pkg/proc: Untangle Arch from G struct

More untangling. Arch doesn't actually need to know anything about a
Goroutine.

pkg/proc/arch.go

@@ -18,7 +18,7 @@ type Arch interface {
 	FixFrameUnwindContext(*frame.FrameContext, uint64, *BinaryInfo) *frame.FrameContext
 	RegSize(uint64) int
 	RegistersToDwarfRegisters(uint64, Registers) op.DwarfRegisters
-	GoroutineToDwarfRegisters(*G) op.DwarfRegisters
+	AddrAndStackRegsToDwarfRegisters(uint64, uint64, uint64, uint64) op.DwarfRegisters
 }
 
 // AMD64 represents the AMD64 CPU architecture.
@@ -293,15 +293,20 @@ func (a *AMD64) RegistersToDwarfRegisters(staticBase uint64, regs Registers) op.
 	}
 }
 
-// GoroutineToDwarfRegisters extract the saved DWARF registers from a parked
-// goroutine in the format used by the DWARF expression interpreter.
-func (a *AMD64) GoroutineToDwarfRegisters(g *G) op.DwarfRegisters {
+// AddrAndStackRegsToDwarfRegisters returns DWARF registers from the passed in
+// PC, SP, and BP registers in the format used by the DWARF expression interpreter.
+func (a *AMD64) AddrAndStackRegsToDwarfRegisters(staticBase, pc, sp, bp uint64) op.DwarfRegisters {
 	dregs := make([]*op.DwarfRegister, amd64DwarfIPRegNum+1)
-	dregs[amd64DwarfIPRegNum] = op.DwarfRegisterFromUint64(g.PC)
-	dregs[amd64DwarfSPRegNum] = op.DwarfRegisterFromUint64(g.SP)
-	dregs[amd64DwarfBPRegNum] = op.DwarfRegisterFromUint64(g.BP)
+	dregs[amd64DwarfIPRegNum] = op.DwarfRegisterFromUint64(pc)
+	dregs[amd64DwarfSPRegNum] = op.DwarfRegisterFromUint64(sp)
+	dregs[amd64DwarfBPRegNum] = op.DwarfRegisterFromUint64(bp)
 
-	so := g.variable.bi.PCToImage(g.PC)
-
-	return op.DwarfRegisters{StaticBase: so.StaticBase, Regs: dregs, ByteOrder: binary.LittleEndian, PCRegNum: amd64DwarfIPRegNum, SPRegNum: amd64DwarfSPRegNum, BPRegNum: amd64DwarfBPRegNum}
+	return op.DwarfRegisters{
+		StaticBase: staticBase,
+		Regs:       dregs,
+		ByteOrder:  binary.LittleEndian,
+		PCRegNum:   amd64DwarfIPRegNum,
+		SPRegNum:   amd64DwarfSPRegNum,
+		BPRegNum:   amd64DwarfBPRegNum,
+	}
 }

pkg/proc/stack.go

@@ -119,9 +119,16 @@ func (g *G) stackIterator() (*stackIterator, error) {
 			return nil, err
 		}
 		so := g.variable.bi.PCToImage(regs.PC())
-		return newStackIterator(g.variable.bi, g.Thread, g.variable.bi.Arch.RegistersToDwarfRegisters(so.StaticBase, regs), g.stackhi, stkbar, g.stkbarPos, g), nil
+		return newStackIterator(
+			g.variable.bi, g.Thread,
+			g.variable.bi.Arch.RegistersToDwarfRegisters(so.StaticBase, regs),
+			g.stackhi, stkbar, g.stkbarPos, g), nil
 	}
-	return newStackIterator(g.variable.bi, g.variable.mem, g.variable.bi.Arch.GoroutineToDwarfRegisters(g), g.stackhi, stkbar, g.stkbarPos, g), nil
+	so := g.variable.bi.PCToImage(g.PC)
+	return newStackIterator(
+		g.variable.bi, g.variable.mem,
+		g.variable.bi.Arch.AddrAndStackRegsToDwarfRegisters(so.StaticBase, g.PC, g.SP, g.BP),
+		g.stackhi, stkbar, g.stkbarPos, g), nil
 }
 
 // Stacktrace returns the stack trace for a goroutine.

pkg/proc/variables.go

@@ -213,6 +213,60 @@ type G struct {
 	Unreadable error // could not read the G struct
 }
 
