From ed5b14ee233de198ddd7e0c1952a7869e1ddbb9f Mon Sep 17 00:00:00 2001
From: Felix Conway <felix.conway@arm.com>
Date: Tue, 29 Jul 2025 12:09:16 +0100
Subject: [PATCH] Use math.gcd() instead of custom function

Signed-off-by: Felix Conway <felix.conway@arm.com>
---
 scripts/generate_bignum_tests.py           | 7 ++++---
 scripts/mbedtls_framework/bignum_common.py | 7 -------
 2 files changed, 4 insertions(+), 10 deletions(-)

diff --git a/scripts/generate_bignum_tests.py b/scripts/generate_bignum_tests.py
index 17ee1bfde..e363c2968 100755
--- a/scripts/generate_bignum_tests.py
+++ b/scripts/generate_bignum_tests.py
@@ -43,6 +43,7 @@ of BaseTarget in test_data_generation.py.
 # SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
 
 import sys
+import math
 
 from abc import ABCMeta
 from typing import List
@@ -188,9 +189,9 @@ class BignumInvMod(BignumOperation):
 
     def __init__(self, val_a: str, val_b: str) -> None:
         super().__init__(val_a, val_b)
-        try:
+        if math.gcd(self.int_a, self.int_b) == 1:
             self._result = bignum_common.invmod_positive(self.int_a, self.int_b)
-        except ValueError:
+        else:
             self._result = -1 # No modular inverse.
 
     def description_suffix(self) -> str:
@@ -264,7 +265,7 @@ class BignumGCD(BignumOperation):
     def __init__(self, val_a: str, val_b: str) -> None:
         super().__init__(val_a, val_b)
         # We always expect a positive result.
-        self._result = abs(bignum_common.gcd(self.int_a, self.int_b))
+        self._result = math.gcd(self.int_a, self.int_b)
 
     def description_suffix(self) -> str:
         suffix = ": "
diff --git a/scripts/mbedtls_framework/bignum_common.py b/scripts/mbedtls_framework/bignum_common.py
index 8bc6a9dd3..58a76a171 100644
--- a/scripts/mbedtls_framework/bignum_common.py
+++ b/scripts/mbedtls_framework/bignum_common.py
@@ -30,13 +30,6 @@ def invmod(a: int, n: int) -> int:
         return b
     raise ValueError("Not invertible")
 
-def gcd(a: int, b: int) -> int:
-    """Return the greatest common divisor of two numbers.
-       The result will match the sign of b."""
-    while b:
-        a, b = b, a % b
-    return a
-
 def invmod_positive(a: int, n: int) -> int:
     """Return a non-negative inverse of a to modulo n.