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#!/usr/bin/env python
#
# Copyright (C) 2024 The Android Open Source Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
"""Utils to determine whether to enable UFFD GC."""
import re
import sys
def should_enable_uffd_gc(kernel_version_file):
with open(kernel_version_file, 'r') as f:
kernel_version = f.read().strip()
return should_enable_uffd_gc_impl(kernel_version)
def should_enable_uffd_gc_impl(kernel_version):
# See https://source.android.com/docs/core/architecture/kernel/gki-versioning#determine-release
p = r"^(?P<w>\d+)[.](?P<x>\d+)[.](?P<y>\d+)(-android(?P<z>\d+)-(?P<k>\d+).*$)?"
m = re.match(p, kernel_version)
if m is not None:
if m.group('z') is not None:
android_release = int(m.group('z'))
# No need to check w, x, y because all Android 12 kernels have backports.
return android_release >= 12
else:
# Old kernel or non-GKI kernel.
version = int(m.group('w'))
patch_level = int(m.group('x'))
if version < 5:
# Old kernel.
return False
elif (version == 5 and patch_level >= 7) or version >= 6:
# New non-GKI kernel. 5.7 supports MREMAP_DONTUNMAP without the need for
# backports.
return True
else:
# Non-GKI kernel between 5 and 5.6. It may have backports.
raise exit_with_error(kernel_version)
elif kernel_version == '<unknown-kernel>':
# The kernel information isn't available to the build system, probably
# because PRODUCT_OTA_ENFORCE_VINTF_KERNEL_REQUIREMENTS is set to false. We
# assume that the kernel supports UFFD GC because it is the case for most of
# the products today and it is the future.
return True
else:
# Unrecognizable non-GKI kernel.
raise exit_with_error(kernel_version)
def exit_with_error(kernel_version):
sys.exit(f"""
Unable to determine UFFD GC flag for kernel version "{kernel_version}".
You can fix this by explicitly setting PRODUCT_ENABLE_UFFD_GC to "true" or
"false" based on the kernel version.
1. Set PRODUCT_ENABLE_UFFD_GC to "true" if the kernel supports userfaultfd(2)
and MREMAP_DONTUNMAP.
2. Set PRODUCT_ENABLE_UFFD_GC to "false" otherwise.""")
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