Re: [Xen-devel] [PATCH v1 1/6] arm: add SMC wrapper that is compatible with SMCCC

[Julien Grall <julien.grall@xxxxxxx>]

On 08/23/2018 03:35 PM, Volodymyr Babchuk wrote:
> Hi,
Hi Volodymyr,


> On 22.08.18 19:46, Julien Grall wrote:
> > Hi Volodymyr,
> >
> > On 22/08/18 15:11, Volodymyr Babchuk wrote:
> > > Existing SMC wrapper call_smc() allows only 4 parameters and
> > > returns only one value. This is enough for existing
> > > use in PSCI code, but TEE mediator will need a call that is
> > > fully compatible with ARM SMCCC.
> > > This patch adds this call for both arm32 and arm64.
> > >
> > > There was similar patch by Edgar E. Iglesias ([1]), but looks
> > > like it is abandoned.
> > >
> > > [1] 
> > > https://lists.xenproject.org/archives/html/xen-devel/2017-02/msg00636.html 
> > >
> > > CC: "Edgar E. Iglesias" <edgar.iglesias@xxxxxxxxxx>
> > >
> > > Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
> > > ---
> > >
> > > changes from "RFC":
> > >    - response now stored in structure instead of array
> > >    - added comments for arm32 assembly code
> > >    - added offset (instead of magic values) for arm32 asm code
> > Did you mean arm64?
> Yes, you are right.
>
> > >   xen/arch/arm/arm32/Makefile      |  1 +
> > >   xen/arch/arm/arm32/smc.S         | 39 
> > > +++++++++++++++++++++++++++++++++++++++
> > >   xen/arch/arm/arm64/Makefile      |  1 +
> > >   xen/arch/arm/arm64/asm-offsets.c |  4 ++++
> > >   xen/arch/arm/arm64/smc.S         | 30 ++++++++++++++++++++++++++++++
> > >   xen/include/asm-arm/processor.h  | 11 +++++++++++
> > >   6 files changed, 86 insertions(+)
> > >   create mode 100644 xen/arch/arm/arm32/smc.S
> > >   create mode 100644 xen/arch/arm/arm64/smc.S
> > >
> > > diff --git a/xen/arch/arm/arm32/Makefile b/xen/arch/arm/arm32/Makefile
> > > index 0ac254f..c69f35e 100644
> > > --- a/xen/arch/arm/arm32/Makefile
> > > +++ b/xen/arch/arm/arm32/Makefile
> > > @@ -10,4 +10,5 @@ obj-y += proc-v7.o proc-caxx.o
> > >   obj-y += smpboot.o
> > >   obj-y += traps.o
> > >   obj-y += vfp.o
> > > +obj-y += smc.o
> > > diff --git a/xen/arch/arm/arm32/smc.S b/xen/arch/arm/arm32/smc.S
> > > new file mode 100644
> > > index 0000000..56f7982
> > > --- /dev/null
> > > +++ b/xen/arch/arm/arm32/smc.S
> > > @@ -0,0 +1,39 @@
> > > +/*
> > > + * xen/arch/arm/arm32/smc.S
> > > + *
> > > + * Wrapper for Secure Monitors Calls
> > > + *
> > > + * This program is free software; you can redistribute it and/or modify
> > > + * it under the terms of the GNU General Public License as published by
> > > + * the Free Software Foundation; either version 2 of the License, or
> > > + * (at your option) any later version.
> > Xen is GPLv2 only. Can you please update the copyright accordingly?
> >
> > Also, the code is pretty much a copy of the Linux part. So it is 
> > probably worth to keep the copy-right around.
> > > + *
> > > + * This program is distributed in the hope that it will be useful,
> > > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > > + * GNU General Public License for more details.
> > > + */
> > > +
> > > +#include <asm/macros.h>
> > > +
> > > +/*
> > > + * void call_smccc_smc(register_t a0, register_t a1, register_t a2,
> > > + *                     register_t a3, register_t a4, register_t a5,
> > > + *                     register_t a6, register_t a7, struct 
> > > smccc_res *res)
> > > + */
> > > +ENTRY(call_smccc_smc)
> > I would rather avoid to have 2 function to handle the same convention. 
> > Can you please either drop call_smc or rework it to handle more 
> > parameters?
> > But it looks like you could re-use arm_smccc_1_1 as it follows the 1.0 
> > convention for 32-bits.
> Oops, I missed introduction of arm_smccc_1_1. I think, it will be 
> sufficient for my tasks. Looks like, I'll drop this patch at all.
Are you suggesting that OP-TEE will always use SMCCC 1.1 calling convention?

I would be quite surprised given that you seem to have platform with 
ancient firmware.
Cheers,

--
Julien Grall

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