Adding upstream version 1.19.8.upstream/1.19.8upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 643 insertions, 0 deletions

diff --git a/src/runtime/cgocall.go b/src/runtime/cgocall.go
new file mode 100644
index 0000000..892654e
--- /dev/null
+++ b/src/runtime/cgocall.go
@@ -0,0 +1,643 @@
+// Copyright 2009 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.
+
+// Cgo call and callback support.
+//
+// To call into the C function f from Go, the cgo-generated code calls
+// runtime.cgocall(_cgo_Cfunc_f, frame), where _cgo_Cfunc_f is a
+// gcc-compiled function written by cgo.
+//
+// runtime.cgocall (below) calls entersyscall so as not to block
+// other goroutines or the garbage collector, and then calls
+// runtime.asmcgocall(_cgo_Cfunc_f, frame).
+//
+// runtime.asmcgocall (in asm_$GOARCH.s) switches to the m->g0 stack
+// (assumed to be an operating system-allocated stack, so safe to run
+// gcc-compiled code on) and calls _cgo_Cfunc_f(frame).
+//
+// _cgo_Cfunc_f invokes the actual C function f with arguments
+// taken from the frame structure, records the results in the frame,
+// and returns to runtime.asmcgocall.
+//
+// After it regains control, runtime.asmcgocall switches back to the
+// original g (m->curg)'s stack and returns to runtime.cgocall.
+//
+// After it regains control, runtime.cgocall calls exitsyscall, which blocks
+// until this m can run Go code without violating the $GOMAXPROCS limit,
+// and then unlocks g from m.
+//
+// The above description skipped over the possibility of the gcc-compiled
+// function f calling back into Go. If that happens, we continue down
+// the rabbit hole during the execution of f.
+//
+// To make it possible for gcc-compiled C code to call a Go function p.GoF,
+// cgo writes a gcc-compiled function named GoF (not p.GoF, since gcc doesn't
+// know about packages).  The gcc-compiled C function f calls GoF.
+//
+// GoF initializes "frame", a structure containing all of its
+// arguments and slots for p.GoF's results. It calls
+// crosscall2(_cgoexp_GoF, frame, framesize, ctxt) using the gcc ABI.
+//
+// crosscall2 (in cgo/asm_$GOARCH.s) is a four-argument adapter from
+// the gcc function call ABI to the gc function call ABI. At this
+// point we're in the Go runtime, but we're still running on m.g0's
+// stack and outside the $GOMAXPROCS limit. crosscall2 calls
+// runtime.cgocallback(_cgoexp_GoF, frame, ctxt) using the gc ABI.
+// (crosscall2's framesize argument is no longer used, but there's one
+// case where SWIG calls crosscall2 directly and expects to pass this
+// argument. See _cgo_panic.)
+//
+// runtime.cgocallback (in asm_$GOARCH.s) switches from m.g0's stack
+// to the original g (m.curg)'s stack, on which it calls
+// runtime.cgocallbackg(_cgoexp_GoF, frame, ctxt). As part of the
+// stack switch, runtime.cgocallback saves the current SP as
+// m.g0.sched.sp, so that any use of m.g0's stack during the execution
+// of the callback will be done below the existing stack frames.
+// Before overwriting m.g0.sched.sp, it pushes the old value on the
+// m.g0 stack, so that it can be restored later.
+//
+// runtime.cgocallbackg (below) is now running on a real goroutine
+// stack (not an m.g0 stack).  First it calls runtime.exitsyscall, which will
+// block until the $GOMAXPROCS limit allows running this goroutine.
+// Once exitsyscall has returned, it is safe to do things like call the memory
+// allocator or invoke the Go callback function.  runtime.cgocallbackg
+// first defers a function to unwind m.g0.sched.sp, so that if p.GoF
+// panics, m.g0.sched.sp will be restored to its old value: the m.g0 stack
+// and the m.curg stack will be unwound in lock step.
+// Then it calls _cgoexp_GoF(frame).
+//
+// _cgoexp_GoF, which was generated by cmd/cgo, unpacks the arguments
+// from frame, calls p.GoF, writes the results back to frame, and
+// returns. Now we start unwinding this whole process.
+//
+// runtime.cgocallbackg pops but does not execute the deferred
+// function to unwind m.g0.sched.sp, calls runtime.entersyscall, and
+// returns to runtime.cgocallback.
+//
+// After it regains control, runtime.cgocallback switches back to
+// m.g0's stack (the pointer is still in m.g0.sched.sp), restores the old
+// m.g0.sched.sp value from the stack, and returns to crosscall2.
+//
+// crosscall2 restores the callee-save registers for gcc and returns
+// to GoF, which unpacks any result values and returns to f.
+
+package runtime
+
+import (
+	"internal/goarch"
+	"runtime/internal/atomic"
+	"runtime/internal/sys"
+	"unsafe"
+)
+
+// Addresses collected in a cgo backtrace when crashing.
+// Length must match arg.Max in x_cgo_callers in runtime/cgo/gcc_traceback.c.
+type cgoCallers [32]uintptr
+
+// argset matches runtime/cgo/linux_syscall.c:argset_t
+type argset struct {
+	args   unsafe.Pointer
+	retval uintptr
+}
+
+// wrapper for syscall package to call cgocall for libc (cgo) calls.
+//
+//go:linkname syscall_cgocaller syscall.cgocaller
+//go:nosplit
+//go:uintptrescapes
+func syscall_cgocaller(fn unsafe.Pointer, args ...uintptr) uintptr {
+	as := argset{args: unsafe.Pointer(&args[0])}
+	cgocall(fn, unsafe.Pointer(&as))
+	return as.retval
+}
+
+var ncgocall uint64 // number of cgo calls in total for dead m
+
+// Call from Go to C.
+//
+// This must be nosplit because it's used for syscalls on some
+// platforms. Syscalls may have untyped arguments on the stack, so
+// it's not safe to grow or scan the stack.
+//
+//go:nosplit
+func cgocall(fn, arg unsafe.Pointer) int32 {
+	if !iscgo && GOOS != "solaris" && GOOS != "illumos" && GOOS != "windows" {
+		throw("cgocall unavailable")
+	}
+
+	if fn == nil {
+		throw("cgocall nil")
+	}
+
+	if raceenabled {
+		racereleasemerge(unsafe.Pointer(&racecgosync))
+	}
+
+	mp := getg().m
+	mp.ncgocall++
+	mp.ncgo++
+
+	// Reset traceback.
+	mp.cgoCallers[0] = 0
+
+	// Announce we are entering a system call
+	// so that the scheduler knows to create another
+	// M to run goroutines while we are in the
+	// foreign code.
+	//
+	// The call to asmcgocall is guaranteed not to
+	// grow the stack and does not allocate memory,
+	// so it is safe to call while "in a system call", outside
+	// the $GOMAXPROCS accounting.
+	//
+	// fn may call back into Go code, in which case we'll exit the
+	// "system call", run the Go code (which may grow the stack),
+	// and then re-enter the "system call" reusing the PC and SP
+	// saved by entersyscall here.
+	entersyscall()
+
+	// Tell asynchronous preemption that we're entering external
+	// code. We do this after entersyscall because this may block
+	// and cause an async preemption to fail, but at this point a
+	// sync preemption will succeed (though this is not a matter
+	// of correctness).
+	osPreemptExtEnter(mp)
+
+	mp.incgo = true
+	errno := asmcgocall(fn, arg)
+
+	// Update accounting before exitsyscall because exitsyscall may
+	// reschedule us on to a different M.
+	mp.incgo = false
+	mp.ncgo--
+
+	osPreemptExtExit(mp)
+
+	exitsyscall()
+
+	// Note that raceacquire must be called only after exitsyscall has
+	// wired this M to a P.
