[dev.link] cmd: support large function alignment
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>
diff --git a/src/cmd/internal/goobj/read.go b/src/cmd/internal/goobj/read.go
index 027c77e..44e619c 100644
--- a/src/cmd/internal/goobj/read.go
+++ b/src/cmd/internal/goobj/read.go
@@ -96,6 +96,7 @@
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 @@
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
diff --git a/src/cmd/internal/goobj2/objfile.go b/src/cmd/internal/goobj2/objfile.go
index c7b508c..52544bf 100644
--- a/src/cmd/internal/goobj2/objfile.go
+++ b/src/cmd/internal/goobj2/objfile.go
@@ -186,11 +186,12 @@
// 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 @@
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 @@
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 }
diff --git a/src/cmd/internal/obj/arm64/asm7.go b/src/cmd/internal/obj/arm64/asm7.go
index e8b092a..8e5b598 100644
--- a/src/cmd/internal/obj/arm64/asm7.go
+++ b/src/cmd/internal/obj/arm64/asm7.go
@@ -886,25 +886,10 @@
// 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 @@
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 @@
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
diff --git a/src/cmd/internal/obj/arm64/asm_test.go b/src/cmd/internal/obj/arm64/asm_test.go
index 1691828..9efdb02 100644
--- a/src/cmd/internal/obj/arm64/asm_test.go
+++ b/src/cmd/internal/obj/arm64/asm_test.go
@@ -18,7 +18,9 @@
// 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")
@@ -41,11 +43,28 @@
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 @@
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")
}
diff --git a/src/cmd/internal/obj/link.go b/src/cmd/internal/obj/link.go
index 9dd821d..ac3621bf 100644
--- a/src/cmd/internal/obj/link.go
+++ b/src/cmd/internal/obj/link.go
@@ -398,6 +398,7 @@
type FuncInfo struct {
Args int32
Locals int32
+ Align int32
Text *Prog
Autot map[*LSym]struct{}
Pcln Pcln
diff --git a/src/cmd/internal/obj/objfile.go b/src/cmd/internal/obj/objfile.go
index 3e97c61..cb6b709 100644
--- a/src/cmd/internal/obj/objfile.go
+++ b/src/cmd/internal/obj/objfile.go
@@ -350,6 +350,7 @@
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() {
diff --git a/src/cmd/internal/obj/objfile2.go b/src/cmd/internal/obj/objfile2.go
index 95f920e..6261924 100644
--- a/src/cmd/internal/obj/objfile2.go
+++ b/src/cmd/internal/obj/objfile2.go
@@ -244,12 +244,17 @@
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)
}
diff --git a/src/cmd/link/internal/ld/data.go b/src/cmd/link/internal/ld/data.go
index bff29fb..7c4b08a 100644
--- a/src/cmd/link/internal/ld/data.go
+++ b/src/cmd/link/internal/ld/data.go
@@ -2256,6 +2256,10 @@
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
diff --git a/src/cmd/link/internal/loader/loader.go b/src/cmd/link/internal/loader/loader.go
index 5f12874..7cc846a 100644
--- a/src/cmd/link/internal/loader/loader.go
+++ b/src/cmd/link/internal/loader/loader.go
@@ -1616,6 +1616,9 @@
strings.HasPrefix(name, "runtime.gcbits.") {
l.SetAttrNotInSymbolTable(gi, true)
}
+ if a := osym.Align(); a != 0 {
+ l.SetSymAlign(gi, int32(a))
+ }
}
}
diff --git a/src/cmd/link/link_test.go b/src/cmd/link/link_test.go
index 5e19cb5..ed2d3f4 100644
--- a/src/cmd/link/link_test.go
+++ b/src/cmd/link/link_test.go
@@ -471,3 +471,73 @@
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)
+ }
+}
diff --git a/src/cmd/oldlink/internal/ld/data.go b/src/cmd/oldlink/internal/ld/data.go
index 3c78896..13f412c 100644
--- a/src/cmd/oldlink/internal/ld/data.go
+++ b/src/cmd/oldlink/internal/ld/data.go
@@ -2119,6 +2119,10 @@
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
diff --git a/src/cmd/oldlink/internal/objfile/objfile.go b/src/cmd/oldlink/internal/objfile/objfile.go
index 7be433a..3a59f6a 100644
--- a/src/cmd/oldlink/internal/objfile/objfile.go
+++ b/src/cmd/oldlink/internal/objfile/objfile.go
@@ -316,6 +316,7 @@
pc.Args = r.readInt32()
pc.Locals = r.readInt32()
+ s.Align = r.readInt32()
if r.readUint8() != 0 {
s.Attr |= sym.AttrNoSplit
}
