Adding upstream version 2.10.0+dfsg.upstream/2.10.0+dfsgupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 819 insertions, 0 deletions

diff --git a/services/spd/tspd/tspd_main.c b/services/spd/tspd/tspd_main.c
new file mode 100644
index 0000000..6cb4992
--- /dev/null
+++ b/services/spd/tspd/tspd_main.c
@@ -0,0 +1,819 @@
+/*
+ * Copyright (c) 2013-2022, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+
+/*******************************************************************************
+ * This is the Secure Payload Dispatcher (SPD). The dispatcher is meant to be a
+ * plug-in component to the Secure Monitor, registered as a runtime service. The
+ * SPD is expected to be a functional extension of the Secure Payload (SP) that
+ * executes in Secure EL1. The Secure Monitor will delegate all SMCs targeting
+ * the Trusted OS/Applications range to the dispatcher. The SPD will either
+ * handle the request locally or delegate it to the Secure Payload. It is also
+ * responsible for initialising and maintaining communication with the SP.
+ ******************************************************************************/
+#include <assert.h>
+#include <errno.h>
+#include <stddef.h>
+#include <string.h>
+
+#include <arch_helpers.h>
+#include <bl31/bl31.h>
+#include <bl31/ehf.h>
+#include <bl32/tsp/tsp.h>
+#include <common/bl_common.h>
+#include <common/debug.h>
+#include <common/runtime_svc.h>
+#include <lib/el3_runtime/context_mgmt.h>
+#include <plat/common/platform.h>
+#include <tools_share/uuid.h>
+
+#include "tspd_private.h"
+
+/*******************************************************************************
+ * Address of the entrypoint vector table in the Secure Payload. It is
+ * initialised once on the primary core after a cold boot.
+ ******************************************************************************/
+tsp_vectors_t *tsp_vectors;
+
+/*******************************************************************************
+ * Array to keep track of per-cpu Secure Payload state
+ ******************************************************************************/
+tsp_context_t tspd_sp_context[TSPD_CORE_COUNT];
+
+
+/* TSP UID */
+DEFINE_SVC_UUID2(tsp_uuid,
+	0xa056305b, 0x9132, 0x7b42, 0x98, 0x11,
+	0x71, 0x68, 0xca, 0x50, 0xf3, 0xfa);
+
+int32_t tspd_init(void);
+
+/*
+ * This helper function handles Secure EL1 preemption. The preemption could be
+ * due Non Secure interrupts or EL3 interrupts. In both the cases we context
+ * switch to the normal world and in case of EL3 interrupts, it will again be
+ * routed to EL3 which will get handled at the exception vectors.
+ */
+uint64_t tspd_handle_sp_preemption(void *handle)
+{
+	cpu_context_t *ns_cpu_context;
+
+	assert(handle == cm_get_context(SECURE));
+	cm_el1_sysregs_context_save(SECURE);
+	/* Get a reference to the non-secure context */
+	ns_cpu_context = cm_get_context(NON_SECURE);
+	assert(ns_cpu_context);
+
+	/*
+	 * To allow Secure EL1 interrupt handler to re-enter TSP while TSP
+	 * is preempted, the secure system register context which will get
+	 * overwritten must be additionally saved. This is currently done
+	 * by the TSPD S-EL1 interrupt handler.
+	 */
+
+	/*
+	 * Restore non-secure state.
+	 */
+	cm_el1_sysregs_context_restore(NON_SECURE);
+	cm_set_next_eret_context(NON_SECURE);
+
+	/*
+	 * The TSP was preempted during execution of a Yielding SMC Call.
+	 * Return back to the normal world with SMC_PREEMPTED as error
+	 * code in x0.
+	 */
+	SMC_RET1(ns_cpu_context, SMC_PREEMPTED);
+}
+
+/*******************************************************************************
+ * This function is the handler registered for S-EL1 interrupts by the TSPD. It
+ * validates the interrupt and upon success arranges entry into the TSP at
+ * 'tsp_sel1_intr_entry()' for handling the interrupt.