+	if raceenabled {
+		raceacquire(unsafe.Pointer(&racecgosync))
+	}
+
+	// From the garbage collector's perspective, time can move
+	// backwards in the sequence above. If there's a callback into
+	// Go code, GC will see this function at the call to
+	// asmcgocall. When the Go call later returns to C, the
+	// syscall PC/SP is rolled back and the GC sees this function
+	// back at the call to entersyscall. Normally, fn and arg
+	// would be live at entersyscall and dead at asmcgocall, so if
+	// time moved backwards, GC would see these arguments as dead
+	// and then live. Prevent these undead arguments from crashing
+	// GC by forcing them to stay live across this time warp.
+	KeepAlive(fn)
+	KeepAlive(arg)
+	KeepAlive(mp)
+
+	return errno
+}
+
+// Call from C back to Go. fn must point to an ABIInternal Go entry-point.
+//
+//go:nosplit
+func cgocallbackg(fn, frame unsafe.Pointer, ctxt uintptr) {
+	gp := getg()
+	if gp != gp.m.curg {
+		println("runtime: bad g in cgocallback")
+		exit(2)
+	}
+
+	// The call from C is on gp.m's g0 stack, so we must ensure
+	// that we stay on that M. We have to do this before calling
+	// exitsyscall, since it would otherwise be free to move us to
+	// a different M. The call to unlockOSThread is in unwindm.
+	lockOSThread()
+
+	checkm := gp.m
+
+	// Save current syscall parameters, so m.syscall can be
+	// used again if callback decide to make syscall.
+	syscall := gp.m.syscall
+
+	// entersyscall saves the caller's SP to allow the GC to trace the Go
+	// stack. However, since we're returning to an earlier stack frame and
+	// need to pair with the entersyscall() call made by cgocall, we must
+	// save syscall* and let reentersyscall restore them.
+	savedsp := unsafe.Pointer(gp.syscallsp)
+	savedpc := gp.syscallpc
+	exitsyscall() // coming out of cgo call
+	gp.m.incgo = false
+
+	osPreemptExtExit(gp.m)
+
+	cgocallbackg1(fn, frame, ctxt) // will call unlockOSThread
+
+	// At this point unlockOSThread has been called.
+	// The following code must not change to a different m.
+	// This is enforced by checking incgo in the schedule function.
+
+	gp.m.incgo = true
+
+	if gp.m != checkm {
+		throw("m changed unexpectedly in cgocallbackg")
+	}
+
+	osPreemptExtEnter(gp.m)
+
+	// going back to cgo call
+	reentersyscall(savedpc, uintptr(savedsp))
+
+	gp.m.syscall = syscall
+}
+
+func cgocallbackg1(fn, frame unsafe.Pointer, ctxt uintptr) {
+	gp := getg()
+
+	// When we return, undo the call to lockOSThread in cgocallbackg.
+	// We must still stay on the same m.
+	defer unlockOSThread()
+
+	if gp.m.needextram || atomic.Load(&extraMWaiters) > 0 {
+		gp.m.needextram = false
+		systemstack(newextram)
+	}
+
+	if ctxt != 0 {
+		s := append(gp.cgoCtxt, ctxt)
+
+		// Now we need to set gp.cgoCtxt = s, but we could get
+		// a SIGPROF signal while manipulating the slice, and
+		// the SIGPROF handler could pick up gp.cgoCtxt while
+		// tracing up the stack.  We need to ensure that the
+		// handler always sees a valid slice, so set the
+		// values in an order such that it always does.
+		p := (*slice)(unsafe.Pointer(&gp.cgoCtxt))
+		atomicstorep(unsafe.Pointer(&p.array), unsafe.Pointer(&s[0]))
+		p.cap = cap(s)
+		p.len = len(s)
+
+		defer func(gp *g) {
+			// Decrease the length of the slice by one, safely.
