Add stack frame support. Architectures are now responsible

for decoding closures.  There is now no notion of a current OS
thread, though that needs to come back in the form of a
current Go thread.  As a result, Process now implements Peek
and Poke and maps them to any stopped OS thread, since they
all share the address space anyways.

R=rsc
APPROVED=rsc
DELTA=322  (310 added, 3 deleted, 9 changed)
OCL=34136
CL=34201

usr/austin/ogle/arch.go

@@ -28,6 +28,7 @@ type Arch interface {
 	ToFloat64(bits uint64) float64;
 	// FromFloat64 is to float64 as FromFloat32 is to float32.
 	FromFloat64(f float64) uint64;
+
 	// IntSize returns the number of bytes in an 'int'.
 	IntSize() int;
 	// PtrSize returns the number of bytes in a 'uintptr'.
@@ -37,8 +38,17 @@ type Arch interface {
 	// Align rounds offset up to the appropriate offset for a
 	// basic type with the given width.
 	Align(offset, width int) int;
+
 	// G returns the current G pointer.
 	G(regs ptrace.Regs) ptrace.Word;
+
+	// ClosureSize returns the number of bytes expected by
+	// ParseClosure.
+	ClosureSize() int;
+	// ParseClosure takes ClosureSize bytes read from a return PC
+	// in a remote process, determines if the code is a closure,
+	// and returns the frame size of the closure if it is.
+	ParseClosure(data []byte) (frame int, ok bool);
 }
 
 type ArchLSB struct {}
@@ -115,4 +125,15 @@ func (a *amd64) G(regs ptrace.Regs) ptrace.Word {
 	return regs.Get(a.gReg);
 }
 
+func (a *amd64) ClosureSize() int {
+	return 8;
+}
+
+func (a *amd64) ParseClosure(data []byte) (int, bool) {
+	if data[0] == 0x48 && data[1] == 0x81 && data[2] == 0xc4 && data[7] == 0xc3 {
+		return int(a.ToWord(data[3:7]) + 8), true;
+	}
+	return 0, false;
+}
+
 var Amd64 = &amd64{gReg: -1};

