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    SubjectRe: [PATCH v33 11/21] x86/sgx: Linux Enclave Driver
    On Thu, Jun 25, 2020 at 07:23:19PM +0200, Borislav Petkov wrote:
    > On Thu, Jun 18, 2020 at 01:08:33AM +0300, Jarkko Sakkinen wrote:
    > > Intel Software Guard eXtensions (SGX) is a set of CPU instructions that
    > > can be used by applications to set aside private regions of code and
    > > data. The code outside the SGX hosted software entity is disallowed to
    > > access the memory inside the enclave enforced by the CPU. We call these
    > > entities as enclaves.
    > >
    > > This commit implements a driver that provides an ioctl API to construct
    > > and run enclaves. Enclaves are constructed from pages residing in
    > > reserved physical memory areas. The contents of these pages can only be
    > > accessed when they are mapped as part of an enclave, by a hardware
    > > thread running inside the enclave.
    > >
    > > The starting state of an enclave consists of a fixed measured set of
    > > pages that are copied to the EPC during the construction process by
    > > using ENCLS leaf functions and Software Enclave Control Structure (SECS)
    > > that defines the enclave properties.
    > >
    > > Enclave are constructed by using ENCLS leaf functions ECREATE, EADD and
    > > EINIT. ECREATE initializes SECS, EADD copies pages from system memory to
    > > the EPC and EINIT check a given signed measurement and moves the enclave
    > > into a state ready for execution.
    > >
    > > An initialized enclave can only be accessed through special Thread Control
    > > Structure (TCS) pages by using ENCLU (ring-3 only) leaf EENTER. This leaf
    > > function converts a thread into enclave mode and continues the execution in
    > > the offset defined by the TCS provided to EENTER. An enclave is exited
    > > through syscall, exception, interrupts or by explicitly calling another
    > > ENCLU leaf EEXIT.
    > >
    > > The permissions, which enclave page is added will set the limit for maximum
    > > permissions that can be set for mmap() and mprotect(). This will
    > > effectively allow to build different security schemes between producers and
    > > consumers of enclaves. Later on we can increase granularity with LSM hooks
    > > for page addition (i.e. for producers) and mapping of the enclave (i.e. for
    > > consumers)
    > >
    > > Cc: linux-security-module@vger.kernel.org
    > > Acked-by: Jethro Beekman <jethro@fortanix.com>
    > > Tested-by: Jethro Beekman <jethro@fortanix.com>
    > > Tested-by: Haitao Huang <haitao.huang@linux.intel.com>
    > > Tested-by: Chunyang Hui <sanqian.hcy@antfin.com>
    > > Tested-by: Jordan Hand <jorhand@linux.microsoft.com>
    > > Tested-by: Nathaniel McCallum <npmccallum@redhat.com>
    > > Tested-by: Seth Moore <sethmo@google.com>
    > > Co-developed-by: Sean Christopherson <sean.j.christopherson@intel.com>
    > > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
    > > Co-developed-by: Suresh Siddha <suresh.b.siddha@intel.com>
    > > Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
    > > Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
    > > ---
    > > .../userspace-api/ioctl/ioctl-number.rst | 1 +
    > > arch/x86/include/uapi/asm/sgx.h | 66 ++
    > > arch/x86/kernel/cpu/sgx/Makefile | 3 +
    > > arch/x86/kernel/cpu/sgx/driver.c | 194 +++++
    > > arch/x86/kernel/cpu/sgx/driver.h | 30 +
    > > arch/x86/kernel/cpu/sgx/encl.c | 335 +++++++++
    > > arch/x86/kernel/cpu/sgx/encl.h | 87 +++
    > > arch/x86/kernel/cpu/sgx/ioctl.c | 706 ++++++++++++++++++
    > > arch/x86/kernel/cpu/sgx/main.c | 11 +
    > > 9 files changed, 1433 insertions(+)
    > > create mode 100644 arch/x86/include/uapi/asm/sgx.h
    > > create mode 100644 arch/x86/kernel/cpu/sgx/driver.c
    > > create mode 100644 arch/x86/kernel/cpu/sgx/driver.h
    > > create mode 100644 arch/x86/kernel/cpu/sgx/encl.c
    > > create mode 100644 arch/x86/kernel/cpu/sgx/encl.h
    > > create mode 100644 arch/x86/kernel/cpu/sgx/ioctl.c
    > >
    > > diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
    > > index 59472cd6a11d..35f713e3a267 100644
    > > --- a/Documentation/userspace-api/ioctl/ioctl-number.rst
    > > +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
    > > @@ -323,6 +323,7 @@ Code Seq# Include File Comments
    > > <mailto:tlewis@mindspring.com>
    > > 0xA3 90-9F linux/dtlk.h
    > > 0xA4 00-1F uapi/linux/tee.h Generic TEE subsystem
    > > +0xA4 00-1F uapi/asm/sgx.h Intel SGX subsystem (a legit conflict as TEE and SGX do not co-exist)
    > > 0xAA 00-3F linux/uapi/linux/userfaultfd.h
    > > 0xAB 00-1F linux/nbd.h
    > > 0xAC 00-1F linux/raw.h
    > > diff --git a/arch/x86/include/uapi/asm/sgx.h b/arch/x86/include/uapi/asm/sgx.h
    > > new file mode 100644
    > > index 000000000000..5edb08ab8fd0
    > > --- /dev/null
    > > +++ b/arch/x86/include/uapi/asm/sgx.h
    > > @@ -0,0 +1,66 @@
    > > +/* SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) WITH Linux-syscall-note */
    >
    > Checkpatch complains here:
    >
    > WARNING: 'SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) WITH Linux-syscall-note */' is not supported in LICENSES/...
    > #114: FILE: arch/x86/include/uapi/asm/sgx.h:1:
    > +/* SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) WITH Linux-syscall-note */
    >
    > Also, you had all patches until now split nice and logically doing one
    > thing only.
    >
    > But this one is huge. Why?
    >
    > Why can't you split out the facilities which the driver uses: encl.[ch]
    > into a patch, then ioctl.c into a separate one and then the driver into
    > a third one? Or do they all belong together inseparably?
    >
    > I guess I'll find out eventually but it would've been nice if they were
    > split out...

    It's still kind a strongly connected set of functionalities, but I get
    your point.

    I'd consider splitting for a slighly different angle:

    1. Commit for the base driver.
    2. Commit for each ioctl, adding the necessary "framework" to get that
    piece of functionality completed. The order would be:
    A. Create
    B. Add
    C. Initialize

    Would be probably easier to review also this way because the commit kind
    of rationalizes why things exist.

    What do you think?

    /Jarkko

    /Jarkko

    /Jarkko

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