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Re: [Xen-devel] [RFC 2/4] arm: add generic TEE mediator framework
Hi Volodymyr,
On 11/10/17 20:01, Volodymyr Babchuk wrote:
This patch adds basic framework for TEE mediators. Guests can't talk
to TEE directly, we need some entity that will intercept request
and decide what to do with them. "TEE mediaor" is a such entity.
s/mediaor/mediator/
This is how it works: user can build XEN with multiple TEE mediators
(see the next patches, where OP-TEE mediator is introduced).
TEE mediator register self with REGISTER_TEE_MEDIATOR() macro in the
same way, as device drivers use DT_DEVICE_START()/DT_DEVICE_END()
macros.
In runtime, during initialization, XEN issues standard SMC to read
TEE UID. Using this UID it selects and initializes one of built-in
mediators. Then generic vSMC handler will call selected mediator
when it intercept SMC that belongs to TEE OS or TEE application.
As you may remember the discussion on the SMCCC support for guests,
there are currently no way to know the SMCCC is present on the platform.
I don't think you can rely on the platform support SMCC nor fully
implementing it. This also bring the question of does every TEE are
supporting SMCCC?
Also, there are hooks for domain construction and destruction, so
TEE mediator can inform TEE about VM lifecycle.
Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
---
MAINTAINERS | 5 ++
xen/arch/arm/Kconfig | 10 ++++
xen/arch/arm/Makefile | 1 +
xen/arch/arm/domain.c | 7 +++
xen/arch/arm/setup.c | 4 ++
xen/arch/arm/tee/Kconfig | 0
xen/arch/arm/tee/Makefile | 1 +
xen/arch/arm/tee/tee.c | 134 ++++++++++++++++++++++++++++++++++++++++++++++
xen/arch/arm/vsmc.c | 5 ++
xen/arch/arm/xen.lds.S | 7 +++
xen/include/asm-arm/tee.h | 79 +++++++++++++++++++++++++++
11 files changed, 253 insertions(+)
create mode 100644 xen/arch/arm/tee/Kconfig
create mode 100644 xen/arch/arm/tee/Makefile
create mode 100644 xen/arch/arm/tee/tee.c
create mode 100644 xen/include/asm-arm/tee.h
diff --git a/MAINTAINERS b/MAINTAINERS
index 77b1e11..ede00c5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -357,6 +357,11 @@ F: config/Stubdom.mk.in
F: m4/stubdom.m4
F: stubdom/
+TEE MEDIATORS
+M: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
+S: Supported
+F: xen/arch/arm/tee/*
+
TOOLSTACK
M: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
M: Wei Liu <wei.liu2@xxxxxxxxxx>
diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
index d46b98c..e1f112a 100644
--- a/xen/arch/arm/Kconfig
+++ b/xen/arch/arm/Kconfig
@@ -50,6 +50,14 @@ config HAS_ITS
prompt "GICv3 ITS MSI controller support" if EXPERT = "y"
depends on HAS_GICV3
+config ARM_TEE
The ARM in the title is a bit pointless. This Kconfig is only used for
Arm architecture.
+ bool "Enable TEE mediators support"
+ default n
+ depends on ARM
No need for that.
+ help
+ This option enables generic TEE mediators support. It allows guests
+ to access real TEE via one of TEE mediators implemented in XEN
Missing full stop.
+
endmenu
menu "ARM errata workaround via the alternative framework"
@@ -167,3 +175,5 @@ endmenu
source "common/Kconfig"
source "drivers/Kconfig"
+
+source "arch/arm/tee/Kconfig"
diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
index ede21fd..2710e0e 100644
--- a/xen/arch/arm/Makefile
+++ b/xen/arch/arm/Makefile
@@ -3,6 +3,7 @@ subdir-$(CONFIG_ARM_64) += arm64
subdir-y += platforms
subdir-$(CONFIG_ARM_64) += efi
subdir-$(CONFIG_ACPI) += acpi
+subdir-$(CONFIG_ARM_TEE) += tee
obj-$(CONFIG_HAS_ALTERNATIVE) += alternative.o
obj-y += bootfdt.init.o
diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
index 784ae39..3290d39 100644
--- a/xen/arch/arm/domain.c
+++ b/xen/arch/arm/domain.c
@@ -31,6 +31,7 @@
#include <asm/platform.h>
#include <asm/procinfo.h>
#include <asm/regs.h>
+#include <asm/tee.h>
#include <asm/vfp.h>
#include <asm/vgic.h>
#include <asm/vtimer.h>
@@ -673,6 +674,9 @@ int arch_domain_create(struct domain *d, unsigned int
domcr_flags,
if ( is_hardware_domain(d) && (rc = domain_vuart_init(d)) )
goto fail;
+ /* Notify TEE that new domain was created */
+ tee_domain_create(d);
I am not a big fan to see this in arch_domain_create until we see how
this is going to fit with guest. For instance, will TEE be for every
guests? What would be the other necessary information to configure it?...
