fdt: Check for overlapping data and FDT
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>
diff --git a/lib/fdtdec.c b/lib/fdtdec.c
index 03c9cea..8d5c688 100644
--- a/lib/fdtdec.c
+++ b/lib/fdtdec.c
@@ -1231,6 +1231,29 @@
#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;