Re: [PATCH v28 21/22] x86/vdso: Implement a vDSO for Intel SGX enclave call

["Xing, Cedric" <cedric.xing@xxxxxxxxx>]

Hi Nathaniel,

I reread your email today and thought I might have misunderstood your 
email earlier. What changes are you asking for exactly? Is that just 
passing @leaf in %ecx rather than in %eax? If so, I wouldn't have any 
problem. I agree with you that the resulted API would then be callable 
from C, even though it wouldn't be able to return back to C due to 
tampered %rbx. But I think the vDSO API can preserve %rbx too, given it 
is used by both EENTER and EEXIT (so is unavailable for parameter 
passing anyway). Alternatively, the C caller can setjmp() to be 
longjmp()'d back from within the exit handler.

-Cedric