+ * Typically, interrupts for a specific security state get handled in the same
+ * security execption level if the execution is in the same security state. For
+ * example, if a non-secure interrupt gets fired when CPU is executing in NS-EL2
+ * it gets handled in the non-secure world.
+ * However, interrupts belonging to the opposite security state typically demand
+ * a world(context) switch. This is inline with the security principle which
+ * states a secure interrupt has to be handled in the secure world.
+ * Hence, the TSPD in EL3 expects the context(handle) for a secure interrupt to
+ * be non-secure and vice versa.
+ * However, a race condition between non-secure and secure interrupts can lead to
+ * a scenario where the above assumptions do not hold true. This is demonstrated
+ * below through Note 1.
+ ******************************************************************************/
+static uint64_t tspd_sel1_interrupt_handler(uint32_t id,
+					    uint32_t flags,
+					    void *handle,
+					    void *cookie)
+{
+	uint32_t linear_id;
+	tsp_context_t *tsp_ctx;
+
+	/* Get a reference to this cpu's TSP context */
+	linear_id = plat_my_core_pos();
+	tsp_ctx = &tspd_sp_context[linear_id];
+
+#if TSP_NS_INTR_ASYNC_PREEMPT
+
+	/*
+	 * Note 1:
+	 * Under the current interrupt routing model, interrupts from other
+	 * world are routed to EL3 when TSP_NS_INTR_ASYNC_PREEMPT is enabled.
+	 * Consider the following scenario:
+	 * 1/ A non-secure payload(like tftf) requests a secure service from
+	 *    TSP by invoking a yielding SMC call.
+	 * 2/ Later, execution jumps to TSP in S-EL1 with the help of TSP
+	 *    Dispatcher in Secure Monitor(EL3).
+	 * 3/ While CPU is executing TSP, a Non-secure interrupt gets fired.
+	 *    this demands a context switch to the non-secure world through
+	 *    secure monitor.
+	 * 4/ Consequently, TSP in S-EL1 get asynchronously pre-empted and
+	 *    execution switches to secure monitor(EL3).
+	 * 5/ EL3 tries to triage the (Non-secure) interrupt based on the
+	 *    highest pending interrupt.
+	 * 6/ However, while the NS Interrupt was pending, secure timer gets
+	 *    fired which makes a S-EL1 interrupt to be pending.
+	 * 7/ Hence, execution jumps to this companion handler of S-EL1
+	 *    interrupt (i.e., tspd_sel1_interrupt_handler) even though the TSP
+	 *    was pre-empted due to non-secure interrupt.
+	 * 8/ The above sequence of events explain how TSP was pre-empted by
+	 *    S-EL1 interrupt indirectly in an asynchronous way.
+	 * 9/ Hence, we track the TSP pre-emption by S-EL1 interrupt using a
+	 *    boolean variable per each core.
+	 * 10/ This helps us to indicate that SMC call for TSP service was
+	 *    pre-empted when execution resumes in non-secure world.
+	 */
+
+	/* Check the security state when the exception was generated */
+	if (get_interrupt_src_ss(flags) == NON_SECURE) {
+		/* Sanity check the pointer to this cpu's context */
+		assert(handle == cm_get_context(NON_SECURE));
+
+		/* Save the non-secure context before entering the TSP */
+		cm_el1_sysregs_context_save(NON_SECURE);
+		tsp_ctx->preempted_by_sel1_intr = false;
+	} else {
+		/* Sanity check the pointer to this cpu's context */
+		assert(handle == cm_get_context(SECURE));
+
+		/* Save the secure context before entering the TSP for S-EL1
+		 * interrupt handling
+		 */
+		cm_el1_sysregs_context_save(SECURE);
+		tsp_ctx->preempted_by_sel1_intr = true;
+	}
+#else
+	/* Check the security state when the exception was generated */
+	assert(get_interrupt_src_ss(flags) == NON_SECURE);
+
+	/* Sanity check the pointer to this cpu's context */
+	assert(handle == cm_get_context(NON_SECURE));
+
+	/* Save the non-secure context before entering the TSP */
+	cm_el1_sysregs_context_save(NON_SECURE);
+#endif
+
+	assert(&tsp_ctx->cpu_ctx == cm_get_context(SECURE));
+
+	/*
+	 * Determine if the TSP was previously preempted. Its last known
+	 * context has to be preserved in this case.
