1 // Copyright 2018 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 package main 6 7 import ( 8 "runtime" 9 "runtime/debug" 10 "unsafe" 11 ) 12 13 func init() { 14 register("BadTraceback", BadTraceback) 15 } 16 17 func BadTraceback() { 18 // Disable GC to prevent traceback at unexpected time. 19 debug.SetGCPercent(-1) 20 21 // Run badLR1 on its own stack to minimize the stack size and 22 // exercise the stack bounds logic in the hex dump. 23 go badLR1() 24 select {} 25 } 26 27 //go:noinline 28 func badLR1() { 29 // We need two frames on LR machines because we'll smash this 30 // frame's saved LR. 31 badLR2(0) 32 } 33 34 //go:noinline 35 func badLR2(arg int) { 36 // Smash the return PC or saved LR. 37 lrOff := unsafe.Sizeof(uintptr(0)) 38 if runtime.GOARCH == "ppc64" || runtime.GOARCH == "ppc64le" { 39 lrOff = 32 // FIXED_FRAME or sys.MinFrameSize 40 } 41 lrPtr := (*uintptr)(unsafe.Pointer(uintptr(unsafe.Pointer(&arg)) - lrOff)) 42 *lrPtr = 0xbad 43 44 // Print a backtrace. This should include diagnostics for the 45 // bad return PC and a hex dump. 46 panic("backtrace") 47 } 48
