From 43a3c1c42abbc4163167467bec6d6821a1dbaf7a Mon Sep 17 00:00:00 2001
From: Aetias <aetias@outlook.com>
Date: Sun, 17 Sep 2023 12:25:20 +0200
Subject: [PATCH] Fix BLX Thumb-to-ARM bug in the assembler

---
 INSTALL.md          |  4 ++--
 tools/patch_mwcc.py | 51 +++++++++++++++++++++++++++++++++++++++++++++
 tools/setup.py      |  5 +++++
 3 files changed, 58 insertions(+), 2 deletions(-)
 create mode 100644 tools/patch_mwcc.py

diff --git a/INSTALL.md b/INSTALL.md
index de15e803..0a8f74a2 100644
--- a/INSTALL.md
+++ b/INSTALL.md
@@ -6,10 +6,10 @@ Contents:
 
 ## Prerequisites
 
-1. Install Python 3.7 or higher
+1. Install Python 3.11 or higher
 2. Install the Python dependencies:
 ```shell
-python3 -m pip install -r tools/requirements.txt
+python -m pip install -r tools/requirements.txt
 ```
 3. Run the setup script:
 ```shell
diff --git a/tools/patch_mwcc.py b/tools/patch_mwcc.py
new file mode 100644
index 00000000..199030d7
--- /dev/null
+++ b/tools/patch_mwcc.py
@@ -0,0 +1,51 @@
+import hashlib
+import sys
+
+class Patch:
+    def __init__(self, name: str, version: str, sha1: str, desc: str, offset: int, write: list[int]) -> None:
+        self.name = name
+        self.version = version
+        self.sha1 = sha1
+        self.desc = desc
+        self.offset = offset
+        self.write = write
+
+VERSION = '1.0'
+PATCHES = [
+    Patch(
+        'mwasmarm', '2.0/sp1p5', '448cb0c7f1ace4393e9a9562f819f7a9f049be83',
+        'Fix 2-aligned Thumb BLX where ARM call target was off by 1',
+        offset=0x1b45b, write=[0xc2]
+    ),
+]
+
+if len(sys.argv) != 2:
+    print(f'patch_mwcc {VERSION}')
+    print()
+    print(f'Usage: {sys.argv[0]} <exe>')
+    print('    <exe>\tPath to mwasmarm.exe')
+    exit()
+
+filename = sys.argv[1]
+
+with open(filename, 'rb', buffering=0) as file:
+    sha1 = hashlib.file_digest(file, 'sha1').hexdigest()
+    file.seek(0, 2)
+    length = file.tell()
+    file.seek(0, 0)
+    file_bytes = bytearray(file.read(length))
+
+num_patches = 0
+for patch in PATCHES:
+    if sha1 == patch.sha1:
+        num_patches += 1
+        print(f'{patch.name} version {patch.version}')
+        print(patch.desc)
+        for i in range(len(patch.write)):
+            file_bytes[patch.offset + i] = patch.write[i]
+        print()
+
+with open(filename, 'wb') as file:
+    file.write(file_bytes)
+
+print(f'Applied {num_patches} patch(es)')
diff --git a/tools/setup.py b/tools/setup.py
index 34f11787..e11daa23 100644
--- a/tools/setup.py
+++ b/tools/setup.py
@@ -2,10 +2,15 @@ import requests
 import zipfile
 import io
 from pathlib import Path
+import subprocess
+import sys
 
 tools_path = Path(__file__).parent
 
+print('\nInstalling toolchain...')
 response = requests.get('https://cdn.discordapp.com/attachments/698589325620936736/845499146982129684/mwccarm.zip')
 zip_file = zipfile.ZipFile(io.BytesIO(response.content))
 zip_file.extractall(tools_path)
 
+print('\nPatching...')
+subprocess.run([sys.executable, 'patch_mwcc.py', 'mwccarm/2.0/sp1p5/mwasmarm.exe'], cwd=tools_path)