If the FDT overlaps with the data region of the image, or with the stack, it can become corrupted before relocation. Add a check for this, behind a debug flag, as it can be very confusing and time-consuming to debug.
Signed-off-by: Simon Glass sjg@chromium.org ---
lib/fdtdec.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+)
diff --git a/lib/fdtdec.c b/lib/fdtdec.c index 03c9ceab773..8d5c68860ec 100644 --- a/lib/fdtdec.c +++ b/lib/fdtdec.c @@ -1231,6 +1231,29 @@ static void *fdt_find_separate(void) #else /* FDT is at end of image */ fdt_blob = (ulong *)&_end; + + if (_DEBUG && !fdtdec_prepare_fdt(fdt_blob)) { + int stack_ptr; + const void *top = fdt_blob + fdt_totalsize(fdt_blob); + + /* + * Perform a sanity check on the memory layout. If this fails, + * it indicates that the device tree is positioned above the + * global data pointer or the stack pointer. This should not + * happen. + * + * If this fails, check that SYS_INIT_SP_ADDR has enough space + * below it for SYS_MALLOC_F_LEN and global_data, as well as the + * stack, without overwriting the device tree or U-Boot itself. + * Since the device tree is sitting at _end (the start of the + * BSS region), we need the top of the device tree to be below + * any memory allocated by board_init_f_alloc_reserve(). + */ + if (top > (void *)gd || top > (void *)&stack_ptr) { + printf("FDT %p gd %p\n", fdt_blob, gd); + panic("FDT overlap"); + } + } #endif
return fdt_blob;