Source file src/runtime/cgocall.go
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/abi" 89 "internal/goarch" 90 "internal/goexperiment" 91 "runtime/internal/sys" 92 "unsafe" 93 ) 94 95 // Addresses collected in a cgo backtrace when crashing. 96 // Length must match arg.Max in x_cgo_callers in runtime/cgo/gcc_traceback.c. 97 type cgoCallers [32]uintptr 98 99 // argset matches runtime/cgo/linux_syscall.c:argset_t 100 type argset struct { 101 args unsafe.Pointer 102 retval uintptr 103 } 104 105 // wrapper for syscall package to call cgocall for libc (cgo) calls. 106 // 107 //go:linkname syscall_cgocaller syscall.cgocaller 108 //go:nosplit 109 //go:uintptrescapes 110 func syscall_cgocaller(fn unsafe.Pointer, args ...uintptr) uintptr { 111 as := argset{args: unsafe.Pointer(&args[0])} 112 cgocall(fn, unsafe.Pointer(&as)) 113 return as.retval 114 } 115 116 var ncgocall uint64 // number of cgo calls in total for dead m 117 118 // Call from Go to C. 119 // 120 // This must be nosplit because it's used for syscalls on some 121 // platforms. Syscalls may have untyped arguments on the stack, so 122 // it's not safe to grow or scan the stack. 123 // 124 // cgocall should be an internal detail, 125 // but widely used packages access it using linkname. 126 // Notable members of the hall of shame include: 127 // - github.com/ebitengine/purego 128 // 129 // Do not remove or change the type signature. 130 // See go.dev/issue/67401. 131 // 132 //go:linkname cgocall 133 //go:nosplit 134 func cgocall(fn, arg unsafe.Pointer) int32 { 135 if !iscgo && GOOS != "solaris" && GOOS != "illumos" && GOOS != "windows" { 136 throw("cgocall unavailable") 137 } 138 139 if fn == nil { 140 throw("cgocall nil") 141 } 142 143 if raceenabled { 144 racereleasemerge(unsafe.Pointer(&racecgosync)) 145 } 146 147 mp := getg().m 148 mp.ncgocall++ 149 150 // Reset traceback. 151 mp.cgoCallers[0] = 0 152 153 // Announce we are entering a system call 154 // so that the scheduler knows to create another 155 // M to run goroutines while we are in the 156 // foreign code. 157 // 158 // The call to asmcgocall is guaranteed not to 159 // grow the stack and does not allocate memory, 160 // so it is safe to call while "in a system call", outside 161 // the $GOMAXPROCS accounting. 162 // 163 // fn may call back into Go code, in which case we'll exit the 164 // "system call", run the Go code (which may grow the stack), 165 // and then re-enter the "system call" reusing the PC and SP 166 // saved by entersyscall here. 167 entersyscall() 168 169 // Tell asynchronous preemption that we're entering external 170 // code. We do this after entersyscall because this may block 171 // and cause an async preemption to fail, but at this point a 172 // sync preemption will succeed (though this is not a matter 173 // of correctness). 174 osPreemptExtEnter(mp) 175 176 mp.incgo = true 177 // We use ncgo as a check during execution tracing for whether there is 178 // any C on the call stack, which there will be after this point. If 179 // there isn't, we can use frame pointer unwinding to collect call 180 // stacks efficiently. This will be the case for the first Go-to-C call 181 // on a stack, so it's preferable to update it here, after we emit a 182 // trace event in entersyscall above. 183 mp.ncgo++ 184 185 errno := asmcgocall(fn, arg) 186 187 // Update accounting before exitsyscall because exitsyscall may 188 // reschedule us on to a different M. 189 mp.incgo = false 190 mp.ncgo-- 191 192 osPreemptExtExit(mp) 193 194 // Save current syscall parameters, so m.winsyscall can be 195 // used again if callback decide to make syscall. 