rwsig: Make it possible to run as a task

(Optionally) split rwsig verification into a separate task. This
allows us to initialize other components (e.g. USB) while the
verification is in progress, speeding up the boot process to active
USB in RO case.

After CONFIG_RWSIG_JUMP_TIMEOUT, the EC will jump to the RW section
if no action is taken by the AP (such as a forced request to jump
to RW, or starting an update).

Note: This comes with a ~36ms boot time regression, as other code
gets to run before verification starts.

BRANCH=none
BUG=b:35587171
TEST=Flash, board boots to RW after 1s
TEST=Change jump timeout to 5s, add 5s delay in check_signature,
     add console command to manually abort/continue rwsig verification.
     'rwsig continue' works => Board jumps to RW after check_signature
     is completed (or immediately while waiting for timeout)
     'rwsig abort' works => Board does not jump to RW.

Change-Id: Ica5732b9298bb4d3b743cae2ba78df259db915ef
Reviewed-on: https://chromium-review.googlesource.com/468709
Commit-Ready: Nicolas Boichat <drinkcat@chromium.org>
Tested-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>

1 files changed, 39 insertions, 2 deletions

diff --git a/include/rwsig.h b/include/rwsig.h
index 138751d3cc..bb70077732 100644
--- a/include/rwsig.h
+++ b/include/rwsig.h
@@ -10,9 +10,46 @@
 #include "rsa.h"
 
 #ifndef __ASSEMBLER__
+#ifdef HAS_TASK_RWSIG
+/* The functions below only make sense if RWSIG task is defined. */
 
-/* Checks RW signature. */
-void check_rw_signature(void);
+/* Current status of RW signature verification */
+enum rwsig_status {
+	RWSIG_UNKNOWN = 0, /* Unknown/not started */
+	RWSIG_IN_PROGRESS,
+	RWSIG_VALID,
+	RWSIG_INVALID,
+	RWSIG_ABORTED,
+};
+
+/* Returns current rwsig verification status. */
+enum rwsig_status rwsig_get_status(void);
+
+/*
+ * Aborts current verification, also prevents RWSIG task from automatically
+ * jumping to RW.
+ * This is used by usb_updater when a RW update is required, giving it enough
+ * time to actually perform the update.
+ */
+void rwsig_abort(void);
+
+/*
+ * Tells RWSIG task to jump to RW immediately, if the signature is correct.
+ * This is used by usb_updater when no RW update is required, to speed up
+ * boot time.
+ */
+void rwsig_continue(void);
+
+#else /* !HAS_TASK_RWSIG */
+/* These functions can only be called directly if RWSIG task is not defined. */
+
+/* Checks RW signature. Returns a boolean indicating success. */
+int rwsig_check_signature(void);
+
+/* Jumps to RW, if signature is fine, returns on error (otherwise, jumps). */
+void rwsig_jump_now(void);
+
+#endif
 
 #endif /* !__ASSEMBLER__ */