tpm: Simplify hardware probe and detection checks

Perform the hardware probe once during setup instead of checking if
the probe has been completed on each measurement event.

Don't probe for hardware during BIOS interface detection.  Just check
if the previous probe found the hardware.

Unify has_working_tpm() with similar tpm_is_working().

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

1 files changed, 36 insertions, 84 deletions

diff --git a/src/tcgbios.c b/src/tcgbios.c
index 55e38a9..d7fe0ad 100644
--- a/src/tcgbios.c
+++ b/src/tcgbios.c
@@ -67,11 +67,7 @@ static const u8 GetCapability_Durations[] = {
  ****************************************************************/
 
 typedef struct {
-    u8            tpm_probed:1;
-    u8            tpm_found:1;
-    u8            tpm_working:1;
     u8            if_shutdown:1;
-    u8            tpm_driver_to_use:4;
     struct tcpa_descriptor_rev2 *tcpa;
 
     /* length of the TCPA log buffer */
@@ -90,9 +86,7 @@ typedef struct {
     u8 *          log_area_last_entry;
 } tpm_state_t;
 
-tpm_state_t tpm_state VARLOW = {
-    .tpm_driver_to_use = TPM_INVALID_DRIVER,
-};
+tpm_state_t tpm_state VARLOW;
 
 typedef u8 tpm_ppi_code;
 
@@ -107,50 +101,27 @@ is_preboot_if_shutdown(void)
  * TPM hardware interface
  ****************************************************************/
 
-static u32
-is_tpm_present(void)
+static u8 TPMHW_driver_to_use = TPM_INVALID_DRIVER;
+
+static int
+tpmhw_probe(void)
 {
-    u32 rc = 0;
     unsigned int i;
-
     for (i = 0; i < TPM_NUM_DRIVERS; i++) {
         struct tpm_driver *td = &tpm_drivers[i];
         if (td->probe() != 0) {
             td->init();
-            tpm_state.tpm_driver_to_use = i;
-            rc = 1;
-            break;
+            TPMHW_driver_to_use = i;
+            return 0;
         }
     }
-
-    return rc;
-}
-
-static void
-probe_tpm(void)
-{
-    if (!tpm_state.tpm_probed) {
-        tpm_state.tpm_probed = 1;
-        tpm_state.tpm_found = (is_tpm_present() != 0);
-        tpm_state.tpm_working = tpm_state.tpm_found;
-    }
+    return -1;
 }
 
 static int
-has_working_tpm(void)
+tpmhw_is_present(void)
 {
-    probe_tpm();
-
-    return tpm_state.tpm_working;
-}
-
-int
-tpm_is_working(void)
-{
-    if (!CONFIG_TCGBIOS)
-        return 0;
-
-    return tpm_state.tpm_working;
+    return TPMHW_driver_to_use != TPM_INVALID_DRIVER;
 }
 
 static u32
@@ -158,10 +129,10 @@ transmit(u8 locty, struct tpm_req_header *req,
          void *respbuffer, u32 *respbufferlen,
          enum tpmDurationType to_t)
 {
-    if (tpm_state.tpm_driver_to_use == TPM_INVALID_DRIVER)
+    if (TPMHW_driver_to_use == TPM_INVALID_DRIVER)
         return TCG_FATAL_COM_ERROR;
 
-    struct tpm_driver *td = &tpm_drivers[tpm_state.tpm_driver_to_use];
+    struct tpm_driver *td = &tpm_drivers[TPMHW_driver_to_use];
 
     u32 irc = td->activate(locty);
     if (irc != 0) {
@@ -329,6 +300,14 @@ tpm_log_event(struct pcpes *pcpes, const void *event)
  * Helper functions
  ****************************************************************/
 
+u8 TPM_working VARLOW;
+
+int
+tpm_is_working(void)
+{
+    return CONFIG_TCGBIOS && TPM_working;
+}
+
 /*
  * Send a TPM command with the given ordinal. Append the given buffer
  * containing all data in network byte order to the command (this is
@@ -394,7 +373,7 @@ tpm_set_failure(void)
                        NULL, 0, NULL, 0, &returnCode,
                        TPM_DURATION_TYPE_SHORT);
 
-    tpm_state.tpm_working = 0;
+    TPM_working = 0;
 }
 
 static u32
@@ -404,7 +383,7 @@ determine_timeouts(void)
     u32 returnCode;
     struct tpm_res_getcap_timeouts timeouts;
     struct tpm_res_getcap_durations durations;
-    struct tpm_driver *td = &tpm_drivers[tpm_state.tpm_driver_to_use];
+    struct tpm_driver *td = &tpm_drivers[TPMHW_driver_to_use];
     u32 i;
 
     rc = build_and_send_cmd(0, TPM_ORD_GetCapability,
@@ -465,7 +444,7 @@ err_exit:
 static u32
 tpm_log_extend_event(struct pcpes *pcpes, const void *event)
 {
-    if (!has_working_tpm())
+    if (!tpm_is_working())
         return TCG_GENERAL_ERROR;
 
     if (pcpes->pcrindex >= 24)
@@ -549,10 +528,7 @@ tpm_add_event_separators(void)
     u32 rc;
     u32 pcrIndex = 0;
 