+	 * The TSP should return control to the TSPD after handling this
+	 * S-EL1 interrupt. Preserve essential EL3 context to allow entry into
+	 * the TSP at the S-EL1 interrupt entry point using the 'cpu_context'
+	 * structure. There is no need to save the secure system register
+	 * context since the TSP is supposed to preserve it during S-EL1
+	 * interrupt handling.
+	 */
+	if (get_yield_smc_active_flag(tsp_ctx->state)) {
+		tsp_ctx->saved_spsr_el3 = (uint32_t)SMC_GET_EL3(&tsp_ctx->cpu_ctx,
+						      CTX_SPSR_EL3);
+		tsp_ctx->saved_elr_el3 = SMC_GET_EL3(&tsp_ctx->cpu_ctx,
+						     CTX_ELR_EL3);
+#if TSP_NS_INTR_ASYNC_PREEMPT
+		memcpy(&tsp_ctx->sp_ctx, &tsp_ctx->cpu_ctx, TSPD_SP_CTX_SIZE);
+#endif
+	}
+
+	cm_el1_sysregs_context_restore(SECURE);
+	cm_set_elr_spsr_el3(SECURE, (uint64_t) &tsp_vectors->sel1_intr_entry,
+		    SPSR_64(MODE_EL1, MODE_SP_ELX, DISABLE_ALL_EXCEPTIONS));
+
+	cm_set_next_eret_context(SECURE);
+
+	/*
+	 * Tell the TSP that it has to handle a S-EL1 interrupt synchronously.
+	 * Also the instruction in normal world where the interrupt was
+	 * generated is passed for debugging purposes. It is safe to retrieve
+	 * this address from ELR_EL3 as the secure context will not take effect
+	 * until el3_exit().
+	 */
+	SMC_RET2(&tsp_ctx->cpu_ctx, TSP_HANDLE_SEL1_INTR_AND_RETURN, read_elr_el3());
+}
+
+#if TSP_NS_INTR_ASYNC_PREEMPT
+/*******************************************************************************
+ * This function is the handler registered for Non secure interrupts by the
+ * TSPD. It validates the interrupt and upon success arranges entry into the
+ * normal world for handling the interrupt.
+ ******************************************************************************/
+static uint64_t tspd_ns_interrupt_handler(uint32_t id,
+					    uint32_t flags,
+					    void *handle,
+					    void *cookie)
+{
+	/* Check the security state when the exception was generated */
+	assert(get_interrupt_src_ss(flags) == SECURE);
+
+	/*
+	 * Disable the routing of NS interrupts from secure world to EL3 while
+	 * interrupted on this core.
+	 */
+	disable_intr_rm_local(INTR_TYPE_NS, SECURE);
+
+	return tspd_handle_sp_preemption(handle);
+}
+#endif
+
+/*******************************************************************************
+ * Secure Payload Dispatcher setup. The SPD finds out the SP entrypoint and type
+ * (aarch32/aarch64) if not already known and initialises the context for entry
+ * into the SP for its initialisation.
+ ******************************************************************************/
+static int32_t tspd_setup(void)
+{
+	entry_point_info_t *tsp_ep_info;
+	uint32_t linear_id;
+
+	linear_id = plat_my_core_pos();
+
+	/*
+	 * Get information about the Secure Payload (BL32) image. Its
+	 * absence is a critical failure.  TODO: Add support to
+	 * conditionally include the SPD service
+	 */
+	tsp_ep_info = bl31_plat_get_next_image_ep_info(SECURE);
+	if (!tsp_ep_info) {
+		WARN("No TSP provided by BL2 boot loader, Booting device"
+			" without TSP initialization. SMC`s destined for TSP"
+			" will return SMC_UNK\n");
+		return 1;
+	}
+
+	/*
+	 * If there's no valid entry point for SP, we return a non-zero value
+	 * signalling failure initializing the service. We bail out without
+	 * registering any handlers
+	 */
+	if (!tsp_ep_info->pc)
+		return 1;
+
+	/*
+	 * We could inspect the SP image and determine its execution
+	 * state i.e whether AArch32 or AArch64. Assuming it's AArch64
+	 * for the time being.
