linux-kernel - Re: [PATCH 03/26] x86/tdx: Add __tdx_module_call() and __tdx

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Date:   Thu, 23 Dec 2021 19:53:50 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, dave.hansen@...el.com,
        luto@...nel.org, peterz@...radead.org,
        sathyanarayanan.kuppuswamy@...ux.intel.com, aarcange@...hat.com,
        ak@...ux.intel.com, dan.j.williams@...el.com, david@...hat.com,
        hpa@...or.com, jgross@...e.com, jmattson@...gle.com,
        joro@...tes.org, jpoimboe@...hat.com, knsathya@...nel.org,
        pbonzini@...hat.com, sdeep@...are.com, seanjc@...gle.com,
        tony.luck@...el.com, vkuznets@...hat.com, wanpengli@...cent.com,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/26] x86/tdx: Add __tdx_module_call() and
 __tdx_hypercall() helper functions

On Thu, Dec 23, 2021 at 07:55:48PM +0300, Kirill A. Shutemov wrote:
> What about this?
> 
> 	In a TDX based VM, since the VMM is an untrusted entity, an intermediary
> 	layer -- TDX module -- facilitates secure communication between the host
> 	and the guest. TDX module is loaded like a firmware into a special CPU
> 	mode called SEAM. TDX guests communicate with the TDX module using the
> 	TDCALL instruction.
> 
> Does it look fine?

Yap, thx.

> Ah, okay. I did not know about special treatment for .L labels.
> Again, will check whole patchset.

Yeah, those are local labels. From the gas manpage:

       -L
       --keep-locals
           Keep (in the symbol table) local symbols.  These symbols start with system-
           specific local label prefixes, typically .L for ELF systems or L for
           traditional a.out systems.

Apparently, one can even add own prefix for local labels too:

       -local-prefix=prefix
           Mark all labels with specified prefix as local. But such label can be marked
           global explicitly in the code. This option do not change default local label
           prefix ".L", it is just adds new one.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette