[PATCH 2/2] tpm: tpm_crb_ffa: maunally register tpm_crb_ffa driver when it's built-in

[Yeoreum Yun]

To integrate tpm_event_log with IMA subsystem,
tpm_crb and tpm_crb_ffa driver should be built as built-in
(CONFIG_TCG_CRB=y && CONFIG_TCG_CRB_FFA=y).

However, this could make failure for ima_init() gets tpm chip when
each initcall function deployed like:

0000000000000888 l       .initcall6.init	0000000000000000 crb_acpi_driver_init
000000000000088c l       .initcall6.init	0000000000000000 tpm_crb_ffa_driver_init

If crb_api_driver_init() is called first, probing tpm device using CRB over
FFA method is deferred since tpm_crb_ffa_driver_init() isn't called yet.

Deferred probe of the tpm device will be probed by system workqueue
in proper time after deferred_probe_initcall() registers the work.
However, ima_init() could be called first if they're deployed like:

000000000000012c l       .initcall7.init	0000000000000000 init_ima
000000000000016c l       .initcall7.init	0000000000000000 deferred_probe_initcall7

In this situation, ima_init() failed to find tpm device and it failed to
generate boot_aggregate with PCR values.

That's why kernel prints log this situation though tpm device exists:
   [    3.080786] ima: No TPM chip found, activating TPM-bypass!

To resolve this, call ffa_register() in tpm_crb_ffa_init() when it was
built with built-in so that ima can generate boot_aggregate log with
PCR values properly.

Signed-off-by: Yeoreum Yun <yeoreum.yun at arm.com>
---
 drivers/char/tpm/tpm_crb_ffa.c | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/drivers/char/tpm/tpm_crb_ffa.c b/drivers/char/tpm/tpm_crb_ffa.c
index 4ead61f01299..2ef29b66fa5d 100644
--- a/drivers/char/tpm/tpm_crb_ffa.c
+++ b/drivers/char/tpm/tpm_crb_ffa.c
@@ -115,6 +115,7 @@ struct tpm_crb_ffa {
 };
 
 static struct tpm_crb_ffa *tpm_crb_ffa;
+static struct ffa_driver tpm_crb_ffa_driver;
 
 static int tpm_crb_ffa_to_linux_errno(int errno)
 {
@@ -168,13 +169,22 @@ static int tpm_crb_ffa_to_linux_errno(int errno)
  */
 int tpm_crb_ffa_init(void)
 {
-	if (!tpm_crb_ffa)
-		return -ENOENT;
+	int ret = 0;
 
-	if (IS_ERR_VALUE(tpm_crb_ffa))
-		return -ENODEV;
+	if (IS_MODULE(CONFIG_TCG_ARM_CRB_FFA)) {
+		if (!tpm_crb_ffa)
+			ret = -ENOENT;
 
-	return 0;
+		if (IS_ERR_VALUE(tpm_crb_ffa))
+			ret = -ENODEV;
+
+		return ret;
+	}
+
+	ret = ffa_register(&tpm_crb_ffa_driver);
+	BUG_ON(!ret && !tpm_crb_ffa);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(tpm_crb_ffa_init);
 
@@ -369,7 +379,9 @@ static struct ffa_driver tpm_crb_ffa_driver = {
 	.id_table = tpm_crb_ffa_device_id,
 };
 
+#ifdef MODULE
 module_ffa_driver(tpm_crb_ffa_driver);
+#endif
 
 MODULE_AUTHOR("Arm");
 MODULE_DESCRIPTION("TPM CRB FFA driver");
-- 
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}