diff --git a/coverage-tool/coverage-reporting/intermediate_layer.py b/coverage-tool/coverage-reporting/intermediate_layer.py
index 55474b91eaa9aa10809ee93f8c87c91be3408e5d..21ba356666508c68efa449fdc9d212f2fa404d76 100644
--- a/coverage-tool/coverage-reporting/intermediate_layer.py
+++ b/coverage-tool/coverage-reporting/intermediate_layer.py
@@ -1,6 +1,6 @@
 # !/usr/bin/env python
 ###############################################################################
-# Copyright (c) 2020-2023, ARM Limited and Contributors. All rights reserved.
+# Copyright (c) 2020-2025, ARM Limited and Contributors. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 ###############################################################################
@@ -29,6 +29,8 @@ from typing import Generator
 from typing import Union
 from typing import Tuple
 import logging
+import sys
+from collections import defaultdict
 
 __version__ = "7.0"
 
@@ -218,10 +220,6 @@ def get_function_line_numbers(source_file: str) -> Dict[str, int]:
     except BaseException:
         logger.warning("Warning: Can't get all function line numbers from %s" %
                        source_file)
-    except Exception as ex:
-        logger.warning(f"Warning: Unknown error '{ex}' when executing command "
-                       f"'{command}'")
-        return {}
     return fln
 
 
@@ -564,6 +562,24 @@ class CoverageHandler(object):
         return self._source_files
 
 
+IDENTIFIER = re.compile(r'\b[A-Za-z_]\w*\b')
+
+def identifiers(filename):
+    with open(filename) as f:
+        for line in f:
+            for match in IDENTIFIER.finditer(line):
+                yield match.group()
+
+def locate_identifiers(ids, filenames):
+    """Map each identifier to the set of files in which it appears."""
+    result = defaultdict(set)
+    for filename in filenames:
+        for s in identifiers(filename):
+            if s in ids:
+                result[s].add(filename)
+    return result
+
+
 class IntermediateCodeCoverage(object):
     """Class used to process the trace data along with the dwarf
     signature files to produce an intermediate layer in json with
@@ -595,6 +611,7 @@ class IntermediateCodeCoverage(object):
         self.elf_map = {}
         # For elf custom mappings
         self.elf_custom = None
+        self.found_source_files = None
 
     def process(self):
         """
@@ -690,6 +707,15 @@ class IntermediateCodeCoverage(object):
         self._process_fn_no_sources(parser)
         return parser
 
+    def find_source_files(self):
+        # Cache the list of .c, .s and .S files found in the local workspace.
+        if self.found_source_files is None:
+            self.found_source_files = [sys.intern(f) for f in subprocess.check_output([
+                'find', self.local_workspace,
+                '(', '-name', '*.c', '-o', '-name', '*.s', '-o', '-name', '*.S', ')',
+                '-type', 'f', '-print0']).decode('utf-8').rstrip('\0').split('\0')]
+        return self.found_source_files
+
     def _process_fn_no_sources(self, parser: BinaryParser):
         """
         Checks function coverage for functions with no dwarf signature i.e.
@@ -705,17 +731,14 @@ class IntermediateCodeCoverage(object):
         traces_address_pointer = 0
         _functions = parser.no_source_functions
         functions_addresses = sorted(_functions.keys())
+        function_names = [v['name'] for v in _functions.values()]
+        hits = locate_identifiers(function_names, self.find_source_files())
         address_size = 4
         for start_address in functions_addresses:
             function_covered = False
             function_name = _functions[start_address]['name']
             # Get all files in the source code where the function is defined
-            source_files = os_command("grep --include '*.c' --include '*.s' "
-                                      "--include '*.S' -nrw '{}' {}"
-                                      "| cut -d: -f1".
-                                      format(function_name,
-                                             self.local_workspace))
-            unique_files = set(source_files.split())
+            unique_files = hits[function_name]
             sources_found = []
             for source_file in unique_files:
                 line_number = parser.function_line_numbers.get_line_number(