binman: Allow for skip_at_start when reading entries

The offset of an entry needs to be adjusted by its skip-at-start value.
This is currently missing when reading entry data. Fix it.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/binman/etype/section.py

@@ -605,10 +605,12 @@ class Entry_section(Entry):
     def ReadData(self, decomp=True):
         tout.Info("ReadData path='%s'" % self.GetPath())
         parent_data = self.section.ReadData(True)
-        tout.Info('%s: Reading data from offset %#x-%#x, size %#x' %
-                  (self.GetPath(), self.offset, self.offset + self.size,
-                   self.size))
-        data = parent_data[self.offset:self.offset + self.size]
+        offset = self.offset - self.section._skip_at_start
+        data = parent_data[offset:offset + self.size]
+        tout.Info(
+            '%s: Reading data from offset %#x-%#x (real %#x), size %#x, got %#x' %
+                  (self.GetPath(), self.offset, self.offset + self.size, offset,
+                   self.size, len(data)))
         return data
 
     def ReadChildData(self, child, decomp=True):

tools/binman/ftest.py

@@ -4226,6 +4226,25 @@ class TestFunctional(unittest.TestCase):
         expect = FILES_DATA[:15] + b'\0' + FILES_DATA[15:]
         self.assertEqual(expect, data)
 
+    def testReadImageSkip(self):
+        """Test reading an image and accessing its FDT map"""
+        data = self.data = self._DoReadFileRealDtb('191_read_image_skip.dts')
+        image_fname = tools.GetOutputFilename('image.bin')
+        orig_image = control.images['image']
+        image = Image.FromFile(image_fname)
+        self.assertEqual(orig_image.GetEntries().keys(),
+                         image.GetEntries().keys())
+
+        orig_entry = orig_image.GetEntries()['fdtmap']
+        entry = image.GetEntries()['fdtmap']
+        self.assertEqual(orig_entry.offset, entry.offset)
+        self.assertEqual(orig_entry.size, entry.size)
+        self.assertEqual(16, entry.image_pos)
+
+        u_boot = image.GetEntries()['section'].GetEntries()['u-boot']
+
+        self.assertEquals(U_BOOT_DATA, u_boot.ReadData())
+
 
 if __name__ == "__main__":
     unittest.main()

tools/binman/test/191_read_image_skip.dts

@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+/dts-v1/;
+
+/ {
+	#address-cells = <1>;
+	#size-cells = <1>;
+
+	binman {
+		end-at-4gb;
+		size = <0x400>;
+		section {
+			size = <0x10>;
+			u-boot {
+			};
+		};
+		fdtmap {
+		};
+		image-header {
+			location = "end";
+		};
+	};
+};