xen/arm: optee: add OP-TEE mediator skeleton

Add very basic OP-TEE mediator. It can probe for OP-TEE presence,
tell it about domain creation/destruction and then return an error
to all calls to the guest.

This code issues two non-preemptible calls to OP-TEE: to create and
to destroy client context. They can't block in OP-TEE, as they are
considered "fast calls" in terms of ARM SMCCC.

Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@epam.com>
Acked-by: Julien Grall <julien.grall@arm.com>

xen/arch/arm/Kconfig

@@ -238,3 +238,5 @@ source "arch/arm/platforms/Kconfig"
 source "common/Kconfig"
 
 source "drivers/Kconfig"
+
+source "arch/arm/tee/Kconfig"

xen/arch/arm/domain.c

@@ -649,7 +649,8 @@ int arch_sanitise_domain_config(struct xen_domctl_createdomain *config)
         return -EINVAL;
     }
 
-    if ( config->arch.tee_type != XEN_DOMCTL_CONFIG_TEE_NONE )
+    if ( config->arch.tee_type != XEN_DOMCTL_CONFIG_TEE_NONE &&
+         config->arch.tee_type != tee_get_type() )
     {
         dprintk(XENLOG_INFO, "Unsupported TEE type\n");
         return -EINVAL;

xen/arch/arm/tee/Kconfig

@@ -0,0 +1,4 @@
+config OPTEE
+	bool "Enable OP-TEE mediator"
+	default n
+	depends on TEE

