openkylin
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platform_build_soong
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Rework how linux_bionic is built with LLD 

In order to simplify the wrapper function, and stop using a linker
script, generate a set of flags to pass to LLD. Then run
host_bionic_inject on the linked binary in order to verify the
embedding, and give the wrapper function the address of the original
entry point (_start).

Bug: 31559095
Test: build host bionic with prebuilts/build-tools/build-prebuilts.sh
Change-Id: I53e326050e0f9caa562c6cf6f76c4d0337bb6faf
This commit is contained in:
Dan Willemsen 2018-10-12 00:24:23 -07:00
parent 9ff34c0ca8
commit a0790e35c7
6 changed files with 295 additions and 68 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
Android.bp
View File

@ -482,7 +482,7 @@ cc_genrule {
}
cc_genrule {
name: "host_bionic_linker_script",
name: "host_bionic_linker_flags",
host_supported: true,
device_supported: false,
target: {
@ -497,7 +497,7 @@ cc_genrule {
},
},
tools: ["extract_linker"],
cmd: "$(location) -T $(out) $(in)",
cmd: "$(location) -f $(out) $(in)",
srcs: [":linker"],
out: ["linker.script"],
out: ["linker.flags"],
}

65
cc/binary.go
View File

@ -15,6 +15,8 @@
package cc
import (
"github.com/google/blueprint"
"android/soong/android"
)
@ -154,7 +156,8 @@ func (binary *binaryDecorator) linkerDeps(ctx DepsContext, deps Deps) Deps {
}
if ctx.Os() == android.LinuxBionic && !binary.static() {
deps.LinkerScript = "host_bionic_linker_script"
deps.DynamicLinker = "linker"
deps.LinkerFlagsFile = "host_bionic_linker_flags"
}
}
@ -244,14 +247,23 @@ func (binary *binaryDecorator) linkerFlags(ctx ModuleContext, flags Flags) Flags
switch ctx.Os() {
case android.Android:
flags.DynamicLinker = "/system/bin/linker"
if flags.Toolchain.Is64Bit() {
flags.DynamicLinker += "64"
}
case android.LinuxBionic:
flags.DynamicLinker = ""
default:
ctx.ModuleErrorf("unknown dynamic linker")
}
if flags.Toolchain.Is64Bit() {
flags.DynamicLinker += "64"
}
}
if ctx.Os() == android.LinuxBionic {
// Use the dlwrap entry point, but keep _start around so
// that it can be used by host_bionic_inject
flags.LdFlags = append(flags.LdFlags,
"-Wl,--entry=__dlwrap__start",
"-Wl,--undefined=_start",
)
}
}
@ -262,7 +274,6 @@ func (binary *binaryDecorator) linkerFlags(ctx ModuleContext, flags Flags) Flags
"-Wl,--gc-sections",
"-Wl,-z,nocopyreloc",
)
}
} else {
if binary.static() {
@ -288,13 +299,15 @@ func (binary *binaryDecorator) link(ctx ModuleContext,
sharedLibs := deps.SharedLibs
sharedLibs = append(sharedLibs, deps.LateSharedLibs...)
if deps.LinkerScript.Valid() {
flags.LdFlags = append(flags.LdFlags, "-Wl,-T,"+deps.LinkerScript.String())
linkerDeps = append(linkerDeps, deps.LinkerScript.Path())
if deps.LinkerFlagsFile.Valid() {
flags.LdFlags = append(flags.LdFlags, "$$(cat "+deps.LinkerFlagsFile.String()+")")
linkerDeps = append(linkerDeps, deps.LinkerFlagsFile.Path())
}
if flags.DynamicLinker != "" {
flags.LdFlags = append(flags.LdFlags, " -Wl,-dynamic-linker,"+flags.DynamicLinker)
flags.LdFlags = append(flags.LdFlags, "-Wl,-dynamic-linker,"+flags.DynamicLinker)
} else if ctx.toolchain().Bionic() && !binary.static() {
flags.LdFlags = append(flags.LdFlags, "-Wl,--no-dynamic-linker")
}
builderFlags := flagsToBuilderFlags(flags)
@ -323,6 +336,17 @@ func (binary *binaryDecorator) link(ctx ModuleContext,
binary.injectVersionSymbol(ctx, outputFile, versionedOutputFile)
}
if ctx.Os() == android.LinuxBionic && !binary.static() {
injectedOutputFile := outputFile
outputFile = android.PathForModuleOut(ctx, "prelinker", fileName)
if !deps.DynamicLinker.Valid() {
panic("Non-static host bionic modules must have a dynamic linker")
}
binary.injectHostBionicLinkerSymbols(ctx, outputFile, deps.DynamicLinker.Path(), injectedOutputFile)
}
linkerDeps = append(linkerDeps, deps.SharedLibsDeps...)
linkerDeps = append(linkerDeps, deps.LateSharedLibsDeps...)
linkerDeps = append(linkerDeps, objs.tidyFiles...)
@ -367,3 +391,26 @@ func (binary *binaryDecorator) install(ctx ModuleContext, file android.Path) {
func (binary *binaryDecorator) hostToolPath() android.OptionalPath {
return binary.toolPath
}
func init() {
pctx.HostBinToolVariable("hostBionicSymbolsInjectCmd", "host_bionic_inject")
}
var injectHostBionicSymbols = pctx.AndroidStaticRule("injectHostBionicSymbols",
blueprint.RuleParams{
Command: "$hostBionicSymbolsInjectCmd -i $in -l $linker -o $out",
CommandDeps: []string{"$hostBionicSymbolsInjectCmd"},
}, "linker")
func (binary *binaryDecorator) injectHostBionicLinkerSymbols(ctx ModuleContext, in, linker android.Path, out android.WritablePath) {
ctx.Build(pctx, android.BuildParams{
Rule: injectHostBionicSymbols,
Description: "inject host bionic symbols",
Input: in,
Implicit: linker,
Output: out,
Args: map[string]string{
"linker": linker.String(),
},
})
}

30
cc/cc.go
View File

@ -83,7 +83,10 @@ type Deps struct {
ReexportGeneratedHeaders []string
CrtBegin, CrtEnd string
LinkerScript string
// Used for host bionic
LinkerFlagsFile string
DynamicLinker string
}
type PathDeps struct {
@ -108,7 +111,12 @@ type PathDeps struct {
// Paths to crt*.o files
CrtBegin, CrtEnd android.OptionalPath
LinkerScript android.OptionalPath
// Path to the file container flags to use with the linker
LinkerFlagsFile android.OptionalPath
// Path to the dynamic linker binary
DynamicLinker android.OptionalPath
}
type Flags struct {
@ -306,7 +314,8 @@ var (
objDepTag = dependencyTag{name: "obj"}
crtBeginDepTag = dependencyTag{name: "crtbegin"}
crtEndDepTag = dependencyTag{name: "crtend"}
linkerScriptDepTag = dependencyTag{name: "linker script"}
linkerFlagsDepTag = dependencyTag{name: "linker flags file"}
dynamicLinkerDepTag = dependencyTag{name: "dynamic linker"}
reuseObjTag = dependencyTag{name: "reuse objects"}
ndkStubDepTag = dependencyTag{name: "ndk stub", library: true}
ndkLateStubDepTag = dependencyTag{name: "ndk late stub", library: true}
@ -1062,8 +1071,11 @@ func (c *Module) DepsMutator(actx android.BottomUpMutatorContext) {
if deps.CrtEnd != "" {
actx.AddVariationDependencies(nil, crtEndDepTag, deps.CrtEnd)
}
if deps.LinkerScript != "" {
actx.AddDependency(c, linkerScriptDepTag, deps.LinkerScript)
if deps.LinkerFlagsFile != "" {
actx.AddDependency(c, linkerFlagsDepTag, deps.LinkerFlagsFile)
}
if deps.DynamicLinker != "" {
actx.AddDependency(c, dynamicLinkerDepTag, deps.DynamicLinker)
}
version := ctx.sdkVersion()
@ -1257,13 +1269,13 @@ func (c *Module) depsToPaths(ctx android.ModuleContext) PathDeps {
} else {
ctx.ModuleErrorf("module %q is not a genrule", depName)
}
case linkerScriptDepTag:
case linkerFlagsDepTag:
if genRule, ok := dep.(genrule.SourceFileGenerator); ok {
files := genRule.GeneratedSourceFiles()
if len(files) == 1 {
depPaths.LinkerScript = android.OptionalPathForPath(files[0])
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 script", depName)
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)
@ -1358,6 +1370,8 @@ func (c *Module) depsToPaths(ctx android.ModuleContext) PathDeps {
depPaths.CrtBegin = linkFile
case crtEndDepTag:
depPaths.CrtEnd = linkFile
case dynamicLinkerDepTag:
depPaths.DynamicLinker = linkFile
}
switch depTag {

69
cmd/extract_linker/main.go
View File

@ -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 script which will embed those segments as sections
// assembly file and linker flags which will embed those segments as sections
// in another binary.
package main
@ -26,38 +26,15 @@ import (
"io/ioutil"
"log"
"os"
"text/template"
"strings"
)
var linkerScriptTemplate = template.Must(template.New("linker_script").Parse(`
ENTRY(__dlwrap__start)
SECTIONS {
__dlwrap_original_start = _start;
/DISCARD/ : { *(.interp) }
{{range .}}
. = {{ printf "0x%x" .Vaddr }};
{{.Name}} : { KEEP(*({{.Name}})) }
{{end}}
.text : { *(.text .text.*) }
.rodata : { *(.rodata .rodata.* .gnu.linkonce.r.*) }
.data : { *(.data .data.* .gnu.linkonce.d.*) }
.bss : { *(.dynbss) *(.bss .bss.* .gnu.linkonce.b.*) *(COMMON) }
}
`))
type LinkerSection struct {
Name string
Vaddr uint64
}
func main() {
var asmPath string
var scriptPath string
var flagsPath string
flag.StringVar(&asmPath, "s", "", "Path to save the assembly file")
flag.StringVar(&scriptPath, "T", "", "Path to save the linker script")
flag.StringVar(&flagsPath, "f", "", "Path to save the linker flags")
flag.Parse()
f, err := os.Open(flag.Arg(0))
@ -72,19 +49,21 @@ func main() {
}
asm := &bytes.Buffer{}
fmt.Fprintln(asm, ".globl __dlwrap_linker_entry")
fmt.Fprintf(asm, ".set __dlwrap_linker_entry, 0x%x\n\n", ef.Entry)
baseLoadAddr := uint64(0x1000)
sections := []LinkerSection{}
load := 0
linkFlags := []string{}
fmt.Fprintln(asm, ".globl __dlwrap_linker_offset")
fmt.Fprintf(asm, ".set __dlwrap_linker_offset, 0x%x\n", baseLoadAddr)
for _, prog := range ef.Progs {
if prog.Type != elf.PT_LOAD {
continue
}
sectionName := fmt.Sprintf(".linker.sect%d", load)
symName := fmt.Sprintf("__dlwrap_linker_sect%d", load)
flags := ""
if prog.Flags&elf.PF_W != 0 {
flags += "w"
@ -94,10 +73,12 @@ func main() {
}
fmt.Fprintf(asm, ".section %s, \"a%s\"\n", sectionName, flags)
if load == 0 {
fmt.Fprintln(asm, ".globl __dlwrap_linker_code_start")
fmt.Fprintln(asm, "__dlwrap_linker_code_start:")
}
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))
buffer, _ := ioutil.ReadAll(prog.Open())
bytesToAsm(asm, buffer)
@ -113,11 +94,6 @@ func main() {
}
fmt.Fprintln(asm)
sections = append(sections, LinkerSection{
Name: sectionName,
Vaddr: baseLoadAddr + prog.Vaddr,
})
load += 1
}
@ -127,13 +103,10 @@ func main() {
}
}
if scriptPath != "" {
buf := &bytes.Buffer{}
if err := linkerScriptTemplate.Execute(buf, sections); err != nil {
log.Fatalf("Failed to create linker script: %v", err)
}
if err := ioutil.WriteFile(scriptPath, buf.Bytes(), 0777); err != nil {
log.Fatalf("Unable to write %q: %v", scriptPath, 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)
}
}
}

19
cmd/host_bionic_inject/Android.bp Normal file
View File

@ -0,0 +1,19 @@
// Copyright 2018 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.
blueprint_go_binary {
name: "host_bionic_inject",
deps: ["soong-symbol_inject"],
srcs: ["host_bionic_inject.go"],
}