usr/austin/ogle/frame.go

+// Copyright 2009 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 ogle
+
+import (
+	"fmt";
+	"ptrace";
+	"sym";
+)
+
+// A Frame represents a single frame on a remote call stack.
+type Frame struct {
+	// pc is the PC of the next instruction that will execute in
+	// this frame.  For lower frames, this is the instruction
+	// following the CALL instruction.
+	pc, sp, fp ptrace.Word;
+	// The runtime.Stktop of the active stack segment
+	stk remoteStruct;
+	// The function this stack frame is in
+	fn *sym.TextSym;
+	// The path and line of the CALL or current instruction.  Note
+	// that this differs slightly from the meaning of Frame.pc.
+	path string;
+	line int;
+	// The inner and outer frames of this frame.  outer is filled
+	// in lazily.
+	inner, outer *Frame;
+}
+
+// NewFrame returns the top-most Frame of the given g's thread.
+// This function can abort.
+func NewFrame(g remoteStruct) *Frame {
+	p := g.r.p;
+	var pc, sp ptrace.Word;
+
+	// Is this G alive?
+	switch g.Field(p.f.G.Status).(remoteInt).Get() {
+	case p.runtime.Gidle, p.runtime.Gmoribund, p.runtime.Gdead:
+		return nil;
+	}
+
+	// Find the OS thread for this G
+
+	// TODO(austin) Ideally, we could look at the G's state and
+	// figure out if it's on an OS thread or not.  However, this
+	// is difficult because the state isn't updated atomically
+	// with scheduling changes.
+	for _, t := range p.Threads() {
+		regs, err := t.Regs();
+		if err != nil {
+			// TODO(austin) What to do?
+			continue;
+		}
+		thisg := p.G(regs);
+		if thisg == g.addr().base {
+			// Found this G's OS thread
+			pc = regs.PC();
+			sp = regs.SP();
+
+			// If this thread crashed, try to recover it
+			if pc == 0 {
+				pc = p.peekUintptr(pc);
+				sp += 8;
+			}
+
+			break;
+		}
+	}
+
+	if pc == 0 && sp == 0 {
+		// G is not mapped to an OS thread.  Use the
+		// scheduler's stored PC and SP.
+		sched := g.Field(p.f.G.Sched).(remoteStruct);
+		pc = ptrace.Word(sched.Field(p.f.Gobuf.Pc).(remoteUint).Get());
+		sp = ptrace.Word(sched.Field(p.f.Gobuf.Sp).(remoteUint).Get());
+	}
+
+	// Get Stktop
+	stk := g.Field(p.f.G.Stackbase).(remotePtr).Get().(remoteStruct);
+
+	return prepareFrame(pc, sp, stk, nil);
+}
+
+// prepareFrame creates a Frame from the PC and SP within that frame,
+// as well as the active stack segment.  This function takes care of
+// traversing stack breaks and unwinding closures.  This function can
+// abort.
+func prepareFrame(pc, sp ptrace.Word, stk remoteStruct, inner *Frame) *Frame {
+	// Based on src/pkg/runtime/amd64/traceback.c:traceback
+	p := stk.r.p;
+	top := inner == nil;
+
+	// Get function
+	var path string;
+	var line int;
+	var fn *sym.TextSym;
+
+	for i := 0; i < 100; i++ {
+		// Traverse segmented stack breaks
+		if p.sys.lessstack != nil && pc == ptrace.Word(p.sys.lessstack.Value) {
+			// Get stk->gobuf.pc
+			pc = ptrace.Word(stk.Field(p.f.Stktop.Gobuf).(remoteStruct).Field(p.f.Gobuf.Pc).(remoteUint).Get());
+			// Get stk->gobuf.sp
+			sp = ptrace.Word(stk.Field(p.f.Stktop.Gobuf).(remoteStruct).Field(p.f.Gobuf.Sp).(remoteUint).Get());
+			// Get stk->stackbase
+			stk = stk.Field(p.f.Stktop.Stackbase).(remotePtr).Get().(remoteStruct);
+			continue;
+		}
+
+		// Get the PC of the call instruction
+		callpc := pc;
+		if !top && (p.sys.goexit == nil || pc != ptrace.Word(p.sys.goexit.Value)) {
+			callpc--;
+		}
+
+		// Look up function
+		path, line, fn = p.syms.LineFromPC(uint64(callpc));
+		if fn != nil {
+			break;
+		}
+
+		// Closure?
+		var buf = make([]byte, p.ClosureSize());
+		if _, err := p.Peek(pc, buf); err != nil {
+			break;
+		}
+		spdelta, ok := p.ParseClosure(buf);
+		if ok {
+			sp += ptrace.Word(spdelta);
+			pc = p.peekUintptr(sp - ptrace.Word(p.PtrSize()));
+		}
+	}
+	if fn == nil {
+		return nil;
+	}
+
+	// Compute frame pointer
+	var fp ptrace.Word;
+	if fn.FrameSize < p.PtrSize() {
+		fp = sp + ptrace.Word(p.PtrSize());
+	} else {
+		fp = sp + ptrace.Word(fn.FrameSize);
+	}
+	// TODO(austin) To really figure out if we're in the prologue,
+	// we need to disassemble the function and look for the call
+	// to morestack.  For now, just special case the entry point.
+	//
+	// TODO(austin) What if we're in the call to morestack in the
+	// prologue?  Then top == false.
+	if top && pc == ptrace.Word(fn.Entry()) {
+		// We're in the function prologue, before SP
+		// has been adjusted for the frame.
+		fp -= ptrace.Word(fn.FrameSize - p.PtrSize());
+	}
+
+	return &Frame{pc, sp, fp, stk, fn, path, line, inner, nil};
+}
+
+// Outer returns the Frame that called this Frame, or nil if this is
+// the outermost frame.  This function can abort.
+func (f *Frame) Outer() *Frame {
+	// Is there a cached outer frame
+	if f.outer != nil {
+		return f.outer;
+	}
+
+	p := f.stk.r.p;
+
+	sp := f.fp;
+	if f.fn == p.sys.newproc && f.fn == p.sys.deferproc {
+		// TODO(rsc) The compiler inserts two push/pop's
+		// around calls to go and defer.  Russ says this
+		// should get fixed in the compiler, but we account
+		// for it for now.
+		sp += ptrace.Word(2 * p.PtrSize());
+	}
+
+	pc := p.peekUintptr(f.fp - ptrace.Word(p.PtrSize()));
+	if pc < 0x1000 {
+		return nil;
+	}
+
+	f.outer = prepareFrame(pc, sp, f.stk, f);
+	return f.outer;
+}
+
+// Inner returns the Frame called by this Frame, or nil if this is the
+// innermost frame.
+func (f *Frame) Inner() *Frame {
+	return f.inner;
+}
+
+func (f *Frame) String() string {
+	res := f.fn.Name;
+	if f.pc > ptrace.Word(f.fn.Value) {
+		res += fmt.Sprintf("+%#x", f.pc - ptrace.Word(f.fn.Entry()));
+	}
+	return res + fmt.Sprintf(" %s:%d", f.path, f.line);
+}

