1 // Copyright 2009 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 // Cgo call and callback support. 6 // 7 // To call into the C function f from Go, the cgo-generated code calls 8 // runtime.cgocall(_cgo_Cfunc_f, frame), where _cgo_Cfunc_f is a 9 // gcc-compiled function written by cgo. 10 // 11 // runtime.cgocall (below) calls entersyscall so as not to block 12 // other goroutines or the garbage collector, and then calls 13 // runtime.asmcgocall(_cgo_Cfunc_f, frame). 14 // 15 // runtime.asmcgocall (in asm_$GOARCH.s) switches to the m->g0 stack 16 // (assumed to be an operating system-allocated stack, so safe to run 17 // gcc-compiled code on) and calls _cgo_Cfunc_f(frame). 18 // 19 // _cgo_Cfunc_f invokes the actual C function f with arguments 20 // taken from the frame structure, records the results in the frame, 21 // and returns to runtime.asmcgocall. 22 // 23 // After it regains control, runtime.asmcgocall switches back to the 24 // original g (m->curg)'s stack and returns to runtime.cgocall. 25 // 26 // After it regains control, runtime.cgocall calls exitsyscall, which blocks 27 // until this m can run Go code without violating the $GOMAXPROCS limit, 28 // and then unlocks g from m. 29 // 30 // The above description skipped over the possibility of the gcc-compiled 31 // function f calling back into Go. If that happens, we continue down 32 // the rabbit hole during the execution of f. 33 // 34 // To make it possible for gcc-compiled C code to call a Go function p.GoF, 35 // cgo writes a gcc-compiled function named GoF (not p.GoF, since gcc doesn't 36 // know about packages). The gcc-compiled C function f calls GoF. 37 // 38 // GoF initializes "frame", a structure containing all of its 39 // arguments and slots for p.GoF's results. It calls 40 // crosscall2(_cgoexp_GoF, frame, framesize, ctxt) using the gcc ABI. 41 // 42 // crosscall2 (in cgo/asm_$GOARCH.s) is a four-argument adapter from 43 // the gcc function call ABI to the gc function call ABI. At this 44 // point we're in the Go runtime, but we're still running on m.g0's 45 // stack and outside the $GOMAXPROCS limit. crosscall2 calls 46 // runtime.cgocallback(_cgoexp_GoF, frame, ctxt) using the gc ABI. 47 // (crosscall2's framesize argument is no longer used, but there's one 48 // case where SWIG calls crosscall2 directly and expects to pass this 49 // argument. See _cgo_panic.) 50 // 51 // runtime.cgocallback (in asm_$GOARCH.s) switches from m.g0's stack 52 // to the original g (m.curg)'s stack, on which it calls 53 // runtime.cgocallbackg(_cgoexp_GoF, frame, ctxt). As part of the 54 // stack switch, runtime.cgocallback saves the current SP as 55 // m.g0.sched.sp, so that any use of m.g0's stack during the execution 56 // of the callback will be done below the existing stack frames. 57 // Before overwriting m.g0.sched.sp, it pushes the old value on the 58 // m.g0 stack, so that it can be restored later. 59 // 60 // runtime.cgocallbackg (below) is now running on a real goroutine 61 // stack (not an m.g0 stack). First it calls runtime.exitsyscall, which will 62 // block until the $GOMAXPROCS limit allows running this goroutine. 63 // Once exitsyscall has returned, it is safe to do things like call the memory 64 // allocator or invoke the Go callback function. runtime.cgocallbackg 65 // first defers a function to unwind m.g0.sched.sp, so that if p.GoF 66 // panics, m.g0.sched.sp will be restored to its old value: the m.g0 stack 67 // and the m.curg stack will be unwound in lock step. 68 // Then it calls _cgoexp_GoF(frame). 69 // 70 // _cgoexp_GoF, which was generated by cmd/cgo, unpacks the arguments 71 // from frame, calls p.GoF, writes the results back to frame, and 72 // returns. Now we start unwinding this whole process. 