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[dev.link] cmd: support large function alignment

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This ports CL 226997 to the dev.link branch.
- The assembler part and old object file writing are unchanged.
- Changes to cmd/link are applied to cmd/oldlink.
- Add alignment field to new object files for the new linker.

Change-Id: Id00f323ae5bdd86b2709a702ee28bcaa9ba962f8
Reviewed-on: https://go-review.googlesource.com/c/go/+/227025
Reviewed-by: Than McIntosh <thanm@google.com>
This commit is contained in:
Cherry Zhang 2020-04-02 12:48:13 -04:00
parent 8cc515ad3f
commit d92a5a80b5
12 changed files with 144 additions and 40 deletions
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2
src/cmd/internal/goobj/read.go
View File

@ -96,6 +96,7 @@ type Var struct {
type Func struct {
Args int64 // size in bytes of argument frame: inputs and outputs
Frame int64 // size in bytes of local variable frame
Align uint32 // alignment requirement in bytes for the address of the function
Leaf bool // function omits save of link register (ARM)
NoSplit bool // function omits stack split prologue
TopFrame bool // function is the top of the call stack
@ -591,6 +592,7 @@ func (r *objReader) parseObject(prefix []byte) error {
s.Func = f
f.Args = r.readInt()
f.Frame = r.readInt()
f.Align = uint32(r.readInt())
flags := r.readInt()
f.Leaf = flags&(1<<0) != 0
f.TopFrame = flags&(1<<4) != 0

23
src/cmd/internal/goobj2/objfile.go
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@ -186,11 +186,12 @@ func (h *Header) Size() int {
// Symbol definition.
type Sym struct {
Name string
ABI uint16
Type uint8
Flag uint8
Siz uint32
Name string
ABI uint16
Type uint8
Flag uint8
Siz uint32
Align uint32
}
const SymABIstatic = ^uint16(0)
@ -216,9 +217,10 @@ func (s *Sym) Write(w *Writer) {
w.Uint8(s.Type)
w.Uint8(s.Flag)
w.Uint32(s.Siz)
w.Uint32(s.Align)
}
const SymSize = stringRefSize + 2 + 1 + 1 + 4
const SymSize = stringRefSize + 2 + 1 + 1 + 4 + 4
type Sym2 [SymSize]byte
@ -228,10 +230,11 @@ func (s *Sym2) Name(r *Reader) string {
return r.StringAt(off, len)
}
func (s *Sym2) ABI() uint16 { return binary.LittleEndian.Uint16(s[8:]) }
func (s *Sym2) Type() uint8 { return s[10] }
func (s *Sym2) Flag() uint8 { return s[11] }
func (s *Sym2) Siz() uint32 { return binary.LittleEndian.Uint32(s[12:]) }
func (s *Sym2) ABI() uint16 { return binary.LittleEndian.Uint16(s[8:]) }
func (s *Sym2) Type() uint8 { return s[10] }
func (s *Sym2) Flag() uint8 { return s[11] }
func (s *Sym2) Siz() uint32 { return binary.LittleEndian.Uint32(s[12:]) }
func (s *Sym2) Align() uint32 { return binary.LittleEndian.Uint32(s[16:]) }
func (s *Sym2) Dupok() bool { return s.Flag()&SymFlagDupok != 0 }
func (s *Sym2) Local() bool { return s.Flag()&SymFlagLocal != 0 }

