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Commit 9cfe6119 authored by Colin Cross's avatar Colin Cross
Browse files

Use a linker script for host bionic embedded linker sections 

Use an implicit linker script instead of flags in a file to specify
the locations of the host bionic embedded linker and to prevent it
from being stripped.

Test: build and run host bionic binary
Change-Id: I64e12118d33c67bab5e657cbc3ea8cde8f0fd7e6
parent cef792e4

Android.bp

+3 −3
Original line number Diff line number Diff line
@@ -92,7 +92,7 @@ cc_genrule { 
}



cc_genrule {

    name: "host_bionic_linker_flags",

    name: "host_bionic_linker_script",

    host_supported: true,

    device_supported: false,

    target: {
@@ -107,9 +107,9 @@ cc_genrule { 
        },

    },

    tools: ["extract_linker"],

    cmd: "$(location) -f $(out) $(in)",

    cmd: "$(location) -T $(out) $(in)",

    srcs: [":linker"],

    out: ["linker.flags"],

    out: ["linker.script"],

}



// Instantiate the dex_bootjars singleton module.

cc/binary.go

+1 −7
Original line number Diff line number Diff line
@@ -178,7 +178,7 @@ func (binary *binaryDecorator) linkerDeps(ctx DepsContext, deps Deps) Deps { 
		// the kernel before jumping to the embedded linker.

		if ctx.Os() == android.LinuxBionic && !binary.static() {

			deps.DynamicLinker = "linker"

			deps.LinkerFlagsFile = "host_bionic_linker_flags"

			deps.CrtBegin = append(deps.CrtBegin, "host_bionic_linker_script")

		}

	}
@@ -345,12 +345,6 @@ func (binary *binaryDecorator) link(ctx ModuleContext, 


	var linkerDeps android.Paths



	// Add flags from linker flags file.

	if deps.LinkerFlagsFile.Valid() {

		flags.Local.LdFlags = append(flags.Local.LdFlags, "$$(cat "+deps.LinkerFlagsFile.String()+")")

		linkerDeps = append(linkerDeps, deps.LinkerFlagsFile.Path())

	}



	if flags.DynamicLinker != "" {

		flags.Local.LdFlags = append(flags.Local.LdFlags, "-Wl,-dynamic-linker,"+flags.DynamicLinker)

	} else if ctx.toolchain().Bionic() && !binary.static() {

cc/cc.go

+1 −20
Original line number Diff line number Diff line
@@ -129,7 +129,6 @@ type Deps struct { 
	CrtBegin, CrtEnd []string



	// Used for host bionic

	LinkerFlagsFile string

	DynamicLinker string



	// List of libs that need to be excluded for APEX variant
@@ -179,9 +178,6 @@ type PathDeps struct { 
	// Paths to crt*.o files

	CrtBegin, CrtEnd android.Paths



	// Path to the file container flags to use with the linker

	LinkerFlagsFile android.OptionalPath



	// Path to the dynamic linker binary

	DynamicLinker android.OptionalPath

}
@@ -717,7 +713,6 @@ var ( 
	genHeaderDepTag       = dependencyTag{name: "gen header"}

	genHeaderExportDepTag = dependencyTag{name: "gen header export"}

	objDepTag             = dependencyTag{name: "obj"}

	linkerFlagsDepTag     = dependencyTag{name: "linker flags file"}

	dynamicLinkerDepTag   = installDependencyTag{name: "dynamic linker"}

	reuseObjTag           = dependencyTag{name: "reuse objects"}

	staticVariantTag      = dependencyTag{name: "static variant"}
@@ -2254,9 +2249,6 @@ func (c *Module) DepsMutator(actx android.BottomUpMutatorContext) { 
		actx.AddVariationDependencies(crtVariations, CrtEndDepTag,

			RewriteSnapshotLib(crt, GetSnapshot(c, &snapshotInfo, actx).Objects))

	}

	if deps.LinkerFlagsFile != "" {

		actx.AddDependency(c, linkerFlagsDepTag, deps.LinkerFlagsFile)

	}

	if deps.DynamicLinker != "" {

		actx.AddDependency(c, dynamicLinkerDepTag, deps.DynamicLinker)

	}
@@ -2555,17 +2547,6 @@ func (c *Module) depsToPaths(ctx android.ModuleContext) PathDeps { 
				} else {

					ctx.ModuleErrorf("module %q is not a genrule", depName)

