lkml.org 
[lkml]   [2020]   [Sep]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v38 21/24] x86/vdso: Implement a vDSO for Intel SGX enclave call
On Fri, Sep 25, 2020 at 07:23:59PM +0100, Andrew Cooper wrote:
> On 15/09/2020 12:28, Jarkko Sakkinen wrote:
> > diff --git a/arch/x86/entry/vdso/vsgx_enter_enclave.S b/arch/x86/entry/vdso/vsgx_enter_enclave.S
> > new file mode 100644
> > index 000000000000..adbd59d41517
> > --- /dev/null
> > +++ b/arch/x86/entry/vdso/vsgx_enter_enclave.S
> > @@ -0,0 +1,157 @@
> > +SYM_FUNC_START(__vdso_sgx_enter_enclave)
> > <snip>
> > +.Lretpoline:
> > + call 2f
> > +1: pause
> > + lfence
> > + jmp 1b
> > +2: mov %rax, (%rsp)
> > + ret
>
> I hate to throw further spanners in the work, but this is not compatible
> with CET, and the user shadow stack work in progress.

CET goes beyond my expertise. Can you describe, at least rudimentary,
how this code is not compatible?

I know CET only conceptual level (separate stack holding return
addresses as an measure against return oriented programming (ROP)).

> Whichever of these two large series lands first is going to inflict
> fixing this problem on the other.
>
> As the vdso text is global (to a first approximation), it must not be a
> retpoline if any other process is liable to want to use CET-SS.

Why is that?

> If the retpoline really does need to stay, then the vdso probably needs
> to gain suitable __x86_indirect_thunk_%reg thunks which are patched at
> boot based on the system properties.
>
> ~Andrew

aka without CET it is patched? With CET, not?

/Jarkko

\
 
 \ /
  Last update: 2020-09-28 02:59    [W:0.235 / U:0.288 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site