Re: [Tee-dev] [PATCH v3 01/11] arm: add generic TEE mediator framework

Hi Volodymyr,

On 12/18/18 9:11 PM, 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 mediator" is a such entity.

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 run-time, during initialization, framework calls probe() function for each available mediator driver to find which TEE is installed on the platform. Then generic vSMC handler will call selected mediator when it intercept SMC/HVC that belongs to TEE OS or TEE application.

Currently TEE mediator is enabled only for Dom0.

Signed-off-by: Volodymyr Babchuk volodymyr_babchuk@epam.com

Changes from v2:

• Removed empty tee/Kconfig file

Changes from v1:

• Removed tee_remove() function
• CONFIG_TEE depends on EXPERT
• tee_domain_created() converted to tee_enable()
• tee_init() is called using initcall() mechanism
• tee_handle_smc() renamed to tee_handle_call()

Changes from "RFC" version:

• renamed CONFIG_ARM_TEE to CONFIG_TEE
• changed discovery mechanism: instead of UUID mathing, TEE-specific probing is used

MAINTAINERS | 6 +++ xen/arch/arm/Kconfig | 7 +++ xen/arch/arm/Makefile | 1 + xen/arch/arm/domain.c | 4 ++ xen/arch/arm/domain_build.c | 4 ++ xen/arch/arm/setup.c | 1 + xen/arch/arm/shutdown.c | 1 + xen/arch/arm/tee/Makefile | 1 + xen/arch/arm/tee/tee.c | 69 ++++++++++++++++++++++++++ xen/arch/arm/vsmc.c | 5 ++ xen/arch/arm/xen.lds.S | 7 +++ xen/include/asm-arm/tee/tee.h | 91 +++++++++++++++++++++++++++++++++++ 12 files changed, 197 insertions(+) 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/tee.h

diff --git a/MAINTAINERS b/MAINTAINERS index 96a0518f49..eac2b40fdf 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -376,6 +376,12 @@ F: config/Stubdom.mk.in F: m4/stubdom.m4 F: stubdom/ +TEE MEDIATORS +M: Volodymyr Babchuk volodymyr_babchuk@epam.com +S: Supported +F: xen/arch/arm/tee/ +F: xen/include/asm-arm/tee

• TOOLSTACK M: Ian Jackson ian.jackson@eu.citrix.com M: Wei Liu wei.liu2@citrix.com

diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig index 581de67b6b..e527b2f885 100644 --- a/xen/arch/arm/Kconfig +++ b/xen/arch/arm/Kconfig @@ -105,6 +105,13 @@ config HARDEN_BRANCH_PREDICTOR If unsure, say Y. +config TEE

• bool "Enable TEE mediators support" if EXPERT = "y"
• default n
• help

•  This option enables generic TEE mediators support. It allows guests
  

•  to access real TEE via one of TEE mediators implemented in XEN.
  

• endmenu

menu "ARM errata workaround via the alternative framework" diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile index cb902cb6fe..5c2aa34557 100644 --- a/xen/arch/arm/Makefile +++ b/xen/arch/arm/Makefile @@ -5,6 +5,7 @@ subdir-$(CONFIG_ACPI) += acpi ifneq ($(CONFIG_NO_PLAT),y) subdir-y += platforms endif +subdir-$(CONFIG_TEE) += tee obj-$(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 1d926dcb29..11b618515b 100644 --- a/xen/arch/arm/domain.c +++ b/xen/arch/arm/domain.c @@ -32,6 +32,7 @@ #include <asm/platform.h> #include <asm/procinfo.h> #include <asm/regs.h> +#include <asm/tee/tee.h> #include <asm/vfp.h> #include <asm/vgic.h> #include <asm/vtimer.h> @@ -931,6 +932,9 @@ int domain_relinquish_resources(struct domain *d) */ domain_vpl011_deinit(d);

•    /* Free TEE mediator resources */
  

•    tee_domain_destroy(d);
  

AFAIR, OP-TEE may have a lot of resources attached to it. So I think it would be best if we introduce a new RELMEM_* for it and make tee_domain_destroy return an int to handle preemption.

      d->arch.relmem = RELMEM_xen;
      /* Fallthrough */

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c index b0ec3f0b72..39a887b505 100644 --- a/xen/arch/arm/domain_build.c +++ b/xen/arch/arm/domain_build.c @@ -24,6 +24,7 @@ #include <asm/setup.h> #include <asm/cpufeature.h> #include <asm/domain_build.h> +#include <asm/tee/tee.h> #include <xen/irq.h> #include <xen/grant_table.h> @@ -1962,6 +1963,9 @@ static int __init construct_domain(struct domain *d, struct kernel_info *kinfo) set_current(saved_current); p2m_restore_state(saved_current);

• /* Enable TEE */
• tee_enable(d);

Why do you need to call TEE here? This should be done through arch_domain_create as for any other domain.

• memset(regs, 0, sizeof(*regs));
  

regs->pc = (register_t)kinfo->entry; diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c index e83221ab79..cad568d432 100644 --- a/xen/arch/arm/setup.c +++ b/xen/arch/arm/setup.c @@ -48,6 +48,7 @@ #include <asm/platform.h> #include <asm/procinfo.h> #include <asm/setup.h> +#include <asm/tee/tee.h>

You don't add specific TEE code in that file. So why do you need to include it?