174
cmd/host_bionic_inject/host_bionic_inject.go Normal file
View File

@ -0,0 +1,174 @@
// Copyright 2018 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.
// Verifies a host bionic executable with an embedded linker, then injects
// the address of the _start function for the linker_wrapper to use.
package main
import (
"debug/elf"
"flag"
"fmt"
"io"
"os"
"android/soong/symbol_inject"
)
func main() {
var inputFile, linkerFile, outputFile string
flag.StringVar(&inputFile, "i", "", "Input file")
flag.StringVar(&linkerFile, "l", "", "Linker file")
flag.StringVar(&outputFile, "o", "", "Output file")
flag.Parse()
if inputFile == "" || linkerFile == "" || outputFile == "" || flag.NArg() != 0 {
flag.Usage()
os.Exit(1)
}
r, err := os.Open(inputFile)
if err != nil {
fmt.Fprintln(os.Stderr, err.Error())
os.Exit(2)
}
defer r.Close()
file, err := symbol_inject.OpenFile(r)
if err != nil {
fmt.Fprintln(os.Stderr, err.Error())
os.Exit(3)
}
linker, err := elf.Open(linkerFile)
if err != nil {
fmt.Fprintln(os.Stderr, err.Error())
os.Exit(4)
}
start_addr, err := parseElf(r, linker)
if err != nil {
fmt.Fprintln(os.Stderr, err.Error())
os.Exit(5)
}
w, err := os.OpenFile(outputFile, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0777)
if err != nil {
fmt.Fprintln(os.Stderr, err.Error())
os.Exit(6)
}
defer w.Close()
err = symbol_inject.InjectUint64Symbol(file, w, "__dlwrap_original_start", start_addr)
if err != nil {
fmt.Fprintln(os.Stderr, err.Error())
os.Exit(7)
}
}
// Check the ELF file, and return the address to the _start function
func parseElf(r io.ReaderAt, linker *elf.File) (uint64, error) {
file, err := elf.NewFile(r)
if err != nil {
return 0, err
}
symbols, err := file.Symbols()
if err != nil {
return 0, err
}
for _, prog := range file.Progs {
if prog.Type == elf.PT_INTERP {
return 0, fmt.Errorf("File should not have a PT_INTERP header")
}
}
if dlwrap_start, err := findSymbol(symbols, "__dlwrap__start"); err != nil {
return 0, err
} else if dlwrap_start.Value != file.Entry {
return 0, fmt.Errorf("Expected file entry(0x%x) to point to __dlwrap_start(0x%x)",
file.Entry, dlwrap_start.Value)
}
err = checkLinker(file, linker, symbols)
if err != nil {
return 0, err
}
start, err := findSymbol(symbols, "_start")
if err != nil {
return 0, fmt.Errorf("Failed to find _start symbol")
}
return start.Value, nil
}
func findSymbol(symbols []elf.Symbol, name string) (elf.Symbol, error) {
for _, sym := range symbols {
if sym.Name == name {
return sym, nil
}
}
return elf.Symbol{}, fmt.Errorf("Failed to find symbol %q", name)
}
// Check that all of the PT_LOAD segments have been embedded properly
func checkLinker(file, linker *elf.File, fileSyms []elf.Symbol) error {
dlwrap_linker_offset, err := findSymbol(fileSyms, "__dlwrap_linker_offset")
if err != nil {
return err
}
for i, lprog := range linker.Progs {
if lprog.Type != elf.PT_LOAD {
continue
}
found := false
for j, prog := range file.Progs {
if prog.Type != elf.PT_LOAD {
continue
}
if lprog.Vaddr+dlwrap_linker_offset.Value != prog.Vaddr {
continue
}
found = true
if lprog.Memsz != prog.Memsz {
return fmt.Errorf("Linker prog %d (0x%x) memsz (0x%x) does not match (0x%x)",
i, lprog.Vaddr, lprog.Memsz, prog.Memsz)
}
// The linker shouldn't be using BSS, since only one
// BSS section is supported per ELF file.
if prog.Memsz != prog.Filesz {
return fmt.Errorf("Embedded prog %d (0x%x) memsz (0x%x) does not match filesz (0x%x)",
j, prog.Vaddr, prog.Memsz, prog.Filesz)
}
if lprog.Flags != prog.Flags {
return fmt.Errorf("Linker prog %d (0x%x) flags (%s) do not match (%s)",
i, lprog.Vaddr, lprog.Flags, prog.Flags)
}
}
if !found {
return fmt.Errorf("Linker prog %d (0x%x) not found at offset 0x%x",
i, lprog.Vaddr, dlwrap_linker_offset.Value)
}
}
return nil
}