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Make dwarf reader more robust.
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@randall77
randall77 committed Nov 7, 2017
1 parent 5d5af8b commit e2c03d6
Showing 1 changed file with 105 additions and 5 deletions.
110 changes: 105 additions & 5 deletions gocore/dwarf.go
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Original file line number Diff line number Diff line change
Expand Up @@ -3,12 +3,42 @@ package gocore
import (
"debug/dwarf"
"fmt"
"os"
"sort"
"strings"

"github.com/randall77/corelib/core"
)

// Wrappers to recover in case debug/dwarf panics.
// TODO: fix the bug in the debug/dwarf library instead.
func wrapType(d *dwarf.Data, off dwarf.Offset) (dt dwarf.Type, err error) {
defer func() {
if r := recover(); r != nil {
if false {
fmt.Fprintf(os.Stderr, "bad offset: %d\n", off)
}
dt = nil
err = r.(error)
}
}()
dt, err = d.Type(off)
return
}

func wrapSize(dt dwarf.Type) (size int64) {
defer func() {
if r := recover(); r != nil {
if false {
fmt.Fprintf(os.Stderr, "bad size: %s\n", dt)
}
size = 0
}
}()
size = dt.Size()
return
}

// read DWARF types from core dump.
func (p *Process) readDWARFTypes() {
d, _ := p.proc.DWARF()
Expand All @@ -19,11 +49,11 @@ func (p *Process) readDWARFTypes() {
for e, err := r.Next(); e != nil && err == nil; e, err = r.Next() {
switch e.Tag {
case dwarf.TagArrayType, dwarf.TagPointerType, dwarf.TagStructType, dwarf.TagBaseType, dwarf.TagSubroutineType, dwarf.TagTypedef:
dt, err := d.Type(e.Offset)
dt, err := wrapType(d, e.Offset)
if err != nil {
continue
}
size := dt.Size()
size := wrapSize(dt)
if size < 0 { // Fix for issue 21097.
size = dwarfSize(dt, p.proc.PtrSize())
}
Expand All @@ -41,6 +71,10 @@ func (p *Process) readDWARFTypes() {
t.Kind = KindArray
t.Elem = p.dwarfMap[x.Type]
t.Count = x.Count
if t.Elem == nil {
// Array type with a non-Go base type - ignore it.
delete(p.dwarfMap, dt)
}
case *dwarf.PtrType:
t.Kind = KindPtr
// unsafe.Pointer has a void base type.
Expand All @@ -50,6 +84,10 @@ func (p *Process) readDWARFTypes() {
case *dwarf.StructType:
t.Kind = KindStruct
for _, f := range x.Field {
if p.dwarfMap[f.Type] == nil {
// Some non-Go type as a field - ignore it.
continue
}
t.Fields = append(t.Fields, Field{Name: f.Name, Type: p.dwarfMap[f.Type], Off: f.ByteOffset})
}
case *dwarf.BoolType:
Expand All @@ -66,6 +104,12 @@ func (p *Process) readDWARFTypes() {
t.Kind = KindFunc
case *dwarf.TypedefType:
// handle these types in the loop below

// C types, might as well handle them.
case *dwarf.CharType:
t.Kind = KindInt
case *dwarf.UcharType:
t.Kind = KindUint
default:
panic(fmt.Sprintf("unknown type %s %T", dt, dt))
}
Expand Down Expand Up @@ -111,6 +155,11 @@ func (p *Process) readDWARFTypes() {

t := p.dwarfMap[dt]
bt := p.dwarfMap[base]
if bt == nil {
// Base type is non-Go, ignore it.
delete(p.dwarfMap, dt)
continue
}

// Copy type info from base. Everything except the name.
name := t.name
Expand Down Expand Up @@ -200,13 +249,22 @@ func dwarfSize(dt dwarf.Type, ptrSize int64) int64 {
return x.Count * dwarfSize(x.Type, ptrSize)
case *dwarf.TypedefType:
return dwarfSize(x.Type, ptrSize)
case *dwarf.UnspecifiedType:
return 0 // TODO: what the heck?
case *dwarf.StructType:
return 0 // TODO
case *dwarf.QualType:
return 0 // TODO
default:
panic("unhandled")
panic(fmt.Sprintf("unhandled %T", dt))
}
}

