[U-Boot] [PATCH 1/6] ARM: add secure monitor handler to switch to non-secure state
Albert ARIBAUD
albert.u.boot at aribaud.net
Thu May 23 12:52:19 CEST 2013
Hi Andre,
On Mon, 6 May 2013 15:17:45 +0200, Andre Przywara
<andre.przywara at linaro.org> wrote:
> A prerequisite for using virtualization is to be in HYP mode, which
> requires the CPU to be in non-secure state.
> Introduce a monitor handler routine which switches the CPU to
> non-secure state by setting the NS and associated bits.
> According to the ARM ARM this should not be done in SVC mode, so we
ARM *TRM*, I suspect. Also, as there are a lot of ARM TRMs, if there is
a more precise reference, please provide it.
> have to setup a SMC handler for this. We reuse the current vector
> table for this and make sure that we only access the MVBAR register
> if the CPU supports the security extension and only if we
> configured the board to use it, since boards entering u-boot already
> in non-secure mode would crash on accessing MVBAR otherwise.
>
> Signed-off-by: Andre Przywara <andre.przywara at linaro.org>
> ---
> arch/arm/cpu/armv7/start.S | 31 ++++++++++++++++++++++++++++---
> 1 file changed, 28 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm/cpu/armv7/start.S b/arch/arm/cpu/armv7/start.S
> index e9e57e6..da48b36 100644
> --- a/arch/arm/cpu/armv7/start.S
> +++ b/arch/arm/cpu/armv7/start.S
> @@ -155,6 +155,13 @@ reset:
> /* Set vector address in CP15 VBAR register */
> ldr r0, =_start
> mcr p15, 0, r0, c12, c0, 0 @Set VBAR
> +
> +#ifdef CONFIG_ARMV7_VIRT
> + mrc p15, 0, r1, c0, c1, 1 @ check for security extension
> + ands r1, r1, #0x30
> + mcrne p15, 0, r0, c12, c0, 1 @ Set secure monitor MVBAR
> +#endif
> +
> #endif
>
> /* the mask ROM code should have PLL and others stable */
> @@ -257,6 +264,12 @@ ENTRY(c_runtime_cpu_setup)
> ldr r0, =_start
> mcr p15, 0, r0, c12, c0, 0 @Set VBAR
>
> +#ifdef CONFIG_ARMV7_VIRT
> + mrc p15, 0, r1, c0, c1, 1 @ check for security extension
> + ands r1, r1, #0x30
> + mcrne p15, 0, r0, c12, c0, 1 @ Set secure monitor MVBAR
> +#endif
> +
> bx lr
>
> ENDPROC(c_runtime_cpu_setup)
> @@ -490,11 +503,23 @@ undefined_instruction:
> bad_save_user_regs
> bl do_undefined_instruction
>
> +/*
> + * software interrupt aka. secure monitor handler
> + * This is executed on a "smc" instruction, we use a "smc #0" to switch
> + * to non-secure state
> + */
> .align 5
> software_interrupt:
> - get_bad_stack_swi
> - bad_save_user_regs
> - bl do_software_interrupt
> + mrc p15, 0, r1, c1, c1, 0 @ read SCR
> + bic r1, r1, #0x07f
> + orr r1, r1, #0x31 @ enable NS, AW, FW
> +
> + mrc p15, 0, r0, c12, c0, 0 @ save secure copy of VBAR
> + mcr p15, 0, r1, c1, c1, 0 @ write SCR, switch to non-sec
> + isb
> + mcr p15, 0, r0, c12, c0, 0 @ write non-secure copy of VBAR
> +
> + movs pc, lr
>
> .align 5
> prefetch_abort:
Amicalement,
--
Albert.
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