+			p := (*slice)(unsafe.Pointer(&gp.cgoCtxt))
+			p.len--
+		}(gp)
+	}
+
+	if gp.m.ncgo == 0 {
+		// The C call to Go came from a thread not currently running
+		// any Go. In the case of -buildmode=c-archive or c-shared,
+		// this call may be coming in before package initialization
+		// is complete. Wait until it is.
+		<-main_init_done
+	}
+
+	// Check whether the profiler needs to be turned on or off; this route to
+	// run Go code does not use runtime.execute, so bypasses the check there.
+	hz := sched.profilehz
+	if gp.m.profilehz != hz {
+		setThreadCPUProfiler(hz)
+	}
+
+	// Add entry to defer stack in case of panic.
+	restore := true
+	defer unwindm(&restore)
+
+	if raceenabled {
+		raceacquire(unsafe.Pointer(&racecgosync))
+	}
+
+	// Invoke callback. This function is generated by cmd/cgo and
+	// will unpack the argument frame and call the Go function.
+	var cb func(frame unsafe.Pointer)
+	cbFV := funcval{uintptr(fn)}
+	*(*unsafe.Pointer)(unsafe.Pointer(&cb)) = noescape(unsafe.Pointer(&cbFV))
+	cb(frame)
+
+	if raceenabled {
+		racereleasemerge(unsafe.Pointer(&racecgosync))
+	}
+
+	// Do not unwind m->g0->sched.sp.
+	// Our caller, cgocallback, will do that.
+	restore = false
+}
+
+func unwindm(restore *bool) {
+	if *restore {
+		// Restore sp saved by cgocallback during
+		// unwind of g's stack (see comment at top of file).
+		mp := acquirem()
+		sched := &mp.g0.sched
+		sched.sp = *(*uintptr)(unsafe.Pointer(sched.sp + alignUp(sys.MinFrameSize, sys.StackAlign)))
+
+		// Do the accounting that cgocall will not have a chance to do
+		// during an unwind.
+		//
+		// In the case where a Go call originates from C, ncgo is 0
+		// and there is no matching cgocall to end.
+		if mp.ncgo > 0 {
+			mp.incgo = false
+			mp.ncgo--
+			osPreemptExtExit(mp)
+		}
+
+		releasem(mp)
+	}
+}
+
+// called from assembly
+func badcgocallback() {
+	throw("misaligned stack in cgocallback")
+}
+
+// called from (incomplete) assembly
+func cgounimpl() {
+	throw("cgo not implemented")
+}
+
+var racecgosync uint64 // represents possible synchronization in C code
+
+// Pointer checking for cgo code.
+
+// We want to detect all cases where a program that does not use
+// unsafe makes a cgo call passing a Go pointer to memory that
+// contains a Go pointer. Here a Go pointer is defined as a pointer
+// to memory allocated by the Go runtime. Programs that use unsafe
+// can evade this restriction easily, so we don't try to catch them.
+// The cgo program will rewrite all possibly bad pointer arguments to
+// call cgoCheckPointer, where we can catch cases of a Go pointer
+// pointing to a Go pointer.
+
+// Complicating matters, taking the address of a slice or array
+// element permits the C program to access all elements of the slice
+// or array. In that case we will see a pointer to a single element,
+// but we need to check the entire data structure.
+
+// The cgoCheckPointer call takes additional arguments indicating that
+// it was called on an address expression. An additional argument of
+// true means that it only needs to check a single element. An
+// additional argument of a slice or array means that it needs to
+// check the entire slice/array, but nothing else. Otherwise, the
+// pointer could be anything, and we check the entire heap object,
+// which is conservative but safe.
+
+// When and if we implement a moving garbage collector,
+// cgoCheckPointer will pin the pointer for the duration of the cgo
+// call.  (This is necessary but not sufficient; the cgo program will
+// also have to change to pin Go pointers that cannot point to Go
+// pointers.)
+
+// cgoCheckPointer checks if the argument contains a Go pointer that
+// points to a Go pointer, and panics if it does.
