[U-Boot] [PATCH 07/15] ARM: PSCI: Allocate PSCI stack in secure stack section

[Hongbo Zhang]

Tested-by: Hongbo Zhang <hongbo.zhang at nxp.com>

On Sun, Jun 19, 2016 at 12:38 PM, Chen-Yu Tsai <wens at csie.org> wrote:
> Now that we have a secure stack section that guarantees usable memory,
> allocate the PSCI stacks in that section.
>
> Also add a diagram detailing how the stacks are placed in memory.
>
> Reserved space for the target PC remains unchanged. This should be
> moved to global variables within a secure data section in the future.
>
> Signed-off-by: Chen-Yu Tsai <wens at csie.org>
> ---
>  arch/arm/cpu/armv7/psci.S | 32 +++++++++++++++++++++-----------
>  1 file changed, 21 insertions(+), 11 deletions(-)
>
> diff --git a/arch/arm/cpu/armv7/psci.S b/arch/arm/cpu/armv7/psci.S
> index 46fcf770c214..bfc4475e360c 100644
> --- a/arch/arm/cpu/armv7/psci.S
> +++ b/arch/arm/cpu/armv7/psci.S
> @@ -196,18 +196,28 @@ ENTRY(psci_cpu_off_common)
>         bx      lr
>  ENDPROC(psci_cpu_off_common)
>
> -@ expects CPU ID in r0 and returns stack top in r0
> +@ The stacks are allocated in reverse order, i.e.
> +@ the stack for CPU0 has the highest memory address.
> +@
> +@ --------------------  __secure_stack_end
> +@ |  CPU0 target PC  |
> +@ |------------------|
> +@ |                  |
> +@ |    CPU0 stack    |
> +@ |                  |
> +@ |------------------|  __secure_stack_end - 1KB
> +@ |        .         |
> +@ |        .         |
> +@ |        .         |
> +@ |        .         |
> +@ --------------------  __secure_stack_start
> +@
> +@ This expects CPU ID in r0 and returns stack top in r0
>  ENTRY(psci_get_cpu_stack_top)
> -       mov     r3, #0x400                      @ 1kB of stack per CPU
> -       mul     r0, r0, r3
> -
> -       ldr     r3, =psci_text_end              @ end of monitor text
> -       add     r3, r3, #0x2000                 @ Skip two pages
> -       lsr     r3, r3, #12                     @ Align to start of page
> -       lsl     r3, r3, #12
> -       sub     r3, r3, #4                      @ reserve 1 word for target PC
> -       sub     r0, r3, r0                      @ here's our stack!
> -
> +       @ stack top = __secure_stack_end - (cpuid << ARM_PSCI_STACK_SHIFT)
> +       ldr     r3, =__secure_stack_end
> +       sub     r0, r3, r0, LSL #ARM_PSCI_STACK_SHIFT
> +       sub     r0, r0, #4              @ Save space for target PC
>         bx      lr
>  ENDPROC(psci_get_cpu_stack_top)
>
> --
> 2.8.1
>