[U-Boot] [PATCH v3 2/7] ARM: add secure monitor handler to switch to non-secure state

[Christoffer Dall]

n Wed, Jul 10, 2013 at 01:54:14AM +0200, Andre Przywara wrote:
> A prerequisite for using virtualization is to be in HYP mode, which
> requires the CPU to be in non-secure state first.
> Add new file in arch/arm/cpu/armv7 to hold a monitor handler routine
> which switches the CPU to non-secure state by setting the NS and
> associated bits.
> According to the ARM architecture reference manual this should not be
> done in SVC mode, so we have to setup a SMC handler for this.
> We create a new vector table to avoid interference with other boards.
> The MVBAR register will be programmed later just before the smc call.
> 
> Signed-off-by: Andre Przywara <andre.przywara at linaro.org>
> ---
>  arch/arm/cpu/armv7/Makefile      |  4 +++
>  arch/arm/cpu/armv7/nonsec_virt.S | 54 ++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 58 insertions(+)
>  create mode 100644 arch/arm/cpu/armv7/nonsec_virt.S
> 
> diff --git a/arch/arm/cpu/armv7/Makefile b/arch/arm/cpu/armv7/Makefile
> index 7a8c2d0..5d75077 100644
> --- a/arch/arm/cpu/armv7/Makefile
> +++ b/arch/arm/cpu/armv7/Makefile
> @@ -36,6 +36,10 @@ ifneq ($(CONFIG_AM33XX)$(CONFIG_OMAP44XX)$(CONFIG_OMAP54XX)$(CONFIG_TEGRA)$(CONF
>  SOBJS	+= lowlevel_init.o
>  endif
>  
> +ifneq ($(CONFIG_ARMV7_NONSEC),)
> +SOBJS   += nonsec_virt.o
> +endif
> +
>  SRCS	:= $(START:.o=.S) $(COBJS:.o=.c)
>  OBJS	:= $(addprefix $(obj),$(COBJS) $(SOBJS))
>  START	:= $(addprefix $(obj),$(START))
> diff --git a/arch/arm/cpu/armv7/nonsec_virt.S b/arch/arm/cpu/armv7/nonsec_virt.S
> new file mode 100644
> index 0000000..68a6b38
> --- /dev/null
> +++ b/arch/arm/cpu/armv7/nonsec_virt.S
> @@ -0,0 +1,54 @@
> +/*
> + * code for switching cores into non-secure state
> + *
> + * Copyright (c) 2013	Andre Przywara <andre.przywara at linaro.org>
> + *
> + * See file CREDITS for list of people who contributed to this
> + * project.
> + *
> + * 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.
> + *
> + * 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.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write to the Free Software
> + * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
> + * MA 02111-1307 USA
> + */
> +
> +#include <config.h>
> +
> +/* the vector table for secure state */
> +_monitor_vectors:
> +	.word 0	/* reset */
> +	.word 0 /* undef */
> +	adr pc, _secure_monitor
> +	.word 0
> +	.word 0
> +	.word 0
> +	.word 0
> +	.word 0
> +	.word 0	/* pad */
> +
> +/*
> + * software interrupt aka. secure monitor handler

a software interrupt is not aka. a secure monitor handler, this is
misleading, it's just the smc handler.

> + * This is executed on a "smc" instruction, we use a "smc #0" to switch
> + * to non-secure state.
> + * We use only r0 and r1 here, due to constraints in the caller.
> + */
> +	.align	5
> +_secure_monitor:
> +	mrc	p15, 0, r1, c1, c1, 0		@ read SCR
> +	bic	r1, r1, #0x4e			@ clear IRQ, FIQ, EA, nET bits
> +	orr	r1, r1, #0x31			@ enable NS, AW, FW bits
> +
> +	mcr	p15, 0, r1, c1, c1, 0		@ write SCR (with NS bit set)
> +
> +	movs	pc, lr				@ return to non-secure SVC
> +
> -- 
> 1.7.12.1
>