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

[Julien Grall <julien.grall@xxxxxxx>]

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?

>   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.
> +        mov     r12, sp
> +        push    {r4-r7}
> +       /*
> +        * According to ARMv7 (or aarch32) ABI, first 4 parameters of
> +        * call_smccc_smc are passed in r0-r3 and other 4 are on stack.
> +        * Load a4-a7 from stack to r4-r7.
> +        */
> +        ldm     r12, {r4-r7}
> +        smc     #0
> +        pop     {r4-r7}
> +       /* Load pointer to res (4th parameter on stack) to r12 */
> +        ldr     r12, [sp, #(4 * 4)]
> +       /* Store returned results from r0-r3 to res */
> +        stm     r12, {r0-r3}
> +        bx      lr
Something looks wrong with the indentation. There seem to be a mix of 
hard tab and soft tab.
> diff --git a/xen/arch/arm/arm64/Makefile b/xen/arch/arm/arm64/Makefile
> index bb5c610..7ecdad7 100644
> --- a/xen/arch/arm/arm64/Makefile
> +++ b/xen/arch/arm/arm64/Makefile
> @@ -9,6 +9,7 @@ obj-y += entry.o
>   obj-y += insn.o
>   obj-$(CONFIG_LIVEPATCH) += livepatch.o
>   obj-y += smpboot.o
> +obj-y += smc.o
>   obj-y += traps.o
>   obj-y += vfp.o
>   obj-y += vsysreg.o
> diff --git a/xen/arch/arm/arm64/asm-offsets.c b/xen/arch/arm/arm64/asm-offsets.c
> index ce24e44..5353fe8 100644
> --- a/xen/arch/arm/arm64/asm-offsets.c
> +++ b/xen/arch/arm/arm64/asm-offsets.c
> @@ -50,6 +50,10 @@ void __dummy__(void)
>   
>      BLANK();
>      OFFSET(INITINFO_stack, struct init_info, stack);
> +
> +   BLANK();
> +   OFFSET(SMCCC_RES_a0, struct smccc_res, a0);
> +   OFFSET(SMCCC_RES_a2, struct smccc_res, a2);
>   }
>   
>   /*
> diff --git a/xen/arch/arm/arm64/smc.S b/xen/arch/arm/arm64/smc.S
> new file mode 100644
> index 0000000..40843c0
> --- /dev/null
> +++ b/xen/arch/arm/arm64/smc.S
> @@ -0,0 +1,30 @@
> +/*
> + * xen/arch/arm/arm64/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/asm_defns.h>
> +#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)
> +        smc     #0
> +        ldr     x4, [sp]
> +        stp     x0, x1, [x4, #SMCCC_RES_a0]
> +        stp     x2, x3, [x4, #SMCCC_RES_a2]
> +        ret
> diff --git a/xen/include/asm-arm/processor.h b/xen/include/asm-arm/processor.h
> index 222a02d..946a2db 100644
> --- a/xen/include/asm-arm/processor.h
> +++ b/xen/include/asm-arm/processor.h
> @@ -650,6 +650,13 @@ union hsr {
>   
>   
>   };
> +
> +struct smccc_res {
> +    register_t a0;
> +    register_t a1;
> +    register_t a2;
> +    register_t a3;
> +};
Any reason to not use arm_smccc_res?

>   #endif
>   
>   /* HSR.EC == HSR_CP{15,14,10}_32 */
> @@ -815,6 +822,10 @@ void vcpu_regs_user_to_hyp(struct vcpu *vcpu,
>   int call_smc(register_t function_id, register_t arg0, register_t arg1,
>                register_t arg2);
>   
> +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);
> +
>   void do_trap_hyp_serror(struct cpu_user_regs *regs);
>   
>   void do_trap_guest_serror(struct cpu_user_regs *regs);
Cheers,

--
Julien Grall

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