+	 */
+	tspd_init_tsp_ep_state(tsp_ep_info,
+				TSP_AARCH64,
+				tsp_ep_info->pc,
+				&tspd_sp_context[linear_id]);
+
+#if TSP_INIT_ASYNC
+	bl31_set_next_image_type(SECURE);
+#else
+	/*
+	 * All TSPD initialization done. Now register our init function with
+	 * BL31 for deferred invocation
+	 */
+	bl31_register_bl32_init(&tspd_init);
+#endif
+	return 0;
+}
+
+/*******************************************************************************
+ * This function passes control to the Secure Payload image (BL32) for the first
+ * time on the primary cpu after a cold boot. It assumes that a valid secure
+ * context has already been created by tspd_setup() which can be directly used.
+ * It also assumes that a valid non-secure context has been initialised by PSCI
+ * so it does not need to save and restore any non-secure state. This function
+ * performs a synchronous entry into the Secure payload. The SP passes control
+ * back to this routine through a SMC.
+ ******************************************************************************/
+int32_t tspd_init(void)
+{
+	uint32_t linear_id = plat_my_core_pos();
+	tsp_context_t *tsp_ctx = &tspd_sp_context[linear_id];
+	entry_point_info_t *tsp_entry_point;
+	uint64_t rc;
+
+	/*
+	 * Get information about the Secure Payload (BL32) image. Its
+	 * absence is a critical failure.
+	 */
+	tsp_entry_point = bl31_plat_get_next_image_ep_info(SECURE);
+	assert(tsp_entry_point);
+
+	cm_init_my_context(tsp_entry_point);
+
+	/*
+	 * Arrange for an entry into the test secure payload. It will be
+	 * returned via TSP_ENTRY_DONE case
+	 */
+	rc = tspd_synchronous_sp_entry(tsp_ctx);
+	assert(rc != 0);
+
+	return rc;
+}
+
+
+/*******************************************************************************
+ * This function is responsible for handling all SMCs in the Trusted OS/App
+ * range from the non-secure state as defined in the SMC Calling Convention
+ * Document. It is also responsible for communicating with the Secure payload
+ * to delegate work and return results back to the non-secure state. Lastly it
+ * will also return any information that the secure payload needs to do the
+ * work assigned to it.
+ ******************************************************************************/
+static uintptr_t tspd_smc_handler(uint32_t smc_fid,
+			 u_register_t x1,
+			 u_register_t x2,
+			 u_register_t x3,
+			 u_register_t x4,
+			 void *cookie,
+			 void *handle,
+			 u_register_t flags)
+{
+	cpu_context_t *ns_cpu_context;
+	uint32_t linear_id = plat_my_core_pos(), ns;
+	tsp_context_t *tsp_ctx = &tspd_sp_context[linear_id];
+	uint64_t rc;
+#if TSP_INIT_ASYNC
+	entry_point_info_t *next_image_info;
+#endif
+
+	/* Determine which security state this SMC originated from */
+	ns = is_caller_non_secure(flags);
+
+	switch (smc_fid) {
+
+	/*
+	 * This function ID is used by TSP to indicate that it was
+	 * preempted by a normal world IRQ.
+	 *
+	 */
+	case TSP_PREEMPTED:
+		if (ns)
+			SMC_RET1(handle, SMC_UNK);
+
+		return tspd_handle_sp_preemption(handle);
+
+	/*
+	 * This function ID is used only by the TSP to indicate that it has
+	 * finished handling a S-EL1 interrupt or was preempted by a higher
+	 * priority pending EL3 interrupt. Execution should resume
+	 * in the normal world.
