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/
breakpoints.go
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/
breakpoints.go
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package proc
import (
"errors"
"fmt"
"go/ast"
"go/constant"
"reflect"
)
// Breakpoint represents a breakpoint. Stores information on the break
// point including the byte of data that originally was stored at that
// address.
type Breakpoint struct {
// File & line information for printing.
FunctionName string
File string
Line int
Addr uint64 // Address breakpoint is set for.
OriginalData []byte // If software breakpoint, the data we replace with breakpoint instruction.
Name string // User defined name of the breakpoint
ID int // Monotonically increasing ID.
Kind BreakpointKind // Whether this is a temp breakpoint (for next'ing or stepping).
// Breakpoint information
Tracepoint bool // Tracepoint flag
Goroutine bool // Retrieve goroutine information
Stacktrace int // Number of stack frames to retrieve
Variables []string // Variables to evaluate
LoadArgs *LoadConfig
LoadLocals *LoadConfig
HitCount map[int]uint64 // Number of times a breakpoint has been reached in a certain goroutine
TotalHitCount uint64 // Number of times a breakpoint has been reached
// DeferReturns: when kind == NextDeferBreakpoint this breakpoint
// will also check if the caller is runtime.gopanic or if the return
// address is in the DeferReturns array.
// Next uses NextDeferBreakpoints for the breakpoint it sets on the
// deferred function, DeferReturns is populated with the
// addresses of calls to runtime.deferreturn in the current
// function. This insures that the breakpoint on the deferred
// function only triggers on panic or on the defer call to
// the function, not when the function is called directly
DeferReturns []uint64
// Cond: if not nil the breakpoint will be triggered only if evaluating Cond returns true
Cond ast.Expr
}
// Breakpoint Kind determines the behavior of delve when the
// breakpoint is reached.
type BreakpointKind int
const (
// UserBreakpoint is a user set breakpoint
UserBreakpoint BreakpointKind = iota
// NextBreakpoint is a breakpoint set by Next, Continue
// will stop on it and delete it
NextBreakpoint
// NextDeferBreakpoint is a breakpoint set by Next on the
// first deferred function. In addition to checking their condition
// breakpoints of this kind will also check that the function has been
// called by runtime.gopanic or through runtime.deferreturn.
NextDeferBreakpoint
// StepBreakpoint is a breakpoint set by Step on a CALL instruction,
// Continue will set a new breakpoint (of NextBreakpoint kind) on the
// destination of CALL, delete this breakpoint and then continue again
StepBreakpoint
)
func (bp *Breakpoint) String() string {
return fmt.Sprintf("Breakpoint %d at %#v %s:%d (%d)", bp.ID, bp.Addr, bp.File, bp.Line, bp.TotalHitCount)
}
// Clear this breakpoint appropriately depending on whether it is a
// hardware or software breakpoint.
func (bp *Breakpoint) Clear(thread *Thread) (*Breakpoint, error) {
if _, err := thread.writeMemory(uintptr(bp.Addr), bp.OriginalData); err != nil {
return nil, fmt.Errorf("could not clear breakpoint %s", err)
}
return bp, nil
}
// BreakpointExistsError is returned when trying to set a breakpoint at
// an address that already has a breakpoint set for it.
type BreakpointExistsError struct {
file string
line int
addr uint64
}
func (bpe BreakpointExistsError) Error() string {
return fmt.Sprintf("Breakpoint exists at %s:%d at %x", bpe.file, bpe.line, bpe.addr)
}
// InvalidAddressError represents the result of
// attempting to set a breakpoint at an invalid address.
type InvalidAddressError struct {
address uint64
}
func (iae InvalidAddressError) Error() string {
return fmt.Sprintf("Invalid address %#v\n", iae.address)
}
func (dbp *Process) setBreakpoint(tid int, addr uint64, kind BreakpointKind) (*Breakpoint, error) {
if bp, ok := dbp.FindBreakpoint(addr); ok {
return nil, BreakpointExistsError{bp.File, bp.Line, bp.Addr}
}
f, l, fn := dbp.goSymTable.PCToLine(uint64(addr))
if fn == nil {
return nil, InvalidAddressError{address: addr}
}
newBreakpoint := &Breakpoint{
FunctionName: fn.Name,
File: f,
Line: l,
Addr: addr,
Kind: kind,
Cond: nil,
HitCount: map[int]uint64{},
}
if kind != UserBreakpoint {
dbp.tempBreakpointIDCounter++
newBreakpoint.ID = dbp.tempBreakpointIDCounter
} else {
dbp.breakpointIDCounter++
newBreakpoint.ID = dbp.breakpointIDCounter
}
thread := dbp.Threads[tid]
originalData, err := thread.readMemory(uintptr(addr), dbp.arch.BreakpointSize())
if err != nil {
return nil, err
}
if err := dbp.writeSoftwareBreakpoint(thread, addr); err != nil {
return nil, err
}
newBreakpoint.OriginalData = originalData
dbp.Breakpoints[addr] = newBreakpoint
return newBreakpoint, nil
}
func (dbp *Process) writeSoftwareBreakpoint(thread *Thread, addr uint64) error {
_, err := thread.writeMemory(uintptr(addr), dbp.arch.BreakpointInstruction())
return err
}
func (bp *Breakpoint) checkCondition(thread *Thread) (bool, error) {
if bp.Cond == nil {
return true, nil
}
if bp.Kind == NextDeferBreakpoint {
frames, err := thread.Stacktrace(2)
if err == nil {
ispanic := len(frames) >= 3 && frames[2].Current.Fn != nil && frames[2].Current.Fn.Name == "runtime.gopanic"
isdeferreturn := false
if len(frames) >= 1 {
for _, pc := range bp.DeferReturns {
if frames[0].Ret == pc {
isdeferreturn = true
break
}
}
}
if !ispanic && !isdeferreturn {
return false, nil
}
}
}
scope, err := thread.Scope()
if err != nil {
return true, err
}
v, err := scope.evalAST(bp.Cond)
if err != nil {
return true, fmt.Errorf("error evaluating expression: %v", err)
}
if v.Unreadable != nil {
return true, fmt.Errorf("condition expression unreadable: %v", v.Unreadable)
}
if v.Kind != reflect.Bool {
return true, errors.New("condition expression not boolean")
}
return constant.BoolVal(v.Value), nil
}
// Internal returns true for breakpoints not set directly by the user.
func (bp *Breakpoint) Internal() bool {
return bp.Kind != UserBreakpoint
}
// NoBreakpointError is returned when trying to
// clear a breakpoint that does not exist.
type NoBreakpointError struct {
addr uint64
}
func (nbp NoBreakpointError) Error() string {
return fmt.Sprintf("no breakpoint at %#v", nbp.addr)
}