selftests/sgx: Ensure expected location of test enclave buffer

The external tests manipulating page permissions expect encl_buffer to be
placed at the start of the test enclave's .data section. As this is not
guaranteed per the C standard, explicitly place encl_buffer in a separate
section that is explicitly placed at the start of the .data segment in the
linker script to avoid the compiler placing it somewhere else in .data.

Signed-off-by: Jo Van Bulck <jo.vanbulck@cs.kuleuven.be>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/all/20231005153854.25566-12-jo.vanbulck%40cs.kuleuven.be

selftests/sgx: Ensure test enclave buffer is entirely preserved

Attach the "used" attribute to instruct the compiler to preserve the static
encl_buffer, even if it appears it is not entirely referenced in the enclave
code, as expected by the external tests manipulating page permissions.

Signed-off-by: Jo Van Bulck <jo.vanbulck@cs.kuleuven.be>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/all/a2732938-f3db-a0af-3d68-a18060f66e79@cs.kuleuven.be/
Link: https://lore.kernel.org/all/20231005153854.25566-11-jo.vanbulck%40cs.kuleuven.be

selftests/sgx: Introduce TCS initialization enclave operation

The Thread Control Structure (TCS) contains meta-data used by the
hardware to save and restore thread specific information when
entering/exiting the enclave. A TCS can be added to an initialized
enclave by first adding a new regular enclave page, initializing the
content of the new page from within the enclave, and then changing that
page's type to a TCS.

Support the initialization of a TCS from within the enclave.
The variable information needed that should be provided from outside
the enclave is the address of the TCS, address of the State Save Area
(SSA), and the entry point that the thread should use to enter the
enclave. With this information provided all needed fields of a TCS
can be initialized.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lkml.kernel.org/r/bad6052056188bde753a54313da1ac8f1e29088a.1652137848.git.reinette.chatre@intel.com

selftests/sgx: Add test for EPCM permission changes

EPCM permission changes could be made from within (to relax
permissions) or out (to restrict permissions) the enclave. Kernel
support is needed when permissions are restricted to be able to
call the privileged ENCLS[EMODPR] instruction. EPCM permissions
can be relaxed via ENCLU[EMODPE] from within the enclave but the
enclave still depends on the kernel to install PTEs with the needed
permissions.

Add a test that exercises a few of the enclave page permission flows:
1) Test starts with a RW (from enclave and kernel perspective)
enclave page that is mapped via a RW VMA.
2) Use the SGX_IOC_ENCLAVE_RESTRICT_PERMISSIONS ioctl() to restrict
the enclave (EPCM) page permissions to read-only.
3) Run ENCLU[EACCEPT] from within the enclave to accept the new page
permissions.
4) Attempt to write to the enclave page from within the enclave - this
should fail with a page fault on the EPCM permissions since the page
table entry continues to allow RW access.
5) Restore EPCM permissions to RW by running ENCLU[EMODPE] from within
the enclave.
6) Attempt to write to the enclave page from within the enclave - this
should succeed since both EPCM and PTE permissions allow this access.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lkml.kernel.org/r/2617bf2b2d1e27ca1d0096e1192ae5896baf3f80.1652137848.git.reinette.chatre@intel.com

selftests/sgx: Add test for multiple TCS entry

Each thread executing in an enclave is associated with a Thread Control
Structure (TCS). The SGX test enclave contains two hardcoded TCS, thus
supporting two threads in the enclave.

Add a test to ensure it is possible to enter enclave at both entrypoints.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lkml.kernel.org/r/7be151a57b4c7959a2364753b995e0006efa3da1.1636997631.git.reinette.chatre@intel.com

selftests/sgx: Add page permission and exception test

The Enclave Page Cache Map (EPCM) is a secure structure used by the
processor to track the contents of the enclave page cache. The EPCM
contains permissions with which enclave pages can be accessed. SGX
support allows EPCM and PTE page permissions to differ - as long as
the PTE permissions do not exceed the EPCM permissions.

Add a test that:
(1) Creates an SGX enclave page with writable EPCM permission.
(2) Changes the PTE permission on the page to read-only. This should
be permitted because the permission does not exceed the EPCM
permission.
(3) Attempts a write to the page. This should generate a page fault
(#PF) because of the read-only PTE even though the EPCM
permissions allow the page to be written to.

This introduces the first test of SGX exception handling. In this test
the issue that caused the exception (PTE page permissions) can be fixed
from outside the enclave and after doing so it is possible to re-enter
enclave at original entrypoint with ERESUME.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lkml.kernel.org/r/3bcc73a4b9fe8780bdb40571805e7ced59e01df7.1636997631.git.reinette.chatre@intel.com

selftests/sgx: Rename test properties in preparation for more enclave tests

SGX selftests prepares a data structure outside of the enclave with
the type of and data for the operation that needs to be run within
the enclave. At this time only two complementary operations are supported
by the enclave: copying a value from outside the enclave into a default
buffer within the enclave and reading a value from the enclave's default
buffer into a variable accessible outside the enclave.

In preparation for more operations supported by the enclave the names of the
current enclave operations are changed to more accurately reflect the
operations and more easily distinguish it from future operations:

* The enums ENCL_OP_PUT and ENCL_OP_GET are renamed to ENCL_OP_PUT_TO_BUFFER
and ENCL_OP_GET_FROM_BUFFER respectively.
* The structs encl_op_put and encl_op_get are renamed to encl_op_put_to_buf
and encl_op_get_from_buf respectively.
* The enclave functions do_encl_op_put and do_encl_op_get are renamed to
do_encl_op_put_to_buf and do_encl_op_get_from_buf respectively.

No functional changes.

Suggested-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lkml.kernel.org/r/023fda047c787cf330b88ed9337705edae6a0078.1636997631.git.reinette.chatre@intel.com

selftests/sgx: Provide per-op parameter structs for the test enclave

To add more operations to the test enclave, the protocol needs to allow
to have operations with varying parameters. Create a separate parameter
struct for each existing operation, with the shared parameters in struct
encl_op_header.

[reinette: rebased to apply on top of oversubscription test series]
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lkml.kernel.org/r/f9a4a8c436b538003b8ebddaa66083992053cef1.1636997631.git.reinette.chatre@intel.com

selftests/sgx: Refine the test enclave to have storage

Extend the enclave to have two operations: ENCL_OP_PUT and ENCL_OP_GET.
ENCL_OP_PUT stores value inside the enclave address space and
ENCL_OP_GET reads it. The internal buffer can be later extended to be
variable size, and allow reclaimer tests.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

x86/sgx: Expose SGX architectural definitions to the kernel

Expose SGX architectural structures, as KVM will use many of the
architectural constants and structs to virtualize SGX.

Name the new header file as asm/sgx.h, rather than asm/sgx_arch.h, to
have single header to provide SGX facilities to share with other kernel
componments. Also update MAINTAINERS to include asm/sgx.h.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Co-developed-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Acked-by: Dave Hansen <dave.hansen@intel.com>
Link: https://lkml.kernel.org/r/6bf47acd91ab4d709e66ad1692c7803e4c9063a0.1616136308.git.kai.huang@intel.com

selftests/x86: Add a selftest for SGX

Add a selftest for SGX. It is a trivial test where a simple enclave
copies one 64-bit word of memory between two memory locations,
but ensures that all SGX hardware and software infrastructure is
functioning.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Jethro Beekman <jethro@fortanix.com>
Cc: linux-kselftest@vger.kernel.org
Link: https://lkml.kernel.org/r/20201112220135.165028-21-jarkko@kernel.org