cmd/link: fix padding for dwarf aranges on 32 bit platforms.

Fixes #14278

Change-Id: I6a0c1370d595f0573ff0eb933450b1eea41f4bb3
Reviewed-on: https://go-review.googlesource.com/19452
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/link/internal/ld/dwarf.go

@@ -1946,7 +1946,9 @@ func writepub(ispub func(*DWDie) bool) int64 {
  */
 func writearanges() int64 {
 	sectionstart := Cpos()
-	headersize := int(Rnd(4+2+4+1+1, int64(Thearch.Ptrsize))) // don't count unit_length field itself
+	// The first tuple is aligned to a multiple of the size of a single tuple
+	// (twice the size of an address)
+	headersize := int(Rnd(4+2+4+1+1, int64(Thearch.Ptrsize*2))) // don't count unit_length field itself
 
 	for compunit := dwroot.child; compunit != nil; compunit = compunit.link {
 		b := getattr(compunit, DW_AT_low_pc)

src/runtime/runtime-lldb_test.go

@@ -0,0 +1,262 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package runtime_test
+
+import (
+	"debug/elf"
+	"debug/macho"
+	"encoding/binary"
+	"internal/testenv"
+	"io"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+)
+
+var lldbPath string
+
+func checkLldbPython(t *testing.T) {
+	cmd := exec.Command("lldb", "-P")
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Skipf("skipping due to issue running lldb: %v\n%s", err, out)
+	}
+	lldbPath = strings.TrimSpace(string(out))
+
+	cmd = exec.Command("/usr/bin/python2.7", "-c", "import sys;sys.path.append(sys.argv[1]);import lldb; print('go lldb python support')", lldbPath)
+	out, err = cmd.CombinedOutput()
+
+	if err != nil {
+		t.Skipf("skipping due to issue running python: %v\n%s", err, out)
+	}
+	if string(out) != "go lldb python support\n" {
+		t.Skipf("skipping due to lack of python lldb support: %s", out)
+	}
+
+	if runtime.GOOS == "darwin" {
+		// Try to see if we have debugging permissions.
+		cmd = exec.Command("/usr/sbin/DevToolsSecurity", "-status")
+		out, err = cmd.CombinedOutput()
+		if err != nil {
+			t.Skipf("DevToolsSecurity failed: %v", err)
+		} else if !strings.Contains(string(out), "enabled") {
+			t.Skip(string(out))
+		}
+		cmd = exec.Command("/usr/bin/groups")
+		out, err = cmd.CombinedOutput()
+		if err != nil {
+			t.Skipf("groups failed: %v", err)
+		} else if !strings.Contains(string(out), "_developer") {
+			t.Skip("Not in _developer group")
+		}
+	}
+}
+
+const lldbHelloSource = `
+package main
+import "fmt"
+func main() {
+	mapvar := make(map[string]string,5)
+	mapvar["abc"] = "def"
+	mapvar["ghi"] = "jkl"
+	intvar := 42
+	ptrvar := &intvar
+	fmt.Println("hi") // line 10
+	_ = ptrvar
+}
+`
+
+const lldbScriptSource = `
+import sys
+sys.path.append(sys.argv[1])
+import lldb
+import os
+
+TIMEOUT_SECS = 5
+
+debugger = lldb.SBDebugger.Create()
+debugger.SetAsync(True)
+target = debugger.CreateTargetWithFileAndArch("a.exe", None)
+if target:
+  print "Created target"
+  main_bp = target.BreakpointCreateByLocation("main.go", 10)
+  if main_bp:
+    print "Created breakpoint"
+  process = target.LaunchSimple(None, None, os.getcwd())
+  if process:
+    print "Process launched"
+    listener = debugger.GetListener()
+    process.broadcaster.AddListener(listener, lldb.SBProcess.eBroadcastBitStateChanged)
+    while True:
+      event = lldb.SBEvent()
+      if listener.WaitForEvent(TIMEOUT_SECS, event):
+        if lldb.SBProcess.GetRestartedFromEvent(event):
+          continue
+        state = process.GetState()
+        if state in [lldb.eStateUnloaded, lldb.eStateLaunching, lldb.eStateRunning]:
+          continue
+      else:
+        print "Timeout launching"
+      break
+    if state == lldb.eStateStopped:
+      for t in process.threads:
+        if t.GetStopReason() == lldb.eStopReasonBreakpoint:
+          print "Hit breakpoint"
+          frame = t.GetFrameAtIndex(0)
+          if frame:
+            if frame.line_entry:
+              print "Stopped at %s:%d" % (frame.line_entry.file.basename, frame.line_entry.line)
+            if frame.function:
+              print "Stopped in %s" % (frame.function.name,)
