On Tue, Nov 13, 2018 at 11:40:09PM +0200, Jarkko Sakkinen wrote:
> 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 given to
> the enclave as arguments.
> 
> Signed-off-by: Jarkko Sakkinen <jarkko.sakki...@linux.intel.com>
> ---
> +SUBDIRS_64 := sgx
> +ASSERT(!DEFINED(.altinstructions), "ALTERNATIVES are not supported in the 
> SGX LE")
> +ASSERT(!DEFINED(.altinstr_replacement), "ALTERNATIVES are not supported in 
> the SGX LE")
> +ASSERT(!DEFINED(.discard.retpoline_safe), "RETPOLINE ALTERNATIVES are not 
> supported in the SGX LE")
> +ASSERT(!DEFINED(.discard.nospec), "RETPOLINE ALTERNATIVES are not supported 
> in the SGX LE")

Maybe this?

s/LE/Test Enclave

> diff --git a/tools/testing/selftests/x86/sgx/encl_bootstrap.S 
> b/tools/testing/selftests/x86/sgx/encl_bootstrap.S
> new file mode 100644
> index 000000000000..62251c7d9927
> --- /dev/null
> +++ b/tools/testing/selftests/x86/sgx/encl_bootstrap.S
> @@ -0,0 +1,94 @@
> +/* SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) */
> +/*
> + * Copyright(c) 2016-18 Intel Corporation.
> + */
> +
> +     .macro ENCLU
> +     .byte 0x0f, 0x01, 0xd7
> +     .endm
> +
> +     .section ".tcs", "a"
> +     .balign 4096
> +
> +     .fill   1, 8, 0                 # STATE (set by CPU)
> +     .fill   1, 8, 0                 # FLAGS
> +     .long   encl_ssa                # OSSA

Any reason not to do .quad for OSSA and OENTRY?

> +     .fill   1, 4, 0
> +     .fill   1, 4, 0                 # CSSA (set by CPU)
> +     .fill   1, 4, 1                 # NSSA
> +     .long   encl_entry              # OENTRY
> +     .fill   1, 4, 0
> +     .fill   1, 8, 0                 # AEP (set by EENTER and ERESUME)
> +     .fill   1, 8, 0                 # OFSBASE
> +     .fill   1, 8, 0                 # OGSBASE
> +     .fill   1, 4, 0xFFFFFFFF        # FSLIMIT
> +     .fill   1, 4, 0xFFFFFFFF        # GSLIMIT
> +     .fill   503, 8, 0               # Reserved

I'd prefer to do 1-byte fill with a size of 4024 to match the SDM.

> +
> +     .text
> +
> +encl_entry:
> +     # %rbx contains the base address for TCS, which is also the first
> +     # address inside the enclave. By adding $le_stack_end to it, we get the
> +     # absolute address for the stack.
> +     lea     (encl_stack)(%rbx), %rax
> +     xchg    %rsp, %rax
> +     push    %rax
> +
> +     push    %rcx # push the address after EENTER
> +     push    %rbx # push the enclave base address
> +
> +     call    encl_body
> +
> +     pop     %rbx # pop the enclave base address
> +
> +     # Restore XSAVE registers to a synthetic state.
> +     mov     $0xFFFFFFFF, %rax
> +     mov     $0xFFFFFFFF, %rdx
> +     lea     (xsave_area)(%rbx), %rdi
> +     fxrstor (%rdi)
> +
> +     # Clear GPRs
> +     xor     %rcx, %rcx
> +     xor     %rdx, %rdx
> +     xor     %rdi, %rdi
> +     xor     %rsi, %rsi
> +     xor     %r8, %r8
> +     xor     %r9, %r9
> +     xor     %r10, %r10
> +     xor     %r11, %r11
> +     xor     %r12, %r12
> +     xor     %r13, %r13
> +     xor     %r14, %r14
> +     xor     %r15, %r15
> +
> +     # Reset status flags
> +     add     %rdx, %rdx # OF = SF = AF = CF = 0; ZF = PF = 1
> +
> +     pop     %rbx # pop the address after EENTER

Probably worth expanding the comment to explain that ENCLU[EEXIT] takes the
target address via %rbx, i.e. we're "returning" from the EENTER "call".

> +
> +     # Restore the caller stack.
> +     pop     %rax
> +     mov     %rax, %rsp
> +
> +     # EEXIT
> +     mov     $4, %rax
> +     enclu
> +
> +     .section ".data", "aw"
> +
> +encl_ssa:
> +     .space 4096
> +
> +xsave_area:
> +     .fill   1, 4, 0x037F            # FCW
> +     .fill   5, 4, 0
> +     .fill   1, 4, 0x1F80            # MXCSR
> +     .fill   1, 4, 0xFFFF            # MXCSR_MASK
> +     .fill   123, 4, 0
> +     .fill   1, 4, 0x80000000        # XCOMP_BV[63] = 1, compaction mode
> +     .fill   12, 4, 0
> +
> +     .balign 4096
> +     .space 8192
> +encl_stack:

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