Abort preempted TSP STD SMC after PSCI CPU suspend

Standard SMC requests that are handled in the secure-world by the Secure
Payload can be preempted by interrupts that must be handled in the
normal world. When the TSP is preempted the secure context is stored and
control is passed to the normal world to handle the non-secure
interrupt. Once completed the preempted secure context is restored. When
restoring the preempted context, the dispatcher assumes that the TSP
preempted context is still stored as the SECURE context by the context
management library.

However, PSCI power management operations causes synchronous entry into
TSP. This overwrites the preempted SECURE context in the context
management library. When restoring back the SECURE context, the Secure
Payload crashes because this context is not the preempted context
anymore.

This patch avoids corruption of the preempted SECURE context by aborting
any preempted SMC during PSCI power management calls. The
abort_std_smc_entry hook of the TSP is called when aborting the SMC
request.

It also exposes this feature as a FAST SMC callable from normal world to
abort preempted SMC with FID TSP_FID_ABORT.

Change-Id: I7a70347e9293f47d87b5de20484b4ffefb56b770
Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>

4 files changed, 91 insertions, 9 deletions

diff --git a/services/spd/tspd/tspd_common.c b/services/spd/tspd/tspd_common.c
index 322413c9..3dcefea9 100644
--- a/services/spd/tspd/tspd_common.c
+++ b/services/spd/tspd/tspd_common.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2014, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2016, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -32,7 +32,9 @@
 #include <assert.h>
 #include <bl_common.h>
 #include <context_mgmt.h>
+#include <debug.h>
 #include <string.h>
+#include <tsp.h>
 #include "tspd_private.h"
 
 /*******************************************************************************
@@ -129,3 +131,31 @@ void tspd_synchronous_sp_exit(tsp_context_t *tsp_ctx, uint64_t ret)
 	/* Should never reach here */
 	assert(0);
 }
+
+/*******************************************************************************
+ * This function takes an SP context pointer and abort any preempted SMC
+ * request.
+ * Return 1 if there was a preempted SMC request, 0 otherwise.
+ ******************************************************************************/
+int tspd_abort_preempted_smc(tsp_context_t *tsp_ctx)
+{
+	if (!get_std_smc_active_flag(tsp_ctx->state))
+		return 0;
+
+	/* Abort any preempted SMC request */
+	clr_std_smc_active_flag(tsp_ctx->state);
+
+	/*
+	 * Arrange for an entry into the test secure payload. It will
+	 * be returned via TSP_ABORT_DONE case in tspd_smc_handler.
+	 */
+	cm_set_elr_el3(SECURE,
+		       (uint64_t) &tsp_vectors->abort_std_smc_entry);
+	uint64_t rc = tspd_synchronous_sp_entry(tsp_ctx);
+
+	if (rc != 0)
+		panic();
+
+	return 1;
+}
+
diff --git a/services/spd/tspd/tspd_main.c b/services/spd/tspd/tspd_main.c
index 1a064594..2850e703 100644
--- a/services/spd/tspd/tspd_main.c
+++ b/services/spd/tspd/tspd_main.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2015, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2016, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -459,6 +459,11 @@ uint64_t tspd_smc_handler(uint32_t smc_fid,
 		 */
 		tspd_synchronous_sp_exit(tsp_ctx, x1);
 #endif
+	/*
+	 * This function ID is used only by the SP to indicate it has finished
+	 * aborting a preempted Standard SMC request.
+	 */
+	case TSP_ABORT_DONE:
 
 	/*
 	 * These function IDs are used only by the SP to indicate it has
@@ -596,6 +601,26 @@ uint64_t tspd_smc_handler(uint32_t smc_fid,
 		}
 
 		break;
+	/*
+	 * Request from the non-secure world to abort a preempted Standard SMC
+	 * call.
+	 */
+	case TSP_FID_ABORT:
+		/* ABORT should only be invoked by normal world */
+		if (!ns) {
+			assert(0);
+			break;
+		}
+
+		/* Abort the preempted SMC request */
+		if (!tspd_abort_preempted_smc(tsp_ctx))
+			/*
+			 * If there was no preempted SMC to abort, return
+			 * SMC_UNK.
+			 */
+			SMC_RET1(handle, SMC_UNK);
+
+		break;
 
 		/*
 		 * Request from non secure world to resume the preempted
diff --git a/services/spd/tspd/tspd_pm.c b/services/spd/tspd/tspd_pm.c
index 55562ba4..bc5435a8 100644
--- a/services/spd/tspd/tspd_pm.c
+++ b/services/spd/tspd/tspd_pm.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2015, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2016, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -58,6 +58,12 @@ static int32_t tspd_cpu_off_handler(uint64_t unused)
 	assert(tsp_vectors);
 	assert(get_tsp_pstate(tsp_ctx->state) == TSP_PSTATE_ON);
 