196 winsyscall := mp.winsyscall 197 198 exitsyscall() 199 200 getg().m.winsyscall = winsyscall 201 202 // Note that raceacquire must be called only after exitsyscall has 203 // wired this M to a P. 204 if raceenabled { 205 raceacquire(unsafe.Pointer(&racecgosync)) 206 } 207 208 // From the garbage collector's perspective, time can move 209 // backwards in the sequence above. If there's a callback into 210 // Go code, GC will see this function at the call to 211 // asmcgocall. When the Go call later returns to C, the 212 // syscall PC/SP is rolled back and the GC sees this function 213 // back at the call to entersyscall. Normally, fn and arg 214 // would be live at entersyscall and dead at asmcgocall, so if 215 // time moved backwards, GC would see these arguments as dead 216 // and then live. Prevent these undead arguments from crashing 217 // GC by forcing them to stay live across this time warp. 218 KeepAlive(fn) 219 KeepAlive(arg) 220 KeepAlive(mp) 221 222 return errno 223 } 224 225 // Set or reset the system stack bounds for a callback on sp. 226 // 227 // Must be nosplit because it is called by needm prior to fully initializing 228 // the M. 229 // 230 //go:nosplit 231 func callbackUpdateSystemStack(mp *m, sp uintptr, signal bool) { 232 g0 := mp.g0 233 234 inBound := sp > g0.stack.lo && sp <= g0.stack.hi 235 if mp.ncgo > 0 && !inBound { 236 // ncgo > 0 indicates that this M was in Go further up the stack 237 // (it called C and is now receiving a callback). 238 // 239 // !inBound indicates that we were called with SP outside the 240 // expected system stack bounds (C changed the stack out from 241 // under us between the cgocall and cgocallback?). 242 // 243 // It is not safe for the C call to change the stack out from 244 // under us, so throw. 245 246 // Note that this case isn't possible for signal == true, as 247 // that is always passing a new M from needm. 248 249 // Stack is bogus, but reset the bounds anyway so we can print. 250 hi := g0.stack.hi 251 lo := g0.stack.lo 252 g0.stack.hi = sp + 1024 253 g0.stack.lo = sp - 32*1024 254 g0.stackguard0 = g0.stack.lo + stackGuard 255 g0.stackguard1 = g0.stackguard0 256 257 print("M ", mp.id, " procid ", mp.procid, " runtime: cgocallback with sp=", hex(sp), " out of bounds [", hex(lo), ", ", hex(hi), "]") 258 print("\n") 259 exit(2) 260 } 261 262 if !mp.isextra { 263 // We allocated the stack for standard Ms. Don't replace the 264 // stack bounds with estimated ones when we already initialized 265 // with the exact ones. 266 return 267 } 268 269 // This M does not have Go further up the stack. However, it may have 270 // previously called into Go, initializing the stack bounds. Between 271 // that call returning and now the stack may have changed (perhaps the 272 // C thread is running a coroutine library). We need to update the 273 // stack bounds for this case. 274 // 275 // N.B. we need to update the stack bounds even if SP appears to 276 // already be in bounds. Our "bounds" may actually be estimated dummy 277 // bounds (below). The actual stack bounds could have shifted but still 278 // have partial overlap with our dummy bounds. If we failed to update 279 // in that case, we could find ourselves seemingly called near the 280 // bottom of the stack bounds, where we quickly run out of space. 281 282 // Set the stack bounds to match the current stack. If we don't 283 // actually know how big the stack is, like we don't know how big any 284 // scheduling stack is, but we assume there's at least 32 kB. If we 285 // can get a more accurate stack bound from pthread, use that, provided 286 // it actually contains SP.. 287 g0.stack.hi = sp + 1024 288 g0.stack.lo = sp - 32*1024 289 if !signal && _cgo_getstackbound != nil { 290 // Don't adjust if called from the signal handler. 291 // We are on the signal stack, not the pthread stack. 