+            var = frame.FindVariable('intvar')
+            if var:
+              print "intvar = %s" % (var.GetValue(),)
+            else:
+              print "no intvar"
+    else:
+      print "Process state", state
+    process.Destroy()
+else:
+  print "Failed to create target a.exe"
+
+lldb.SBDebugger.Destroy(debugger)
+sys.exit()
+`
+
+const expectedLldbOutput = `Created target
+Created breakpoint
+Process launched
+Hit breakpoint
+Stopped at main.go:10
+Stopped in main.main
+intvar = 42
+`
+
+func TestLldbPython(t *testing.T) {
+	testenv.MustHaveGoBuild(t)
+	if final := os.Getenv("GOROOT_FINAL"); final != "" && runtime.GOROOT() != final {
+		t.Skip("gdb test can fail with GOROOT_FINAL pending")
+	}
+
+	checkLldbPython(t)
+
+	dir, err := ioutil.TempDir("", "go-build")
+	if err != nil {
+		t.Fatalf("failed to create temp directory: %v", err)
+	}
+	defer os.RemoveAll(dir)
+
+	src := filepath.Join(dir, "main.go")
+	err = ioutil.WriteFile(src, []byte(lldbHelloSource), 0644)
+	if err != nil {
+		t.Fatalf("failed to create file: %v", err)
+	}
+
+	cmd := exec.Command("go", "build", "-gcflags", "-N -l", "-o", "a.exe")
+	cmd.Dir = dir
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("building source %v\n%s", err, out)
+	}
+
+	src = filepath.Join(dir, "script.py")
+	err = ioutil.WriteFile(src, []byte(lldbScriptSource), 0755)
+	if err != nil {
+		t.Fatalf("failed to create script: %v", err)
+	}
+
+	cmd = exec.Command("/usr/bin/python2.7", "script.py", lldbPath)
+	cmd.Dir = dir
+	got, _ := cmd.CombinedOutput()
+
+	if string(got) != expectedLldbOutput {
+		if strings.Contains(string(got), "Timeout launching") {
+			t.Skip("Timeout launching")
+		}
+		t.Fatalf("Unexpected lldb output:\n%s", got)
+	}
+}
+
+// Check that aranges are valid even when lldb isn't installed.
+func TestDwarfAranges(t *testing.T) {
+	testenv.MustHaveGoBuild(t)
+	dir, err := ioutil.TempDir("", "go-build")
+	if err != nil {
+		t.Fatalf("failed to create temp directory: %v", err)
+	}
+	defer os.RemoveAll(dir)
+
+	src := filepath.Join(dir, "main.go")
+	err = ioutil.WriteFile(src, []byte(lldbHelloSource), 0644)
+	if err != nil {
+		t.Fatalf("failed to create file: %v", err)
+	}
+
+	cmd := exec.Command("go", "build", "-o", "a.exe")
+	cmd.Dir = dir
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("building source %v\n%s", err, out)
+	}
+
+	filename := filepath.Join(dir, "a.exe")
+	if f, err := elf.Open(filename); err == nil {
+		sect := f.Section(".debug_aranges")
+		if sect == nil {
+			t.Fatal("Missing aranges section")
+		}
+		verifyAranges(t, f.ByteOrder, sect.Open())
+	} else if f, err := macho.Open(filename); err == nil {
+		sect := f.Section("__debug_aranges")
+		if sect == nil {
+			t.Fatal("Missing aranges section")
+		}
+		verifyAranges(t, f.ByteOrder, sect.Open())
+	} else {
+		t.Skip("Not an elf or macho binary.")
+	}
+}
+
+func verifyAranges(t *testing.T, byteorder binary.ByteOrder, data io.ReadSeeker) {
+	var header struct {
+		UnitLength  uint32 // does not include the UnitLength field
+		Version     uint16
+		Offset      uint32
+		AddressSize uint8
+		SegmentSize uint8
+	}
+	for {
+		offset, err := data.Seek(0, 1)
+		if err != nil {
+			t.Fatalf("Seek error: %v", err)
+		}
+		if err = binary.Read(data, byteorder, &header); err == io.EOF {
+			return
+		} else if err != nil {
+			t.Fatalf("Error reading arange header: %v", err)
+		}
+		tupleSize := int64(header.SegmentSize) + 2*int64(header.AddressSize)
+		lastTupleOffset := offset + int64(header.UnitLength) + 4 - tupleSize
+		if lastTupleOffset%tupleSize != 0 {
+			t.Fatalf("Invalid arange length %d, (addr %d, seg %d)", header.UnitLength, header.AddressSize, header.SegmentSize)
+		}
+		if _, err = data.Seek(lastTupleOffset, 0); err != nil {
+			t.Fatalf("Seek error: %v", err)
+		}
+		buf := make([]byte, tupleSize)
+		if n, err := data.Read(buf); err != nil || int64(n) < tupleSize {
+			t.Fatalf("Read error: %v", err)
+		}
+		for _, val := range buf {
+			if val != 0 {
+				t.Fatalf("Invalid terminator")
+			}
+		}
+	}
+}