Add sort_bss_symbols_by_size property for shared libs

If sort_bss_symbols_by_size is true, a shared library is built twice.
The first build generates an unsorted output file, which is used to
generate the symbol ordering file.  The output of the second build is
a shared library with its bss symbols sorted by their size.

With this, the only user of symbol_ordering_file, libc, is migrated to
use the new property, so we remove symbol_ordering_file support as well.

Bug: 135754984
Test: Build and check the resulting libc.so has its bss symbols sorted.
Change-Id: I5c892b44d82eb99cbc070cfa2c680be3087f3364

cc/library.go

@@ -110,6 +110,9 @@ type LibraryProperties struct {
 		// Symbol tags that should be ignored from the symbol file
 		Exclude_symbol_tags []string
 	}
+
+	// Order symbols in .bss section by their sizes.  Only useful for shared libraries.
+	Sort_bss_symbols_by_size *bool
 }
 
 type LibraryMutatedProperties struct {
@@ -758,6 +761,18 @@ func (library *libraryDecorator) linkShared(ctx ModuleContext,
 	linkerDeps = append(linkerDeps, deps.LateSharedLibsDeps...)
 	linkerDeps = append(linkerDeps, objs.tidyFiles...)
 
+	if Bool(library.Properties.Sort_bss_symbols_by_size) {
+		unsortedOutputFile := android.PathForModuleOut(ctx, "unsorted", fileName)
+		TransformObjToDynamicBinary(ctx, objs.objFiles, sharedLibs,
+			deps.StaticLibs, deps.LateStaticLibs, deps.WholeStaticLibs,
+			linkerDeps, deps.CrtBegin, deps.CrtEnd, false, builderFlags, unsortedOutputFile, implicitOutputs)
+
+		symbolOrderingFile := android.PathForModuleOut(ctx, "unsorted", fileName+".symbol_order")
+		symbolOrderingFlag := library.baseLinker.sortBssSymbolsBySize(ctx, unsortedOutputFile, symbolOrderingFile, builderFlags)
+		builderFlags.ldFlags += " " + symbolOrderingFlag
+		linkerDeps = append(linkerDeps, symbolOrderingFile)
+	}
+
 	TransformObjToDynamicBinary(ctx, objs.objFiles, sharedLibs,
 		deps.StaticLibs, deps.LateStaticLibs, deps.WholeStaticLibs,
 		linkerDeps, deps.CrtBegin, deps.CrtEnd, false, builderFlags, outputFile, implicitOutputs)

cc/linker.go

@@ -147,9 +147,6 @@ type BaseLinkerProperties struct {
 
 	// local file name to pass to the linker as --version_script
 	Version_script *string `android:"path,arch_variant"`
-
-	// Local file name to pass to the linker as --symbol-ordering-file
-	Symbol_ordering_file *string `android:"arch_variant"`
 }
 
 func NewBaseLinker(sanitize *sanitize) *baseLinker {
@@ -442,16 +439,6 @@ func (linker *baseLinker) linkerFlags(ctx ModuleContext, flags Flags) Flags {
 		}
 	}
 
-	if !linker.dynamicProperties.BuildStubs {
-		symbolOrderingFile := ctx.ExpandOptionalSource(
-			linker.Properties.Symbol_ordering_file, "Symbol_ordering_file")
-		if symbolOrderingFile.Valid() {
-			flags.LdFlags = append(flags.LdFlags,
-				"-Wl,--symbol-ordering-file,"+symbolOrderingFile.String())
-			flags.LdFlagsDeps = append(flags.LdFlagsDeps, symbolOrderingFile.Path())
-		}
-	}
-
 	return flags
 }
 
@@ -487,3 +474,29 @@ func (linker *baseLinker) injectVersionSymbol(ctx ModuleContext, in android.Path
 		},
 	})
 }
+
+// Rule to generate .bss symbol ordering file.
+
+var (
+	_                      = pctx.SourcePathVariable("genSortedBssSymbolsPath", "build/soong/scripts/gen_sorted_bss_symbols.sh")
+	gen_sorted_bss_symbols = pctx.AndroidStaticRule("gen_sorted_bss_symbols",
+		blueprint.RuleParams{
+			Command:     "CROSS_COMPILE=$crossCompile $genSortedBssSymbolsPath ${in} ${out}",
+			CommandDeps: []string{"$genSortedBssSymbolsPath"},
+		},
+		"crossCompile")
+)
+
+func (linker *baseLinker) sortBssSymbolsBySize(ctx ModuleContext, in android.Path, symbolOrderingFile android.ModuleOutPath, flags builderFlags) string {
+	crossCompile := gccCmd(flags.toolchain, "")
+	ctx.Build(pctx, android.BuildParams{
+		Rule:        gen_sorted_bss_symbols,
+		Description: "generate bss symbol order " + symbolOrderingFile.Base(),
+		Output:      symbolOrderingFile,
+		Input:       in,
+		Args: map[string]string{
+			"crossCompile": crossCompile,
+		},
+	})
+	return "-Wl,--symbol-ordering-file," + symbolOrderingFile.String()
+}

scripts/gen_sorted_bss_symbols.sh

@@ -0,0 +1,28 @@
+#!/bin/bash -e
+
+# Copyright 2019 Google Inc. All rights reserved.
+#
+# 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.
+
+# Script to generate a symbol ordering file that sorts bss section symbols by
+# their sizes.
+# Inputs:
+#  Environment:
+#   CROSS_COMPILE: prefix added to nm tools
+#  Arguments:
+#   $1: Input ELF file
+#   $2: Output symbol ordering file
+
+set -o pipefail
+
+${CROSS_COMPILE}nm --size-sort $1 | awk '{if ($2 == "b" || $2 == "B") print $3}' > $2