On Wed, Sep 26, 2018 at 03:37:45PM -0700, Andy Lutomirski wrote: > Yeah. Maybe like this: > > xorl %eax,%eax > eenter_insn: > ENCLU[whatever] > eenter_landing_pad: > ret > > And the kernel would use the existing vdso2c vdso-symbol-finding > mechanism to do the fixup. > > > > > How would a syscall work, though? I assume we can't just enter the > > enclave from ring0. > > My understanding of how AEX works is a bit vague, but maybe a syscall > could reuse the mechanism? The vDSO approach seems considerably > simpler. > > We do need to make sure that a fault that happens on or after return > from an AEX event does the right thing. But I'm still vague on how > that works, sigh. > > --Andy Returning from AEX does not differ from any other memory access event so AFAIK it should be handled right with the proposed solution already. For convenience I think we could have a fixed trampoline for AEX e.g. this how it is implemented in the open source LE that I did: sgx_get_token: push %rbx mov $0x02, %rax mov %rsi, %rbx mov %rdx, %rsi mov $sgx_async_exit, %rcx sgx_async_exit: ENCLU pop %rbx ret BTW, if I converted the in-kernel LE as a standalone test program, would that be useful for basic testing of the series? /Jarkko
