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 "internal/runtime/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 if !mp.isextra { 235 // We allocated the stack for standard Ms. Don't replace the 236 // stack bounds with estimated ones when we already initialized 237 // with the exact ones. 238 return 239 } 240 241 inBound := sp > g0.stack.lo && sp <= g0.stack.hi 242 if inBound && mp.g0StackAccurate { 243 // This M has called into Go before and has the stack bounds 244 // initialized. We have the accurate stack bounds, and the SP 245 // is in bounds. We expect it continues to run within the same 246 // bounds. 247 return 248 } 249 250 // We don't have an accurate stack bounds (either it never calls 251 // into Go before, or we couldn't get the accurate bounds), or the 252 // current SP is not within the previous bounds (the stack may have 253 // changed between calls). We need to update the stack bounds. 254 // 255 // N.B. we need to update the stack bounds even if SP appears to 256 // already be in bounds, if our bounds are estimated dummy bounds 257 // (below). We may be in a different region within the same actual 258 // stack bounds, but our estimates were not accurate. Or the actual 259 // stack bounds could have shifted but still have partial overlap with 260 // our dummy bounds. If we failed to update in that case, we could find 261 // ourselves seemingly called near the bottom of the stack bounds, where 262 // we quickly run out of space. 263 264 // Set the stack bounds to match the current stack. If we don't 265 // actually know how big the stack is, like we don't know how big any 266 // scheduling stack is, but we assume there's at least 32 kB. If we 267 // can get a more accurate stack bound from pthread, use that, provided 268 // it actually contains SP. 269 g0.stack.hi = sp + 1024 270 g0.stack.lo = sp - 32*1024 271 mp.g0StackAccurate = false 272 if !signal && _cgo_getstackbound != nil { 273 // Don't adjust if called from the signal handler. 274 // We are on the signal stack, not the pthread stack. 275 // (We could get the stack bounds from sigaltstack, but 276 // we're getting out of the signal handler very soon 277 // anyway. Not worth it.) 278 var bounds [2]uintptr 279 asmcgocall(_cgo_getstackbound, unsafe.Pointer(&bounds)) 280 // getstackbound is an unsupported no-op on Windows. 281 // 282 // On Unix systems, if the API to get accurate stack bounds is 283 // not available, it returns zeros. 284 // 285 // Don't use these bounds if they don't contain SP. Perhaps we 286 // were called by something not using the standard thread 287 // stack. 288 if bounds[0] != 0 && sp > bounds[0] && sp <= bounds[1] { 289 g0.stack.lo = bounds[0] 290 g0.stack.hi = bounds[1] 291 mp.g0StackAccurate = true 292 } 293 } 294 g0.stackguard0 = g0.stack.lo + stackGuard 295 g0.stackguard1 = g0.stackguard0 296 } 297 298 // Call from C back to Go. fn must point to an ABIInternal Go entry-point. 299 // 300 //go:nosplit 301 func cgocallbackg(fn, frame unsafe.Pointer, ctxt uintptr) { 302 gp := getg() 303 if gp != gp.m.curg { 304 println("runtime: bad g in cgocallback") 305 exit(2) 306 } 307 308 sp := gp.m.g0.sched.sp // system sp saved by cgocallback. 309 oldStack := gp.m.g0.stack 310 oldAccurate := gp.m.g0StackAccurate 311 callbackUpdateSystemStack(gp.m, sp, false) 312 313 // The call from C is on gp.m's g0 stack, so we must ensure 314 // that we stay on that M. We have to do this before calling 315 // exitsyscall, since it would otherwise be free to move us to 316 // a different M. The call to unlockOSThread is in this function 317 // after cgocallbackg1, or in the case of panicking, in unwindm. 