292 // (We could get the stack bounds from sigaltstack, but 293 // we're getting out of the signal handler very soon 294 // anyway. Not worth it.) 295 var bounds [2]uintptr 296 asmcgocall(_cgo_getstackbound, unsafe.Pointer(&bounds)) 297 // getstackbound is an unsupported no-op on Windows. 298 // 299 // Don't use these bounds if they don't contain SP. Perhaps we 300 // were called by something not using the standard thread 301 // stack. 302 if bounds[0] != 0 && sp > bounds[0] && sp <= bounds[1] { 303 g0.stack.lo = bounds[0] 304 g0.stack.hi = bounds[1] 305 } 306 } 307 g0.stackguard0 = g0.stack.lo + stackGuard 308 g0.stackguard1 = g0.stackguard0 309 } 310 311 // Call from C back to Go. fn must point to an ABIInternal Go entry-point. 312 // 313 //go:nosplit 314 func cgocallbackg(fn, frame unsafe.Pointer, ctxt uintptr) { 315 gp := getg() 316 if gp != gp.m.curg { 317 println("runtime: bad g in cgocallback") 318 exit(2) 319 } 320 321 sp := gp.m.g0.sched.sp // system sp saved by cgocallback. 322 callbackUpdateSystemStack(gp.m, sp, false) 323 324 // The call from C is on gp.m's g0 stack, so we must ensure 325 // that we stay on that M. We have to do this before calling 326 // exitsyscall, since it would otherwise be free to move us to 327 // a different M. The call to unlockOSThread is in this function 328 // after cgocallbackg1, or in the case of panicking, in unwindm. 329 lockOSThread() 330 331 checkm := gp.m 332 333 // Save current syscall parameters, so m.winsyscall can be 334 // used again if callback decide to make syscall. 335 winsyscall := gp.m.winsyscall 336 337 // entersyscall saves the caller's SP to allow the GC to trace the Go 338 // stack. However, since we're returning to an earlier stack frame and 339 // need to pair with the entersyscall() call made by cgocall, we must 340 // save syscall* and let reentersyscall restore them. 341 // 342 // Note: savedsp and savedbp MUST be held in locals as an unsafe.Pointer. 343 // When we call into Go, the stack is free to be moved. If these locals 344 // aren't visible in the stack maps, they won't get updated properly, 345 // and will end up being stale when restored by reentersyscall. 346 savedsp := unsafe.Pointer(gp.syscallsp) 347 savedpc := gp.syscallpc 348 savedbp := unsafe.Pointer(gp.syscallbp) 349 exitsyscall() // coming out of cgo call 350 gp.m.incgo = false 351 if gp.m.isextra { 352 gp.m.isExtraInC = false 353 } 354 355 osPreemptExtExit(gp.m) 356 357 if gp.nocgocallback { 358 panic("runtime: function marked with #cgo nocallback called back into Go") 359 } 360 361 cgocallbackg1(fn, frame, ctxt) 362 363 // At this point we're about to call unlockOSThread. 364 // The following code must not change to a different m. 365 // This is enforced by checking incgo in the schedule function. 366 gp.m.incgo = true 367 unlockOSThread() 368 369 if gp.m.isextra { 370 gp.m.isExtraInC = true 371 } 372 373 if gp.m != checkm { 374 throw("m changed unexpectedly in cgocallbackg") 375 } 376 377 osPreemptExtEnter(gp.m) 378 379 // going back to cgo call 380 reentersyscall(savedpc, uintptr(savedsp), uintptr(savedbp)) 381 382 gp.m.winsyscall = winsyscall 383 } 384 385 func cgocallbackg1(fn, frame unsafe.Pointer, ctxt uintptr) { 386 gp := getg() 387 388 if gp.m.needextram || extraMWaiters.Load() > 0 { 389 gp.m.needextram = false 390 systemstack(newextram) 391 } 392 393 if ctxt != 0 { 394 s := append(gp.cgoCtxt, ctxt) 395 396 // Now we need to set gp.cgoCtxt = s, but we could get 397 // a SIGPROF signal while manipulating the slice, and 398 // the SIGPROF handler could pick up gp.cgoCtxt while 399 // tracing up the stack. We need to ensure that the 400 // handler always sees a valid slice, so set the 401 // values in an order such that it always does. 402 p := (*slice)(unsafe.Pointer(&gp.cgoCtxt)) 403 atomicstorep(unsafe.Pointer(&p.array), unsafe.Pointer(&s[0])) 404 p.cap = cap(s) 405 p.len = len(s) 406 407 defer func(gp *g) { 408 // Decrease the length of the slice by one, safely. 