#include <xsm/xsm.h> #include <asm/acpi.h> diff --git a/xen/arch/arm/shutdown.c b/xen/arch/arm/shutdown.c index b32f07ec0e..30c69506ff 100644 --- a/xen/arch/arm/shutdown.c +++ b/xen/arch/arm/shutdown.c @@ -5,6 +5,7 @@ #include <xen/smp.h> #include <asm/platform.h> #include <asm/psci.h> +#include <asm/tee/tee.h>

Ditto.

static void noreturn halt_this_cpu(void *arg) { diff --git a/xen/arch/arm/tee/Makefile b/xen/arch/arm/tee/Makefile new file mode 100644 index 0000000000..c54d4796ff --- /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 0000000000..7fd0148b8a --- /dev/null +++ b/xen/arch/arm/tee/tee.c @@ -0,0 +1,69 @@ +/*

• • xen/arch/arm/tee/tee.c
• • Generic part of TEE mediator subsystem
• • Volodymyr Babchuk volodymyr_babchuk@epam.com
• • 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/init.h>

This should be after xen/errno.h

+#include <xen/errno.h> +#include <xen/types.h> +#include <asm/tee/tee.h>

+extern const struct tee_mediator_desc _steemediator[], _eteemediator[]; +static const struct tee_mediator_ops *mediator_ops;

+bool tee_handle_call(struct cpu_user_regs *regs) +{

• if ( !mediator_ops )

•    return false;
  

• return mediator_ops->handle_call(regs);

+}

+int tee_enable(struct domain *d)

I would prefer if you stay consistent with the naming of tee_domain_destroy. So this should be called tee_domain_init.

• if ( !mediator_ops )

•    return -ENODEV;
  

• return mediator_ops->enable(d);

+}

+void tee_domain_destroy(struct domain *d) +{

• if ( !mediator_ops )

•    return;
  

• return mediator_ops->domain_destroy(d);

+}

+static int __init tee_init(void) +{

• const struct tee_mediator_desc *desc;
• for ( desc = _steemediator; desc != _eteemediator; desc++ )

For clarity:

{

•    if ( desc->ops->probe() )
  

•    {
  

•        printk(XENLOG_INFO "Using TEE mediator for %s\n", desc->name);
  

•        mediator_ops = desc->ops;
  

•        return 0;
  

•    }
  

}

And add a newline before return.

• return 0;

+}

+__initcall(tee_init);

+/*

• • 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 c4ccae6030..d0199c7874 100644 --- a/xen/arch/arm/vsmc.c +++ b/xen/arch/arm/vsmc.c @@ -23,6 +23,7 @@ #include <asm/monitor.h> #include <asm/regs.h> #include <asm/smccc.h> +#include <asm/tee/tee.h> #include <asm/traps.h> #include <asm/vpsci.h> @@ -272,6 +273,10 @@ 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_call(regs);
  

•        break;
      }
  }
  

diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S index 1e72906477..e664c4441a 100644 --- a/xen/arch/arm/xen.lds.S +++ b/xen/arch/arm/xen.lds.S @@ -137,6 +137,13 @@ 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/tee.h b/xen/include/asm-arm/tee/tee.h new file mode 100644 index 0000000000..0e8b576372 --- /dev/null +++ b/xen/include/asm-arm/tee/tee.h @@ -0,0 +1,91 @@ +/*

• • xen/include/asm-arm/tee/tee.h
• • Generic part of TEE mediator subsystem
• • Volodymyr Babchuk volodymyr_babchuk@epam.com
• • 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.
• */

+#ifndef __ARCH_ARM_TEE_TEE_H__ +#define __ARCH_ARM_TEE_TEE_H__

+#include <xen/lib.h> +#include <xen/types.h>

Newline here please.

+#include <asm/regs.h>

+#ifdef CONFIG_TEE

+struct tee_mediator_ops {

See my comments above regarding some of the prototype.

• /*

• * Probe for TEE. Should return true if TEE found and
  

• * mediator is initialized.
  

• */
  

• bool (*probe)(void);
• /*

• * Called during domain construction if toolstack requests to enable
  

• * TEE support so mediator can inform TEE about new
  

• * guest and create own structures for the new domain.
  

• */
  

• int (*enable)(struct domain *d);
• /*

• * Called during domain destruction to inform TEE that guest is now dead
  

• * and to destroy all resources allocated for the domain being destroyed.
  

• */
  

• void (*domain_destroy)(struct domain *d);
• /* Handle SMCCC call for current domain. */
• bool (*handle_call)(struct cpu_user_regs *regs);

+};

+struct tee_mediator_desc {

• /* Name of the TEE. Just for debugging purposes. */
• const char *name;
• /* Mediator callbacks as described above. */
• const struct tee_mediator_ops *ops;

+};

+bool tee_handle_call(struct cpu_user_regs *regs); +int tee_enable(struct domain *d); +void tee_domain_destroy(struct domain *d);

+#define REGISTER_TEE_MEDIATOR(_name, _namestr, _ops) \ +static const struct tee_mediator_desc __tee_desc_##_name __used \ +__section(".teemediator.info") = { \

• .name = _namestr, \
• .ops = _ops \

+}

+#else

+static inline bool tee_handle_call(struct cpu_user_regs *regs) +{

• return false;

+}

+static inline int tee_enable(struct domain *d) +{

• return -ENODEV;

+}

+static inline void tee_domain_destroy(struct domain *d) {}

+#endif /* CONFIG_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,