+	 */
+	case TSP_HANDLED_S_EL1_INTR:
+		if (ns)
+			SMC_RET1(handle, SMC_UNK);
+
+		assert(handle == cm_get_context(SECURE));
+
+		/*
+		 * Restore the relevant EL3 state which saved to service
+		 * this SMC.
+		 */
+		if (get_yield_smc_active_flag(tsp_ctx->state)) {
+			SMC_SET_EL3(&tsp_ctx->cpu_ctx,
+				    CTX_SPSR_EL3,
+				    tsp_ctx->saved_spsr_el3);
+			SMC_SET_EL3(&tsp_ctx->cpu_ctx,
+				    CTX_ELR_EL3,
+				    tsp_ctx->saved_elr_el3);
+#if TSP_NS_INTR_ASYNC_PREEMPT
+			/*
+			 * Need to restore the previously interrupted
+			 * secure context.
+			 */
+			memcpy(&tsp_ctx->cpu_ctx, &tsp_ctx->sp_ctx,
+				TSPD_SP_CTX_SIZE);
+#endif
+		}
+
+		/* Get a reference to the non-secure context */
+		ns_cpu_context = cm_get_context(NON_SECURE);
+		assert(ns_cpu_context);
+
+		/*
+		 * Restore non-secure state. There is no need to save the
+		 * secure system register context since the TSP was supposed
+		 * to preserve it during S-EL1 interrupt handling.
+		 */
+		cm_el1_sysregs_context_restore(NON_SECURE);
+		cm_set_next_eret_context(NON_SECURE);
+
+		/* Refer to Note 1 in function tspd_sel1_interrupt_handler()*/
+#if TSP_NS_INTR_ASYNC_PREEMPT
+		if (tsp_ctx->preempted_by_sel1_intr) {
+			/* Reset the flag */
+			tsp_ctx->preempted_by_sel1_intr = false;
+
+			SMC_RET1(ns_cpu_context, SMC_PREEMPTED);
+		} else {
+			SMC_RET0((uint64_t) ns_cpu_context);
+		}
+#else
+		SMC_RET0((uint64_t) ns_cpu_context);
+#endif
+
+
+	/*
+	 * This function ID is used only by the SP to indicate it has
+	 * finished initialising itself after a cold boot
+	 */
+	case TSP_ENTRY_DONE:
+		if (ns)
+			SMC_RET1(handle, SMC_UNK);
+
+		/*
+		 * Stash the SP entry points information. This is done
+		 * only once on the primary cpu
+		 */
+		assert(tsp_vectors == NULL);
+		tsp_vectors = (tsp_vectors_t *) x1;
+
+		if (tsp_vectors) {
+			set_tsp_pstate(tsp_ctx->state, TSP_PSTATE_ON);
+
+			/*
+			 * TSP has been successfully initialized. Register power
+			 * management hooks with PSCI
+			 */
+			psci_register_spd_pm_hook(&tspd_pm);
+
+			/*
+			 * Register an interrupt handler for S-EL1 interrupts
+			 * when generated during code executing in the
+			 * non-secure state.
+			 */
+			flags = 0;
+			set_interrupt_rm_flag(flags, NON_SECURE);
+			rc = register_interrupt_type_handler(INTR_TYPE_S_EL1,
+						tspd_sel1_interrupt_handler,
+						flags);
+			if (rc)
+				panic();
+
+#if TSP_NS_INTR_ASYNC_PREEMPT
+			/*
+			 * Register an interrupt handler for NS interrupts when
+			 * generated during code executing in secure state are
+			 * routed to EL3.
+			 */
+			flags = 0;
+			set_interrupt_rm_flag(flags, SECURE);
+
+			rc = register_interrupt_type_handler(INTR_TYPE_NS,
+						tspd_ns_interrupt_handler,
+						flags);
+			if (rc)
+				panic();
+
+			/*
+			 * Disable the NS interrupt locally.
