Patch wrong tls alignment for Android Q compatibility (fixes #370) (#374

)

* Patch go wrong tls alignment for Android Q compatibility (fixes #370)

* Remove wrong x86 patch

* Incorporate @kvaster's Android Q patch into build script (fixes #370)

Thanks for the contributon!

* Update build script for Python 2 compatibility

* Second attempt for python 2

syncthing/build-syncthing.py

@@ -22,12 +22,14 @@
         'goarch': 'arm',
         'jni_dir': 'armeabi',
         'cc': 'arm-linux-androideabi-clang',
+        'patch_underaligned_tls': 'yes',
     },
     {
         'arch': 'arm64',
         'goarch': 'arm64',
         'jni_dir': 'arm64-v8a',
         'cc': 'aarch64-linux-android-clang',
+        'patch_underaligned_tls': 'yes',
         'min_sdk': 21,
     },
     {
@@ -247,6 +249,55 @@ def install_ndk():
     os.environ["ANDROID_NDK_HOME"] = ndk_home_path
 
 
+def artifact_patch_underaligned_tls(artifact_fullfn):
+    import struct
+
+    with open(artifact_fullfn, 'r+b') as f:
+        f.seek(0)
+        hdr = struct.unpack('16c', f.read(16))
+        if hdr[0] != b'\x7f' or hdr[1] != b'E' or hdr[2] != b'L' or hdr[3] != b'F':
+            print('artifact_patch_underaligned_tls: Not an ELF file')
+            return None
+
+        if hdr[4] == b'\x01':
+            # 32 bit code
+            f.seek(28)
+            offset = struct.unpack('<I', f.read(4))[0]
+            f.seek(42)
+            phsize = struct.unpack('<H', f.read(2))[0]
+            phnum = struct.unpack('<H', f.read(2))[0]
+            for i in range(0, phnum):
+                f.seek(offset + i * phsize)
+                t = struct.unpack('<I', f.read(4))[0]
+                if t == 7:
+                    f.seek(28 - 4, 1)
+                    align = struct.unpack('<I', f.read(4))[0]
+                    if (align < 32):
+                        print('artifact_patch_underaligned_tls: Patching underaligned TLS segment from ' + str(align) + ' to 32')
+                        f.seek(-4, 1)
+                        f.write(struct.pack('<I', 32))
+
+        elif hdr[4] == b'\x02':
+            # 64 bit code
+            f.seek(32)
+            offset = struct.unpack('<Q', f.read(8))[0]
+            f.seek(54)
+            phsize = struct.unpack('<H', f.read(2))[0]
+            phnum = struct.unpack('<H', f.read(2))[0]
+            for i in range(0, phnum):
+                f.seek(offset + i * phsize)
+                t = struct.unpack('<I', f.read(4))[0]
+                if t == 7:
+                    f.seek(48 - 4, 1)
+                    align = struct.unpack('<Q', f.read(8))[0]
+                    if (align < 64):
+                        print('artifact_patch_underaligned_tls: Patching underaligned TLS segment from ' + str(align) + ' to 64')
+                        f.seek(-8, 1)
+                        f.write(struct.pack('<H', 64))
+
+        else:
+            print('artifact_patch_underaligned_tls: Unknown ELF file class')
+
 
 #
 # BUILD SCRIPT MAIN.
@@ -313,6 +364,7 @@ def install_ndk():
     '--always'
 ]).strip();
 syncthingVersion = syncthingVersion.decode().replace("rc", "preview");
+print('Building syncthing version', syncthingVersion);
 
 for target in BUILD_TARGETS:
     target_min_sdk = str(target.get('min_sdk', min_sdk))
@@ -349,14 +401,23 @@ def install_ndk():
         'CGO_ENABLED': '1',
     })
 
-    print('Building syncthing version', syncthingVersion);
     subprocess.check_call([go_bin, 'mod', 'download'], cwd=syncthing_dir)
     subprocess.check_call([
                               go_bin, 'run', 'build.go', '-goos', 'android', '-goarch', target['goarch'],
                               '-cc', os.path.join(standalone_ndk_dir, 'bin', target['cc']),
                               '-version', syncthingVersion
                           ] + pkg_argument + ['-no-upgrade', 'build'], env=environ, cwd=syncthing_dir)
 
+    # Determine path of source artifact
+    source_artifact = os.path.join(syncthing_dir, 'syncthing')
+
+    # Patch artifact to work around golang bug.
+    # See issues:
+    # - https://github.com/Catfriend1/syncthing-android/issues/370
+    # - https://github.com/golang/go/issues/29674
+    if 'patch_underaligned_tls' in target:
+        artifact_patch_underaligned_tls(source_artifact)
+
     # Copy compiled binary to jniLibs folder
     target_dir = os.path.join(project_dir, 'app', 'src', 'main', 'jniLibs', target['jni_dir'])
     if not os.path.isdir(target_dir):