+// Defer returns the top-most defer of the goroutine.
+func (g *G) Defer() *Defer {
+	if g.variable.Unreadable != nil {
+		return nil
+	}
+	dvar := g.variable.fieldVariable("_defer").maybeDereference()
+	if dvar.Addr == 0 {
+		return nil
+	}
+	d := &Defer{variable: dvar}
+	d.load()
+	return d
+}
+
+// UserCurrent returns the location the users code is at,
+// or was at before entering a runtime function.
+func (g *G) UserCurrent() Location {
+	it, err := g.stackIterator()
+	if err != nil {
+		return g.CurrentLoc
+	}
+	for it.Next() {
+		frame := it.Frame()
+		if frame.Call.Fn != nil {
+			name := frame.Call.Fn.Name
+			if strings.Contains(name, ".") && (!strings.HasPrefix(name, "runtime.") || isExportedRuntime(name)) {
+				return frame.Call
+			}
+		}
+	}
+	return g.CurrentLoc
+}
+
+// Go returns the location of the 'go' statement
+// that spawned this goroutine.
+func (g *G) Go() Location {
+	pc := g.GoPC
+	if fn := g.variable.bi.PCToFunc(pc); fn != nil {
+		// Backup to CALL instruction.
+		// Mimics runtime/traceback.go:677.
+		if g.GoPC > fn.Entry {
+			pc--
+		}
+	}
+	f, l, fn := g.variable.bi.PCToLine(pc)
+	return Location{PC: g.GoPC, File: f, Line: l, Fn: fn}
+}
+
+// StartLoc returns the starting location of the goroutine.
+func (g *G) StartLoc() Location {
+	f, l, fn := g.variable.bi.PCToLine(g.StartPC)
+	return Location{PC: g.StartPC, File: f, Line: l, Fn: fn}
+}
+
 type Ancestor struct {
 	ID         int64 // Goroutine ID
 	Unreadable error
@@ -601,20 +655,6 @@ func (v *Variable) fieldVariable(name string) *Variable {
 	return nil
 }
 
-// Defer returns the top-most defer of the goroutine.
-func (g *G) Defer() *Defer {
-	if g.variable.Unreadable != nil {
-		return nil
-	}
-	dvar := g.variable.fieldVariable("_defer").maybeDereference()
-	if dvar.Addr == 0 {
-		return nil
-	}
-	d := &Defer{variable: dvar}
-	d.load()
-	return d
-}
-
 // From $GOROOT/src/runtime/traceback.go:597
 // isExportedRuntime reports whether name is an exported runtime function.
 // It is only for runtime functions, so ASCII A-Z is fine.
@@ -623,46 +663,6 @@ func isExportedRuntime(name string) bool {
 	return len(name) > n && name[:n] == "runtime." && 'A' <= name[n] && name[n] <= 'Z'
 }
 
-// UserCurrent returns the location the users code is at,
-// or was at before entering a runtime function.
-func (g *G) UserCurrent() Location {
-	it, err := g.stackIterator()
-	if err != nil {
-		return g.CurrentLoc
-	}
-	for it.Next() {
-		frame := it.Frame()
-		if frame.Call.Fn != nil {
-			name := frame.Call.Fn.Name
-			if strings.Contains(name, ".") && (!strings.HasPrefix(name, "runtime.") || isExportedRuntime(name)) {
-				return frame.Call
-			}
-		}
-	}
-	return g.CurrentLoc
-}
-
-// Go returns the location of the 'go' statement
-// that spawned this goroutine.
-func (g *G) Go() Location {
-	pc := g.GoPC
-	if fn := g.variable.bi.PCToFunc(pc); fn != nil {
-		// Backup to CALL instruction.
-		// Mimics runtime/traceback.go:677.
-		if g.GoPC > fn.Entry {
-			pc--
-		}
-	}
-	f, l, fn := g.variable.bi.PCToLine(pc)
-	return Location{PC: g.GoPC, File: f, Line: l, Fn: fn}
-}
-
-// StartLoc returns the starting location of the goroutine.
-func (g *G) StartLoc() Location {
-	f, l, fn := g.variable.bi.PCToLine(g.StartPC)
-	return Location{PC: g.StartPC, File: f, Line: l, Fn: fn}
-}
-
 var errTracebackAncestorsDisabled = errors.New("tracebackancestors is disabled")
 
 // Ancestors returns the list of ancestors for g.