Hi Simon,
On Mon, May 4, 2015 at 12:31 PM, Simon Glass sjg@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@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