[nrf noup] scripts: imgtool: add pad-value

adds parameter that allows to set either 0x00 or 0xff
for header padding.

Signed-off-by: Mateusz Michalek <mateusz.michalek@nordicsemi.no>

Author: michalek-no

scripts/imgtool/image.py

@@ -352,8 +352,8 @@ def __init__(self, version=None, header_size=IMAGE_HEADER_SIZE,
                  pad_header=False, pad=False, confirm=False, align=1,
                  slot_size=0, max_sectors=DEFAULT_MAX_SECTORS,
                  overwrite_only=False, endian="little", load_addr=0,
-                 rom_fixed=None, erased_val=None, save_enctlv=False,
-                 security_counter=None, max_align=None,
+                 rom_fixed=None, erased_val=None, pad_value=None,
+                 save_enctlv=False, security_counter=None, max_align=None,
                  non_bootable=False, vid=None, cid=None,
                  edt_config=None, manifest=None):
 
@@ -376,7 +376,11 @@ def __init__(self, version=None, header_size=IMAGE_HEADER_SIZE,
         self.base_addr = None
         self.load_addr = 0 if load_addr is None else load_addr
         self.rom_fixed = rom_fixed
-        self.erased_val = 0xff if erased_val is None else int(erased_val, 0)
+        self.pad_value = pad_value
+        if pad_value is not None:
+            self.erased_val = int(pad_value, 0)
+        else:
+            self.erased_val = 0xff if erased_val is None else int(erased_val, 0)
         self.payload = []
         self.infile_data = []
         self.enckey = None
@@ -455,13 +459,7 @@ def load(self, path):
         except FileNotFoundError:
             raise click.UsageError("Input file not found")
 
-        # Add the image header if needed.
-        if self.pad_header and self.header_size > 0:
-            if self.base_addr:
-                # Adjust base_addr for new header
-                self.base_addr -= self.header_size
-            self.payload = bytes([self.erased_val] * self.header_size) + \
-                self.payload
+        self._apply_header_padding()
 
         self.image_size = len(self.payload) - self.header_size
 
@@ -472,20 +470,7 @@ def load_compressed(self, data, compression_header):
         self.payload = compression_header + data
         self.image_size = len(self.payload)
 
-        # Add the image header if needed.
-        if self.header_size > 0:
-            if self.pad_header:
-                if self.base_addr:
-                    # Adjust base_addr for new header
-                    self.base_addr -= self.header_size
-                self.payload = bytes([self.erased_val] * self.header_size) + \
-                    self.payload
-            else:
-                # Fill header padding with zeros to align with what is expected
-                # for uncompressed images when no pad_header is requested
-                # (see self.check_header())
-                self.payload = bytes([0] * self.header_size) + \
-                    self.payload
+        self._apply_header_padding(default_zero_fill=True)
 
     def save(self, path, hex_addr=None):
         """Save an image from a given file"""
@@ -523,8 +508,31 @@ def save(self, path, hex_addr=None):
             with open(path, 'wb') as f:
                 f.write(self.payload)
 
+    def _apply_header_padding(self, default_zero_fill=False):
+        """Apply header padding using the configured pad value."""
+        if self.header_size <= 0:
+            return
+
+        padding = bytes([self.erased_val] * self.header_size)
+
+        if self.pad_header:
+            if self.base_addr:
+                # Adjust base_addr for new header
+                self.base_addr -= self.header_size
+            self.payload = padding + self.payload
+        elif self.pad_value is not None:
+            if len(self.payload) >= self.header_size:
+                self.payload = padding + bytes(self.payload[self.header_size:])
+            else:
+                self.payload = padding + self.payload
+        elif default_zero_fill:
+            # Fill header padding with zeros to align with what is expected
+            # for uncompressed images when no pad_header is requested
+            # (see self.check_header())
+            self.payload = bytes([0] * self.header_size) + self.payload
+
     def check_header(self):
-        if self.header_size > 0 and not self.pad_header:
+        if self.header_size > 0 and not self.pad_header and self.pad_value is None:
             if any(v != 0 for v in self.payload[0:self.header_size]):
                 raise click.UsageError("Header padding was not requested and "
                                        "image does not start with zeros")

scripts/imgtool/main.py

@@ -348,6 +348,11 @@ def convert(self, value, param, ctx):
 @click.option('-R', '--erased-val', type=click.Choice(['0', '0xff']),
               required=False,
               help='The value that is read back from erased flash.')
+@click.option('--pad-value', type=click.Choice(['0', '0xff']),
+              required=False,
+              help='Byte value used for header and slot padding. When set, '
+                   'header padding is applied with this value regardless of '
+                   'whether --pad-header is used.')
 @click.option('-x', '--hex-addr', type=BasedIntParamType(), required=False,
               help='Adjust address in hex output file.')
 @click.option('-L', '--load-addr', type=BasedIntParamType(), required=False,
@@ -466,7 +471,7 @@ def convert(self, value, param, ctx):
 def sign(key, public_key_format, align, version, pad_sig, header_size,
          pad_header, slot_size, pad, confirm, max_sectors, overwrite_only,
          endian, encrypt_keylen, encrypt, compression, infile, outfile,
-         dependencies, load_addr, hex_addr, erased_val, save_enctlv,
+         dependencies, load_addr, hex_addr, erased_val, pad_value, save_enctlv,
          security_counter, boot_record, custom_tlv, custom_tlv_file, rom_fixed, max_align,
          clear, fix_sig, fix_sig_pubkey, sig_out, user_sha, hmac_sha, is_pure,
          vector_to_sign, non_bootable, vid, cid, edt_config, manifest,
@@ -481,7 +486,8 @@ def sign(key, public_key_format, align, version, pad_sig, header_size,
                       align=int(align), slot_size=slot_size,
                       max_sectors=max_sectors, overwrite_only=overwrite_only,
                       endian=endian, load_addr=load_addr, rom_fixed=rom_fixed,
-                      erased_val=erased_val, save_enctlv=save_enctlv,
+                      erased_val=erased_val, pad_value=pad_value,
+                      save_enctlv=save_enctlv,
                       security_counter=security_counter, max_align=max_align,
                       non_bootable=non_bootable, vid=vid, cid=cid,
                       edt_config=edt_config, manifest=manifest)
@@ -557,7 +563,8 @@ def sign(key, public_key_format, align, version, pad_sig, header_size,
                   slot_size=slot_size, max_sectors=max_sectors,
                   overwrite_only=overwrite_only, endian=endian,
                   load_addr=load_addr, rom_fixed=rom_fixed,
-                  erased_val=erased_val, save_enctlv=save_enctlv,
+                  erased_val=erased_val, pad_value=pad_value,
+                  save_enctlv=save_enctlv,
                   security_counter=security_counter, max_align=max_align,
                   vid=vid, cid=cid, edt_config=edt_config, manifest=manifest)
         compression_filters = [