Build targets for checking GKI KMI compatibility

Current/latest kernel symbol information files default to:
- kernel/prebuilts/5.4/arm64/Module.symvers (for GKI 5.4)
- kernel/prebuilts/5.10/arm64/vmlinux.symvers (for GKI 5.10)

All kernel symbol information files in this CL are manually copied
from AB of corresponding kernel branches.

The history kernel symbol information files in this CL are
sym-5.*/ directories. The ones without build ID suffix are
symbolic links to the latest ones and can be used for
testing the build test of this CL (see Test below).

After *.symvers diles are released to kernel/prebuilts/5.*/arm64
directories on the Android branch, they will be used as the
current/latest kernel symbol files by default.

3 moudules are created in this CL:
  gki_5_4_kmi_compatibility_test (for arm64 GKI 5.4)
  gki_5_10_kmi_compatibility_test (for arm64 GKI 5.10)
  gki_kmi_compatibility_test (for both arm64 GKI 5.4 & 5.10)

Bug: 206064990
Test: $ m gki_kmi_compatibility_test
Change-Id: I2e966070a392cfd6284676c7598138b5cad4717b

gki/Android.mk

@@ -0,0 +1,21 @@
+#
+# Copyright 2021 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.
+#
+
+LOCAL_PATH := $(call my-dir)
+
+gki_path := $(LOCAL_PATH)
+
+include $(gki_path)/kmi_abi_chk/kmi_compatibility_test.mk

gki/OWNERS

@@ -0,0 +1,3 @@
+howardsoc@google.com
+hsinyichen@google.com
+ycchen@google.com

gki/kmi_abi_chk/kmi_compatibility_test.mk

@@ -0,0 +1,62 @@
+# Copyright (C) 2021 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.
+LOCAL_PATH := $(call my-dir)
+
+KMI_CHK_SCRIPT := $(LOCAL_PATH)/kmi_compatibility_test.sh
+
+# Current kernel symbol files to be checked
+# Use the one under $(LOCAL_PATH)/sym-5.* by default for self testing.
+# The reason not to use the one under kernel/prebuilts/5.* by default
+# is because the KMI ABI may not be stable during development.
+#
+# Set CURR_5_4_SYMVERS/CURR_5_10_SYMVERS explicitly for the actual
+# current kernel symbol file to be checked. E.g.,
+# $ m CURR_5_10_SYMVERS=kernel/prebuilts/5.10/arm64/vmlinux.symvers \
+#     gki_5_10_kmi_compatibility_test
+CURR_5_4_SYMVERS ?= development/gki/kmi_abi_chk/sym-5.4/Module.symvers
+CURR_5_10_SYMVERS ?= development/gki/kmi_abi_chk/sym-5.10/vmlinux.symvers
+
+# Previous kernel symbol files, against which the latest one is checked
+# The file names of previous kernel symbol files are of this form:
+#     *.symvers-$(BID)
+# Here *.symvers is a symbolic link to the latest build.
+PREV_5_4_SYMVERS := $(LOCAL_PATH)/sym-5.4/Module.symvers
+PREV_5_10_SYMVERS := $(LOCAL_PATH)/sym-5.10/vmlinux.symvers
+
+include $(CLEAR_VARS)
+LOCAL_MODULE := gki_5_4_kmi_compatibility_test
+LOCAL_MODULE_CLASS := FAKE
+LOCAL_MODULE_TAGS := optional
+include $(BUILD_SYSTEM)/base_rules.mk
+
+$(LOCAL_BUILT_MODULE): $(KMI_CHK_SCRIPT) $(CURR_5_4_SYMVERS) $(PREV_5_4_SYMVERS)
+	@mkdir -p $(dir $@)
+	$(hide) $(KMI_CHK_SCRIPT) $(CURR_5_4_SYMVERS) $(PREV_5_4_SYMVERS)
+	$(hide) touch $@
+
+include $(CLEAR_VARS)
+LOCAL_MODULE := gki_5_10_kmi_compatibility_test
+LOCAL_MODULE_CLASS := FAKE
+LOCAL_MODULE_TAGS := optional
+include $(BUILD_SYSTEM)/base_rules.mk
+
+$(LOCAL_BUILT_MODULE): $(KMI_CHK_SCRIPT) $(CURR_5_10_SYMVERS) $(PREV_5_10_SYMVERS)
+	@mkdir -p $(dir $@)
+	$(hide) $(KMI_CHK_SCRIPT) $(CURR_5_10_SYMVERS) $(PREV_5_10_SYMVERS)
+	$(hide) touch $@
+
+include $(CLEAR_VARS)
+LOCAL_MODULE := gki_kmi_compatibility_test
+LOCAL_REQUIRED_MODULES := gki_5_4_kmi_compatibility_test gki_5_10_kmi_compatibility_test
+include $(BUILD_PHONY_PACKAGE)