409 p := (*slice)(unsafe.Pointer(&gp.cgoCtxt)) 410 p.len-- 411 }(gp) 412 } 413 414 if gp.m.ncgo == 0 { 415 // The C call to Go came from a thread not currently running 416 // any Go. In the case of -buildmode=c-archive or c-shared, 417 // this call may be coming in before package initialization 418 // is complete. Wait until it is. 419 <-main_init_done 420 } 421 422 // Check whether the profiler needs to be turned on or off; this route to 423 // run Go code does not use runtime.execute, so bypasses the check there. 424 hz := sched.profilehz 425 if gp.m.profilehz != hz { 426 setThreadCPUProfiler(hz) 427 } 428 429 // Add entry to defer stack in case of panic. 430 restore := true 431 defer unwindm(&restore) 432 433 if raceenabled { 434 raceacquire(unsafe.Pointer(&racecgosync)) 435 } 436 437 // Invoke callback. This function is generated by cmd/cgo and 438 // will unpack the argument frame and call the Go function. 439 var cb func(frame unsafe.Pointer) 440 cbFV := funcval{uintptr(fn)} 441 *(*unsafe.Pointer)(unsafe.Pointer(&cb)) = noescape(unsafe.Pointer(&cbFV)) 442 cb(frame) 443 444 if raceenabled { 445 racereleasemerge(unsafe.Pointer(&racecgosync)) 446 } 447 448 // Do not unwind m->g0->sched.sp. 449 // Our caller, cgocallback, will do that. 450 restore = false 451 } 452 453 func unwindm(restore *bool) { 454 if *restore { 455 // Restore sp saved by cgocallback during 456 // unwind of g's stack (see comment at top of file). 457 mp := acquirem() 458 sched := &mp.g0.sched 459 sched.sp = *(*uintptr)(unsafe.Pointer(sched.sp + alignUp(sys.MinFrameSize, sys.StackAlign))) 460 461 // Do the accounting that cgocall will not have a chance to do 462 // during an unwind. 463 // 464 // In the case where a Go call originates from C, ncgo is 0 465 // and there is no matching cgocall to end. 466 if mp.ncgo > 0 { 467 mp.incgo = false 468 mp.ncgo-- 469 osPreemptExtExit(mp) 470 } 471 472 // Undo the call to lockOSThread in cgocallbackg, only on the 473 // panicking path. In normal return case cgocallbackg will call 474 // unlockOSThread, ensuring no preemption point after the unlock. 475 // Here we don't need to worry about preemption, because we're 476 // panicking out of the callback and unwinding the g0 stack, 477 // instead of reentering cgo (which requires the same thread). 478 unlockOSThread() 479 480 releasem(mp) 481 } 482 } 483 484 // called from assembly. 485 func badcgocallback() { 486 throw("misaligned stack in cgocallback") 487 } 488 489 // called from (incomplete) assembly. 490 func cgounimpl() { 491 throw("cgo not implemented") 492 } 493 494 var racecgosync uint64 // represents possible synchronization in C code 495 496 // Pointer checking for cgo code. 497 498 // We want to detect all cases where a program that does not use 499 // unsafe makes a cgo call passing a Go pointer to memory that 500 // contains an unpinned Go pointer. Here a Go pointer is defined as a 501 // pointer to memory allocated by the Go runtime. Programs that use 502 // unsafe can evade this restriction easily, so we don't try to catch 503 // them. The cgo program will rewrite all possibly bad pointer 504 // arguments to call cgoCheckPointer, where we can catch cases of a Go 505 // pointer pointing to an unpinned Go pointer. 506 507 // Complicating matters, taking the address of a slice or array 508 // element permits the C program to access all elements of the slice 509 // or array. In that case we will see a pointer to a single element, 510 // but we need to check the entire data structure. 