[U-Boot] [PATCH 11/24] arm: spl: Enable detecting when U-Boot is started from SPL

[Joe Hershberger]

Hi Simon,

On Mon, May 4, 2015 at 12:31 PM, Simon Glass <sjg at chromium.org> wrote:
> For secure boot systems it is common to have a read-only U-Boot which starts
> the machine and jumps to a read-write U-Boot for actual booting the OS. This
> allows the read-write U-Boot to be upgraded without risk of permanently
> bricking the machine. In the event that the read-write U-Boot is corrupted,
> the read-only U-Boot can detect this with a checksum and boot into a
> recovery flow.
>
> To support this, add a way to detect when U-Boot is run from SPL as opposed
> to some other method, such as booted directly (no SPL) or started from
> another source (e.g. a primary U-Boot). This works by putting a special value
> in r0.
>
> For now we rely on board-specific code to actually check the register and
> set a flag. At some point this could be generalised, perhaps by using a spare
> register and passing a flag to _main and/or board_init_f().
>
> Signed-off-by: Simon Glass <sjg at chromium.org>
> ---
>
>  include/spl.h | 13 +++++++++++++
>  1 file changed, 13 insertions(+)

Part of this patch seems to be missing. I don't see how these changes
can accomplish what is described in the commit log.

> diff --git a/include/spl.h b/include/spl.h
> index b2e5bf7..cdd63a7 100644
> --- a/include/spl.h
> +++ b/include/spl.h
> @@ -11,6 +11,8 @@
>  #include <linux/compiler.h>
>  #include <asm/spl.h>
>
> +/* Value in r0 indicates we booted from U-Boot */
> +#define SPL_RUNNING_FROM_UBOOT 0x13578642
>
>  /* Boot type */
>  #define MMCSD_MODE_UNDEFINED   0
> @@ -82,4 +84,15 @@ int spl_load_image_ext_os(block_dev_desc_t *block_dev, int partition);
>  #ifdef CONFIG_SPL_BOARD_INIT
>  void spl_board_init(void);
>  #endif
> +
> +/**
> + * spl_was_boot_source() - check if U-Boot booted from SPL
> + *
> + * This will normally be true, but if U-Boot jumps to second U-Boot, it will
> + * be false. This should be implemented by board-specific code.
> + *
> + * @return true if U-Boot booted from SPL, else false
> + */
> +bool spl_was_boot_source(void);
> +
>  #endif
> --

Thanks,
-Joe