elfloader: Don't overwrite the platform DTB

If a DTB has been passed in from an earlier stage boot loader during an
elfloader image relocation, make sure that it doesn't get overwritten.

On Arm this isn't relevant as the protocol when relocation happens
doesn't also pass in a DTB.

Signed-off-by: Kent McLeod <[email protected]>

elfloader-tool/src/arch-arm/64/crt0.S

@@ -23,6 +23,7 @@ BEGIN_FUNC(_start)
      * Binary images may not be loaded in the correct location.
      * Try and move ourselves so we're in the right place.
      */
+    mov     x0, #0 /* Arg 0 of fixup_image_base is NULL */
     bl      fixup_image_base
     mov     x2, x0
     /* restore original arguments for next step */

elfloader-tool/src/arch-riscv/crt0.S

@@ -62,6 +62,7 @@ _start:
    * Binary images may not be loaded in the correct location.
    * Try and move ourselves so we're in the right place.
    */
+  mv a0, a1 /* Pass dtb as first argument */
   jal fixup_image_base
   /* fixup_image_base returns 0 if no need to move */
   beqz     a0, 1f

elfloader-tool/src/common.c

@@ -635,7 +635,7 @@ extern void invalidate_icache(void);
  * to ensure that it doesn't occupy memory that it needs to load the
  * kernel and user applications into.
  */
-char * fixup_image_base(void) {
+char * fixup_image_base(char const *fdt) {
     char *load_base = _start;
     char *target_base = (char *) IMAGE_START_ADDR;
     if (load_base == target_base) {
@@ -659,6 +659,24 @@ char * fixup_image_base(void) {
         abort();
     }
 
+    /* If a fdt was passed in from the previous boot stage, also
+     * check that it isn't overwritten.
+     */
+    if (fdt) {
+        size_t dtb_size = fdt_size(fdt);
+        const char * fdt_end = fdt + dtb_size;
+        if (image_size < dtb_size) {
+            /* Assume the dtb is smaller than the images size to
+             * simplify region check */
+            abort();
+        }
+        if ((fdt >= target_base && fdt < target_end) ||
+            (fdt_end >= target_base && fdt_end < target_end)) {
+            abort();
+        }
+    }
+
+
     /* Perform the move and clean/invalidate caches if necessary */
     char *ret = memmove(target_base, load_base, image_size);
 #ifdef CONFIG_ARCH_ARM