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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [RFC 2/4] arm: add generic TEE mediator framework
On Mon, Oct 16, 2017 at 02:00:32PM +0100, Julien Grall wrote:
> Hi Volodymyr,
Hi Julien,
[...]
> >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.
Ah, yes. Device tree, then.
> 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?
Honestly, I don't know. I suppose that there can be TEEs the are not
compatible with SMCCC. Okay, instead of UID comparison in generic
framework, I can introduce probe() functions for each mediator.
On other hand, DT bindings, can work even better.
How about this: TEE mediator registers with DT_DEVICE_START() as
any other driver. If, during init() it finds compatible TEE,
then TEE mediator registers itself in TEE framework.
During registration it provides supported SMC fn ranges. This is for
case when TEE is not SMCCC-compatible and uses function numbers
outside ARM_SMCCC_OWNER_TRUSTED_OS range.
> >
> >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.
Just plain TEE then?
> >+ bool "Enable TEE mediators support"
> >+ default n
> >+ depends on ARM
>
> No need for that.
Right.
> >+ 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?...
I think I'll call XSM in tee_domain_create() to check if this domain allowed
to work with TEE. I can't imagine what additional information will be needed.
This interface can be extended in the future, though.
> >+
> > 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.
It only used there. I'm not sure if I should define it globally.
> >+
> >+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; ... )
Yeah, sorry. It is hard to hold multiple coding styles in mind at the
same time. I hope, Yurii will finish his coding style validator soon :)
> >+ 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.
Yeah, looks like this part will be completely reworked.
> >+ 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.
I put it for neat formatting. Probably, I can put double space after commas.
Will be okay?
> >+ 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.
Why? Platform is not obligued to have any TEE.
> >+ 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.
Good question. Do you want to allow TEE to prevent domain creation?
> >+}
> >+
> >+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.
Sorry, missed to call it.
[...]
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