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Subject[PATCH V6 1/4] tpm: Abstract crypto agile event size calculations
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From: Matthew Garrett <mjg59@google.com>

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>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
---
drivers/char/tpm/eventlog/tpm2.c | 47 +---------------------
include/linux/tpm_eventlog.h | 68 ++++++++++++++++++++++++++++++++
2 files changed, 69 insertions(+), 46 deletions(-)

diff --git a/drivers/char/tpm/eventlog/tpm2.c b/drivers/char/tpm/eventlog/tpm2.c
index f824563fc28d..1a977bdd3bd2 100644
--- a/drivers/char/tpm/eventlog/tpm2.c
+++ b/drivers/char/tpm/eventlog/tpm2.c
@@ -40,52 +40,7 @@
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 81519f163211..6a86144e13f1 100644
--- 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
--
2.21.0.1020.gf2820cf01a-goog
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