xen/arch/arm/tee/Makefile

@@ -1 +1,2 @@
 obj-y += tee.o
+obj-$(CONFIG_OPTEE) += optee.o

xen/arch/arm/tee/optee.c

@@ -0,0 +1,166 @@
+/*
+ * xen/arch/arm/tee/optee.c
+ *
+ * OP-TEE mediator. It sits in between OP-TEE and guests and performs
+ * actual calls to OP-TEE when some guest tries to interact with
+ * OP-TEE. As OP-TEE does not know about second stage MMU translation,
+ * mediator does this translation and performs other housekeeping tasks.
+ *
+ * OP-TEE ABI/protocol is described in two header files:
+ *  - optee_smc.h provides information about SMCs: all possible calls,
+ *    register allocation and return codes.
+ *  - optee_msg.h provides format for messages that are passed with
+ *    standard call OPTEE_SMC_CALL_WITH_ARG.
+ *
+ * Volodymyr Babchuk <volodymyr_babchuk@epam.com>
+ * Copyright (c) 2018-2019 EPAM Systems.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <xen/device_tree.h>
+#include <xen/sched.h>
+
+#include <asm/smccc.h>
+#include <asm/tee/tee.h>
+#include <asm/tee/optee_msg.h>
+#include <asm/tee/optee_smc.h>
+
+/* Client ID 0 is reserved for the hypervisor itself */
+#define OPTEE_CLIENT_ID(domain) ((domain)->domain_id + 1)
+
+/* Domain context */
+struct optee_domain {
+};
+
+static bool optee_probe(void)
+{
+    struct dt_device_node *node;
+    struct arm_smccc_res resp;
+
+    /* Check for entry in dtb */
+    node = dt_find_compatible_node(NULL, NULL, "linaro,optee-tz");
+    if ( !node )
+        return false;
+
+    /* Check UID */
+    arm_smccc_smc(ARM_SMCCC_CALL_UID_FID(TRUSTED_OS_END), &resp);
+
+    if ( (uint32_t)resp.a0 != OPTEE_MSG_UID_0 ||
+         (uint32_t)resp.a1 != OPTEE_MSG_UID_1 ||
+         (uint32_t)resp.a2 != OPTEE_MSG_UID_2 ||
+         (uint32_t)resp.a3 != OPTEE_MSG_UID_3 )
+        return false;
+
+    return true;
+}
+
+static int optee_domain_init(struct domain *d)
+{
+    struct arm_smccc_res resp;
+    struct optee_domain *ctx;
+
+    ctx = xzalloc(struct optee_domain);
+    if ( !ctx )
+        return -ENOMEM;
+
+    /*
+     * Inform OP-TEE about a new guest.  This is a "Fast" call in
+     * terms of OP-TEE. This basically means that it can't be
+     * preempted, because there is no thread allocated for it in
+     * OP-TEE. No blocking calls can be issued and interrupts are
+     * disabled.
+     *
+     * a7 should be 0, so we can't skip last 6 parameters of arm_smccc_smc()
+     */
+    arm_smccc_smc(OPTEE_SMC_VM_CREATED, OPTEE_CLIENT_ID(d), 0, 0, 0, 0, 0, 0,
+                  &resp);
+    if ( resp.a0 != OPTEE_SMC_RETURN_OK )
+    {
+        printk(XENLOG_WARNING "%pd: Unable to create OPTEE client: rc = 0x%X\n",
+               d, (uint32_t)resp.a0);
+
+        xfree(ctx);
+
+        return -ENODEV;
+    }
+
+    d->arch.tee = ctx;
+
+    return 0;
+}
+
+static int optee_relinquish_resources(struct domain *d)
+{
+    struct arm_smccc_res resp;
+
+    if ( !d->arch.tee )
+        return 0;
+
+    /*
+     * Inform OP-TEE that domain is shutting down. This is
+     * also a fast SMC call, like OPTEE_SMC_VM_CREATED, so
+     * it is also non-preemptible.
+     * At this time all domain VCPUs should be stopped. OP-TEE
+     * relies on this.
+     *
+     * a7 should be 0, so we can't skip last 6 parameters of arm_smccc_smc()
+     */
+    arm_smccc_smc(OPTEE_SMC_VM_DESTROYED, OPTEE_CLIENT_ID(d), 0, 0, 0, 0, 0, 0,
+                  &resp);
+
+    XFREE(d->arch.tee);
+
+    return 0;
+}
+
+static bool optee_handle_call(struct cpu_user_regs *regs)
+{
+    if ( !current->domain->arch.tee )
+        return false;
+
+    switch ( get_user_reg(regs, 0) )
+    {
+    case OPTEE_SMC_CALLS_COUNT:
+    case OPTEE_SMC_CALLS_UID:
+    case OPTEE_SMC_CALLS_REVISION:
+    case OPTEE_SMC_CALL_GET_OS_UUID:
+    case OPTEE_SMC_CALL_GET_OS_REVISION:
+    case OPTEE_SMC_ENABLE_SHM_CACHE:
+    case OPTEE_SMC_DISABLE_SHM_CACHE:
+    case OPTEE_SMC_GET_SHM_CONFIG:
+    case OPTEE_SMC_EXCHANGE_CAPABILITIES:
+    case OPTEE_SMC_CALL_WITH_ARG:
+    case OPTEE_SMC_CALL_RETURN_FROM_RPC:
+        set_user_reg(regs, 0, OPTEE_SMC_RETURN_ENOTAVAIL);
+        return true;
+
+    default:
+        return false;
+    }
+}
+
+static const struct tee_mediator_ops optee_ops =
+{
+    .probe = optee_probe,
+    .domain_init = optee_domain_init,
+    .relinquish_resources = optee_relinquish_resources,
+    .handle_call = optee_handle_call,
+};
+
+REGISTER_TEE_MEDIATOR(optee, "OP-TEE", XEN_DOMCTL_CONFIG_TEE_OPTEE, &optee_ops);
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */

xen/include/asm-arm/domain.h

@@ -98,6 +98,9 @@ struct arch_domain
     struct vpl011 vpl011;
 #endif
 
+#ifdef CONFIG_TEE
+    void *tee;
+#endif
 }  __cacheline_aligned;
 
 struct arch_vcpu

xen/include/public/arch-arm.h

@@ -306,6 +306,7 @@ DEFINE_XEN_GUEST_HANDLE(vcpu_guest_context_t);
 #define XEN_DOMCTL_CONFIG_GIC_V3        2
 
 #define XEN_DOMCTL_CONFIG_TEE_NONE      0
+#define XEN_DOMCTL_CONFIG_TEE_OPTEE     1
 
 struct xen_arch_domainconfig {
     /* IN/OUT */