+
return 0;
fail:
@@ -684,6 +688,9 @@ fail:
void arch_domain_destroy(struct domain *d)
{
+ /* Notify TEE that domain is being destroyed */
+ tee_domain_destroy(d);
+
/* IOMMU page table is shared with P2M, always call
* iommu_domain_destroy() before p2m_teardown().
*/
diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index 92f173b..8a4fcd8 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -47,6 +47,7 @@
#include <asm/platform.h>
#include <asm/procinfo.h>
#include <asm/setup.h>
+#include <asm/tee.h>
#include <xsm/xsm.h>
#include <asm/acpi.h>
@@ -846,6 +847,9 @@ void __init start_xen(unsigned long boot_phys_offset,
*/
apply_alternatives_all();
+ /* Initialize TEE mediator */
+ tee_init();
+
/* Create initial domain 0. */
/* The vGIC for DOM0 is exactly emulating the hardware GIC */
config.gic_version = XEN_DOMCTL_CONFIG_GIC_NATIVE;
diff --git a/xen/arch/arm/tee/Kconfig b/xen/arch/arm/tee/Kconfig
new file mode 100644
index 0000000..e69de29
diff --git a/xen/arch/arm/tee/Makefile b/xen/arch/arm/tee/Makefile
new file mode 100644
index 0000000..c54d479
--- /dev/null
+++ b/xen/arch/arm/tee/Makefile
@@ -0,0 +1 @@
+obj-y += tee.o
diff --git a/xen/arch/arm/tee/tee.c b/xen/arch/arm/tee/tee.c
new file mode 100644
index 0000000..7f7a846
--- /dev/null
+++ b/xen/arch/arm/tee/tee.c
@@ -0,0 +1,134 @@
+/*
+ * xen/arch/arm/tee/tee.c
+ *
+ * Generic part of TEE mediator subsystem
+ *
+ * Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
+ * Copyright (c) 2017 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/types.h>
+#include <asm/smccc.h>
+#include <asm/tee.h>
+
+/*
+ * According to ARM SMCCC (ARM DEN 0028B, page 17), service owner
+ * for generic TEE queries is 63.
+ */
+#define TRUSTED_OS_GENERIC_API_OWNER 63
+
+#define ARM_SMCCC_FUNC_GET_TEE_UID \
+ ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
+ ARM_SMCCC_CONV_32, \
+ TRUSTED_OS_GENERIC_API_OWNER, \
+ ARM_SMCCC_FUNC_CALL_UID)
This likely needs to be defined in smccc as AFAIU it is part of the SMCCC.
+
+extern const struct tee_mediator_desc _steemediator[], _eteemediator[];
+static const struct tee_mediator_ops *mediator_ops;
+
+/* Helper function to read UID returned by SMC */
+static void parse_uid(const register_t regs[4], xen_uuid_t *uid)
+{
+ uint8_t *bytes = uid->a;
+ int n;
unsigned int please.
+
+ /*
+ * UID is returned in registers r0..r3, four bytes per register,
+ * first byte is stored in low-order bits of a register.
+ * (ARM DEN 0028B page 14)
+ */
+ for (n = 0; n < 16; n++)
for ( n = 0; ... )
+ bytes[n] = (uint8_t)(regs[n/4] >> ((n & 3) * 8));
+
+}
+
+void tee_init(void)
+{
+ const struct tee_mediator_desc *desc;
+ register_t resp[4];
+ xen_uuid_t tee_uid;
+ int ret;
+
+ /* Read UUID to determine which TEE is running */
You can't assume the platform is supporting SMCCC. See my comment at the
beginning of the e-mail.
+ call_smccc_smc(ARM_SMCCC_FUNC_GET_TEE_UID, 0, 0, 0, 0, 0, 0, 0, resp);
+ if ( resp[0] == 0xFFFFFFFF ) {
You likely want to use ARM_SMCCC_ERR_UNKOWN_FUNCTION here.
+ printk("No TEE found\n");
+ return;
+ }
+
+ parse_uid(resp, &tee_uid);
+
+ printk("TEE UID:
%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x\n",
+ tee_uid.a[0 ], tee_uid.a[1 ], tee_uid.a[2 ], tee_uid.a[3 ],
Please no space before ]. This is making more confusing to read.
+ tee_uid.a[4 ], tee_uid.a[5 ], tee_uid.a[6 ], tee_uid.a[7 ],
+ tee_uid.a[8 ], tee_uid.a[9 ], tee_uid.a[10], tee_uid.a[11],
+ tee_uid.a[12], tee_uid.a[13], tee_uid.a[14], tee_uid.a[15]);
+
+ for ( desc = _steemediator; desc != _eteemediator; desc++ )
{
+ if ( memcmp(&desc->uid, &tee_uid, sizeof(xen_uuid_t)) == 0 )
+ {
+ printk("Using TEE mediator for %sp\n", desc->name);
+ mediator_ops = desc->ops;
+ break;
+ }
}
+
+ if ( !mediator_ops )
A warning here would be useful.
