delve/pkg/proc/proc.go
Alessandro Arzilli 07e53f7cbb proc: fix interaction of RequestManualStop and conditional breakpoints (#876)
* proc: fix interaction of RequestManualStop and conditional breakpoints

A conditional breakpoint that is hit but has the condition evaluate to
false can block a RequestManualStop from working. If the conditional
breakpoint is set on an instruction that is executed very frequently by
multiple goroutines (or many conditional breakpoints are set) it could
prevent all calls to RequestManualStop from working.

This commit fixes the problem by changing proc.Continue to exit
unconditionally after a RequestManualStop is called.

* proc/gdbserial: fix ContinueOnce getting stuck on macOS

Fixes #902
2017-07-07 16:29:37 -07:00

494 lines
12 KiB
Go

package proc
import (
"encoding/binary"
"errors"
"fmt"
"go/ast"
"go/token"
"path/filepath"
"strconv"
"golang.org/x/debug/dwarf"
)
type functionDebugInfo struct {
lowpc, highpc uint64
offset dwarf.Offset
}
var NotExecutableErr = errors.New("not an executable file")
var NotRecordedErr = errors.New("not a recording")
// ProcessExitedError indicates that the process has exited and contains both
// process id and exit status.
type ProcessExitedError struct {
Pid int
Status int
}
func (pe ProcessExitedError) Error() string {
return fmt.Sprintf("Process %d has exited with status %d", pe.Pid, pe.Status)
}
// FindFileLocation returns the PC for a given file:line.
// Assumes that `file` is normailzed to lower case and '/' on Windows.
func FindFileLocation(p Process, fileName string, lineno int) (uint64, error) {
pc, fn, err := p.BinInfo().goSymTable.LineToPC(fileName, lineno)
if err != nil {
return 0, err
}
if fn.Entry == pc {
pc, _ = FirstPCAfterPrologue(p, fn, true)
}
return pc, nil
}
// FindFunctionLocation finds address of a function's line
// If firstLine == true is passed FindFunctionLocation will attempt to find the first line of the function
// If lineOffset is passed FindFunctionLocation will return the address of that line
// Pass lineOffset == 0 and firstLine == false if you want the address for the function's entry point
// Note that setting breakpoints at that address will cause surprising behavior:
// https://github.com/derekparker/delve/issues/170
func FindFunctionLocation(p Process, funcName string, firstLine bool, lineOffset int) (uint64, error) {
bi := p.BinInfo()
origfn := bi.goSymTable.LookupFunc(funcName)
if origfn == nil {
return 0, fmt.Errorf("Could not find function %s\n", funcName)
}
if firstLine {
return FirstPCAfterPrologue(p, origfn, false)
} else if lineOffset > 0 {
filename, lineno, _ := bi.goSymTable.PCToLine(origfn.Entry)
breakAddr, _, err := bi.goSymTable.LineToPC(filename, lineno+lineOffset)
return breakAddr, err
}
return origfn.Entry, nil
}
// Next continues execution until the next source line.
func Next(dbp Process) (err error) {
if dbp.Exited() {
return &ProcessExitedError{}
}
for _, bp := range dbp.Breakpoints() {
if bp.Internal() {
return fmt.Errorf("next while nexting")
}
}
if err = next(dbp, false); err != nil {
switch err.(type) {
case ThreadBlockedError, NoReturnAddr: // Noop
default:
dbp.ClearInternalBreakpoints()
return
}
}
return Continue(dbp)
}
// Continue continues execution of the debugged
// process. It will continue until it hits a breakpoint
// or is otherwise stopped.
func Continue(dbp Process) error {
dbp.ManualStopRequested()
for {
if dbp.ManualStopRequested() {
return nil
}
trapthread, err := dbp.ContinueOnce()
if err != nil {
return err
}
threads := dbp.ThreadList()
if err := pickCurrentThread(dbp, trapthread, threads); err != nil {
return err
}
curthread := dbp.CurrentThread()
curbp, curbpActive, _ := curthread.Breakpoint()
switch {
case curbp == nil:
// runtime.Breakpoint or manual stop
if recorded, _ := dbp.Recorded(); onRuntimeBreakpoint(curthread) && !recorded {
// Single-step current thread until we exit runtime.breakpoint and
// runtime.Breakpoint.
// On go < 1.8 it was sufficient to single-step twice on go1.8 a change
// to the compiler requires 4 steps.
for {
if err = curthread.StepInstruction(); err != nil {
return err
}
loc, err := curthread.Location()
if err != nil || loc.Fn == nil || (loc.Fn.Name != "runtime.breakpoint" && loc.Fn.Name != "runtime.Breakpoint") {