73 // 74 // runtime.cgocallbackg pops but does not execute the deferred 75 // function to unwind m.g0.sched.sp, calls runtime.entersyscall, and 76 // returns to runtime.cgocallback. 77 // 78 // After it regains control, runtime.cgocallback switches back to 79 // m.g0's stack (the pointer is still in m.g0.sched.sp), restores the old 80 // m.g0.sched.sp value from the stack, and returns to crosscall2. 81 // 82 // crosscall2 restores the callee-save registers for gcc and returns 83 // to GoF, which unpacks any result values and returns to f. 84 85 package runtime 86 87 import ( 88 "internal/goarch" 89 "internal/goexperiment" 90 "runtime/internal/sys" 91 "unsafe" 92 ) 93 94 // Addresses collected in a cgo backtrace when crashing. 95 // Length must match arg.Max in x_cgo_callers in runtime/cgo/gcc_traceback.c. 96 type cgoCallers [32]uintptr 97 98 // argset matches runtime/cgo/linux_syscall.c:argset_t 99 type argset struct { 100 args unsafe.Pointer 101 retval uintptr 102 } 103 104 // wrapper for syscall package to call cgocall for libc (cgo) calls. 105 // 106 //go:linkname syscall_cgocaller syscall.cgocaller 107 //go:nosplit 108 //go:uintptrescapes 109 func syscall_cgocaller(fn unsafe.Pointer, args ...uintptr) uintptr { 110 as := argset{args: unsafe.Pointer(&args[0])} 111 cgocall(fn, unsafe.Pointer(&as)) 112 return as.retval 113 } 114 115 var ncgocall uint64 // number of cgo calls in total for dead m 116 117 // Call from Go to C. 118 // 119 // This must be nosplit because it's used for syscalls on some 120 // platforms. Syscalls may have untyped arguments on the stack, so 121 // it's not safe to grow or scan the stack. 122 // 123 //go:nosplit 124 func cgocall(fn, arg unsafe.Pointer) int32 { 125 if !iscgo && GOOS != "solaris" && GOOS != "illumos" && GOOS != "windows" { 126 throw("cgocall unavailable") 127 } 128 129 if fn == nil { 130 throw("cgocall nil") 131 } 132 133 if raceenabled { 134 racereleasemerge(unsafe.Pointer(&racecgosync)) 135 } 136 137 mp := getg().m 138 mp.ncgocall++ 139 140 // Reset traceback. 141 mp.cgoCallers[0] = 0 142 143 // Announce we are entering a system call 144 // so that the scheduler knows to create another 145 // M to run goroutines while we are in the 146 // foreign code. 147 // 148 // The call to asmcgocall is guaranteed not to 149 // grow the stack and does not allocate memory, 150 // so it is safe to call while "in a system call", outside 151 // the $GOMAXPROCS accounting. 152 // 153 // fn may call back into Go code, in which case we'll exit the 154 // "system call", run the Go code (which may grow the stack), 155 // and then re-enter the "system call" reusing the PC and SP 156 // saved by entersyscall here. 157 entersyscall() 158 159 // Tell asynchronous preemption that we're entering external 160 // code. We do this after entersyscall because this may block 161 // and cause an async preemption to fail, but at this point a 162 // sync preemption will succeed (though this is not a matter 163 // of correctness). 164 osPreemptExtEnter(mp) 165 166 mp.incgo = true 167 // We use ncgo as a check during execution tracing for whether there is 168 // any C on the call stack, which there will be after this point. If 169 // there isn't, we can use frame pointer unwinding to collect call 170 // stacks efficiently. This will be the case for the first Go-to-C call 171 // on a stack, so it's preferable to update it here, after we emit a 172 // trace event in entersyscall above. 