usr/austin/ogle/process.go

@@ -29,6 +29,14 @@ func (e UnknownArchitecture) String() string {
 	return "unknown architecture: " + sym.ElfMachine(e).String();
 }
 
+// A ProcessNotStopped error occurs when attempting to read or write
+// memory or registers of a process that is not stopped.
+type ProcessNotStopped struct {}
+
+func (e ProcessNotStopped) String() string {
+	return "process not stopped";
+}
+
 // A Process represents a remote attached process.
 type Process struct {
 	Arch;
@@ -37,10 +45,11 @@ type Process struct {
 	// The symbol table of this process
 	syms *sym.GoSymTable;
 
-	// Current thread
-	thread ptrace.Thread;
 	// Current frame, or nil if the current thread is not stopped
-	frame *frame;
+	frame *Frame;
+
+	// A possibly-stopped OS thread, or nil
+	threadCache ptrace.Thread;
 
 	// Types parsed from the remote process
 	types map[ptrace.Word] *remoteType;
@@ -50,6 +59,11 @@ type Process struct {
 
 	// Runtime field indexes
 	f runtimeIndexes;
+
+	// Globals from the sys package (or from no package)
+	sys struct {
+		lessstack, goexit, newproc, deferproc *sym.TextSym;
+	};
 }
 
 // NewProcess constructs a new remote process around a ptrace'd
@@ -59,7 +73,6 @@ func NewProcess(proc ptrace.Process, arch Arch, syms *sym.GoSymTable) *Process {
 		Arch: arch,
 		Process: proc,
 		syms: syms,
-		thread: proc.Threads()[0],
 		types: make(map[ptrace.Word] *remoteType),
 	};
 
@@ -124,6 +137,57 @@ func (p *Process) bootstrap() {
 		rtv.Field(i).(*reflect.Uint64Value).Set(sym.Common().Value);
 	}
 
-	// Get field indexes
+	// Get runtime field indexes
 	fillRuntimeIndexes(&p.runtime, &p.f);
+
+	// Fill G status
+	p.runtime.runtimeGStatus = rt1GStatus;
+
+	// Get globals
+	globalFn := func(name string) *sym.TextSym {
+		if sym, ok := p.syms.SymFromName(name).(*sym.TextSym); ok {
+			return sym;
+		}
+		return nil;
+	};
+	p.sys.lessstack = globalFn("sys·lessstack");
+	p.sys.goexit = globalFn("goexit");
+	p.sys.newproc = globalFn("sys·newproc");
+	p.sys.deferproc = globalFn("sys·deferproc");
+}
+
+func (p *Process) someStoppedThread() ptrace.Thread {
+	if p.threadCache != nil {
+		if _, err := p.threadCache.Stopped(); err == nil {
+			return p.threadCache;
+		}
+	}
+
+	for _, t := range p.Threads() {
+		if _, err := t.Stopped(); err == nil {
+			p.threadCache = t;
+			return t;
+		}
+	}
+	return nil;
+}
+
+func (p *Process) Peek(addr ptrace.Word, out []byte) (int, os.Error) {
+	thr := p.someStoppedThread();
+	if thr == nil {
+		return 0, ProcessNotStopped{};
+	}
+	return thr.Peek(addr, out);
+}
+
+func (p *Process) Poke(addr ptrace.Word, b []byte) (int, os.Error) {
+	thr := p.someStoppedThread();
+	if thr == nil {
+		return 0, ProcessNotStopped{};
+	}
+	return thr.Poke(addr, b);
+}
+
+func (p *Process) peekUintptr(addr ptrace.Word) ptrace.Word {
+	return ptrace.Word(mkUintptr(remote{addr, p}).(remoteUint).Get());
 }