+func cgoCheckPointer(ptr any, arg any) {
+	if debug.cgocheck == 0 {
+		return
+	}
+
+	ep := efaceOf(&ptr)
+	t := ep._type
+
+	top := true
+	if arg != nil && (t.kind&kindMask == kindPtr || t.kind&kindMask == kindUnsafePointer) {
+		p := ep.data
+		if t.kind&kindDirectIface == 0 {
+			p = *(*unsafe.Pointer)(p)
+		}
+		if p == nil || !cgoIsGoPointer(p) {
+			return
+		}
+		aep := efaceOf(&arg)
+		switch aep._type.kind & kindMask {
+		case kindBool:
+			if t.kind&kindMask == kindUnsafePointer {
+				// We don't know the type of the element.
+				break
+			}
+			pt := (*ptrtype)(unsafe.Pointer(t))
+			cgoCheckArg(pt.elem, p, true, false, cgoCheckPointerFail)
+			return
+		case kindSlice:
+			// Check the slice rather than the pointer.
+			ep = aep
+			t = ep._type
+		case kindArray:
+			// Check the array rather than the pointer.
+			// Pass top as false since we have a pointer
+			// to the array.
+			ep = aep
+			t = ep._type
+			top = false
+		default:
+			throw("can't happen")
+		}
+	}
+
+	cgoCheckArg(t, ep.data, t.kind&kindDirectIface == 0, top, cgoCheckPointerFail)
+}
+
+const cgoCheckPointerFail = "cgo argument has Go pointer to Go pointer"
+const cgoResultFail = "cgo result has Go pointer"
+
+// cgoCheckArg is the real work of cgoCheckPointer. The argument p
+// is either a pointer to the value (of type t), or the value itself,
+// depending on indir. The top parameter is whether we are at the top
+// level, where Go pointers are allowed.
+func cgoCheckArg(t *_type, p unsafe.Pointer, indir, top bool, msg string) {
+	if t.ptrdata == 0 || p == nil {
+		// If the type has no pointers there is nothing to do.
+		return
+	}
+
+	switch t.kind & kindMask {
+	default:
+		throw("can't happen")
+	case kindArray:
+		at := (*arraytype)(unsafe.Pointer(t))
+		if !indir {
+			if at.len != 1 {
+				throw("can't happen")
+			}
+			cgoCheckArg(at.elem, p, at.elem.kind&kindDirectIface == 0, top, msg)
+			return
+		}
+		for i := uintptr(0); i < at.len; i++ {
+			cgoCheckArg(at.elem, p, true, top, msg)
+			p = add(p, at.elem.size)
+		}
+	case kindChan, kindMap:
+		// These types contain internal pointers that will
+		// always be allocated in the Go heap. It's never OK
+		// to pass them to C.
+		panic(errorString(msg))
+	case kindFunc:
+		if indir {
+			p = *(*unsafe.Pointer)(p)
+		}
+		if !cgoIsGoPointer(p) {
+			return
+		}
+		panic(errorString(msg))
+	case kindInterface:
+		it := *(**_type)(p)
+		if it == nil {
+			return
+		}
+		// A type known at compile time is OK since it's
+		// constant. A type not known at compile time will be
+		// in the heap and will not be OK.