173 mp.ncgo++ 174 175 errno := asmcgocall(fn, arg) 176 177 // Update accounting before exitsyscall because exitsyscall may 178 // reschedule us on to a different M. 179 mp.incgo = false 180 mp.ncgo-- 181 182 osPreemptExtExit(mp) 183 184 exitsyscall() 185 186 // Note that raceacquire must be called only after exitsyscall has 187 // wired this M to a P. 188 if raceenabled { 189 raceacquire(unsafe.Pointer(&racecgosync)) 190 } 191 192 // From the garbage collector's perspective, time can move 193 // backwards in the sequence above. If there's a callback into 194 // Go code, GC will see this function at the call to 195 // asmcgocall. When the Go call later returns to C, the 196 // syscall PC/SP is rolled back and the GC sees this function 197 // back at the call to entersyscall. Normally, fn and arg 198 // would be live at entersyscall and dead at asmcgocall, so if 199 // time moved backwards, GC would see these arguments as dead 200 // and then live. Prevent these undead arguments from crashing 201 // GC by forcing them to stay live across this time warp. 202 KeepAlive(fn) 203 KeepAlive(arg) 204 KeepAlive(mp) 205 206 return errno 207 } 208 209 // Set or reset the system stack bounds for a callback on sp. 210 // 211 // Must be nosplit because it is called by needm prior to fully initializing 212 // the M. 213 // 214 //go:nosplit 215 func callbackUpdateSystemStack(mp *m, sp uintptr, signal bool) { 216 g0 := mp.g0 217 if sp > g0.stack.lo && sp <= g0.stack.hi { 218 // Stack already in bounds, nothing to do. 219 return 220 } 221 222 if mp.ncgo > 0 { 223 // ncgo > 0 indicates that this M was in Go further up the stack 224 // (it called C and is now receiving a callback). It is not 225 // safe for the C call to change the stack out from under us. 226 227 // Note that this case isn't possible for signal == true, as 228 // that is always passing a new M from needm. 229 230 // Stack is bogus, but reset the bounds anyway so we can print. 231 hi := g0.stack.hi 232 lo := g0.stack.lo 233 g0.stack.hi = sp + 1024 234 g0.stack.lo = sp - 32*1024 235 g0.stackguard0 = g0.stack.lo + stackGuard 236 g0.stackguard1 = g0.stackguard0 237 238 print("M ", mp.id, " procid ", mp.procid, " runtime: cgocallback with sp=", hex(sp), " out of bounds [", hex(lo), ", ", hex(hi), "]") 239 print("\n") 240 exit(2) 241 } 242 243 // This M does not have Go further up the stack. However, it may have 244 // previously called into Go, initializing the stack bounds. Between 245 // that call returning and now the stack may have changed (perhaps the 246 // C thread is running a coroutine library). We need to update the 247 // stack bounds for this case. 248 // 249 // Set the stack bounds to match the current stack. If we don't 250 // actually know how big the stack is, like we don't know how big any 251 // scheduling stack is, but we assume there's at least 32 kB. If we 252 // can get a more accurate stack bound from pthread, use that, provided 253 // it actually contains SP.. 254 g0.stack.hi = sp + 1024 255 g0.stack.lo = sp - 32*1024 256 if !signal && _cgo_getstackbound != nil { 257 // Don't adjust if called from the signal handler. 258 // We are on the signal stack, not the pthread stack. 259 // (We could get the stack bounds from sigaltstack, but 260 // we're getting out of the signal handler very soon 261 // anyway. Not worth it.) 262 var bounds [2]uintptr 263 asmcgocall(_cgo_getstackbound, unsafe.Pointer(&bounds)) 264 // getstackbound is an unsupported no-op on Windows. 265 // 266 // Don't use these bounds if they don't contain SP. Perhaps we 267 // were called by something not using the standard thread 268 // stack. 