debug/pe: truncate pe sections to their size in memory

Section.Data returns disk section data, but those are rounded up to
some predefined value. Processing these as is confuses dwarf parser
because of garbage at the end. Truncate Section.Data as per memory
section description.

Sometimes dwarf sections have memory section size of 0
(for pe object files). Keep those to their disk size.

Fixes #11608

Change-Id: I8de0a2271201a24aa9ac8dac44f1e9c8a9285183
Reviewed-on: https://go-review.googlesource.com/11950Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/debug/pe/file.go

@@ -310,6 +310,9 @@ func (f *File) DWARF() (*dwarf.Data, error) {
 		if err != nil && uint32(len(b)) < s.Size {
 			return nil, err
 		}
+		if 0 < s.VirtualSize && s.VirtualSize < s.Size {
+			b = b[:s.VirtualSize]
+		}
 		dat[i] = b
 	}
 

src/debug/pe/file_test.go

@@ -5,24 +5,30 @@
 package pe
 
 import (
+	"debug/dwarf"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path/filepath"
 	"reflect"
+	"runtime"
 	"testing"
 )
 
 type fileTest struct {
-	file     string
-	hdr      FileHeader
-	opthdr   interface{}
-	sections []*SectionHeader
-	symbols  []*Symbol
+	file           string
+	hdr            FileHeader
+	opthdr         interface{}
+	sections       []*SectionHeader
+	symbols        []*Symbol
+	hasNoDwarfInfo bool
 }
 
 var fileTests = []fileTest{
 	{
-		"testdata/gcc-386-mingw-obj",
-		FileHeader{0x014c, 0x000c, 0x0, 0x64a, 0x1e, 0x0, 0x104},
-		nil,
-		[]*SectionHeader{
+		file: "testdata/gcc-386-mingw-obj",
+		hdr:  FileHeader{0x014c, 0x000c, 0x0, 0x64a, 0x1e, 0x0, 0x104},
+		sections: []*SectionHeader{
 			{".text", 0, 0, 36, 500, 1440, 0, 3, 0, 0x60300020},
 			{".data", 0, 0, 0, 0, 0, 0, 0, 0, 3224371264},
 			{".bss", 0, 0, 0, 0, 0, 0, 0, 0, 3224371328},
@@ -36,7 +42,7 @@ var fileTests = []fileTest{
 			{".debug_pubtypes", 0, 0, 38, 1370, 1580, 0, 1, 0, 1108344832},
 			{".debug_aranges", 0, 0, 32, 1408, 1590, 0, 2, 0, 1108344832},
 		},
-		[]*Symbol{
+		symbols: []*Symbol{
 			{".file", 0x0, -2, 0x0, 0x67},
 			{"_main", 0x0, 1, 0x20, 0x2},
 			{".text", 0x0, 1, 0x0, 0x3},
@@ -56,9 +62,9 @@ var fileTests = []fileTest{
 		},
 	},
 	{
-		"testdata/gcc-386-mingw-exec",
-		FileHeader{0x014c, 0x000f, 0x4c6a1b60, 0x3c00, 0x282, 0xe0, 0x107},
-		&OptionalHeader32{
+		file: "testdata/gcc-386-mingw-exec",
+		hdr:  FileHeader{0x014c, 0x000f, 0x4c6a1b60, 0x3c00, 0x282, 0xe0, 0x107},
+		opthdr: &OptionalHeader32{
 			0x10b, 0x2, 0x38, 0xe00, 0x1a00, 0x200, 0x1160, 0x1000, 0x2000, 0x400000, 0x1000, 0x200, 0x4, 0x0, 0x1, 0x0, 0x4, 0x0, 0x0, 0x10000, 0x400, 0x14abb, 0x3, 0x0, 0x200000, 0x1000, 0x100000, 0x1000, 0x0, 0x10,
 			[16]DataDirectory{
 				{0x0, 0x0},
@@ -79,7 +85,7 @@ var fileTests = []fileTest{
 				{0x0, 0x0},
 			},
 		},
-		[]*SectionHeader{
+		sections: []*SectionHeader{
 			{".text", 0xcd8, 0x1000, 0xe00, 0x400, 0x0, 0x0, 0x0, 0x0, 0x60500060},
 			{".data", 0x10, 0x2000, 0x200, 0x1200, 0x0, 0x0, 0x0, 0x0, 0xc0300040},
 			{".rdata", 0x120, 0x3000, 0x200, 0x1400, 0x0, 0x0, 0x0, 0x0, 0x40300040},
@@ -96,13 +102,11 @@ var fileTests = []fileTest{
 			{".debug_frame", 0x34, 0xe000, 0x200, 0x3800, 0x0, 0x0, 0x0, 0x0, 0x42300000},
 			{".debug_loc", 0x38, 0xf000, 0x200, 0x3a00, 0x0, 0x0, 0x0, 0x0, 0x42100000},
 		},
-		[]*Symbol{},
 	},
 	{
-		"testdata/gcc-amd64-mingw-obj",
-		FileHeader{0x8664, 0x6, 0x0, 0x198, 0x12, 0x0, 0x4},
-		nil,
-		[]*SectionHeader{
+		file: "testdata/gcc-amd64-mingw-obj",
+		hdr:  FileHeader{0x8664, 0x6, 0x0, 0x198, 0x12, 0x0, 0x4},
+		sections: []*SectionHeader{
 			{".text", 0x0, 0x0, 0x30, 0x104, 0x15c, 0x0, 0x3, 0x0, 0x60500020},
 			{".data", 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0xc0500040},
 			{".bss", 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0xc0500080},
@@ -110,7 +114,7 @@ var fileTests = []fileTest{
 			{".xdata", 0x0, 0x0, 0xc, 0x144, 0x0, 0x0, 0x0, 0x0, 0x40300040},
 			{".pdata", 0x0, 0x0, 0xc, 0x150, 0x17a, 0x0, 0x3, 0x0, 0x40300040},
 		},
-		[]*Symbol{
+		symbols: []*Symbol{
 			{".file", 0x0, -2, 0x0, 0x67},
 			{"main", 0x0, 1, 0x20, 0x2},
 			{".text", 0x0, 1, 0x0, 0x3},
@@ -122,11 +126,12 @@ var fileTests = []fileTest{
 			{"__main", 0x0, 0, 0x20, 0x2},
 			{"puts", 0x0, 0, 0x20, 0x2},
 		},
+		hasNoDwarfInfo: true,
 	},
 	{
-		"testdata/gcc-amd64-mingw-exec",
-		FileHeader{0x8664, 0x11, 0x53e4364f, 0x39600, 0x6fc, 0xf0, 0x27},
-		&OptionalHeader64{
+		file: "testdata/gcc-amd64-mingw-exec",
+		hdr:  FileHeader{0x8664, 0x11, 0x53e4364f, 0x39600, 0x6fc, 0xf0, 0x27},
+		opthdr: &OptionalHeader64{
 			0x20b, 0x2, 0x16, 0x6a00, 0x2400, 0x1600, 0x14e0, 0x1000, 0x400000, 0x1000, 0x200, 0x4, 0x0, 0x0, 0x0, 0x5, 0x2, 0x0, 0x45000, 0x600, 0x46f19, 0x3, 0x0, 0x200000, 0x1000, 0x100000, 0x1000, 0x0, 0x10,
 			[16]DataDirectory{
 				{0x0, 0x0},
@@ -146,7 +151,7 @@ var fileTests = []fileTest{
 				{0x0, 0x0},
 				{0x0, 0x0},
 			}},
-		[]*SectionHeader{
+		sections: []*SectionHeader{
 			{".text", 0x6860, 0x1000, 0x6a00, 0x600, 0x0, 0x0, 0x0, 0x0, 0x60500020},
 			{".data", 0xe0, 0x8000, 0x200, 0x7000, 0x0, 0x0, 0x0, 0x0, 0xc0500040},
 			{".rdata", 0x6b0, 0x9000, 0x800, 0x7200, 0x0, 0x0, 0x0, 0x0, 0x40600040},
@@ -165,7 +170,6 @@ var fileTests = []fileTest{
 			{".debug_loc", 0x13240, 0x30000, 0x13400, 0x25600, 0x0, 0x0, 0x0, 0x0, 0x42100040},
 			{".debug_ranges", 0xa70, 0x44000, 0xc00, 0x38a00, 0x0, 0x0, 0x0, 0x0, 0x42100040},
 		},
-		[]*Symbol{},
 	},
 }
 