break
}
}
}
return conditionErrors(threads)
case curbpActive && curbp.Internal():
if curbp.Kind == StepBreakpoint {
// See description of proc.(*Process).next for the meaning of StepBreakpoints
if err := conditionErrors(threads); err != nil {
return err
}
regs, err := curthread.Registers(false)
if err != nil {
return err
}
pc := regs.PC()
text, err := disassemble(curthread, regs, dbp.Breakpoints(), dbp.BinInfo(), pc, pc+maxInstructionLength)
if err != nil {
return err
}
// here we either set a breakpoint into the destination of the CALL
// instruction or we determined that the called function is hidden,
// either way we need to resume execution
if err = setStepIntoBreakpoint(dbp, text, SameGoroutineCondition(dbp.SelectedGoroutine())); err != nil {
return err
}
} else {
if err := dbp.ClearInternalBreakpoints(); err != nil {
return err
}
return conditionErrors(threads)
}
case curbpActive:
onNextGoroutine, err := onNextGoroutine(curthread, dbp.Breakpoints())
if err != nil {
return err
}
if onNextGoroutine {
err := dbp.ClearInternalBreakpoints()
if err != nil {
return err
}
}
return conditionErrors(threads)
default:
// not a manual stop, not on runtime.Breakpoint, not on a breakpoint, just repeat
}
}
}
func conditionErrors(threads []Thread) error {
var condErr error
for _, th := range threads {
if bp, _, bperr := th.Breakpoint(); bp != nil && bperr != nil {
if condErr == nil {
condErr = bperr
} else {
return fmt.Errorf("multiple errors evaluating conditions")
}
}
}
return condErr
}
// pick a new dbp.currentThread, with the following priority:
// - a thread with onTriggeredInternalBreakpoint() == true
// - a thread with onTriggeredBreakpoint() == true (prioritizing trapthread)
// - trapthread
func pickCurrentThread(dbp Process, trapthread Thread, threads []Thread) error {
for _, th := range threads {
if bp, active, _ := th.Breakpoint(); active && bp.Internal() {
return dbp.SwitchThread(th.ThreadID())
}
}
if _, active, _ := trapthread.Breakpoint(); active {
return dbp.SwitchThread(trapthread.ThreadID())
}
for _, th := range threads {
if _, active, _ := th.Breakpoint(); active {
return dbp.SwitchThread(th.ThreadID())
}
}
return dbp.SwitchThread(trapthread.ThreadID())
}
// Step will continue until another source line is reached.
// Will step into functions.
func Step(dbp Process) (err error) {
if dbp.Exited() {
return &ProcessExitedError{}
}
for _, bp := range dbp.Breakpoints() {
if bp.Internal() {
return fmt.Errorf("next while nexting")
}
}
if err = next(dbp, true); err != nil {
switch err.(type) {
case ThreadBlockedError, NoReturnAddr: // Noop
default:
dbp.ClearInternalBreakpoints()
return
}
}
return Continue(dbp)
}
// SameGoroutineCondition returns an expression that evaluates to true when
// the current goroutine is g.
func SameGoroutineCondition(g *G) ast.Expr {
if g == nil {
return nil
}
return &ast.BinaryExpr{
Op: token.EQL,
X: &ast.SelectorExpr{
X: &ast.SelectorExpr{
X: &ast.Ident{Name: "runtime"},
Sel: &ast.Ident{Name: "curg"},
},
Sel: &ast.Ident{Name: "goid"},
},
Y: &ast.BasicLit{Kind: token.INT, Value: strconv.Itoa(g.ID)},
}
}
func frameoffCondition(frameoff int64) ast.Expr {
return &ast.BinaryExpr{
Op: token.EQL,
X: &ast.SelectorExpr{
X: &ast.Ident{Name: "runtime"},
Sel: &ast.Ident{Name: "frameoff"},
},
Y: &ast.BasicLit{Kind: token.INT, Value: strconv.FormatInt(frameoff, 10)},
}
}
func andFrameoffCondition(cond ast.Expr, frameoff int64) ast.Expr {
if cond == nil {
return nil
}
return &ast.BinaryExpr{
Op: token.LAND,
X: cond,
Y: frameoffCondition(frameoff),
}
}
// StepOut will continue until the current goroutine exits the
// function currently being executed or a deferred function is executed
func StepOut(dbp Process) error {
selg := dbp.SelectedGoroutine()
curthread := dbp.CurrentThread()
topframe, retframe, err := topframe(selg, curthread)
if err != nil {
return err
}
sameGCond := SameGoroutineCondition(selg)
retFrameCond := andFrameoffCondition(sameGCond, retframe.CFA-int64(retframe.StackHi))
var deferpc uint64 = 0
if filepath.Ext(topframe.Current.File) == ".go" {
if selg != nil {
deferPCEntry := selg.DeferPC()
if deferPCEntry != 0 {
_, _, deferfn := dbp.BinInfo().PCToLine(deferPCEntry)