269 if bounds[0] != 0 && sp > bounds[0] && sp <= bounds[1] { 270 g0.stack.lo = bounds[0] 271 g0.stack.hi = bounds[1] 272 } 273 } 274 g0.stackguard0 = g0.stack.lo + stackGuard 275 g0.stackguard1 = g0.stackguard0 276 } 277 278 // Call from C back to Go. fn must point to an ABIInternal Go entry-point. 279 // 280 //go:nosplit 281 func cgocallbackg(fn, frame unsafe.Pointer, ctxt uintptr) { 282 gp := getg() 283 if gp != gp.m.curg { 284 println("runtime: bad g in cgocallback") 285 exit(2) 286 } 287 288 sp := gp.m.g0.sched.sp // system sp saved by cgocallback. 289 callbackUpdateSystemStack(gp.m, sp, false) 290 291 // The call from C is on gp.m's g0 stack, so we must ensure 292 // that we stay on that M. We have to do this before calling 293 // exitsyscall, since it would otherwise be free to move us to 294 // a different M. The call to unlockOSThread is in this function 295 // after cgocallbackg1, or in the case of panicking, in unwindm. 296 lockOSThread() 297 298 checkm := gp.m 299 300 // Save current syscall parameters, so m.syscall can be 301 // used again if callback decide to make syscall. 302 syscall := gp.m.syscall 303 304 // entersyscall saves the caller's SP to allow the GC to trace the Go 305 // stack. However, since we're returning to an earlier stack frame and 306 // need to pair with the entersyscall() call made by cgocall, we must 307 // save syscall* and let reentersyscall restore them. 308 savedsp := unsafe.Pointer(gp.syscallsp) 309 savedpc := gp.syscallpc 310 exitsyscall() // coming out of cgo call 311 gp.m.incgo = false 312 if gp.m.isextra { 313 gp.m.isExtraInC = false 314 } 315 316 osPreemptExtExit(gp.m) 317 318 if gp.nocgocallback { 319 panic("runtime: function marked with #cgo nocallback called back into Go") 320 } 321 322 cgocallbackg1(fn, frame, ctxt) 323 324 // At this point we're about to call unlockOSThread. 325 // The following code must not change to a different m. 326 // This is enforced by checking incgo in the schedule function. 327 gp.m.incgo = true 328 unlockOSThread() 329 330 if gp.m.isextra { 331 gp.m.isExtraInC = true 332 } 333 334 if gp.m != checkm { 335 throw("m changed unexpectedly in cgocallbackg") 336 } 337 338 osPreemptExtEnter(gp.m) 339 340 // going back to cgo call 341 reentersyscall(savedpc, uintptr(savedsp)) 342 343 gp.m.syscall = syscall 344 } 345 346 func cgocallbackg1(fn, frame unsafe.Pointer, ctxt uintptr) { 347 gp := getg() 348 349 if gp.m.needextram || extraMWaiters.Load() > 0 { 350 gp.m.needextram = false 351 systemstack(newextram) 352 } 353 354 if ctxt != 0 { 355 s := append(gp.cgoCtxt, ctxt) 356 357 // Now we need to set gp.cgoCtxt = s, but we could get 358 // a SIGPROF signal while manipulating the slice, and 359 // the SIGPROF handler could pick up gp.cgoCtxt while 360 // tracing up the stack. We need to ensure that the 361 // handler always sees a valid slice, so set the 362 // values in an order such that it always does. 363 p := (*slice)(unsafe.Pointer(&gp.cgoCtxt)) 364 atomicstorep(unsafe.Pointer(&p.array), unsafe.Pointer(&s[0])) 365 p.cap = cap(s) 366 p.len = len(s) 367 368 defer func(gp *g) { 369 // Decrease the length of the slice by one, safely. 370 p := (*slice)(unsafe.Pointer(&gp.cgoCtxt)) 371 p.len-- 372 }(gp) 373 } 374 375 if gp.m.ncgo == 0 { 376 // The C call to Go came from a thread not currently running 377 // any Go. In the case of -buildmode=c-archive or c-shared, 378 // this call may be coming in before package initialization 379 // is complete. Wait until it is. 380 <-main_init_done 381 } 382 383 // Check whether the profiler needs to be turned on or off; this route to 384 // run Go code does not use runtime.execute, so bypasses the check there. 385 hz := sched.profilehz 386 if gp.m.profilehz != hz { 387 setThreadCPUProfiler(hz) 388 } 389 390 // Add entry to defer stack in case of panic. 