33
src/cmd/internal/obj/arm64/asm7.go
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@ -886,25 +886,10 @@ const OP_NOOP = 0xd503201f
// align code to a certain length by padding bytes.
func pcAlignPadLength(pc int64, alignedValue int64, ctxt *obj.Link) int {
switch alignedValue {
case 8:
if pc%8 == 4 {
return 4
}
case 16:
switch pc % 16 {
case 4:
return 12
case 8:
return 8
case 12:
return 4
}
default:
ctxt.Diag("Unexpected alignment: %d for PCALIGN directive\n", alignedValue)
if !((alignedValue&(alignedValue-1) == 0) && 8 <= alignedValue && alignedValue <= 2048) {
ctxt.Diag("alignment value of an instruction must be a power of two and in the range [8, 2048], got %d\n", alignedValue)
}
return 0
return int(-pc & (alignedValue - 1))
}
func span7(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
@ -940,8 +925,12 @@ func span7(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
if m == 0 {
switch p.As {
case obj.APCALIGN:
a := p.From.Offset
m = pcAlignPadLength(pc, a, ctxt)
alignedValue := p.From.Offset
m = pcAlignPadLength(pc, alignedValue, ctxt)
// Update the current text symbol alignment value.
if int32(alignedValue) > cursym.Func.Align {
cursym.Func.Align = int32(alignedValue)
}
break
case obj.ANOP, obj.AFUNCDATA, obj.APCDATA:
continue
@ -1017,8 +1006,8 @@ func span7(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
if m == 0 {
switch p.As {
case obj.APCALIGN:
a := p.From.Offset
m = pcAlignPadLength(pc, a, ctxt)
alignedValue := p.From.Offset
m = pcAlignPadLength(pc, alignedValue, ctxt)
break
case obj.ANOP, obj.AFUNCDATA, obj.APCDATA:
continue

27
src/cmd/internal/obj/arm64/asm_test.go
View File

@ -18,7 +18,9 @@ import (
// TestLarge generates a very large file to verify that large
// program builds successfully, in particular, too-far
// conditional branches are fixed.
// conditional branches are fixed, and also verify that the
// instruction's pc can be correctly aligned even when branches
// need to be fixed.
func TestLarge(t *testing.T) {
if testing.Short() {
t.Skip("Skip in short mode")
@ -41,10 +43,27 @@ func TestLarge(t *testing.T) {
t.Fatalf("can't write output: %v\n", err)
}
// build generated file
cmd := exec.Command(testenv.GoToolPath(t), "tool", "asm", "-o", filepath.Join(dir, "x.o"), tmpfile)
pattern := `0x0080\s00128\s\(.*\)\tMOVD\t\$3,\sR3`
// assemble generated file
cmd := exec.Command(testenv.GoToolPath(t), "tool", "asm", "-S", "-o", filepath.Join(dir, "test.o"), tmpfile)
cmd.Env = append(os.Environ(), "GOARCH=arm64", "GOOS=linux")
out, err := cmd.CombinedOutput()
if err != nil {
t.Errorf("Assemble failed: %v, output: %s", err, out)
}
matched, err := regexp.MatchString(pattern, string(out))
if err != nil {
t.Fatal(err)
}
if !matched {
t.Errorf("The alignment is not correct: %t, output:%s\n", matched, out)
}
// build generated file
cmd = exec.Command(testenv.GoToolPath(t), "tool", "asm", "-o", filepath.Join(dir, "x.o"), tmpfile)
cmd.Env = append(os.Environ(), "GOARCH=arm64", "GOOS=linux")
out, err = cmd.CombinedOutput()
if err != nil {
t.Errorf("Build failed: %v, output: %s", err, out)
}
@ -56,6 +75,8 @@ func gen(buf *bytes.Buffer) {
fmt.Fprintln(buf, "TBZ $5, R0, label")
fmt.Fprintln(buf, "CBZ R0, label")
fmt.Fprintln(buf, "BEQ label")
fmt.Fprintln(buf, "PCALIGN $128")
fmt.Fprintln(buf, "MOVD $3, R3")
for i := 0; i < 1<<19; i++ {
fmt.Fprintln(buf, "MOVD R0, R1")
}

1
src/cmd/internal/obj/link.go
View File

@ -398,6 +398,7 @@ type LSym struct {
type FuncInfo struct {
Args int32
Locals int32
Align int32
Text *Prog
Autot map[*LSym]struct{}
Pcln Pcln

1
src/cmd/internal/obj/objfile.go
View File

@ -350,6 +350,7 @@ func (w *objWriter) writeSym(s *LSym) {
w.writeInt(int64(s.Func.Args))
w.writeInt(int64(s.Func.Locals))
w.writeInt(int64(s.Func.Align))
w.writeBool(s.NoSplit())
flags = int64(0)
if s.Leaf() {

15
src/cmd/internal/obj/objfile2.go
View File

@ -244,12 +244,17 @@ func (w *writer) Sym(s *LSym) {
if strings.HasPrefix(name, "gofile..") {
name = filepath.ToSlash(name)
}
var align uint32
if s.Func != nil {
align = uint32(s.Func.Align)
}
o := goobj2.Sym{
Name: name,
ABI: abi,
Type: uint8(s.Type),
Flag: flag,
Siz: uint32(s.Size),
Name: name,
ABI: abi,
Type: uint8(s.Type),
Flag: flag,
Siz: uint32(s.Size),
Align: align,
}
o.Write(w.Writer)
}