+			 */
+			disable_intr_rm_local(INTR_TYPE_NS, SECURE);
+#endif
+		}
+
+
+#if TSP_INIT_ASYNC
+		/* Save the Secure EL1 system register context */
+		assert(cm_get_context(SECURE) == &tsp_ctx->cpu_ctx);
+		cm_el1_sysregs_context_save(SECURE);
+
+		/* Program EL3 registers to enable entry into the next EL */
+		next_image_info = bl31_plat_get_next_image_ep_info(NON_SECURE);
+		assert(next_image_info);
+		assert(NON_SECURE ==
+				GET_SECURITY_STATE(next_image_info->h.attr));
+
+		cm_init_my_context(next_image_info);
+		cm_prepare_el3_exit(NON_SECURE);
+		SMC_RET0(cm_get_context(NON_SECURE));
+#else
+		/*
+		 * SP reports completion. The SPD must have initiated
+		 * the original request through a synchronous entry
+		 * into the SP. Jump back to the original C runtime
+		 * context.
+		 */
+		tspd_synchronous_sp_exit(tsp_ctx, x1);
+		break;
+#endif
+	/*
+	 * This function ID is used only by the SP to indicate it has finished
+	 * aborting a preempted Yielding SMC Call.
+	 */
+	case TSP_ABORT_DONE:
+
+	/*
+	 * These function IDs are used only by the SP to indicate it has
+	 * finished:
+	 * 1. turning itself on in response to an earlier psci
+	 *    cpu_on request
+	 * 2. resuming itself after an earlier psci cpu_suspend
+	 *    request.
+	 */
+	case TSP_ON_DONE:
+	case TSP_RESUME_DONE:
+
+	/*
+	 * These function IDs are used only by the SP to indicate it has
+	 * finished:
+	 * 1. suspending itself after an earlier psci cpu_suspend
+	 *    request.
+	 * 2. turning itself off in response to an earlier psci
+	 *    cpu_off request.
+	 */
+	case TSP_OFF_DONE:
+	case TSP_SUSPEND_DONE:
+	case TSP_SYSTEM_OFF_DONE:
+	case TSP_SYSTEM_RESET_DONE:
+		if (ns)
+			SMC_RET1(handle, SMC_UNK);
+
+		/*
+		 * SP reports completion. The SPD must have initiated the
+		 * original request through a synchronous entry into the SP.
+		 * Jump back to the original C runtime context, and pass x1 as
+		 * return value to the caller
+		 */
+		tspd_synchronous_sp_exit(tsp_ctx, x1);
+		break;
+
+		/*
+		 * Request from non-secure client to perform an
+		 * arithmetic operation or response from secure
+		 * payload to an earlier request.
+		 */
+	case TSP_FAST_FID(TSP_ADD):
+	case TSP_FAST_FID(TSP_SUB):
+	case TSP_FAST_FID(TSP_MUL):
+	case TSP_FAST_FID(TSP_DIV):
+
+	case TSP_YIELD_FID(TSP_ADD):
+	case TSP_YIELD_FID(TSP_SUB):
+	case TSP_YIELD_FID(TSP_MUL):
+	case TSP_YIELD_FID(TSP_DIV):
+		/*
+		 * Request from non-secure client to perform a check
+		 * of the DIT PSTATE bit.
+		 */
+	case TSP_YIELD_FID(TSP_CHECK_DIT):
+		if (ns) {
+			/*
+			 * This is a fresh request from the non-secure client.
+			 * The parameters are in x1 and x2. Figure out which
+			 * registers need to be preserved, save the non-secure
+			 * state and send the request to the secure payload.
+			 */
+			assert(handle == cm_get_context(NON_SECURE));
+
+			/* Check if we are already preempted */
+			if (get_yield_smc_active_flag(tsp_ctx->state))
+				SMC_RET1(handle, SMC_UNK);
+
+			cm_el1_sysregs_context_save(NON_SECURE);
+
+			/* Save x1 and x2 for use by TSP_GET_ARGS call below */
+			store_tsp_args(tsp_ctx, x1, x2);
+
+			/*
+			 * We are done stashing the non-secure context. Ask the
+			 * secure payload to do the work now.