391 restore := true 392 defer unwindm(&restore) 393 394 if raceenabled { 395 raceacquire(unsafe.Pointer(&racecgosync)) 396 } 397 398 // Invoke callback. This function is generated by cmd/cgo and 399 // will unpack the argument frame and call the Go function. 400 var cb func(frame unsafe.Pointer) 401 cbFV := funcval{uintptr(fn)} 402 *(*unsafe.Pointer)(unsafe.Pointer(&cb)) = noescape(unsafe.Pointer(&cbFV)) 403 cb(frame) 404 405 if raceenabled { 406 racereleasemerge(unsafe.Pointer(&racecgosync)) 407 } 408 409 // Do not unwind m->g0->sched.sp. 410 // Our caller, cgocallback, will do that. 411 restore = false 412 } 413 414 func unwindm(restore *bool) { 415 if *restore { 416 // Restore sp saved by cgocallback during 417 // unwind of g's stack (see comment at top of file). 418 mp := acquirem() 419 sched := &mp.g0.sched 420 sched.sp = *(*uintptr)(unsafe.Pointer(sched.sp + alignUp(sys.MinFrameSize, sys.StackAlign))) 421 422 // Do the accounting that cgocall will not have a chance to do 423 // during an unwind. 424 // 425 // In the case where a Go call originates from C, ncgo is 0 426 // and there is no matching cgocall to end. 427 if mp.ncgo > 0 { 428 mp.incgo = false 429 mp.ncgo-- 430 osPreemptExtExit(mp) 431 } 432 433 // Undo the call to lockOSThread in cgocallbackg, only on the 434 // panicking path. In normal return case cgocallbackg will call 435 // unlockOSThread, ensuring no preemption point after the unlock. 436 // Here we don't need to worry about preemption, because we're 437 // panicking out of the callback and unwinding the g0 stack, 438 // instead of reentering cgo (which requires the same thread). 439 unlockOSThread() 440 441 releasem(mp) 442 } 443 } 444 445 // called from assembly. 446 func badcgocallback() { 447 throw("misaligned stack in cgocallback") 448 } 449 450 // called from (incomplete) assembly. 451 func cgounimpl() { 452 throw("cgo not implemented") 453 } 454 455 var racecgosync uint64 // represents possible synchronization in C code 456 457 // Pointer checking for cgo code. 458 459 // We want to detect all cases where a program that does not use 460 // unsafe makes a cgo call passing a Go pointer to memory that 461 // contains an unpinned Go pointer. Here a Go pointer is defined as a 462 // pointer to memory allocated by the Go runtime. Programs that use 463 // unsafe can evade this restriction easily, so we don't try to catch 464 // them. The cgo program will rewrite all possibly bad pointer 465 // arguments to call cgoCheckPointer, where we can catch cases of a Go 466 // pointer pointing to an unpinned Go pointer. 467 468 // Complicating matters, taking the address of a slice or array 469 // element permits the C program to access all elements of the slice 470 // or array. In that case we will see a pointer to a single element, 471 // but we need to check the entire data structure. 472 473 // The cgoCheckPointer call takes additional arguments indicating that 474 // it was called on an address expression. An additional argument of 475 // true means that it only needs to check a single element. An 476 // additional argument of a slice or array means that it needs to 477 // check the entire slice/array, but nothing else. Otherwise, the 478 // pointer could be anything, and we check the entire heap object, 479 // which is conservative but safe. 480 481 // When and if we implement a moving garbage collector, 482 // cgoCheckPointer will pin the pointer for the duration of the cgo 483 // call. (This is necessary but not sufficient; the cgo program will 484 // also have to change to pin Go pointers that cannot point to Go 485 // pointers.) 