deferpc, err = FirstPCAfterPrologue(dbp, deferfn, false)
if err != nil {
return err
}
}
}
}
if topframe.Ret == 0 && deferpc == 0 {
return errors.New("nothing to stepout to")
}
if deferpc != 0 && deferpc != topframe.Current.PC {
bp, err := dbp.SetBreakpoint(deferpc, NextDeferBreakpoint, sameGCond)
if err != nil {
if _, ok := err.(BreakpointExistsError); !ok {
dbp.ClearInternalBreakpoints()
return err
}
}
if bp != nil {
// For StepOut we do not want to step into the deferred function
// when it's called by runtime.deferreturn so we do not populate
// DeferReturns.
bp.DeferReturns = []uint64{}
}
}
if topframe.Ret != 0 {
_, err := dbp.SetBreakpoint(topframe.Ret, NextBreakpoint, retFrameCond)
if err != nil {
if _, isexists := err.(BreakpointExistsError); !isexists {
dbp.ClearInternalBreakpoints()
return err
}
}
}
if bp, _, _ := curthread.Breakpoint(); bp == nil {
curthread.SetCurrentBreakpoint()
}
return Continue(dbp)
}
// If the argument of GoroutinesInfo implements AllGCache GoroutinesInfo
// will use the pointer returned by AllGCache as a cache.
type AllGCache interface {
AllGCache() *[]*G
}
// GoroutinesInfo returns an array of G structures representing the information
// Delve cares about from the internal runtime G structure.
func GoroutinesInfo(dbp Process) ([]*G, error) {
if dbp.Exited() {
return nil, &ProcessExitedError{}
}
if dbp, ok := dbp.(AllGCache); ok {
if allGCache := dbp.AllGCache(); *allGCache != nil {
return *allGCache, nil
}
}
var (
threadg = map[int]Thread{}
allg []*G
rdr = dbp.BinInfo().DwarfReader()
)
threads := dbp.ThreadList()
for _, th := range threads {
if th.Blocked() {
continue
}
g, _ := GetG(th)
if g != nil {
threadg[g.ID] = th
}
}
addr, err := rdr.AddrFor("runtime.allglen")
if err != nil {
return nil, err
}
allglenBytes := make([]byte, 8)
_, err = dbp.CurrentThread().ReadMemory(allglenBytes, uintptr(addr))
if err != nil {
return nil, err
}
allglen := binary.LittleEndian.Uint64(allglenBytes)
rdr.Seek(0)
allgentryaddr, err := rdr.AddrFor("runtime.allgs")
if err != nil {
// try old name (pre Go 1.6)
allgentryaddr, err = rdr.AddrFor("runtime.allg")
if err != nil {
return nil, err
}
}
faddr := make([]byte, dbp.BinInfo().Arch.PtrSize())
_, err = dbp.CurrentThread().ReadMemory(faddr, uintptr(allgentryaddr))
if err != nil {
return nil, err
}
allgptr := binary.LittleEndian.Uint64(faddr)
for i := uint64(0); i < allglen; i++ {
gvar, err := newGVariable(dbp.CurrentThread(), uintptr(allgptr+(i*uint64(dbp.BinInfo().Arch.PtrSize()))), true)
if err != nil {
return nil, err
}
g, err := gvar.parseG()
if err != nil {
return nil, err
}
if thread, allocated := threadg[g.ID]; allocated {
loc, err := thread.Location()
if err != nil {
return nil, err
}
g.Thread = thread
// Prefer actual thread location information.
g.CurrentLoc = *loc
}
if g.Status != Gdead {
allg = append(allg, g)
}
}
if dbp, ok := dbp.(AllGCache); ok {
allGCache := dbp.AllGCache()
*allGCache = allg
}
return allg, nil
}
// FindGoroutine returns a G struct representing the goroutine
// specified by `gid`.
func FindGoroutine(dbp Process, gid int) (*G, error) {
if gid == -1 {
return dbp.SelectedGoroutine(), nil
}
gs, err := GoroutinesInfo(dbp)
if err != nil {
return nil, err
}
for i := range gs {
if gs[i].ID == gid {
return gs[i], nil
}
}
return nil, fmt.Errorf("Unknown goroutine %d", gid)
}
// ConvertEvalScope returns a new EvalScope in the context of the
// specified goroutine ID and stack frame.
func ConvertEvalScope(dbp Process, gid, frame int) (*EvalScope, error) {
ct := dbp.CurrentThread()
g, err := FindGoroutine(dbp, gid)
if err != nil {
return nil, err
}
if g == nil {
return ThreadScope(ct)
}
var thread MemoryReadWriter
if g.Thread == nil {
thread = ct
} else {
thread = g.Thread
}
locs, err := g.Stacktrace(frame)
if err != nil {
return nil, err
}
if frame >= len(locs) {
return nil, fmt.Errorf("Frame %d does not exist in goroutine %d", frame, gid)
}
PC, CFA := locs[frame].Current.PC, locs[frame].CFA
return &EvalScope{PC, CFA, thread, g.variable, dbp.BinInfo(), g.stackhi}, nil
}
// FrameToScope returns a new EvalScope for this frame
func FrameToScope(p Process, frame Stackframe) *EvalScope {
return &EvalScope{frame.Current.PC, frame.CFA, p.CurrentThread(), nil, p.BinInfo(), frame.StackHi}
}