+	/*
+	 * Abort any preempted SMC request before overwriting the SECURE
+	 * context.
+	 */
+	tspd_abort_preempted_smc(tsp_ctx);
+
 	/* Program the entry point and enter the TSP */
 	cm_set_elr_el3(SECURE, (uint64_t) &tsp_vectors->cpu_off_entry);
 	rc = tspd_synchronous_sp_entry(tsp_ctx);
@@ -75,7 +81,7 @@ static int32_t tspd_cpu_off_handler(uint64_t unused)
 	 */
 	set_tsp_pstate(tsp_ctx->state, TSP_PSTATE_OFF);
 
-	 return 0;
+	return 0;
 }
 
 /*******************************************************************************
@@ -91,6 +97,12 @@ static void tspd_cpu_suspend_handler(uint64_t max_off_pwrlvl)
 	assert(tsp_vectors);
 	assert(get_tsp_pstate(tsp_ctx->state) == TSP_PSTATE_ON);
 
+	/*
+	 * Abort any preempted SMC request before overwriting the SECURE
+	 * context.
+	 */
+	tspd_abort_preempted_smc(tsp_ctx);
+
 	/* Program the entry point and enter the TSP */
 	cm_set_elr_el3(SECURE, (uint64_t) &tsp_vectors->cpu_suspend_entry);
 	rc = tspd_synchronous_sp_entry(tsp_ctx);
@@ -99,7 +111,7 @@ static void tspd_cpu_suspend_handler(uint64_t max_off_pwrlvl)
 	 * Read the response from the TSP. A non-zero return means that
 	 * something went wrong while communicating with the TSP.
 	 */
-	if (rc != 0)
+	if (rc)
 		panic();
 
 	/* Update its context to reflect the state the TSP is in */
@@ -108,7 +120,7 @@ static void tspd_cpu_suspend_handler(uint64_t max_off_pwrlvl)
 
 /*******************************************************************************
  * This cpu has been turned on. Enter the TSP to initialise S-EL1 and other bits
- * before passing control back to the Secure Monitor. Entry in S-El1 is done
+ * before passing control back to the Secure Monitor. Entry in S-EL1 is done
  * after initialising minimal architectural state that guarantees safe
  * execution.
  ******************************************************************************/
@@ -205,6 +217,12 @@ static void tspd_system_off(void)
 	assert(tsp_vectors);
 	assert(get_tsp_pstate(tsp_ctx->state) == TSP_PSTATE_ON);
 
+	/*
+	 * Abort any preempted SMC request before overwriting the SECURE
+	 * context.
+	 */
+	tspd_abort_preempted_smc(tsp_ctx);
+
 	/* Program the entry point */
 	cm_set_elr_el3(SECURE, (uint64_t) &tsp_vectors->system_off_entry);
 
@@ -225,11 +243,19 @@ static void tspd_system_reset(void)
 	assert(tsp_vectors);
 	assert(get_tsp_pstate(tsp_ctx->state) == TSP_PSTATE_ON);
 
+	/*
+	 * Abort any preempted SMC request before overwriting the SECURE
+	 * context.
+	 */
+	tspd_abort_preempted_smc(tsp_ctx);
+
 	/* Program the entry point */
 	cm_set_elr_el3(SECURE, (uint64_t) &tsp_vectors->system_reset_entry);
 
-	/* Enter the TSP. We do not care about the return value because we
-	 * must continue the reset anyway */
+	/*
+	 * Enter the TSP. We do not care about the return value because we
+	 * must continue the reset anyway
+	 */
 	tspd_synchronous_sp_entry(tsp_ctx);
 }
 
diff --git a/services/spd/tspd/tspd_private.h b/services/spd/tspd/tspd_private.h
index cadc6aaa..82039a42 100644
--- a/services/spd/tspd/tspd_private.h
+++ b/services/spd/tspd/tspd_private.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2014, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2016, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -242,6 +242,7 @@ void tspd_init_tsp_ep_state(struct entry_point_info *tsp_ep,
 				uint32_t rw,
 				uint64_t pc,
 				tsp_context_t *tsp_ctx);
+int tspd_abort_preempted_smc(tsp_context_t *tsp_ctx);
 
 extern tsp_context_t tspd_sp_context[TSPD_CORE_COUNT];
 extern struct tsp_vectors *tsp_vectors;