0;
+
+       for (i = 0; i < event->count; i++) {
+               halg_size = sizeof(event->digests[i].alg_id);
+               memcpy(&halg, marker, halg_size);
+               marker = marker + halg_size;
+               for (j = 0; j < efispecid->num_algs; j++) {
+                       if (halg == efispecid->digest_sizes[j].alg_id) {
+                               marker +=
+                                       efispecid->digest_sizes[j].digest_size;
+                               break;
+                       }
+               }
+               /* Algorithm without known length. Such event is unparseable. */
+               if (j == efispecid->num_algs)
+                       return 0;
+       }
+
+       event_field = (struct tcg_event_field *)marker;
+       marker = marker + sizeof(event_field->event_size)
+               + event_field->event_size;
+       size = marker - marker_start;
+
+       if ((event->event_type == 0) && (event_field->event_size == 0))
+               return 0;
+
+       return size;
+}
 #endif