4
src/cmd/link/internal/ld/data.go
View File

@ -2256,6 +2256,10 @@ func assignAddress(ctxt *Link, sect *sym.Section, n int, s *sym.Symbol, va uint6
funcsize = uint64(s.Size)
}
if sect.Align < s.Align {
sect.Align = s.Align
}
// On ppc64x a text section should not be larger than 2^26 bytes due to the size of
// call target offset field in the bl instruction. Splitting into smaller text
// sections smaller than this limit allows the GNU linker to modify the long calls

3
src/cmd/link/internal/loader/loader.go
View File

@ -1616,6 +1616,9 @@ func (l *Loader) preloadSyms(r *oReader, kind int) {
strings.HasPrefix(name, "runtime.gcbits.") {
l.SetAttrNotInSymbolTable(gi, true)
}
if a := osym.Align(); a != 0 {
l.SetSymAlign(gi, int32(a))
}
}
}

70
src/cmd/link/link_test.go
View File

@ -471,3 +471,73 @@ func TestOldLink(t *testing.T) {
t.Errorf("%v: %v:\n%s", cmd.Args, err, out)
}
}
const testFuncAlignSrc = `
package main
import (
"fmt"
"reflect"
)
func alignPc()
func main() {
addr := reflect.ValueOf(alignPc).Pointer()
if (addr % 512) != 0 {
fmt.Printf("expected 512 bytes alignment, got %v\n", addr)
} else {
fmt.Printf("PASS")
}
}
`
const testFuncAlignAsmSrc = `
#include "textflag.h"
TEXT ·alignPc(SB),NOSPLIT, $0-0
MOVD $2, R0
PCALIGN $512
MOVD $3, R1
RET
`
// TestFuncAlign verifies that the address of a function can be aligned
// with a specfic value on arm64.
func TestFuncAlign(t *testing.T) {
if runtime.GOARCH != "arm64" || runtime.GOOS != "linux" {
t.Skip("skipping on non-linux/arm64 platform")
}
testenv.MustHaveGoBuild(t)
tmpdir, err := ioutil.TempDir("", "TestFuncAlign")
if err != nil {
t.Fatal(err)
}
defer os.RemoveAll(tmpdir)
src := filepath.Join(tmpdir, "falign.go")
err = ioutil.WriteFile(src, []byte(testFuncAlignSrc), 0666)
if err != nil {
t.Fatal(err)
}
src = filepath.Join(tmpdir, "falign.s")
err = ioutil.WriteFile(src, []byte(testFuncAlignAsmSrc), 0666)
if err != nil {
t.Fatal(err)
}
// Build and run with old object file format.
cmd := exec.Command(testenv.GoToolPath(t), "build", "-o", "falign")
cmd.Dir = tmpdir
out, err := cmd.CombinedOutput()
if err != nil {
t.Errorf("build failed: %v", err)
}
cmd = exec.Command(tmpdir + "/falign")
out, err = cmd.CombinedOutput()
if err != nil {
t.Errorf("failed to run with err %v, output: %s", err, out)
}
if string(out) != "PASS" {
t.Errorf("unexpected output: %s\n", out)
}
}

4
src/cmd/oldlink/internal/ld/data.go
View File

@ -2119,6 +2119,10 @@ func assignAddress(ctxt *Link, sect *sym.Section, n int, s *sym.Symbol, va uint6
funcsize = uint64(s.Size)
}
if sect.Align < s.Align {
sect.Align = s.Align
}
// On ppc64x a text section should not be larger than 2^26 bytes due to the size of
// call target offset field in the bl instruction. Splitting into smaller text
// sections smaller than this limit allows the GNU linker to modify the long calls

1
src/cmd/oldlink/internal/objfile/objfile.go
View File

@ -316,6 +316,7 @@ overwrite:
pc.Args = r.readInt32()
pc.Locals = r.readInt32()
s.Align = r.readInt32()
if r.readUint8() != 0 {
s.Attr |= sym.AttrNoSplit
}