16k: Align shared libraries and executables to 4k by default

The default ELF segment alignment will be 4096. This alignment
can be overriden by setting the desired alignment in
PRODUCT_MAX_PAGE_SIZE_SUPPORTED flag. The alignment has to be
a multiple of the configured kernel page size.

Test: Built changes for Pixel 4a, 6 and checked alignment.
Bug: 276963698
Bug: 276801883
Change-Id: Icb380041a5b27da1fa0d86b302e1e7cde9a236d7

android/config.go

@@ -176,6 +176,13 @@ func (c Config) RunningInsideUnitTest() bool {
 	return c.config.TestProductVariables != nil
 }
 
+// MaxPageSizeSupported returns the max page size supported by the device. This
+// value will define the ELF segment alignment for binaries (executables and
+// shared libraries).
+func (c Config) MaxPageSizeSupported() string {
+	return String(c.config.productVariables.DeviceMaxPageSizeSupported)
+}
+
 // A DeviceConfig object represents the configuration for a particular device
 // being built. For now there will only be one of these, but in the future there
 // may be multiple devices being built.

android/variable.go

@@ -218,6 +218,7 @@ type productVariables struct {
 	DeviceVndkVersion                     *string  `json:",omitempty"`
 	DeviceCurrentApiLevelForVendorModules *string  `json:",omitempty"`
 	DeviceSystemSdkVersions               []string `json:",omitempty"`
+	DeviceMaxPageSizeSupported            *string  `json:",omitempty"`
 
 	RecoverySnapshotVersion *string `json:",omitempty"`
 
@@ -505,6 +506,7 @@ func (v *productVariables) SetDefaultConfig() {
 		DeviceSecondaryArchVariant: stringPtr("armv8-a"),
 		DeviceSecondaryCpuVariant:  stringPtr("generic"),
 		DeviceSecondaryAbi:         []string{"armeabi-v7a", "armeabi"},
+		DeviceMaxPageSizeSupported: stringPtr("4096"),
 
 		AAPTConfig:          []string{"normal", "large", "xlarge", "hdpi", "xhdpi", "xxhdpi"},
 		AAPTPreferredConfig: stringPtr("xhdpi"),

cc/config/arm64_device.go

@@ -53,8 +53,7 @@ var (
 		"-Wl,-z,separate-code",
 	}
 
-	arm64Lldflags = append(arm64Ldflags,
+	arm64Lldflags = arm64Ldflags
-		"-Wl,-z,max-page-size=4096")
 
 	arm64Cppflags = []string{}
 
@@ -93,7 +92,13 @@ var (
 
 func init() {
 	exportedVars.ExportStringListStaticVariable("Arm64Ldflags", arm64Ldflags)
-	exportedVars.ExportStringListStaticVariable("Arm64Lldflags", arm64Lldflags)
+
+	exportedVars.ExportStringList("Arm64Lldflags", arm64Lldflags)
+	pctx.VariableFunc("Arm64Lldflags", func(ctx android.PackageVarContext) string {
+		maxPageSizeFlag := "-Wl,-z,max-page-size=" + ctx.Config().MaxPageSizeSupported()
+		flags := append(arm64Lldflags, maxPageSizeFlag)
+		return strings.Join(flags, " ")
+	})
 
 	exportedVars.ExportStringListStaticVariable("Arm64Cflags", arm64Cflags)
 	exportedVars.ExportStringListStaticVariable("Arm64Cppflags", arm64Cppflags)

cc/config/arm_device.go

@@ -185,7 +185,12 @@ func init() {
 	exportedVars.ExportString("ArmClangTriple", clangTriple)
 
 	exportedVars.ExportStringListStaticVariable("ArmLdflags", armLdflags)
-	exportedVars.ExportStringListStaticVariable("ArmLldflags", armLldflags)
+	exportedVars.ExportStringList("ArmLldflags", armLldflags)
+	pctx.VariableFunc("ArmLldflags", func(ctx android.PackageVarContext) string {
+		maxPageSizeFlag := "-Wl,-z,max-page-size=" + ctx.Config().MaxPageSizeSupported()
+		flags := append(armLldflags, maxPageSizeFlag)
+		return strings.Join(flags, " ")
+	})
 
 	exportedVars.ExportStringListStaticVariable("ArmFixCortexA8LdFlags", armFixCortexA8LdFlags)
 	exportedVars.ExportStringListStaticVariable("ArmNoFixCortexA8LdFlags", armNoFixCortexA8LdFlags)