gki/kmi_abi_chk/kmi_compatibility_test.sh

@@ -0,0 +1,78 @@
+#!/bin/bash
+
+# Copyright (C) 2021 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.
+
+# Usage:
+#   development/gki/kmi_abi_chk/kmi_static_chk.sh \
+#     <current_symbol_info> <previous_symbol_info> ...
+#
+if [[ "$#" -lt 2 ]]; then
+  echo "Usage: $0 <current_symbol_info> <previous_symbol_info> ..."
+  exit 1
+fi
+
+ret=0
+for f in "$@"; do
+  if [[ ! -e "$f" ]]; then
+    echo "Kernel symbol file $f does not exist!" >&2
+    ret=1
+  elif ! grep -iE "^0x[0-9a-f]{8}+.[_0-9a-z]+.vmlinux.EXPORT_SYMBOL" $f > /dev/null; then
+    ret=1
+    echo "$f doesn't look like kernel symbol file!" >&2
+  fi
+done
+
+if [[ ! ret -eq 0 ]]; then
+  exit $ret
+fi
+
+tmp=$(mktemp /tmp/linux-symvers.XXXXXX)
+trap "rm -f $tmp" EXIT
+
+curr=$1
+shift
+
+# Filter for vmlinux EXPORTE_SYMBOL* and remove trailing white spaces.
+# The reason trailing white spaces is removed only for the current
+# symbol file is because the following example/possibility:
+#
+# In the current symbol file:
+# 0x8581ad8e	get_net_ns_by_fd	vmlinux	EXPORT_SYMBOL\t
+#
+# In the previous symbol file:
+# 0x8581ad8e	get_net_ns_by_fd	vmlinux	EXPORT_SYMBOL_GPL\t
+#
+# The symbol is GPLed previously, but not in the current release, which won't
+# break KMI ABI, because the requirement is "relaxed". We want this case to
+# pass so a keyword like "...EXPORT_SYMBOL" in the current symbol file can
+# still match "...EXPORT_SYMBOL_GPL" in the previous symbol file.
+grep "vmlinux.EXPORT_SYMBOL" $curr | sed 's/[ \t]*$//' > $tmp
+
+echo "Current kernel symbol file, $curr, is checking against:"
+
+for f in "$@"; do
+  echo "	$f"
+# if nothing is found, grep returns 1, which means every symbol in the
+# previous release (usually in *.symvers-$BID) can be found in the current
+# release, so is considered successful here.
+# if grep returns 0, which means some symbols are found in the previous
+# symbol file but not in the current symbol file, then something wrong!
+  if grep -vf $tmp $f; then
+    ret=1
+    echo "$f contains symbol(s) not found in, or incompatible with, $curr." >&2
+  fi
+done
+
+exit $ret

gki/kmi_abi_chk/sym-5.10/vmlinux.symvers

@@ -0,0 +1 @@
+vmlinux.symvers-7833008

gki/kmi_abi_chk/sym-5.4/Module.symvers

@@ -0,0 +1 @@
+Module.symvers-7855344