1 files changed, 182 insertions, 0 deletions
diff --git a/src/runtime/export_debug_test.go b/src/runtime/export_debug_test.go
new file mode 100644
index 0000000..2d8a133
--- /dev/null
+++ b/src/runtime/export_debug_test.go
@@ -0,0 +1,182 @@
+// 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.
+
+//go:build (amd64 || arm64) && linux
+
+package runtime
+
+import (
+	"internal/abi"
+	"unsafe"
+)
+
+// InjectDebugCall injects a debugger call to fn into g. regArgs must
+// contain any arguments to fn that are passed in registers, according
+// to the internal Go ABI. It may be nil if no arguments are passed in
+// registers to fn. args must be a pointer to a valid call frame (including
+// arguments and return space) for fn, or nil. tkill must be a function that
+// will send SIGTRAP to thread ID tid. gp must be locked to its OS thread and
+// running.
+//
+// On success, InjectDebugCall returns the panic value of fn or nil.
+// If fn did not panic, its results will be available in args.
+func InjectDebugCall(gp *g, fn any, regArgs *abi.RegArgs, stackArgs any, tkill func(tid int) error, returnOnUnsafePoint bool) (any, error) {
+	if gp.lockedm == 0 {
+		return nil, plainError("goroutine not locked to thread")
+	}
+
+	tid := int(gp.lockedm.ptr().procid)
+	if tid == 0 {
+		return nil, plainError("missing tid")
+	}
+
+	f := efaceOf(&fn)
+	if f._type == nil || f._type.kind&kindMask != kindFunc {
+		return nil, plainError("fn must be a function")
+	}
+	fv := (*funcval)(f.data)
+
+	a := efaceOf(&stackArgs)
+	if a._type != nil && a._type.kind&kindMask != kindPtr {
+		return nil, plainError("args must be a pointer or nil")
+	}
+	argp := a.data
+	var argSize uintptr
+	if argp != nil {
+		argSize = (*ptrtype)(unsafe.Pointer(a._type)).elem.size
+	}
+
+	h := new(debugCallHandler)
+	h.gp = gp
+	// gp may not be running right now, but we can still get the M
+	// it will run on since it's locked.
+	h.mp = gp.lockedm.ptr()
+	h.fv, h.regArgs, h.argp, h.argSize = fv, regArgs, argp, argSize
+	h.handleF = h.handle // Avoid allocating closure during signal
+
+	defer func() { testSigtrap = nil }()
+	for i := 0; ; i++ {
+		testSigtrap = h.inject
+		noteclear(&h.done)
+		h.err = ""
+
+		if err := tkill(tid); err != nil {
+			return nil, err
+		}
+		// Wait for completion.
+		notetsleepg(&h.done, -1)
+		if h.err != "" {
+			switch h.err {
+			case "call not at safe point":
+				if returnOnUnsafePoint {
+					// This is for TestDebugCallUnsafePoint.
+					return nil, h.err
+				}
+				fallthrough
+			case "retry _Grunnable", "executing on Go runtime stack", "call from within the Go runtime":
+				// These are transient states. Try to get out of them.
+				if i < 100 {
+					usleep(100)
+					Gosched()
+					continue
+				}
+			}
+			return nil, h.err
+		}
+		return h.panic, nil
+	}
+}
+
+type debugCallHandler struct {
+	gp      *g
+	mp      *m
+	fv      *funcval
+	regArgs *abi.RegArgs
+	argp    unsafe.Pointer
+	argSize uintptr
+	panic   any
+
+	handleF func(info *siginfo, ctxt *sigctxt, gp2 *g) bool
+
+	err     plainError
+	done    note
+	sigCtxt sigContext
+}
+
+func (h *debugCallHandler) inject(info *siginfo, ctxt *sigctxt, gp2 *g) bool {
+	// TODO(49370): This code is riddled with write barriers, but called from
+	// a signal handler. Add the go:nowritebarrierrec annotation and restructure
+	// this to avoid write barriers.
+
+	switch h.gp.atomicstatus.Load() {
+	case _Grunning:
+		if getg().m != h.mp {
+			println("trap on wrong M", getg().m, h.mp)
+			return false
+		}
+		// Save the signal context
+		h.saveSigContext(ctxt)
+		// Set PC to debugCallV2.
+		ctxt.setsigpc(uint64(abi.FuncPCABIInternal(debugCallV2)))
+		// Call injected. Switch to the debugCall protocol.
+		testSigtrap = h.handleF
+	case _Grunnable:
+		// Ask InjectDebugCall to pause for a bit and then try
+		// again to interrupt this goroutine.
+		h.err = plainError("retry _Grunnable")
+		notewakeup(&h.done)
+	default:
+		h.err = plainError("goroutine in unexpected state at call inject")
+		notewakeup(&h.done)
+	}
+	// Resume execution.
+	return true
+}
+
+func (h *debugCallHandler) handle(info *siginfo, ctxt *sigctxt, gp2 *g) bool {
+	// TODO(49370): This code is riddled with write barriers, but called from
+	// a signal handler. Add the go:nowritebarrierrec annotation and restructure
+	// this to avoid write barriers.
+
+	// Double-check m.
+	if getg().m != h.mp {
+		println("trap on wrong M", getg().m, h.mp)
+		return false
+	}
+	f := findfunc(ctxt.sigpc())
+	if !(hasPrefix(funcname(f), "runtime.debugCall") || hasPrefix(funcname(f), "debugCall")) {
+		println("trap in unknown function", funcname(f))
+		return false
+	}
+	if !sigctxtAtTrapInstruction(ctxt) {
+		println("trap at non-INT3 instruction pc =", hex(ctxt.sigpc()))
+		return false
+	}
+
+	switch status := sigctxtStatus(ctxt); status {
+	case 0:
+		// Frame is ready. Copy the arguments to the frame and to registers.
+		// Call the debug function.
+		h.debugCallRun(ctxt)
+	case 1:
+		// Function returned. Copy frame and result registers back out.
+		h.debugCallReturn(ctxt)
+	case 2:
+		// Function panicked. Copy panic out.
+		h.debugCallPanicOut(ctxt)
+	case 8:
+		// Call isn't safe. Get the reason.
+		h.debugCallUnsafe(ctxt)
+		// Don't wake h.done. We need to transition to status 16 first.
+	case 16:
+		h.restoreSigContext(ctxt)
+		// Done
+		notewakeup(&h.done)
+	default:
+		h.err = plainError("unexpected debugCallV2 status")
+		notewakeup(&h.done)
+	}
+	// Resume execution.
+	return true
+}