@@ -231,6 +235,12 @@ func TestOpen(t *testing.T) {
 				t.Errorf("open %s, symbol %d:\n\thave %#v\n\twant %#v\n", tt.file, i, have, want)
 			}
 		}
+		if !tt.hasNoDwarfInfo {
+			_, err = f.DWARF()
+			if err != nil {
+				t.Errorf("fetching %s dwarf details failed: %v", tt.file, err)
+			}
+		}
 	}
 }
 
@@ -241,3 +251,59 @@ func TestOpenFailure(t *testing.T) {
 		t.Errorf("open %s: succeeded unexpectedly", filename)
 	}
 }
+
+func TestDWARF(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		t.Skip("skipping windows only test")
+	}
+
+	tmpdir, err := ioutil.TempDir("", "TestDWARF")
+	if err != nil {
+		t.Fatal("TempDir failed: ", err)
+	}
+	defer os.RemoveAll(tmpdir)
+
+	prog := `
+package main
+func main() {
+}
+`
+	src := filepath.Join(tmpdir, "a.go")
+	exe := filepath.Join(tmpdir, "a.exe")
+	err = ioutil.WriteFile(src, []byte(prog), 0644)
+	output, err := exec.Command("go", "build", "-o", exe, src).CombinedOutput()
+	if err != nil {
+		t.Fatalf("building test executable failed: %s %s", err, output)
+	}
+
+	f, err := Open(exe)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+
+	d, err := f.DWARF()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// look for main.main
+	r := d.Reader()
+	for {
+		e, err := r.Next()
+		if err != nil {
+			t.Fatal("r.Next:", err)
+		}
+		if e == nil {
+			break
+		}
+		if e.Tag == dwarf.TagSubprogram {
+			for _, f := range e.Field {
+				if f.Attr == dwarf.AttrName && e.Val(dwarf.AttrName) == "main.main" {
+					return
+				}
+			}
+		}
+	}
+	t.Fatal("main.main not found")
+}