486 487 // cgoCheckPointer checks if the argument contains a Go pointer that 488 // points to an unpinned Go pointer, and panics if it does. 489 func cgoCheckPointer(ptr any, arg any) { 490 if !goexperiment.CgoCheck2 && debug.cgocheck == 0 { 491 return 492 } 493 494 ep := efaceOf(&ptr) 495 t := ep._type 496 497 top := true 498 if arg != nil && (t.Kind_&kindMask == kindPtr || t.Kind_&kindMask == kindUnsafePointer) { 499 p := ep.data 500 if t.Kind_&kindDirectIface == 0 { 501 p = *(*unsafe.Pointer)(p) 502 } 503 if p == nil || !cgoIsGoPointer(p) { 504 return 505 } 506 aep := efaceOf(&arg) 507 switch aep._type.Kind_ & kindMask { 508 case kindBool: 509 if t.Kind_&kindMask == kindUnsafePointer { 510 // We don't know the type of the element. 511 break 512 } 513 pt := (*ptrtype)(unsafe.Pointer(t)) 514 cgoCheckArg(pt.Elem, p, true, false, cgoCheckPointerFail) 515 return 516 case kindSlice: 517 // Check the slice rather than the pointer. 518 ep = aep 519 t = ep._type 520 case kindArray: 521 // Check the array rather than the pointer. 522 // Pass top as false since we have a pointer 523 // to the array. 524 ep = aep 525 t = ep._type 526 top = false 527 default: 528 throw("can't happen") 529 } 530 } 531 532 cgoCheckArg(t, ep.data, t.Kind_&kindDirectIface == 0, top, cgoCheckPointerFail) 533 } 534 535 const cgoCheckPointerFail = "cgo argument has Go pointer to unpinned Go pointer" 536 const cgoResultFail = "cgo result is unpinned Go pointer or points to unpinned Go pointer" 537 538 // cgoCheckArg is the real work of cgoCheckPointer. The argument p 539 // is either a pointer to the value (of type t), or the value itself, 540 // depending on indir. The top parameter is whether we are at the top 541 // level, where Go pointers are allowed. Go pointers to pinned objects are 542 // allowed as long as they don't reference other unpinned pointers. 543 func cgoCheckArg(t *_type, p unsafe.Pointer, indir, top bool, msg string) { 544 if t.PtrBytes == 0 || p == nil { 545 // If the type has no pointers there is nothing to do. 546 return 547 } 548 549 switch t.Kind_ & kindMask { 550 default: 551 throw("can't happen") 552 case kindArray: 553 at := (*arraytype)(unsafe.Pointer(t)) 554 if !indir { 555 if at.Len != 1 { 556 throw("can't happen") 557 } 558 cgoCheckArg(at.Elem, p, at.Elem.Kind_&kindDirectIface == 0, top, msg) 559 return 560 } 561 for i := uintptr(0); i < at.Len; i++ { 562 cgoCheckArg(at.Elem, p, true, top, msg) 563 p = add(p, at.Elem.Size_) 564 } 565 case kindChan, kindMap: 566 // These types contain internal pointers that will 567 // always be allocated in the Go heap. It's never OK 568 // to pass them to C. 569 panic(errorString(msg)) 570 case kindFunc: 571 if indir { 572 p = *(*unsafe.Pointer)(p) 573 } 574 if !cgoIsGoPointer(p) { 575 return 576 } 577 panic(errorString(msg)) 578 case kindInterface: 579 it := *(**_type)(p) 580 if it == nil { 581 return 582 } 583 // A type known at compile time is OK since it's 584 // constant. A type not known at compile time will be 585 // in the heap and will not be OK. 586 if inheap(uintptr(unsafe.Pointer(it))) { 587 panic(errorString(msg)) 588 } 589 p = *(*unsafe.Pointer)(add(p, goarch.PtrSize)) 590 if !cgoIsGoPointer(p) { 591 return 592 } 593 if !top && !isPinned(p) { 594 panic(errorString(msg)) 595 } 596 cgoCheckArg(it, p, it.Kind_&kindDirectIface == 0, false, msg) 597 case kindSlice: 598 st := (*slicetype)(unsafe.Pointer(t)) 599 s := (*slice)(p) 600 p = s.array 601 if p == nil || !cgoIsGoPointer(p) { 602 return 603 } 604 if !top && !isPinned(p) { 605 panic(errorString(msg)) 606 } 607 if st.Elem.PtrBytes == 0 { 608 return 609 } 610 for i := 0; i < s.cap; i++ { 611 cgoCheckArg(st.Elem, p, true, false, msg) 612 