[PATCH v3 07/10] ARM: install HYP vectors at PBL and Barebox entry

[Sascha Hauer]

On Mon, Mar 26, 2018 at 09:20:22PM +0200, Lucas Stach wrote:
> If the CPU was already in HYP mode when entering the PBL, install a
> simple trap handler to allow to get back from SVC to HYP before
> switching to HYP mode.
> 
> As the vectors are part of the currently running binary, we need to
> do the same setup when starting the real Barebox binary, as the PBL
> setup vectors might get overwritten. To do this we trap into HYP mode
> just before jumping to Barebox and then re-do the vector setup and
> SVC switch as the first thing in Barebox proper.
> 
> Signed-off-by: Lucas Stach <l.stach at pengutronix.de>
> Tested-by: Roland Hieber <r.hieber at pengutronix.de>
> ---
>  arch/arm/cpu/lowlevel.S   | 3 +++
>  arch/arm/cpu/start-pbl.c  | 4 ++++
>  arch/arm/cpu/start.c      | 3 +++
>  arch/arm/cpu/uncompress.c | 4 ++++
>  4 files changed, 14 insertions(+)
> 
> diff --git a/arch/arm/cpu/lowlevel.S b/arch/arm/cpu/lowlevel.S
> index 43665981e48b..13dfe496ad17 100644
> --- a/arch/arm/cpu/lowlevel.S
> +++ b/arch/arm/cpu/lowlevel.S
> @@ -8,6 +8,9 @@ ENTRY(arm_cpu_lowlevel_init)
>  	/* save lr, since it may be banked away with a processor mode change */
>  	mov	r2, lr
>  
> +	/* careful: the hyp install corrupts r0 and r1 */
> +	bl	__hyp_install
> +
>  	/* set the cpu to SVC32 mode, mask irq and fiq */
>  	mrs	r12, cpsr
>  	eor	r12, r12, #HYP_MODE
> diff --git a/arch/arm/cpu/start-pbl.c b/arch/arm/cpu/start-pbl.c
> index e851b4a2da5e..e0793579e2e8 100644
> --- a/arch/arm/cpu/start-pbl.c
> +++ b/arch/arm/cpu/start-pbl.c
> @@ -26,6 +26,7 @@
>  #include <asm/barebox-arm-head.h>
>  #include <asm-generic/memory_layout.h>
>  #include <asm/sections.h>
> +#include <asm/secure.h>
>  #include <asm/pgtable.h>
>  #include <asm/cache.h>
>  #include <asm/unaligned.h>
> @@ -100,5 +101,8 @@ __noreturn void barebox_single_pbl_start(unsigned long membase,
>  	else
>  		barebox = (void *)barebox_base;
>  
> +	if (__boot_cpu_mode == HYP_MODE)
> +		armv7_switch_to_hyp();
> +
>  	barebox(membase, memsize, boarddata);
>  }
> diff --git a/arch/arm/cpu/start.c b/arch/arm/cpu/start.c
> index 171e6ad0eb7a..a0db6436f387 100644
> --- a/arch/arm/cpu/start.c
> +++ b/arch/arm/cpu/start.c
> @@ -24,6 +24,7 @@
>  #include <asm/barebox-arm-head.h>
>  #include <asm-generic/memory_layout.h>
>  #include <asm/sections.h>
> +#include <asm/secure.h>
>  #include <asm/unaligned.h>
>  #include <asm/cache.h>
>  #include <memory.h>
> @@ -145,6 +146,8 @@ __noreturn void barebox_non_pbl_start(unsigned long membase,
>  	unsigned long malloc_start, malloc_end;
>  	unsigned long barebox_size = barebox_image_size + MAX_BSS_SIZE;
>  
> +	armv7_hyp_install();

Calling a armv7 specific function in a generic code path is not so nice.
If this is really necessary then I suggest to #ifdef it here rather than
in the header file (where armv7_hyp_install() expands to a noop for
armv8. And what about the older architectures? A quick test revealed
this works on armv5, but is this intentional or by accident?

Sascha

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