-    if (!CONFIG_TCGBIOS)
-        return 0;
-
-    if (!has_working_tpm())
+    if (!tpm_is_working())
         return TCG_GENERAL_ERROR;
 
     static const u8 evt_separator[] = {0xff,0xff,0xff,0xff};
@@ -572,10 +548,7 @@ tpm_add_event_separators(void)
 static u32
 tpm_smbios_measure(void)
 {
-    if (!CONFIG_TCGBIOS)
-        return 0;
-
-    if (!has_working_tpm())
+    if (!tpm_is_working())
         return TCG_GENERAL_ERROR;
 
     u32 rc;
@@ -607,7 +580,7 @@ tpm_startup(void)
     u32 rc;
     u32 returnCode;
 
-    if (!has_working_tpm())
+    if (!tpm_is_working())
         return TCG_GENERAL_ERROR;
 
     dprintf(DEBUG_tcg, "TCGBIOS: Starting with TPM_Startup(ST_CLEAR)\n");
@@ -677,15 +650,12 @@ err_exit:
 static void
 tpm_acpi_init(void)
 {
-    tpm_state.if_shutdown = 0;
-    tpm_state.tpm_probed = 0;
-    tpm_state.tpm_found = 0;
-    tpm_state.tpm_working = 0;
-
-    if (!has_working_tpm()) {
+    int ret = tpmhw_probe();
+    if (ret) {
         tpm_state.if_shutdown = 1;
         return;
     }
+    TPM_working = 1;
 
     reset_acpi_log();
 }
@@ -709,10 +679,7 @@ tpm_prepboot(void)
     u32 rc;
     u32 returnCode;
 
-    if (!CONFIG_TCGBIOS)
-        return;
-
-    if (!has_working_tpm())
+    if (!tpm_is_working())
         return;
 
     rc = build_and_send_cmd(0, TPM_ORD_PhysicalPresence,
@@ -751,10 +718,7 @@ err_exit:
 u32
 tpm_option_rom(const void *addr, u32 len)
 {
-    if (!CONFIG_TCGBIOS)
-        return 0;
-
-    if (!has_working_tpm())
+    if (!tpm_is_working())
         return TCG_GENERAL_ERROR;
 
     u32 rc;
@@ -776,10 +740,7 @@ tpm_option_rom(const void *addr, u32 len)
 u32
 tpm_add_bcv(u32 bootdrv, const u8 *addr, u32 length)
 {
-    if (!CONFIG_TCGBIOS)
-        return 0;
-
-    if (!has_working_tpm())
+    if (!tpm_is_working())
         return TCG_GENERAL_ERROR;
 
     if (length < 0x200)
@@ -811,10 +772,7 @@ tpm_add_bcv(u32 bootdrv, const u8 *addr, u32 length)
 u32
 tpm_add_cdrom(u32 bootdrv, const u8 *addr, u32 length)
 {
-    if (!CONFIG_TCGBIOS)
-        return 0;
-
-    if (!has_working_tpm())
+    if (!tpm_is_working())
         return TCG_GENERAL_ERROR;
 
     u32 rc = tpm_add_action(4, "Booting from CD ROM device");
@@ -831,10 +789,7 @@ tpm_add_cdrom(u32 bootdrv, const u8 *addr, u32 length)
 u32
 tpm_add_cdrom_catalog(const u8 *addr, u32 length)
 {
-    if (!CONFIG_TCGBIOS)
-        return 0;
-
-    if (!has_working_tpm())
+    if (!tpm_is_working())
         return TCG_GENERAL_ERROR;
 
     u32 rc = tpm_add_action(4, "Booting from CD ROM device");
@@ -854,10 +809,7 @@ tpm_s3_resume(void)
     u32 rc;
     u32 returnCode;
 
-    if (!CONFIG_TCGBIOS)
-        return;
-
-    if (!has_working_tpm())
+    if (!tpm_is_working())
         return;
 
     dprintf(DEBUG_tcg, "TCGBIOS: Resuming with TPM_Startup(ST_STATE)\n");
@@ -1123,7 +1075,7 @@ tpm_interrupt_handler32(struct bregs *regs)
 
     switch ((enum irq_ids)regs->al) {
     case TCG_StatusCheck:
-        if (is_tpm_present() == 0) {
+        if (!tpmhw_is_present()) {
             /* no TPM available */
             regs->eax = TCG_PC_TPM_NOT_PRESENT;
         } else {