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Diffstat (limited to '')
| -rw-r--r-- | src/runtime/debugcall.go | 241 |
1 files changed, 241 insertions, 0 deletions
diff --git a/src/runtime/debugcall.go b/src/runtime/debugcall.go new file mode 100644 index 0000000..efc68a7 --- /dev/null +++ b/src/runtime/debugcall.go @@ -0,0 +1,241 @@ +// 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. + +// +build amd64 + +package runtime + +import "unsafe" + +const ( + debugCallSystemStack = "executing on Go runtime stack" + debugCallUnknownFunc = "call from unknown function" + debugCallRuntime = "call from within the Go runtime" + debugCallUnsafePoint = "call not at safe point" +) + +func debugCallV1() +func debugCallPanicked(val interface{}) + +// debugCallCheck checks whether it is safe to inject a debugger +// function call with return PC pc. If not, it returns a string +// explaining why. +// +//go:nosplit +func debugCallCheck(pc uintptr) string { + // No user calls from the system stack. + if getg() != getg().m.curg { + return debugCallSystemStack + } + if sp := getcallersp(); !(getg().stack.lo < sp && sp <= getg().stack.hi) { + // Fast syscalls (nanotime) and racecall switch to the + // g0 stack without switching g. We can't safely make + // a call in this state. (We can't even safely + // systemstack.) + return debugCallSystemStack + } + + // Switch to the system stack to avoid overflowing the user + // stack. + var ret string + systemstack(func() { + f := findfunc(pc) + if !f.valid() { + ret = debugCallUnknownFunc + return + } + + name := funcname(f) + + switch name { + case "debugCall32", + "debugCall64", + "debugCall128", + "debugCall256", + "debugCall512", + "debugCall1024", + "debugCall2048", + "debugCall4096", + "debugCall8192", + "debugCall16384", + "debugCall32768", + "debugCall65536": + // These functions are allowed so that the debugger can initiate multiple function calls. + // See: https://golang.org/cl/161137/ + return + } + + // Disallow calls from the runtime. We could + // potentially make this condition tighter (e.g., not + // when locks are held), but there are enough tightly + // coded sequences (e.g., defer handling) that it's + // better to play it safe. + if pfx := "runtime."; len(name) > len(pfx) && name[:len(pfx)] == pfx { + ret = debugCallRuntime + return + } + + // Check that this isn't an unsafe-point. + if pc != f.entry { + pc-- + } + up := pcdatavalue(f, _PCDATA_UnsafePoint, pc, nil) + if up != _PCDATA_UnsafePointSafe { + // Not at a safe point. + ret = debugCallUnsafePoint + } + }) + return ret +} + +// debugCallWrap starts a new goroutine to run a debug call and blocks +// the calling goroutine. On the goroutine, it prepares to recover +// panics from the debug call, and then calls the call dispatching +// function at PC dispatch. +// +// This must be deeply nosplit because there are untyped values on the +// stack from debugCallV1. +// +//go:nosplit +func debugCallWrap(dispatch uintptr) { + var lockedm bool + var lockedExt uint32 + callerpc := getcallerpc() + gp := getg() + + // Create a new goroutine to execute the call on. Run this on + // the system stack to avoid growing our stack. + systemstack(func() { + var args struct { + dispatch uintptr + callingG *g + } + args.dispatch = dispatch + args.callingG = gp + fn := debugCallWrap1 + newg := newproc1(*(**funcval)(unsafe.Pointer(&fn)), unsafe.Pointer(&args), int32(unsafe.Sizeof(args)), gp, callerpc) + + // If the current G is locked, then transfer that + // locked-ness to the new goroutine. + if gp.lockedm != 0 { + // Save lock state to restore later. + mp := gp.m + if mp != gp.lockedm.ptr() { + throw("inconsistent lockedm") + } + + lockedm = true + lockedExt = mp.lockedExt + + // Transfer external lock count to internal so + // it can't be unlocked from the debug call. + mp.lockedInt++ + mp.lockedExt = 0 + + mp.lockedg.set(newg) + newg.lockedm.set(mp) + gp.lockedm = 0 + } + + // Mark the calling goroutine as being at an async + // safe-point, since it has a few conservative frames + // at the bottom of the stack. This also prevents + // stack shrinks. + gp.asyncSafePoint = true + + // Stash newg away so we can execute it below (mcall's + // closure can't capture anything). + gp.schedlink.set(newg) + }) + + // Switch to the new goroutine. + mcall(func(gp *g) { + // Get newg. + newg := gp.schedlink.ptr() + gp.schedlink = 0 + + // Park the calling goroutine. + gp.waitreason = waitReasonDebugCall + if trace.enabled { + traceGoPark(traceEvGoBlock, 1) + } + casgstatus(gp, _Grunning, _Gwaiting) + dropg() + + // Directly execute the new goroutine. The debug + // protocol will continue on the new goroutine, so + // it's important we not just let the scheduler do + // this or it may resume a different goroutine. + execute(newg, true) + }) + + // We'll resume here when the call returns. + + // Restore locked state. + if lockedm { + mp := gp.m + mp.lockedExt = lockedExt + mp.lockedInt-- + mp.lockedg.set(gp) + gp.lockedm.set(mp) + } + + gp.asyncSafePoint = false +} + +// debugCallWrap1 is the continuation of debugCallWrap on the callee +// goroutine. +func debugCallWrap1(dispatch uintptr, callingG *g) { + // Dispatch call and trap panics. + debugCallWrap2(dispatch) + + // Resume the caller goroutine. + getg().schedlink.set(callingG) + mcall(func(gp *g) { + callingG := gp.schedlink.ptr() + gp.schedlink = 0 + + // Unlock this goroutine from the M if necessary. The + // calling G will relock. + if gp.lockedm != 0 { + gp.lockedm = 0 + gp.m.lockedg = 0 + } + + // Switch back to the calling goroutine. At some point + // the scheduler will schedule us again and we'll + // finish exiting. + if trace.enabled { + traceGoSched() + } + casgstatus(gp, _Grunning, _Grunnable) + dropg() + lock(&sched.lock) + globrunqput(gp) + unlock(&sched.lock) + + if trace.enabled { + traceGoUnpark(callingG, 0) + } + casgstatus(callingG, _Gwaiting, _Grunnable) + execute(callingG, true) + }) +} + +func debugCallWrap2(dispatch uintptr) { + // Call the dispatch function and trap panics. + var dispatchF func() + dispatchFV := funcval{dispatch} + *(*unsafe.Pointer)(unsafe.Pointer(&dispatchF)) = noescape(unsafe.Pointer(&dispatchFV)) + + var ok bool + defer func() { + if !ok { + err := recover() + debugCallPanicked(err) + } + }() + dispatchF() + ok = true +} |