				}

			case linkerFlagsDepTag:

				if genRule, ok := dep.(genrule.SourceFileGenerator); ok {

					files := genRule.GeneratedSourceFiles()

					if len(files) == 1 {

						depPaths.LinkerFlagsFile = android.OptionalPathForPath(files[0])

					} else if len(files) > 1 {

						ctx.ModuleErrorf("module %q can only generate a single file if used for a linker flag file", depName)

					}

				} else {

					ctx.ModuleErrorf("module %q is not a genrule", depName)

				}

			case CrtBeginDepTag:

				depPaths.CrtBegin = append(depPaths.CrtBegin, android.OutputFileForModule(ctx, dep, ""))

			case CrtEndDepTag:

cc/testing.go

+2 −2
Original line number Diff line number Diff line
@@ -490,7 +490,7 @@ func withLinuxBionic() string { 
				}



				cc_genrule {

					name: "host_bionic_linker_flags",

					name: "host_bionic_linker_script",

					host_supported: true,

					device_supported: false,

					target: {
@@ -501,7 +501,7 @@ func withLinuxBionic() string { 
							enabled: true,

						},

					},

					out: ["linker.flags"],

					out: ["linker.script"],

				}



				cc_defaults {

cmd/extract_linker/main.go

+16 −12
Original line number Diff line number Diff line
@@ -13,7 +13,7 @@ 
// limitations under the License.



// This tool extracts ELF LOAD segments from our linker binary, and produces an

// assembly file and linker flags which will embed those segments as sections

// assembly file and linker script which will embed those segments as sections

// in another binary.

package main
@@ -31,10 +31,10 @@ import ( 


func main() {

	var asmPath string

	var flagsPath string

	var scriptPath string



	flag.StringVar(&asmPath, "s", "", "Path to save the assembly file")

	flag.StringVar(&flagsPath, "f", "", "Path to save the linker flags")

	flag.StringVar(&scriptPath, "T", "", "Path to save the linker script")

	flag.Parse()



	f, err := os.Open(flag.Arg(0))
@@ -49,13 +49,16 @@ func main() { 
	}



	asm := &bytes.Buffer{}

	script := &bytes.Buffer{}

	baseLoadAddr := uint64(0x1000)

	load := 0

	linkFlags := []string{}



	fmt.Fprintln(asm, ".globl __dlwrap_linker_offset")

	fmt.Fprintf(asm, ".set __dlwrap_linker_offset, 0x%x\n", baseLoadAddr)



	fmt.Fprintln(script, "ENTRY(__dlwrap__start)")

	fmt.Fprintln(script, "SECTIONS {")



	for _, prog := range ef.Progs {

		if prog.Type != elf.PT_LOAD {

			continue
@@ -82,10 +85,9 @@ func main() { 


		fmt.Fprintf(asm, ".globl %s\n%s:\n\n", symName, symName)



		linkFlags = append(linkFlags,

			fmt.Sprintf("-Wl,--undefined=%s", symName),

			fmt.Sprintf("-Wl,--section-start=%s=0x%x",

				sectionName, baseLoadAddr+prog.Vaddr))

		fmt.Fprintf(script, "  %s %d : {\n", sectionName, baseLoadAddr+prog.Vaddr)

		fmt.Fprintf(script, "    KEEP(*(%s));\n", sectionName)

		fmt.Fprintln(script, "  }")



		buffer, _ := ioutil.ReadAll(prog.Open())

		bytesToAsm(asm, buffer)
@@ -104,16 +106,18 @@ func main() { 
		load += 1

	}



	fmt.Fprintln(script, "}")

	fmt.Fprintln(script, "INSERT BEFORE .note.android.ident;")



	if asmPath != "" {

		if err := ioutil.WriteFile(asmPath, asm.Bytes(), 0777); err != nil {

			log.Fatalf("Unable to write %q: %v", asmPath, err)

		}

	}



	if flagsPath != "" {

		flags := strings.Join(linkFlags, " ")

		if err := ioutil.WriteFile(flagsPath, []byte(flags), 0777); err != nil {

			log.Fatalf("Unable to write %q: %v", flagsPath, err)

	if scriptPath != "" {

		if err := ioutil.WriteFile(scriptPath, script.Bytes(), 0777); err != nil {

			log.Fatalf("Unable to write %q: %v", scriptPath, err)

		}

	}

}