usr/austin/ogle/rruntime.go

@@ -123,10 +123,28 @@ type rt1Gobuf struct {
 }
 
 type rt1G struct {
-	stackguard uintptr;
+	// Fields beginning with _ are only for padding
+	_stackguard uintptr;
 	stackbase *rt1Stktop;
+	_defer uintptr;
+	sched rt1Gobuf;
+	_stack0 uintptr;
+	_entry uintptr;
+	alllink *rt1G;
+	_param uintptr;
+	status int16;
 }
 
+var rt1GStatus = runtimeGStatus{
+	Gidle: 0,
+	Grunnable: 1,
+	Grunning: 2,
+	Gsyscall: 3,
+	Gwaiting: 4,
+	Gmoribund: 5,
+	Gdead: 6,
+};
+
 // runtimeIndexes stores the indexes of fields in the runtime
 // structures.  It is filled in using reflection, so the name of the
 // fields must match the names of the remoteType's in runtimeValues
@@ -175,10 +193,15 @@ type runtimeIndexes struct {
 		Sp, Pc, G int;
 	};
 	G struct {
-		Stackguard, Stackbase int;
+		Stackbase, Sched, Status int;
 	};
 }
 
+// Values of G status codes
+type runtimeGStatus struct {
+	Gidle, Grunnable, Grunning, Gsyscall, Gwaiting, Gmoribund, Gdead int64;
+}
+
 // runtimeValues stores the types and values that correspond to those
 // in the remote runtime package.
 type runtimeValues struct {
@@ -200,6 +223,8 @@ type runtimeValues struct {
 	PArrayType, PStringType, PStructType, PPtrType, PFuncType,
 	PInterfaceType, PSliceType, PMapType, PChanType,
 	PDotDotDotType, PUnsafePointerType ptrace.Word;
+	// G status values
+	runtimeGStatus;
 }
 
 // fillRuntimeIndexes fills a runtimeIndexes structure will the field

usr/austin/ogle/rvalue.go

@@ -53,7 +53,7 @@ func (v remote) Get(size int) uint64 {
 	// collector from collecting objects out from under us.
 	var arr [8]byte;
 	buf := arr[0:size];
-	_, err := v.p.thread.Peek(v.base, buf);
+	_, err := v.p.Peek(v.base, buf);
 	if err != nil {
 		eval.Abort(err);
 	}
@@ -64,7 +64,7 @@ func (v remote) Set(size int, x uint64) {
 	var arr [8]byte;
 	buf := arr[0:size];
 	v.p.FromWord(ptrace.Word(x), buf);
-	_, err := v.p.thread.Poke(v.base, buf);
+	_, err := v.p.Poke(v.base, buf);
 	if err != nil {
 		eval.Abort(err);
 	}
@@ -291,7 +291,7 @@ func (v remoteString) Get() string {
 	len := rs.Field(v.r.p.f.String.Len).(remoteInt).Get();
 	
 	bytes := make([]uint8, len);
-	_, err := v.r.p.thread.Peek(str, bytes);
+	_, err := v.r.p.Peek(str, bytes);
 	if err != nil {
 		eval.Abort(err);
 	}