Supporting changes for CFI toolchain features

Mostly exporting variables to Bazel, but also allowlisting a BUILD
file.

Bug: 251217226
Test: Unit tests
Change-Id: Id87015a3cd5d970700c4058ec989bb0c14c36bcb

android/allowlists/allowlists.go

@@ -388,6 +388,8 @@ var (
 		"external/protobuf":/* recursive = */ false,
 		"external/python/absl-py":/* recursive = */ true,
 
+		"external/compiler-rt/lib/cfi":/* recursive = */ false,
+
 		// this BUILD file is globbed by //external/icu/icu4c/source:icu4c_test_data's "data/**/*".
 		"external/icu/icu4c/source/data/unidata/norm2":/* recursive = */ false,
 

cc/config/global.go

@@ -313,6 +313,8 @@ var (
 		"device/",
 		"vendor/",
 	}
+
+	VersionScriptFlagPrefix = "-Wl,--version-script,"
 )
 
 // BazelCcToolchainVars generates bzl file content containing variables for
@@ -401,6 +403,8 @@ func init() {
 	exportedVars.ExportString("ExperimentalCStdVersion", ExperimentalCStdVersion)
 	exportedVars.ExportString("ExperimentalCppStdVersion", ExperimentalCppStdVersion)
 
+	exportedVars.ExportString("VersionScriptFlagPrefix", VersionScriptFlagPrefix)
+
 	// Everything in these lists is a crime against abstraction and dependency tracking.
 	// Do not add anything to this list.
 	commonGlobalIncludes := []string{

cc/linker.go

@@ -15,11 +15,12 @@
 package cc
 
 import (
-	"android/soong/android"
-	"android/soong/cc/config"
 	"fmt"
 	"path/filepath"
 
+	"android/soong/android"
+	"android/soong/cc/config"
+
 	"github.com/google/blueprint"
 	"github.com/google/blueprint/proptools"
 )
@@ -542,13 +543,13 @@ func (linker *baseLinker) linkerFlags(ctx ModuleContext, flags Flags) Flags {
 				ctx.PropertyErrorf("version_script", "Not supported on Darwin")
 			} else {
 				flags.Local.LdFlags = append(flags.Local.LdFlags,
-					"-Wl,--version-script,"+versionScript.String())
+					config.VersionScriptFlagPrefix+versionScript.String())
 				flags.LdFlagsDeps = append(flags.LdFlagsDeps, versionScript.Path())
 
 				if linker.sanitize.isSanitizerEnabled(cfi) {
-					cfiExportsMap := android.PathForSource(ctx, cfiExportsMapPath)
+					cfiExportsMap := android.PathForSource(ctx, cfiExportsMapPath+"/"+cfiExportsMapFilename)
 					flags.Local.LdFlags = append(flags.Local.LdFlags,
-						"-Wl,--version-script,"+cfiExportsMap.String())
+						config.VersionScriptFlagPrefix+cfiExportsMap.String())
 					flags.LdFlagsDeps = append(flags.LdFlagsDeps, cfiExportsMap)
 				}
 			}

cc/sanitize.go

@@ -62,14 +62,18 @@ var (
 		"-fast-isel=false",
 	}
 
-	cfiCflags = []string{"-flto", "-fsanitize-cfi-cross-dso",
-		"-fsanitize-ignorelist=external/compiler-rt/lib/cfi/cfi_blocklist.txt"}
+	cfiBlocklistPath     = "external/compiler-rt/lib/cfi"
+	cfiBlocklistFilename = "cfi_blocklist.txt"
+	cfiCflags            = []string{"-flto", "-fsanitize-cfi-cross-dso",
+		"-fsanitize-ignorelist=" + cfiBlocklistPath + "/" + cfiBlocklistFilename}
 	// -flto and -fvisibility are required by clang when -fsanitize=cfi is
 	// used, but have no effect on assembly files
 	cfiAsflags = []string{"-flto", "-fvisibility=default"}
 	cfiLdflags = []string{"-flto", "-fsanitize-cfi-cross-dso", "-fsanitize=cfi",
 		"-Wl,-plugin-opt,O1"}
-	cfiExportsMapPath = "build/soong/cc/config/cfi_exports.map"
+	cfiExportsMapPath      = "build/soong/cc/config"
+	cfiExportsMapFilename  = "cfi_exports.map"
+	cfiAssemblySupportFlag = "-fno-sanitize-cfi-canonical-jump-tables"
 
 	intOverflowCflags = []string{"-fsanitize-ignorelist=build/soong/cc/config/integer_overflow_blocklist.txt"}
 
@@ -388,6 +392,18 @@ func init() {
 	exportedVars.ExportStringListStaticVariable("HostOnlySanitizeFlags", hostOnlySanitizeFlags)
 	exportedVars.ExportStringList("DeviceOnlySanitizeFlags", deviceOnlySanitizeFlags)
 
+	// Leave out "-flto" from the slices exported to bazel, as we will use the
+	// dedicated LTO feature for this
+	exportedVars.ExportStringList("CfiCFlags", cfiCflags[1:])
+	exportedVars.ExportStringList("CfiAsFlags", cfiAsflags[1:])
+	exportedVars.ExportStringList("CfiLdFlags", cfiLdflags[1:])
+
+	exportedVars.ExportString("CfiBlocklistPath", cfiBlocklistPath)
+	exportedVars.ExportString("CfiBlocklistFilename", cfiBlocklistFilename)
+	exportedVars.ExportString("CfiExportsMapPath", cfiExportsMapPath)
+	exportedVars.ExportString("CfiExportsMapFilename", cfiExportsMapFilename)
+	exportedVars.ExportString("CfiAssemblySupportFlag", cfiAssemblySupportFlag)
+
 	android.RegisterMakeVarsProvider(pctx, cfiMakeVarsProvider)
 	android.RegisterMakeVarsProvider(pctx, hwasanMakeVarsProvider)
 }
@@ -810,7 +826,7 @@ func (s *sanitize) flags(ctx ModuleContext, flags Flags) Flags {
 		flags.Local.CFlags = append(flags.Local.CFlags, cfiCflags...)
 		flags.Local.AsFlags = append(flags.Local.AsFlags, cfiAsflags...)
 		if Bool(s.Properties.Sanitize.Config.Cfi_assembly_support) {
-			flags.Local.CFlags = append(flags.Local.CFlags, "-fno-sanitize-cfi-canonical-jump-tables")
+			flags.Local.CFlags = append(flags.Local.CFlags, cfiAssemblySupportFlag)
 		}
 		// Only append the default visibility flag if -fvisibility has not already been set
 		// to hidden.

tests/lib.sh

@@ -91,6 +91,7 @@ function create_mock_soong {
   symlink_directory prebuilts/go
   symlink_directory prebuilts/build-tools
   symlink_directory prebuilts/clang/host
+  symlink_directory external/compiler-rt
   symlink_directory external/go-cmp
   symlink_directory external/golang-protobuf
   symlink_directory external/starlark-go