+ return;
+
+ ret = mediator_ops->init();
+ if ( ret )
+ {
+ printk("TEE mediator failed to initialize :%d\n", ret);
+ mediator_ops = NULL;
+ }
+}
+
+bool tee_handle_smc(struct cpu_user_regs *regs)
+{
+ if ( !mediator_ops )
+ return false;
+
+ return mediator_ops->handle_smc(regs);
+}
+
+void tee_domain_create(struct domain *d)
+{
+ if ( !mediator_ops )
+ return;
+
+ return mediator_ops->domain_create(d);
return here is not necessary. However, I am slightly surprised that
tee_domain_create could never fail.
+}
+
+void tee_domain_destroy(struct domain *d)
+{
+ if ( !mediator_ops )
+ return;
+
+ return mediator_ops->domain_destroy(d);
Same here.
+}
+
+void tee_remove(void)
What is this callback for? I don't see any use within this series.
+{
+ if ( !mediator_ops )
+ return;
+
+ return mediator_ops->remove();
+}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/arch/arm/vsmc.c b/xen/arch/arm/vsmc.c
index 7bd6008..186e34b 100644
--- a/xen/arch/arm/vsmc.c
+++ b/xen/arch/arm/vsmc.c
@@ -22,6 +22,7 @@
#include <asm/psci.h>
#include <asm/regs.h>
#include <asm/smccc.h>
+#include <asm/tee.h>
#include <asm/traps.h>
/* Number of functions currently supported by Hypervisor Service. */
@@ -288,6 +289,10 @@ static bool vsmccc_handle_call(struct cpu_user_regs *regs)
case ARM_SMCCC_OWNER_STANDARD:
handled = handle_sssc(regs);
break;
+ case ARM_SMCCC_OWNER_TRUSTED_APP ... ARM_SMCCC_OWNER_TRUSTED_APP_END:
+ case ARM_SMCCC_OWNER_TRUSTED_OS ... ARM_SMCCC_OWNER_TRUSTED_OS_END:
+ handled = tee_handle_smc(regs);
+ break;
}
}
diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
index c9b9546..b78b7f1 100644
--- a/xen/arch/arm/xen.lds.S
+++ b/xen/arch/arm/xen.lds.S
@@ -126,6 +126,13 @@ SECTIONS
_aedevice = .;
} :text
+ . = ALIGN(8);
+ .teemediator.info : {
+ _steemediator = .;
+ *(.teemediator.info)
+ _eteemediator = .;
+ } :text
+
. = ALIGN(PAGE_SIZE); /* Init code and data */
__init_begin = .;
.init.text : {
diff --git a/xen/include/asm-arm/tee.h b/xen/include/asm-arm/tee.h
new file mode 100644
index 0000000..7f500ac
--- /dev/null
+++ b/xen/include/asm-arm/tee.h
@@ -0,0 +1,79 @@
+/*
+ * xen/include/asm-arm/tee.h
+ *
+ * Generic part of TEE mediator subsystem
+ *
+ * Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
+ * Copyright (c) 2017 EPAM Systems.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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.
+ */
+
+#ifndef __ARCH_ARM_TEE_TEE_H__
+#define __ARCH_ARM_TEE_TEE_H__
+
+#include <xen/lib.h>
+#include <xen/types.h>
+#include <asm/regs.h>
+
+#ifdef CONFIG_ARM_TEE
+
+struct tee_mediator_ops {
Please add documentations on all the fields to explain their purposes.
+ int (*init)(void);
+ void (*domain_create)(struct domain *d);
+ void (*domain_destroy)(struct domain *d);
+ bool (*handle_smc)(struct cpu_user_regs *regs);
+ void (*remove)(void);
+};
+
+struct tee_mediator_desc {
Ditto.
+ const char *name;
+ const xen_uuid_t uid;
+ const struct tee_mediator_ops *ops;
+};
+
+void tee_init(void);
+bool tee_handle_smc(struct cpu_user_regs *regs);
+void tee_domain_create(struct domain *d);
+void tee_domain_destroy(struct domain *d);
+void tee_remove(void);
+
+#define REGISTER_TEE_MEDIATOR(_name, _namestr, _uid, _ops) \
+static const struct tee_mediator_desc __tee_desc_##_name __used \
+__section(".teemediator.info") = { \
+ .name = _namestr, \
+ .uid = _uid, \
+ .ops = _ops \
+}
+
+#else
+
+static inline void tee_init(void) {}
+static inline bool tee_handle_smc(struct cpu_user_regs *regs)
+{
+ return false;
+}
+static inline void tee_domain_create(struct domain *d) {}
+static inline tee_domain_destroy(struct domain *d) {}
+static inline tee_remove(void) {}
+
+#endif /* CONFIG_ARM_TEE */
+
+#endif /* __ARCH_ARM_TEE_TEE_H__ */
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
Cheers,
--
Julien Grall
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