[Xen-devel] [PATCH v4 03/10] xen/arm: optee: add OP-TEE mediator skeleton

[Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>]

From: Volodymyr Babchuk <vlad.babchuk@xxxxxxxxx>

Add very basic OP-TEE mediator. It can probe for OP-TEE presence,
tell it about domain creation/destruction and forward all known
calls.

This is all what is needed for Dom0 to work with OP-TEE as long as
Dom0 shares 1:1 mapped pages with OP-TEE. Any attempt to call OP-TEE
from DomU will fail and will lead to random memory corruption. But
this is impossible, because there is no means to enable TEE support
for DomUs right now. Also, problems can arise if Dom0 uses pages
mapped from other domains. This will be fixed in the following
patches, as more of the mediator functionality will be added.

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 <vlad.babchuk@xxxxxxxxx>

---

 All the patches to optee.c should be merged together. They were
 split to ease up review. But they depend heavily on each other.

Changes from v3:
  - Introduced optee_relinquish_resources() function to free
    mediator resources in a more controllable way

Changes from v2:
  - Fixed coding style
  - Introduced tee/Kconfig
  - Fixed error messages
---
 xen/arch/arm/Kconfig         |   2 +
 xen/arch/arm/tee/Kconfig     |   4 +
 xen/arch/arm/tee/Makefile    |   1 +
 xen/arch/arm/tee/optee.c     | 170 +++++++++++++++++++++++++++++++++++
 xen/include/asm-arm/domain.h |   3 +
 5 files changed, 180 insertions(+)
 create mode 100644 xen/arch/arm/tee/Kconfig
 create mode 100644 xen/arch/arm/tee/optee.c

diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
index e527b2f885..99e6f0ebb2 100644
--- a/xen/arch/arm/Kconfig
+++ b/xen/arch/arm/Kconfig
@@ -237,3 +237,5 @@ source "arch/arm/platforms/Kconfig"
 source "common/Kconfig"
 
 source "drivers/Kconfig"
+
+source "arch/arm/tee/Kconfig"
diff --git a/xen/arch/arm/tee/Kconfig b/xen/arch/arm/tee/Kconfig
new file mode 100644
index 0000000000..5b829db2e9
--- /dev/null
+++ b/xen/arch/arm/tee/Kconfig
@@ -0,0 +1,4 @@
+config OPTEE
+       bool "Enable OP-TEE mediator"
+       default n
+       depends on TEE
diff --git a/xen/arch/arm/tee/Makefile b/xen/arch/arm/tee/Makefile
index c54d4796ff..982c879684 100644
--- a/xen/arch/arm/tee/Makefile
+++ b/xen/arch/arm/tee/Makefile
@@ -1 +1,2 @@
 obj-y += tee.o
+obj-$(CONFIG_OPTEE) += optee.o
diff --git a/xen/arch/arm/tee/optee.c b/xen/arch/arm/tee/optee.c
new file mode 100644
index 0000000000..b50c581aaf
--- /dev/null
+++ b/xen/arch/arm/tee/optee.c
@@ -0,0 +1,170 @@
+/*
+ * xen/arch/arm/tee/optee.c
+ *
+ * OP-TEE mediator
+ *
+ * Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
+ * Copyright (c) 2018 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.
+ */
+
+#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>
+
+#define OPTEE_ENABLED ((void*)0x1)
+
+/* Client ID 0 is reserved for hypervisor itself */
+#define OPTEE_CLIENT_ID(domain) ((domain)->domain_id + 1)
+
+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;
+
+    /*
+     * 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. It is close to atomic
+     * context in linux kernel: E.g. no blocking calls can be issued.
+     * Also, 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 )
+    {
+        gprintk(XENLOG_WARNING, "Unable to create OPTEE client: rc = 0x%X\n",
+                (uint32_t)resp.a0);
+
+        return -ENODEV;
+    }
+
+    d->arch.tee = OPTEE_ENABLED;
+
+    return 0;
+}
+
+static void forward_call(struct cpu_user_regs *regs)
+{
+    struct arm_smccc_res resp;
+
+    arm_smccc_smc(get_user_reg(regs, 0),
+                  get_user_reg(regs, 1),
+                  get_user_reg(regs, 2),
+                  get_user_reg(regs, 3),
+                  get_user_reg(regs, 4),
+                  get_user_reg(regs, 5),
+                  get_user_reg(regs, 6),
+                  OPTEE_CLIENT_ID(current->domain),
+                  &resp);
+
+    set_user_reg(regs, 0, resp.a0);
+    set_user_reg(regs, 1, resp.a1);
+    set_user_reg(regs, 2, resp.a2);
+    set_user_reg(regs, 3, resp.a3);
+    set_user_reg(regs, 4, 0);
+    set_user_reg(regs, 5, 0);
+    set_user_reg(regs, 6, 0);
+    set_user_reg(regs, 7, 0);
+}
+
+static int optee_relinquish_resources(struct domain *d)
+{
+    return 0;
+}
+
+static void optee_domain_destroy(struct domain *d)
+{
+    struct arm_smccc_res resp;
+
+    if ( !d->arch.tee )
+        return;
+
+    /*
+     * 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 od arm_smccc_smc()
+     */
+    arm_smccc_smc(OPTEE_SMC_VM_DESTROYED, OPTEE_CLIENT_ID(d), 0, 0, 0, 0, 0, 0,
+                  &resp);
+}
+
+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_FUNCID_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:
+        forward_call(regs);
+        return true;
+    default:
+        return false;
+    }
+}
+
+static const struct tee_mediator_ops optee_ops =
+{
+    .probe = optee_probe,
+    .domain_init = optee_domain_init,
+    .domain_destroy = optee_domain_destroy,
+    .relinquish_resources = optee_relinquish_resources,
+    .handle_call = optee_handle_call,
+};
+
+REGISTER_TEE_MEDIATOR(optee, "OP-TEE", &optee_ops);
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
index 0f15372098..2960a53e69 100644
--- a/xen/include/asm-arm/domain.h
+++ b/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
-- 
2.21.0

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