+			 */
+
+			/*
+			 * Verify if there is a valid context to use, copy the
+			 * operation type and parameters to the secure context
+			 * and jump to the fast smc entry point in the secure
+			 * payload. Entry into S-EL1 will take place upon exit
+			 * from this function.
+			 */
+			assert(&tsp_ctx->cpu_ctx == cm_get_context(SECURE));
+
+			/* Set appropriate entry for SMC.
+			 * We expect the TSP to manage the PSTATE.I and PSTATE.F
+			 * flags as appropriate.
+			 */
+			if (GET_SMC_TYPE(smc_fid) == SMC_TYPE_FAST) {
+				cm_set_elr_el3(SECURE, (uint64_t)
+						&tsp_vectors->fast_smc_entry);
+			} else {
+				set_yield_smc_active_flag(tsp_ctx->state);
+				cm_set_elr_el3(SECURE, (uint64_t)
+						&tsp_vectors->yield_smc_entry);
+#if TSP_NS_INTR_ASYNC_PREEMPT
+				/*
+				 * Enable the routing of NS interrupts to EL3
+				 * during processing of a Yielding SMC Call on
+				 * this core.
+				 */
+				enable_intr_rm_local(INTR_TYPE_NS, SECURE);
+#endif
+
+#if EL3_EXCEPTION_HANDLING
+				/*
+				 * With EL3 exception handling, while an SMC is
+				 * being processed, Non-secure interrupts can't
+				 * preempt Secure execution. However, for
+				 * yielding SMCs, we want preemption to happen;
+				 * so explicitly allow NS preemption in this
+				 * case, and supply the preemption return code
+				 * for TSP.
+				 */
+				ehf_allow_ns_preemption(TSP_PREEMPTED);
+#endif
+			}
+
+			cm_el1_sysregs_context_restore(SECURE);
+			cm_set_next_eret_context(SECURE);
+			SMC_RET3(&tsp_ctx->cpu_ctx, smc_fid, x1, x2);
+		} else {
+			/*
+			 * This is the result from the secure client of an
+			 * earlier request. The results are in x1-x3. Copy it
+			 * into the non-secure context, save the secure state
+			 * and return to the non-secure state.
+			 */
+			assert(handle == cm_get_context(SECURE));
+			cm_el1_sysregs_context_save(SECURE);
+
+			/* Get a reference to the non-secure context */
+			ns_cpu_context = cm_get_context(NON_SECURE);
+			assert(ns_cpu_context);
+
+			/* Restore non-secure state */
+			cm_el1_sysregs_context_restore(NON_SECURE);
+			cm_set_next_eret_context(NON_SECURE);
+			if (GET_SMC_TYPE(smc_fid) == SMC_TYPE_YIELD) {
+				clr_yield_smc_active_flag(tsp_ctx->state);
+#if TSP_NS_INTR_ASYNC_PREEMPT
+				/*
+				 * Disable the routing of NS interrupts to EL3
+				 * after processing of a Yielding SMC Call on
+				 * this core is finished.
+				 */
+				disable_intr_rm_local(INTR_TYPE_NS, SECURE);
+#endif
+			}
+
+			SMC_RET3(ns_cpu_context, x1, x2, x3);
+		}
+		assert(0); /* Unreachable */
+
+	/*
+	 * Request from the non-secure world to abort a preempted Yielding SMC
+	 * Call.
+	 */
+	case TSP_FID_ABORT:
+		/* ABORT should only be invoked by normal world */
+		if (!ns) {
+			assert(0);
+			break;
+		}
+
+		assert(handle == cm_get_context(NON_SECURE));
+		cm_el1_sysregs_context_save(NON_SECURE);
+
+		/* Abort the preempted SMC request */
+		if (!tspd_abort_preempted_smc(tsp_ctx)) {
+			/*
+			 * If there was no preempted SMC to abort, return
+			 * SMC_UNK.