511 512 // The cgoCheckPointer call takes additional arguments indicating that 513 // it was called on an address expression. An additional argument of 514 // true means that it only needs to check a single element. An 515 // additional argument of a slice or array means that it needs to 516 // check the entire slice/array, but nothing else. Otherwise, the 517 // pointer could be anything, and we check the entire heap object, 518 // which is conservative but safe. 519 520 // When and if we implement a moving garbage collector, 521 // cgoCheckPointer will pin the pointer for the duration of the cgo 522 // call. (This is necessary but not sufficient; the cgo program will 523 // also have to change to pin Go pointers that cannot point to Go 524 // pointers.) 525 526 // cgoCheckPointer checks if the argument contains a Go pointer that 527 // points to an unpinned Go pointer, and panics if it does. 528 func cgoCheckPointer(ptr any, arg any) { 529 if !goexperiment.CgoCheck2 && debug.cgocheck == 0 { 530 return 531 } 532 533 ep := efaceOf(&ptr) 534 t := ep._type 535 536 top := true 537 if arg != nil && (t.Kind_&abi.KindMask == abi.Pointer || t.Kind_&abi.KindMask == abi.UnsafePointer) { 538 p := ep.data 539 if t.Kind_&abi.KindDirectIface == 0 { 540 p = *(*unsafe.Pointer)(p) 541 } 542 if p == nil || !cgoIsGoPointer(p) { 543 return 544 } 545 aep := efaceOf(&arg) 546 switch aep._type.Kind_ & abi.KindMask { 547 case abi.Bool: 548 if t.Kind_&abi.KindMask == abi.UnsafePointer { 549 // We don't know the type of the element. 550 break 551 } 552 pt := (*ptrtype)(unsafe.Pointer(t)) 553 cgoCheckArg(pt.Elem, p, true, false, cgoCheckPointerFail) 554 return 555 case abi.Slice: 556 // Check the slice rather than the pointer. 557 ep = aep 558 t = ep._type 559 case abi.Array: 560 // Check the array rather than the pointer. 561 // Pass top as false since we have a pointer 562 // to the array. 563 ep = aep 564 t = ep._type 565 top = false 566 default: 567 throw("can't happen") 568 } 569 } 570 571 cgoCheckArg(t, ep.data, t.Kind_&abi.KindDirectIface == 0, top, cgoCheckPointerFail) 572 } 573 574 const cgoCheckPointerFail = "cgo argument has Go pointer to unpinned Go pointer" 575 const cgoResultFail = "cgo result is unpinned Go pointer or points to unpinned Go pointer" 576 577 // cgoCheckArg is the real work of cgoCheckPointer. The argument p 578 // is either a pointer to the value (of type t), or the value itself, 579 // depending on indir. The top parameter is whether we are at the top 580 // level, where Go pointers are allowed. Go pointers to pinned objects are 581 // allowed as long as they don't reference other unpinned pointers. 582 func cgoCheckArg(t *_type, p unsafe.Pointer, indir, top bool, msg string) { 583 if !t.Pointers() || p == nil { 584 // If the type has no pointers there is nothing to do. 585 return 586 } 587 588 switch t.Kind_ & abi.KindMask { 589 default: 590 throw("can't happen") 591 case abi.Array: 592 at := (*arraytype)(unsafe.Pointer(t)) 593 if !indir { 594 if at.Len != 1 { 595 throw("can't happen") 596 } 597 cgoCheckArg(at.Elem, p, at.Elem.Kind_&abi.KindDirectIface == 0, top, msg) 598 return 599 } 600 for i := uintptr(0); i < at.Len; i++ { 601 cgoCheckArg(at.Elem, p, true, top, msg) 602 p = add(p, at.Elem.Size_) 603 } 604 case abi.Chan, abi.Map: 605 // These types contain internal pointers that will 606 // always be allocated in the Go heap. It's never OK 607 // to pass them to C. 608 panic(errorString(msg)) 609 case abi.Func: 610 if indir { 611 p = *(*unsafe.Pointer)(p) 612 } 613 if !cgoIsGoPointer(p) { 614 return 615 } 616 panic(errorString(msg)) 617 case abi.Interface: 618 it := *(**_type)(p) 619 if it == nil { 620 return 621 } 622 // A type known at compile time is OK since it's 623 // constant. A type not known at compile time will be 624 // in the heap and will not be OK. 625 if inheap(uintptr(unsafe.Pointer(it))) { 626 panic(errorString(msg)) 627 } 628 p = *(*unsafe.Pointer)(add(p, goarch.PtrSize)) 629 if !cgoIsGoPointer(p) { 630 return 631 } 632 if !top && !isPinned(p) { 633 panic(errorString(msg)) 634 } 635 cgoCheckArg(it, p, it.Kind_&abi.KindDirectIface == 0, false, msg) 636 case abi.Slice: 637 st := (*slicetype)(unsafe.Pointer(t)) 638 s := (*slice)(p) 639 p = s.array 640 if p == nil || !cgoIsGoPointer(p) { 641 return 642 } 643 if !top && !isPinned(p) { 644 panic(errorString(msg)) 645 } 646 if !st.Elem.Pointers() { 647 return 648 } 649 for i := 0; i < s.cap; i++ { 650 cgoCheckArg(st.Elem, p, true, false, msg) 651 p = add(p, st.Elem.Size_) 652 } 653 case abi.String: 654 ss := (*stringStruct)(p) 655 if !cgoIsGoPointer(ss.str) { 656 return 657 } 658 if !top && !isPinned(ss.str) { 659 panic(errorString(msg)) 660 } 661 case abi.Struct: 662 st := (*structtype)(unsafe.Pointer(t)) 663 if !indir { 664 if len(st.Fields) != 1 { 665 throw("can't happen") 666 } 667 cgoCheckArg(st.Fields[0].Typ, p, st.Fields[0].Typ.Kind_&abi.KindDirectIface == 0, top, msg) 668 return 669 } 670 for _, f := range st.Fields { 671 if !f.Typ.Pointers() { 672 continue 673 } 674 cgoCheckArg(f.Typ, add(p, f.Offset), true, top, msg) 675 } 676 case abi.Pointer, abi.UnsafePointer: 677 if indir { 678 p = *(*unsafe.Pointer)(p) 679 if p == nil { 680 return 681 } 682 } 683 684 if !cgoIsGoPointer(p) { 685 return 686 } 687 if !top && !isPinned(p) { 688 panic(errorString(msg)) 689 } 690 691 cgoCheckUnknownPointer(p, msg) 692 } 693 } 694 695 // cgoCheckUnknownPointer is called for an arbitrary pointer into Go 696 // memory. It checks whether that Go memory contains any other 697 // pointer into unpinned Go memory. If it does, we panic. 698 // The return values are unused but useful to see in panic tracebacks. 699 func cgoCheckUnknownPointer(p unsafe.Pointer, msg string) (base, i uintptr) { 700 if inheap(uintptr(p)) { 701 b, span, _ := findObject(uintptr(p), 0, 0) 702 base = b 703 if base == 0 { 704 return 705 } 706 tp := span.typePointersOfUnchecked(base) 707 for { 708 var addr uintptr 709 if tp, addr = tp.next(base + span.elemsize); addr == 0 { 710 break 711 } 712 pp := *(*unsafe.Pointer)(unsafe.Pointer(addr)) 713 if cgoIsGoPointer(pp) && !isPinned(pp) { 714 panic(errorString(msg)) 715 } 716 } 717 return 718 } 719 720 for _, datap := range activeModules() { 721 if cgoInRange(p, datap.data, datap.edata) || cgoInRange(p, datap.bss, datap.ebss) { 722 // We have no way to know the size of the object. 723 // We have to assume that it might contain a pointer. 724 panic(errorString(msg)) 725 } 726 // In the text or noptr sections, we know that the 727 // pointer does not point to a Go pointer. 728 } 729 730 return 731 } 732 733 // cgoIsGoPointer reports whether the pointer is a Go pointer--a 734 // pointer to Go memory. We only care about Go memory that might 735 // contain pointers. 736 // 737 //go:nosplit 738 //go:nowritebarrierrec 739 func cgoIsGoPointer(p unsafe.Pointer) bool { 740 if p == nil { 741 return false 742 } 743 744 if inHeapOrStack(uintptr(p)) { 745 return true 746 } 747 748 for _, datap := range activeModules() { 749 if cgoInRange(p, datap.data, datap.edata) || cgoInRange(p, datap.bss, datap.ebss) { 750 return true 751 } 752 } 753 754 return false 755 } 756 757 // cgoInRange reports whether p is between start and end. 758 // 759 //go:nosplit 760 //go:nowritebarrierrec 761 func cgoInRange(p unsafe.Pointer, start, end uintptr) bool { 762 return start <= uintptr(p) && uintptr(p) < end 763 } 764 765 // cgoCheckResult is called to check the result parameter of an 766 // exported Go function. It panics if the result is or contains any 767 // other pointer into unpinned Go memory. 768 func cgoCheckResult(val any) { 769 if !goexperiment.CgoCheck2 && debug.cgocheck == 0 { 770 return 771 } 772 773 ep := efaceOf(&val) 774 t := ep._type 775 cgoCheckArg(t, ep.data, t.Kind_&abi.KindDirectIface == 0, false, cgoResultFail) 776 } 777