[bazel,otp] update ROM_EXT immutable section OTP gen tooling

This updates the logic to consider both `_ottf_start_address` and
 `_rom_ext_start_address` when determining the manifest start address.
This ensures compatibility with different ELF file formats that
generated from linker scripts such as `ottf_silicon_owner_a.ld` and
`rom_ext_slot_a.ld`, which may use either symbol to represent the start
address of the ROM_EXT section.

This also introduces a new feature that conditionally updates the OTP
JSON file with data from immutable ROM_EXT section. This update is
performed only if the immutable ROM_EXT is enabled.

Signed-off-by: Anthony Chen <[email protected]>

rules/otp.bzl

@@ -169,6 +169,7 @@ def _otp_json_immutable_rom_ext_impl(ctx):
     args.add("--input", intput_file)
     args.add("--elf", rom_ext_elf_file)
     args.add("--output", output_file)
+    args.add("--hardened-true-value", CONST.HARDENED_TRUE)
 
     tc = ctx.toolchains[LOCALTOOLS_TOOLCHAIN]
     ctx.actions.run(

util/design/gen-otp-immutable-rom-ext-json.py

@@ -16,8 +16,10 @@
 _OTP_PARTITION_NAME = "CREATOR_SW_CFG"
 
 _OTTF_START_OFFSET_SYMBOL_NAME = "_ottf_start_address"
+_ROM_EXT_SATRT_OFFSET_SYMBOL_NAME = "_rom_ext_start_address"
 _ROM_EXT_IMMUTABLE_SECTION_NAME = ".rom_ext_immutable"
 
+_ENABLE_FIELD_NAME = "CREATOR_SW_CFG_IMMUTABLE_ROM_EXT_EN"
 _START_OFFSET_FIELD_NAME = "CREATOR_SW_CFG_IMMUTABLE_ROM_EXT_START_OFFSET"
 _SIZE_FIELD_NAME = "CREATOR_SW_CFG_IMMUTABLE_ROM_EXT_LENGTH"
 _HASH_FIELD_NAME = "CREATOR_SW_CFG_IMMUTABLE_ROM_EXT_SHA256_HASH"
@@ -33,11 +35,21 @@ def __init__(self, rom_ext_elf, json_data):
         self.start_offset = None
         self.size_in_bytes = None
         self.hash = None
+
         with open(self.rom_ext_elf, 'rb') as f:
             elf = elffile.ELFFile(f)
             # Find the offset of the current slot we are in.
             for symbol in elf.get_section_by_name(".symtab").iter_symbols():
-                if symbol.name == _OTTF_START_OFFSET_SYMBOL_NAME:
+                if symbol.name in [
+                    _OTTF_START_OFFSET_SYMBOL_NAME,
+                    _ROM_EXT_SATRT_OFFSET_SYMBOL_NAME,
+                ]:
+                    if self.manifest_offset is not None:
+                        raise ValueError(
+                            f"More than one manifest start address exists. "
+                            f"Current offset: {self.manifest_offset}, "
+                            f"new offset: {symbol.entry['st_value']}"
+                        )
                     self.manifest_offset = symbol.entry["st_value"]
             assert self.manifest_offset, "Manifest start address not found."
 
@@ -74,6 +86,20 @@ def insert_key_value(self, item_name: str, value: str):
                         return
                 partition["items"].append({"name": item_name, "value": value})
 
+    def get_key_value(self, item_name: str):
+        """Get the value of the item if it exists.
+        Args:
+            item_name: The name of the item to insert.
+        Returns:
+            The value of the item if found, otherwise "0x0".
+        """
+        for partition in self.json_data["partitions"]:
+            if partition["name"] == _OTP_PARTITION_NAME:
+                for item in partition["items"]:
+                    if item["name"] == item_name:
+                        return item["value"]
+        return "0x0"
+
     def update_json_with_immutable_rom_ext_section_data(self):
         """Update the JSON with the ROM_EXT immutable section data.
         Args:
@@ -86,6 +112,22 @@ def update_json_with_immutable_rom_ext_section_data(self):
         self.insert_key_value(_SIZE_FIELD_NAME, f"{hex(self.size_in_bytes)}")
         self.insert_key_value(_HASH_FIELD_NAME, f"0x{self.hash.hex()}")
 
+    def immutable_rom_ext_enable(self, hardened_true_value: int):
+        """Checks if immutable ROM extension is enabled.
+
+        This method retrieves the value of the enable field from the OTP
+        partition and compares it with the provided hardened true value.
+
+        Args:
+            hardened_true_value: The expected value for the enable field
+                                when immutable ROM extension is enabled.
+
+        Returns:
+            True if immutable ROM extension is enabled, False otherwise.
+        """
+        immutable_rom_ext_en_value = int(self.get_key_value(_ENABLE_FIELD_NAME), 0)
+        return immutable_rom_ext_en_value == hardened_true_value
+
 
 def main():
     parser = argparse.ArgumentParser(
@@ -107,6 +149,10 @@ def main():
                         type=str,
                         metavar='<path>',
                         help='Output JSON file path.')
+    parser.add_argument('--hardened-true-value',
+                        type=int,
+                        help='The integer value representing "true" for the '
+                        'enable field in the OTP partition.')
     args = parser.parse_args()
 
     # Read in the OTP fields (encoded in JSON) we will be updating.
@@ -121,7 +167,9 @@ def main():
         logging.error("Cannot find {} section in ROM_EXT ELF {}.".format(
             _ROM_EXT_IMMUTABLE_SECTION_NAME, args.elf))
         sys.exit(1)
-    imm_section_otp.update_json_with_immutable_rom_ext_section_data()
+
+    if imm_section_otp.immutable_rom_ext_enable(args.hardened_true_value):
+        imm_section_otp.update_json_with_immutable_rom_ext_section_data()
 
     # Write out the OTP fields to a JSON file.
     with open(args.output, 'w') as f: