dtmerge/dtoverlay: Pass all regression tests

Using dtoverlay to create a runtime overlay and merging that with a
base dtb, then comparing against merging the overlay directly with
the base dtb, showed some difference (and therefore errors).

Fix those errors by passing the stringlist length around, and by
correctly remembering the offset of the used value in a lookup table.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>

Author: pelwell

dtmerge/dtoverlay.c

@@ -676,7 +676,8 @@ static int dtoverlay_phandle_relocate(DTBLOB_T *dtb, int node_off,
 
 // Returns 0 on success, or an FDT error code
 static int dtoverlay_apply_fixups(DTBLOB_T *dtb, const char *fixups_stringlist,
-                                  uint32_t phandle, fixup_type_t type)
+                                  int fixups_len, uint32_t phandle,
+                                  fixup_type_t type)
 {
     // The fixups arrive as a sequence of NUL-terminated strings, of the form:
     //   "path:property:offset"
@@ -687,8 +688,9 @@ static int dtoverlay_apply_fixups(DTBLOB_T *dtb, const char *fixups_stringlist,
     // 4) the code is simpler as a result.
 
     const char *fixup = fixups_stringlist;
+    const char *end  = fixup + fixups_len;
 
-    while  (fixup[0])
+    while  (fixup < end && fixup[0])
     {
         const char *prop_name, *offset_str;
         char *offset_end;
@@ -853,7 +855,7 @@ static int dtoverlay_resolve_phandles(DTBLOB_T *base_dtb, DTBLOB_T *overlay_dtb)
         if (fixups_stringlist)
         {
             // Relocate the overlay phandle references
-            err = dtoverlay_apply_fixups(overlay_dtb, fixups_stringlist,
+            err = dtoverlay_apply_fixups(overlay_dtb, fixups_stringlist, err,
                                          base_dtb->max_phandle, FIXUP_RELATIVE);
         }
         else
@@ -906,7 +908,7 @@ static int dtoverlay_resolve_fixups(DTBLOB_T *base_dtb, DTBLOB_T *overlay_dtb)
         {
             const char *fixups_stringlist, *symbol_name, *target_path;
             const char *ref_type;
-            int target_off;
+            int target_off, fixups_len;
             uint32_t target_phandle;
 
             // The property name identifies a symbol (or alias) in the base.
@@ -920,6 +922,8 @@ static int dtoverlay_resolve_fixups(DTBLOB_T *base_dtb, DTBLOB_T *overlay_dtb)
                 break;
             }
 
+            fixups_len = err;
+
             // 1) Find the target node.
             if (symbol_name[0] == '/')
             {
@@ -973,10 +977,13 @@ static int dtoverlay_resolve_fixups(DTBLOB_T *base_dtb, DTBLOB_T *overlay_dtb)
 
             // Now apply the valid target_phandle to the items in the fixup string
 
-            err = dtoverlay_apply_fixups(overlay_dtb, fixups_stringlist,
+            err = dtoverlay_apply_fixups(overlay_dtb, fixups_stringlist, fixups_len,
                                          target_phandle, FIXUP_ABSOLUTE);
             if (err)
+            {
+                dtoverlay_error("failed to apply fixups");
                 break;
+            }
         }
     }
 
@@ -2343,9 +2350,11 @@ static const char *dtoverlay_extract_immediate(const char *data, const char *dat
             return NULL;
         }
         val = dtoverlay_read_u32(data, 0);
-        cell_source = data;
         if (buf)
+        {
+            cell_source = data;
             snprintf(buf, buf_len, "%d", val);
+        }
         data += 4;
     }
     else if (data[0] == '\'')