318 lockOSThread() 319 320 checkm := gp.m 321 322 // Save current syscall parameters, so m.winsyscall can be 323 // used again if callback decide to make syscall. 324 winsyscall := gp.m.winsyscall 325 326 // entersyscall saves the caller's SP to allow the GC to trace the Go 327 // stack. However, since we're returning to an earlier stack frame and 328 // need to pair with the entersyscall() call made by cgocall, we must 329 // save syscall* and let reentersyscall restore them. 330 // 331 // Note: savedsp and savedbp MUST be held in locals as an unsafe.Pointer. 332 // When we call into Go, the stack is free to be moved. If these locals 333 // aren't visible in the stack maps, they won't get updated properly, 334 // and will end up being stale when restored by reentersyscall. 335 savedsp := unsafe.Pointer(gp.syscallsp) 336 savedpc := gp.syscallpc 337 savedbp := unsafe.Pointer(gp.syscallbp) 338 exitsyscall() // coming out of cgo call 339 gp.m.incgo = false 340 if gp.m.isextra { 341 gp.m.isExtraInC = false 342 } 343 344 osPreemptExtExit(gp.m) 345 346 if gp.nocgocallback { 347 panic("runtime: function marked with #cgo nocallback called back into Go") 348 } 349 350 cgocallbackg1(fn, frame, ctxt) 351 352 // At this point we're about to call unlockOSThread. 353 // The following code must not change to a different m. 354 // This is enforced by checking incgo in the schedule function. 355 gp.m.incgo = true 356 unlockOSThread() 357 358 if gp.m.isextra && gp.m.ncgo == 0 { 359 // There are no active cgocalls above this frame (ncgo == 0), 360 // thus there can't be more Go frames above this frame. 361 gp.m.isExtraInC = true 362 } 363 364 if gp.m != checkm { 365 throw("m changed unexpectedly in cgocallbackg") 366 } 367 368 osPreemptExtEnter(gp.m) 369 370 // going back to cgo call 371 reentersyscall(savedpc, uintptr(savedsp), uintptr(savedbp)) 372 373 gp.m.winsyscall = winsyscall 374 375 // Restore the old g0 stack bounds 376 gp.m.g0.stack = oldStack 377 gp.m.g0.stackguard0 = oldStack.lo + stackGuard 378 gp.m.g0.stackguard1 = gp.m.g0.stackguard0 379 gp.m.g0StackAccurate = oldAccurate 380 } 381 382 func cgocallbackg1(fn, frame unsafe.Pointer, ctxt uintptr) { 383 gp := getg() 384 385 if gp.m.needextram || extraMWaiters.Load() > 0 { 386 gp.m.needextram = false 387 systemstack(newextram) 388 } 389 390 if ctxt != 0 { 391 s := append(gp.cgoCtxt, ctxt) 392 393 // Now we need to set gp.cgoCtxt = s, but we could get 394 // a SIGPROF signal while manipulating the slice, and 395 // the SIGPROF handler could pick up gp.cgoCtxt while 396 // tracing up the stack. We need to ensure that the 397 // handler always sees a valid slice, so set the 398 // values in an order such that it always does. 399 p := (*slice)(unsafe.Pointer(&gp.cgoCtxt)) 400 atomicstorep(unsafe.Pointer(&p.array), unsafe.Pointer(&s[0])) 401 p.cap = cap(s) 402 p.len = len(s) 403 404 defer func(gp *g) { 405 // Decrease the length of the slice by one, safely. 406 p := (*slice)(unsafe.Pointer(&gp.cgoCtxt)) 407 p.len-- 408 }(gp) 409 } 410 411 if gp.m.ncgo == 0 { 412 // The C call to Go came from a thread not currently running 413 // any Go. In the case of -buildmode=c-archive or c-shared, 414 // this call may be coming in before package initialization 415 // is complete. Wait until it is. 416 <-main_init_done 417 } 418 419 // Check whether the profiler needs to be turned on or off; this route to 420 // run Go code does not use runtime.execute, so bypasses the check there. 421 hz := sched.profilehz 422 if gp.m.profilehz != hz { 423 setThreadCPUProfiler(hz) 424 } 425 426 // Add entry to defer stack in case of panic. 