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// Copyright 2018 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 main
import (
"runtime"
"runtime/debug"
"unsafe"
)
func init() {
register("BadTraceback", BadTraceback)
}
func BadTraceback() {
// Disable GC to prevent traceback at unexpected time.
debug.SetGCPercent(-1)
// Run badLR1 on its own stack to minimize the stack size and
// exercise the stack bounds logic in the hex dump.
go badLR1()
select {}
}
//go:noinline
func badLR1() {
// We need two frames on LR machines because we'll smash this
// frame's saved LR.
badLR2(0)
}
//go:noinline
func badLR2(arg int) {
// Smash the return PC or saved LR.
lrOff := unsafe.Sizeof(uintptr(0))
if runtime.GOARCH == "ppc64" || runtime.GOARCH == "ppc64le" {
lrOff = 32 // FIXED_FRAME or sys.MinFrameSize
}
lrPtr := (*uintptr)(unsafe.Pointer(uintptr(unsafe.Pointer(&arg)) - lrOff))
*lrPtr = 0xbad
// Print a backtrace. This should include diagnostics for the
// bad return PC and a hex dump.
panic("backtrace")
}
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