+			 *
+			 * Restoring the NON_SECURE context is not necessary as
+			 * the synchronous entry did not take place if the
+			 * return code of tspd_abort_preempted_smc is zero.
+			 */
+			cm_set_next_eret_context(NON_SECURE);
+			break;
+		}
+
+		cm_el1_sysregs_context_restore(NON_SECURE);
+		cm_set_next_eret_context(NON_SECURE);
+		SMC_RET1(handle, SMC_OK);
+
+		/*
+		 * Request from non secure world to resume the preempted
+		 * Yielding SMC Call.
+		 */
+	case TSP_FID_RESUME:
+		/* RESUME should be invoked only by normal world */
+		if (!ns) {
+			assert(0);
+			break;
+		}
+
+		/*
+		 * This is a resume request from the non-secure client.
+		 * save the non-secure state and send the request to
+		 * the secure payload.
+		 */
+		assert(handle == cm_get_context(NON_SECURE));
+
+		/* Check if we are already preempted before resume */
+		if (!get_yield_smc_active_flag(tsp_ctx->state))
+			SMC_RET1(handle, SMC_UNK);
+
+		cm_el1_sysregs_context_save(NON_SECURE);
+
+		/*
+		 * We are done stashing the non-secure context. Ask the
+		 * secure payload to do the work now.
+		 */
+#if TSP_NS_INTR_ASYNC_PREEMPT
+		/*
+		 * Enable the routing of NS interrupts to EL3 during resumption
+		 * of a Yielding SMC Call on this core.
+		 */
+		enable_intr_rm_local(INTR_TYPE_NS, SECURE);
+#endif
+
+#if EL3_EXCEPTION_HANDLING
+		/*
+		 * Allow the resumed yielding SMC processing to be preempted by
+		 * Non-secure interrupts. Also, supply the preemption return
+		 * code for TSP.
+		 */
+		ehf_allow_ns_preemption(TSP_PREEMPTED);
+#endif
+
+		/* We just need to return to the preempted point in
+		 * TSP and the execution will resume as normal.
+		 */
+		cm_el1_sysregs_context_restore(SECURE);
+		cm_set_next_eret_context(SECURE);
+		SMC_RET0(&tsp_ctx->cpu_ctx);
+
+		/*
+		 * This is a request from the secure payload for more arguments
+		 * for an ongoing arithmetic operation requested by the
+		 * non-secure world. Simply return the arguments from the non-
+		 * secure client in the original call.
+		 */
+	case TSP_GET_ARGS:
+		if (ns)
+			SMC_RET1(handle, SMC_UNK);
+
+		get_tsp_args(tsp_ctx, x1, x2);
+		SMC_RET2(handle, x1, x2);
+
+	case TOS_CALL_COUNT:
+		/*
+		 * Return the number of service function IDs implemented to
+		 * provide service to non-secure
+		 */
+		SMC_RET1(handle, TSP_NUM_FID);
+
+	case TOS_UID:
+		/* Return TSP UID to the caller */
+		SMC_UUID_RET(handle, tsp_uuid);
+
+	case TOS_CALL_VERSION:
+		/* Return the version of current implementation */
+		SMC_RET2(handle, TSP_VERSION_MAJOR, TSP_VERSION_MINOR);
+
+	default:
+		break;
+	}
+
+	SMC_RET1(handle, SMC_UNK);
+}
+
+/* Define a SPD runtime service descriptor for fast SMC calls */
+DECLARE_RT_SVC(
+	tspd_fast,
+
+	OEN_TOS_START,
+	OEN_TOS_END,
+	SMC_TYPE_FAST,
+	tspd_setup,
+	tspd_smc_handler
+);
+
+/* Define a SPD runtime service descriptor for Yielding SMC Calls */
+DECLARE_RT_SVC(
+	tspd_std,
+
+	OEN_TOS_START,
+	OEN_TOS_END,
+	SMC_TYPE_YIELD,
+	NULL,
+	tspd_smc_handler
+);