427 restore := true 428 defer unwindm(&restore) 429 430 var ditAlreadySet bool 431 if debug.dataindependenttiming == 1 && gp.m.isextra { 432 // We only need to enable DIT for threads that were created by C, as it 433 // should already by enabled on threads that were created by Go. 434 ditAlreadySet = sys.EnableDIT() 435 } 436 437 if raceenabled { 438 raceacquire(unsafe.Pointer(&racecgosync)) 439 } 440 441 // Invoke callback. This function is generated by cmd/cgo and 442 // will unpack the argument frame and call the Go function. 443 var cb func(frame unsafe.Pointer) 444 cbFV := funcval{uintptr(fn)} 445 *(*unsafe.Pointer)(unsafe.Pointer(&cb)) = noescape(unsafe.Pointer(&cbFV)) 446 cb(frame) 447 448 if raceenabled { 449 racereleasemerge(unsafe.Pointer(&racecgosync)) 450 } 451 452 if debug.dataindependenttiming == 1 && !ditAlreadySet { 453 // Only unset DIT if it wasn't already enabled when cgocallback was called. 454 sys.DisableDIT() 455 } 456 457 // Do not unwind m->g0->sched.sp. 458 // Our caller, cgocallback, will do that. 459 restore = false 460 } 461 462 func unwindm(restore *bool) { 463 if *restore { 464 // Restore sp saved by cgocallback during 465 // unwind of g's stack (see comment at top of file). 466 mp := acquirem() 467 sched := &mp.g0.sched 468 sched.sp = *(*uintptr)(unsafe.Pointer(sched.sp + alignUp(sys.MinFrameSize, sys.StackAlign))) 469 470 // Do the accounting that cgocall will not have a chance to do 471 // during an unwind. 472 // 473 // In the case where a Go call originates from C, ncgo is 0 474 // and there is no matching cgocall to end. 475 if mp.ncgo > 0 { 476 mp.incgo = false 477 mp.ncgo-- 478 osPreemptExtExit(mp) 479 } 480 481 // Undo the call to lockOSThread in cgocallbackg, only on the 482 // panicking path. In normal return case cgocallbackg will call 483 // unlockOSThread, ensuring no preemption point after the unlock. 484 // Here we don't need to worry about preemption, because we're 485 // panicking out of the callback and unwinding the g0 stack, 486 // instead of reentering cgo (which requires the same thread). 487 unlockOSThread() 488 489 releasem(mp) 490 } 491 } 492 493 // called from assembly. 494 func badcgocallback() { 495 throw("misaligned stack in cgocallback") 496 } 497 498 // called from (incomplete) assembly. 499 func cgounimpl() { 500 throw("cgo not implemented") 501 } 502 503 var racecgosync uint64 // represents possible synchronization in C code 504 505 // Pointer checking for cgo code. 506 507 // We want to detect all cases where a program that does not use 508 // unsafe makes a cgo call passing a Go pointer to memory that 509 // contains an unpinned Go pointer. Here a Go pointer is defined as a 510 // pointer to memory allocated by the Go runtime. Programs that use 511 // unsafe can evade this restriction easily, so we don't try to catch 512 // them. The cgo program will rewrite all possibly bad pointer 513 // arguments to call cgoCheckPointer, where we can catch cases of a Go 514 // pointer pointing to an unpinned Go pointer. 515 516 // Complicating matters, taking the address of a slice or array 517 // element permits the C program to access all elements of the slice 518 // or array. In that case we will see a pointer to a single element, 519 // but we need to check the entire data structure. 