Re: [PATCH v38 21/24] x86/vdso: Implement a vDSO for Intel SGX enclave call

[Jarkko Sakkinen]

On Fri, Sep 25, 2020 at 10:39:58AM +0200, Jethro Beekman wrote:
> On 2020-09-25 03:00, Jarkko Sakkinen wrote:
> > End result:
> > 
> > https://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-sgx.git/tree/arch/x86/include/uapi/asm/sgx.h
> > 
> > I'm wondering this sentence:
> > 
> > "The calling convention is custom and does not follow System V x86-64 ABI."
> > 
> > AFAIK, now the vDSO is fully C-callable but waiting for feedback before
> > removing it.
> 
> It's C-callable *iff your enclave follows the System V x86-64 ABI*. In
> addition, all registers not clobbered by the SGX ISA are passed to the
> enclave, not just those specified as parameter passing registers in
> the ABI. This is intentional to make the vDSO function usable in
> applications that use the current flexibility of ENCLU.

Hold on, I really want to fix this bit of documentation before sending
any new version, so I'll explain how I understand it.

I think it is just SystemV ABI call with six parameters in the usual
GPRs (rdi, rsi, rdx, rcx, r8, r9).

I'm looking at vdso_sgx_enter_enclave.

What I'm not getting?

> --
> Jethro Beekman | Fortanix

/Jarkko