// gocoreName generates the name this package uses to refer to a dwarf type.
func gocoreName(dt dwarf.Type) string {
if dt == nil {
return "<badtype>"
}
switch x := dt.(type) {
case *dwarf.PtrType:
if _, ok := x.Type.(*dwarf.VoidType); ok {
Expand Down Expand Up @@ -247,6 +305,9 @@ func gocoreName(dt dwarf.Type) string {
// Generate the name the runtime uses for a dwarf type. The DWARF generator
// and the runtime use slightly different names for the same underlying type.
func runtimeName(dt dwarf.Type) string {
if dt == nil {
return "<badtype>"
}
switch x := dt.(type) {
case *dwarf.PtrType:
if _, ok := x.Type.(*dwarf.VoidType); ok {
Expand Down Expand Up @@ -377,6 +438,9 @@ func (p *Process) typeHeap() {
if a == 0 { // nil pointer
return
}
if t == nil { //huh?
return
}
i, off := p.findObjectIndex(a)
if i < 0 { // pointer doesn't point to an object in the Go heap
return
Expand Down Expand Up @@ -578,6 +642,10 @@ func (p *Process) typeObject(a core.Address, t *Type, r reader, add func(core.Ad
}
}
}
if dt.Kind == KindFunc {
// TODO: branch fo KindFunc case?
return
}
if dt.Kind != KindPtr {
panic(fmt.Sprintf("direct type isn't a pointer %s", dt.Kind))
}
Expand Down Expand Up @@ -647,6 +715,8 @@ func (p *Process) typeObject(a core.Address, t *Type, r reader, add func(core.Ad
for _, f := range t.Fields {
p.typeObject(a.Add(f.Off), f.Type, r, add)
}
case KindNone:
return // TODO: avoid this?
default:
panic(fmt.Sprintf("unknown type kind %s\n", t.Kind))
}
Expand Down Expand Up @@ -713,7 +783,13 @@ func (p *Process) readGlobals() {
if e.Tag != dwarf.TagVariable {
continue
}
loc := e.AttrField(dwarf.AttrLocation).Val.([]byte)
if e.AttrField(dwarf.AttrLocation) == nil {
continue
}
loc, ok := e.AttrField(dwarf.AttrLocation).Val.([]byte)
if !ok {
continue // Sometimes an int64?
}
if loc[0] != _DW_OP_addr {
continue
}
Expand All @@ -728,13 +804,19 @@ func (p *Process) readGlobals() {
// TODO: keep roots around anyway?
continue
}
if e.AttrField(dwarf.AttrType) == nil {
continue
}
dt, err := d.Type(e.AttrField(dwarf.AttrType).Val.(dwarf.Offset))
if err != nil {
panic(err)
}
if _, ok := dt.(*dwarf.UnspecifiedType); ok {
continue // Ignore markers like data/edata.
}
if p.dwarfMap[dt] == nil {
continue
}
p.globals = append(p.globals, &Root{
Name: e.AttrField(dwarf.AttrName).Val.(string),
Addr: a,
Expand All @@ -756,7 +838,19 @@ func (p *Process) readStackVars() {
r := d.Reader()
for e, err := r.Next(); e != nil && err == nil; e, err = r.Next() {
if e.Tag == dwarf.TagSubprogram {
if e.AttrField(dwarf.AttrLowpc) == nil {
continue
}
if _, ok := e.AttrField(dwarf.AttrLowpc).Val.(uint64); !ok {
continue
}
min := core.Address(e.AttrField(dwarf.AttrLowpc).Val.(uint64))
if e.AttrField(dwarf.AttrHighpc) == nil {
continue
}
if _, ok := e.AttrField(dwarf.AttrHighpc).Val.(uint64); !ok {
continue
}
max := core.Address(e.AttrField(dwarf.AttrHighpc).Val.(uint64))
f := p.funcTab.find(min)
if f == nil {
Expand All @@ -780,7 +874,10 @@ func (p *Process) readStackVars() {
if aloc == nil {
continue
}
loc := aloc.Val.([]byte)
loc, ok := aloc.Val.([]byte)
if !ok {
continue
}
if len(loc) == 0 || loc[0] != _DW_OP_call_frame_cfa {
continue
}
Expand Down Expand Up @@ -812,6 +909,9 @@ func (p *Process) readStackVars() {
panic(err)
}
name := e.AttrField(dwarf.AttrName).Val.(string)
if p.dwarfMap[dt] == nil {
continue
}
vars[curfn] = append(vars[curfn], Var{name: name, off: off, typ: p.dwarfMap[dt]})
}

Expand Down

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