520 521 // The cgoCheckPointer call takes additional arguments indicating that 522 // it was called on an address expression. An additional argument of 523 // true means that it only needs to check a single element. An 524 // additional argument of a slice or array means that it needs to 525 // check the entire slice/array, but nothing else. Otherwise, the 526 // pointer could be anything, and we check the entire heap object, 527 // which is conservative but safe. 528 529 // When and if we implement a moving garbage collector, 530 // cgoCheckPointer will pin the pointer for the duration of the cgo 531 // call. (This is necessary but not sufficient; the cgo program will 532 // also have to change to pin Go pointers that cannot point to Go 533 // pointers.) 534 535 // cgoCheckPointer checks if the argument contains a Go pointer that 536 // points to an unpinned Go pointer, and panics if it does. 537 func cgoCheckPointer(ptr any, arg any) { 538 if !goexperiment.CgoCheck2 && debug.cgocheck == 0 { 539 return 540 } 541 542 ep := efaceOf(&ptr) 543 t := ep._type 544 545 top := true 546 if arg != nil && (t.Kind_&abi.KindMask == abi.Pointer || t.Kind_&abi.KindMask == abi.UnsafePointer) { 547 p := ep.data 548 if t.Kind_&abi.KindDirectIface == 0 { 549 p = *(*unsafe.Pointer)(p) 550 } 551 if p == nil || !cgoIsGoPointer(p) { 552 return 553 } 554 aep := efaceOf(&arg) 555 switch aep._type.Kind_ & abi.KindMask { 556 case abi.Bool: 557 if t.Kind_&abi.KindMask == abi.UnsafePointer { 558 // We don't know the type of the element. 559 break 560 } 561 pt := (*ptrtype)(unsafe.Pointer(t)) 562 cgoCheckArg(pt.Elem, p, true, false, cgoCheckPointerFail) 563 return 564 case abi.Slice: 565 // Check the slice rather than the pointer. 566 ep = aep 567 t = ep._type 568 case abi.Array: 569 // Check the array rather than the pointer. 570 // Pass top as false since we have a pointer 571 // to the array. 572 ep = aep 573 t = ep._type 574 top = false 575 case abi.Pointer: 576 // The Go code is indexing into a pointer to an array, 577 // and we have been passed the pointer-to-array. 578 // Check the array rather than the pointer. 579 pt := (*abi.PtrType)(unsafe.Pointer(aep._type)) 580 t = pt.Elem 581 if t.Kind_&abi.KindMask != abi.Array { 582 throw("can't happen") 583 } 584 ep = aep 585 top = false 586 default: 587 throw("can't happen") 588 } 589 } 590 591 cgoCheckArg(t, ep.data, t.Kind_&abi.KindDirectIface == 0, top, cgoCheckPointerFail) 592 } 593 594 const cgoCheckPointerFail = "cgo argument has Go pointer to unpinned Go pointer" 595 const cgoResultFail = "cgo result is unpinned Go pointer or points to unpinned Go pointer" 596 597 // cgoCheckArg is the real work of cgoCheckPointer. The argument p 598 // is either a pointer to the value (of type t), or the value itself, 599 // depending on indir. The top parameter is whether we are at the top 600 // level, where Go pointers are allowed. Go pointers to pinned objects are 601 // allowed as long as they don't reference other unpinned pointers. 602 func cgoCheckArg(t *_type, p unsafe.Pointer, indir, top bool, msg string) { 603 if !t.Pointers() || p == nil { 604 // If the type has no pointers there is nothing to do. 605 return 606 } 607 608 switch t.Kind_ & abi.KindMask { 609 default: 610 throw("can't happen") 611 case abi.Array: 612 at := (*arraytype)(unsafe.Pointer(t)) 613 if !indir { 614 if at.Len != 1 { 615 throw("can't happen") 616 } 617 cgoCheckArg(at.Elem, p, at.Elem.Kind_&abi.KindDirectIface == 0, top, msg) 618 return 619 } 620 for i := uintptr(0); i < at.Len; i++ { 621 cgoCheckArg(at.Elem, p, true, top, msg) 622 p = add(p, at.Elem.Size_) 623 } 624 case abi.Chan, abi.Map: 625 // These types contain internal pointers that will 626 // always be allocated in the Go heap. It's never OK 627 // to pass them to C. 628 panic(errorString(msg)) 629 case abi.Func: 630 if indir { 631 p = *(*unsafe.Pointer)(p) 632 } 633 if !cgoIsGoPointer(p) { 634 