p = add(p, st.Elem.Size_) 613 } 614 case kindString: 615 ss := (*stringStruct)(p) 616 if !cgoIsGoPointer(ss.str) { 617 return 618 } 619 if !top && !isPinned(ss.str) { 620 panic(errorString(msg)) 621 } 622 case kindStruct: 623 st := (*structtype)(unsafe.Pointer(t)) 624 if !indir { 625 if len(st.Fields) != 1 { 626 throw("can't happen") 627 } 628 cgoCheckArg(st.Fields[0].Typ, p, st.Fields[0].Typ.Kind_&kindDirectIface == 0, top, msg) 629 return 630 } 631 for _, f := range st.Fields { 632 if f.Typ.PtrBytes == 0 { 633 continue 634 } 635 cgoCheckArg(f.Typ, add(p, f.Offset), true, top, msg) 636 } 637 case kindPtr, kindUnsafePointer: 638 if indir { 639 p = *(*unsafe.Pointer)(p) 640 if p == nil { 641 return 642 } 643 } 644 645 if !cgoIsGoPointer(p) { 646 return 647 } 648 if !top && !isPinned(p) { 649 panic(errorString(msg)) 650 } 651 652 cgoCheckUnknownPointer(p, msg) 653 } 654 } 655 656 // cgoCheckUnknownPointer is called for an arbitrary pointer into Go 657 // memory. It checks whether that Go memory contains any other 658 // pointer into unpinned Go memory. If it does, we panic. 659 // The return values are unused but useful to see in panic tracebacks. 660 func cgoCheckUnknownPointer(p unsafe.Pointer, msg string) (base, i uintptr) { 661 if inheap(uintptr(p)) { 662 b, span, _ := findObject(uintptr(p), 0, 0) 663 base = b 664 if base == 0 { 665 return 666 } 667 if goexperiment.AllocHeaders { 668 tp := span.typePointersOfUnchecked(base) 669 for { 670 var addr uintptr 671 if tp, addr = tp.next(base + span.elemsize); addr == 0 { 672 break 673 } 674 pp := *(*unsafe.Pointer)(unsafe.Pointer(addr)) 675 if cgoIsGoPointer(pp) && !isPinned(pp) { 676 panic(errorString(msg)) 677 } 678 } 679 } else { 680 n := span.elemsize 681 hbits := heapBitsForAddr(base, n) 682 for { 683 var addr uintptr 684 if hbits, addr = hbits.next(); addr == 0 { 685 break 686 } 687 pp := *(*unsafe.Pointer)(unsafe.Pointer(addr)) 688 if cgoIsGoPointer(pp) && !isPinned(pp) { 689 panic(errorString(msg)) 690 } 691 } 692 } 693 return 694 } 695 696 for _, datap := range activeModules() { 697 if cgoInRange(p, datap.data, datap.edata) || cgoInRange(p, datap.bss, datap.ebss) { 698 // We have no way to know the size of the object. 699 // We have to assume that it might contain a pointer. 700 panic(errorString(msg)) 701 } 702 // In the text or noptr sections, we know that the 703 // pointer does not point to a Go pointer. 704 } 705 706 return 707 } 708 709 // cgoIsGoPointer reports whether the pointer is a Go pointer--a 710 // pointer to Go memory. We only care about Go memory that might 711 // contain pointers. 712 // 713 //go:nosplit 714 //go:nowritebarrierrec 715 func cgoIsGoPointer(p unsafe.Pointer) bool { 716 if p == nil { 717 return false 718 } 719 720 if inHeapOrStack(uintptr(p)) { 721 return true 722 } 723 724 for _, datap := range activeModules() { 725 if cgoInRange(p, datap.data, datap.edata) || cgoInRange(p, datap.bss, datap.ebss) { 726 return true 727 } 728 } 729 730 return false 731 } 732 733 // cgoInRange reports whether p is between start and end. 734 // 735 //go:nosplit 736 //go:nowritebarrierrec 737 func cgoInRange(p unsafe.Pointer, start, end uintptr) bool { 738 return start <= uintptr(p) && uintptr(p) < end 739 } 740 741 // cgoCheckResult is called to check the result parameter of an 742 // exported Go function. It panics if the result is or contains any 743 // other pointer into unpinned Go memory. 744 func cgoCheckResult(val any) { 745 if !goexperiment.CgoCheck2 && debug.cgocheck == 0 { 746 return 747 } 748 749 ep := efaceOf(&val) 750 t := ep._type 751 cgoCheckArg(t, ep.data, t.Kind_&kindDirectIface == 0, false, cgoResultFail) 752 } 753