1// Copyright 2018 Google Inc. All Rights Reserved. 2// 3// Licensed under the Apache License, Version 2.0 (the "License"); 4// you may not use this file except in compliance with the License. 5// You may obtain a copy of the License at 6// 7// http://www.apache.org/licenses/LICENSE-2.0 8// 9// Unless required by applicable law or agreed to in writing, software 10// distributed under the License is distributed on an "AS IS" BASIS, 11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12// See the License for the specific language governing permissions and 13// limitations under the License. 14 15// +build linux 16 17package server 18 19import ( 20 "fmt" 21 "os" 22 "runtime" 23 "syscall" 24 "time" 25) 26 27// ptraceRun runs all the closures from fc on a dedicated OS thread. Errors 28// are returned on ec. Both channels must be unbuffered, to ensure that the 29// resultant error is sent back to the same goroutine that sent the closure. 30func ptraceRun(fc chan func() error, ec chan error) { 31 if cap(fc) != 0 || cap(ec) != 0 { 32 panic("ptraceRun was given buffered channels") 33 } 34 runtime.LockOSThread() 35 for f := range fc { 36 ec <- f() 37 } 38} 39 40func (s *Server) startProcess(name string, argv []string, attr *os.ProcAttr) (proc *os.Process, err error) { 41 s.fc <- func() error { 42 var err1 error 43 proc, err1 = os.StartProcess(name, argv, attr) 44 return err1 45 } 46 err = <-s.ec 47 return 48} 49 50func (s *Server) ptraceCont(pid int, signal int) (err error) { 51 s.fc <- func() error { 52 return syscall.PtraceCont(pid, signal) 53 } 54 return <-s.ec 55} 56 57func (s *Server) ptraceGetRegs(pid int, regsout *syscall.PtraceRegs) (err error) { 58 s.fc <- func() error { 59 return syscall.PtraceGetRegs(pid, regsout) 60 } 61 return <-s.ec 62} 63 64func (s *Server) ptracePeek(pid int, addr uintptr, out []byte) (err error) { 65 s.fc <- func() error { 66 n, err := syscall.PtracePeekText(pid, addr, out) 67 if err != nil { 68 return err 69 } 70 if n != len(out) { 71 return fmt.Errorf("ptracePeek: peeked %d bytes, want %d", n, len(out)) 72 } 73 return nil 74 } 75 return <-s.ec 76} 77 78func (s *Server) ptracePoke(pid int, addr uintptr, data []byte) (err error) { 79 s.fc <- func() error { 80 n, err := syscall.PtracePokeText(pid, addr, data) 81 if err != nil { 82 return err 83 } 84 if n != len(data) { 85 return fmt.Errorf("ptracePoke: poked %d bytes, want %d", n, len(data)) 86 } 87 return nil 88 } 89 return <-s.ec 90} 91 92func (s *Server) ptraceSetOptions(pid int, options int) (err error) { 93 s.fc <- func() error { 94 return syscall.PtraceSetOptions(pid, options) 95 } 96 return <-s.ec 97} 98 99func (s *Server) ptraceSetRegs(pid int, regs *syscall.PtraceRegs) (err error) { 100 s.fc <- func() error { 101 return syscall.PtraceSetRegs(pid, regs) 102 } 103 return <-s.ec 104} 105 106func (s *Server) ptraceSingleStep(pid int) (err error) { 107 s.fc <- func() error { 108 return syscall.PtraceSingleStep(pid) 109 } 110 return <-s.ec 111} 112 113type breakpointsChangedError struct { 114 call call 115} 116 117func (*breakpointsChangedError) Error() string { 118 return "breakpoints changed" 119} 120 121func (s *Server) wait(pid int, allowBreakpointsChange bool) (wpid int, status syscall.WaitStatus, err error) { 122 // We poll syscall.Wait4 with WNOHANG, sleeping in between, as a poor man's 123 // waitpid-with-timeout. This allows adding and removing breakpoints 124 // concurrently with waiting to hit an existing breakpoint. 125 f := func() error { 126 var err1 error 127 wpid, err1 = syscall.Wait4(pid, &status, syscall.WALL|syscall.WNOHANG, nil) 128 return err1 129 } 130 131 const ( 132 minSleep = 1 * time.Microsecond 133 maxSleep = 100 * time.Millisecond 134 ) 135 for sleep := minSleep; ; { 136 s.fc <- f 137 err = <-s.ec 138 139 // wpid == 0 means that wait found nothing (and returned due to WNOHANG). 140 if wpid != 0 { 141 return 142 } 143 144 if allowBreakpointsChange { 145 select { 146 case c := <-s.breakpointc: 147 return 0, 0, &breakpointsChangedError{c} 148 default: 149 } 150 } 151 152 time.Sleep(sleep) 153 if sleep < maxSleep { 154 sleep *= 10 155 } 156 } 157} 158