+		if inheap(uintptr(unsafe.Pointer(it))) {
+			panic(errorString(msg))
+		}
+		p = *(*unsafe.Pointer)(add(p, goarch.PtrSize))
+		if !cgoIsGoPointer(p) {
+			return
+		}
+		if !top {
+			panic(errorString(msg))
+		}
+		cgoCheckArg(it, p, it.kind&kindDirectIface == 0, false, msg)
+	case kindSlice:
+		st := (*slicetype)(unsafe.Pointer(t))
+		s := (*slice)(p)
+		p = s.array
+		if p == nil || !cgoIsGoPointer(p) {
+			return
+		}
+		if !top {
+			panic(errorString(msg))
+		}
+		if st.elem.ptrdata == 0 {
+			return
+		}
+		for i := 0; i < s.cap; i++ {
+			cgoCheckArg(st.elem, p, true, false, msg)
+			p = add(p, st.elem.size)
+		}
+	case kindString:
+		ss := (*stringStruct)(p)
+		if !cgoIsGoPointer(ss.str) {
+			return
+		}
+		if !top {
+			panic(errorString(msg))
+		}
+	case kindStruct:
+		st := (*structtype)(unsafe.Pointer(t))
+		if !indir {
+			if len(st.fields) != 1 {
+				throw("can't happen")
+			}
+			cgoCheckArg(st.fields[0].typ, p, st.fields[0].typ.kind&kindDirectIface == 0, top, msg)
+			return
+		}
+		for _, f := range st.fields {
+			if f.typ.ptrdata == 0 {
+				continue
+			}
+			cgoCheckArg(f.typ, add(p, f.offset), true, top, msg)
+		}
+	case kindPtr, kindUnsafePointer:
+		if indir {
+			p = *(*unsafe.Pointer)(p)
+			if p == nil {
+				return
+			}
+		}
+
+		if !cgoIsGoPointer(p) {
+			return
+		}
+		if !top {
+			panic(errorString(msg))
+		}
+
+		cgoCheckUnknownPointer(p, msg)
+	}
+}
+
+// cgoCheckUnknownPointer is called for an arbitrary pointer into Go
+// memory. It checks whether that Go memory contains any other
+// pointer into Go memory. If it does, we panic.
+// The return values are unused but useful to see in panic tracebacks.
+func cgoCheckUnknownPointer(p unsafe.Pointer, msg string) (base, i uintptr) {
+	if inheap(uintptr(p)) {
+		b, span, _ := findObject(uintptr(p), 0, 0)
+		base = b
+		if base == 0 {
+			return
+		}
+		hbits := heapBitsForAddr(base)
+		n := span.elemsize
+		for i = uintptr(0); i < n; i += goarch.PtrSize {
+			if !hbits.morePointers() {
+				// No more possible pointers.
+				break
+			}
+			if hbits.isPointer() && cgoIsGoPointer(*(*unsafe.Pointer)(unsafe.Pointer(base + i))) {
+				panic(errorString(msg))
+			}
+			hbits = hbits.next()
+		}
+
+		return
+	}
+
+	for _, datap := range activeModules() {
+		if cgoInRange(p, datap.data, datap.edata) || cgoInRange(p, datap.bss, datap.ebss) {
+			// We have no way to know the size of the object.
+			// We have to assume that it might contain a pointer.
+			panic(errorString(msg))
+		}
+		// In the text or noptr sections, we know that the
+		// pointer does not point to a Go pointer.
+	}
+
+	return
+}
+
+// cgoIsGoPointer reports whether the pointer is a Go pointer--a
+// pointer to Go memory. We only care about Go memory that might
+// contain pointers.
+//
+//go:nosplit
+//go:nowritebarrierrec
+func cgoIsGoPointer(p unsafe.Pointer) bool {
+	if p == nil {
+		return false
+	}
+
+	if inHeapOrStack(uintptr(p)) {
+		return true
+	}
+
+	for _, datap := range activeModules() {
+		if cgoInRange(p, datap.data, datap.edata) || cgoInRange(p, datap.bss, datap.ebss) {
+			return true
+		}
+	}
+
+	return false
+}
+
+// cgoInRange reports whether p is between start and end.
+//
+//go:nosplit
+//go:nowritebarrierrec
+func cgoInRange(p unsafe.Pointer, start, end uintptr) bool {
+	return start <= uintptr(p) && uintptr(p) < end
+}
+
+// cgoCheckResult is called to check the result parameter of an
+// exported Go function. It panics if the result is or contains a Go
+// pointer.
+func cgoCheckResult(val any) {
+	if debug.cgocheck == 0 {
+		return
+	}
+
+	ep := efaceOf(&val)
+	t := ep._type
+	cgoCheckArg(t, ep.data, t.kind&kindDirectIface == 0, false, cgoResultFail)
+}