return 635 } 636 panic(errorString(msg)) 637 case abi.Interface: 638 it := *(**_type)(p) 639 if it == nil { 640 return 641 } 642 // A type known at compile time is OK since it's 643 // constant. A type not known at compile time will be 644 // in the heap and will not be OK. 645 if inheap(uintptr(unsafe.Pointer(it))) { 646 panic(errorString(msg)) 647 } 648 p = *(*unsafe.Pointer)(add(p, goarch.PtrSize)) 649 if !cgoIsGoPointer(p) { 650 return 651 } 652 if !top && !isPinned(p) { 653 panic(errorString(msg)) 654 } 655 cgoCheckArg(it, p, it.Kind_&abi.KindDirectIface == 0, false, msg) 656 case abi.Slice: 657 st := (*slicetype)(unsafe.Pointer(t)) 658 s := (*slice)(p) 659 p = s.array 660 if p == nil || !cgoIsGoPointer(p) { 661 return 662 } 663 if !top && !isPinned(p) { 664 panic(errorString(msg)) 665 } 666 if !st.Elem.Pointers() { 667 return 668 } 669 for i := 0; i < s.cap; i++ { 670 cgoCheckArg(st.Elem, p, true, false, msg) 671 p = add(p, st.Elem.Size_) 672 } 673 case abi.String: 674 ss := (*stringStruct)(p) 675 if !cgoIsGoPointer(ss.str) { 676 return 677 } 678 if !top && !isPinned(ss.str) { 679 panic(errorString(msg)) 680 } 681 case abi.Struct: 682 st := (*structtype)(unsafe.Pointer(t)) 683 if !indir { 684 if len(st.Fields) != 1 { 685 throw("can't happen") 686 } 687 cgoCheckArg(st.Fields[0].Typ, p, st.Fields[0].Typ.Kind_&abi.KindDirectIface == 0, top, msg) 688 return 689 } 690 for _, f := range st.Fields { 691 if !f.Typ.Pointers() { 692 continue 693 } 694 cgoCheckArg(f.Typ, add(p, f.Offset), true, top, msg) 695 } 696 case abi.Pointer, abi.UnsafePointer: 697 if indir { 698 p = *(*unsafe.Pointer)(p) 699 if p == nil { 700 return 701 } 702 } 703 704 if !cgoIsGoPointer(p) { 705 return 706 } 707 if !top && !isPinned(p) { 708 panic(errorString(msg)) 709 } 710 711 cgoCheckUnknownPointer(p, msg) 712 } 713 } 714 715 // cgoCheckUnknownPointer is called for an arbitrary pointer into Go 716 // memory. It checks whether that Go memory contains any other 717 // pointer into unpinned Go memory. If it does, we panic. 718 // The return values are unused but useful to see in panic tracebacks. 719 func cgoCheckUnknownPointer(p unsafe.Pointer, msg string) (base, i uintptr) { 720 if inheap(uintptr(p)) { 721 b, span, _ := findObject(uintptr(p), 0, 0) 722 base = b 723 if base == 0 { 724 return 725 } 726 tp := span.typePointersOfUnchecked(base) 727 for { 728 var addr uintptr 729 if tp, addr = tp.next(base + span.elemsize); addr == 0 { 730 break 731 } 732 pp := *(*unsafe.Pointer)(unsafe.Pointer(addr)) 733 if cgoIsGoPointer(pp) && !isPinned(pp) { 734 panic(errorString(msg)) 735 } 736 } 737 return 738 } 739 740 for _, datap := range activeModules() { 741 if cgoInRange(p, datap.data, datap.edata) || cgoInRange(p, datap.bss, datap.ebss) { 742 // We have no way to know the size of the object. 743 // We have to assume that it might contain a pointer. 744 panic(errorString(msg)) 745 } 746 // In the text or noptr sections, we know that the 747 // pointer does not point to a Go pointer. 748 } 749 750 return 751 } 752 753 // cgoIsGoPointer reports whether the pointer is a Go pointer--a 754 // pointer to Go memory. We only care about Go memory that might 755 // contain pointers. 756 // 757 //go:nosplit 758 //go:nowritebarrierrec 759 func cgoIsGoPointer(p unsafe.Pointer) bool { 760 if p == nil { 761 return false 762 } 763 764 if inHeapOrStack(uintptr(p)) { 765 return true 766 } 767 768 for _, datap := range activeModules() { 769 if cgoInRange(p, datap.data, datap.edata) || cgoInRange(p, datap.bss, datap.ebss) { 770 return true 771 } 772 } 773 774 return false 775 } 776 777 // cgoInRange reports whether p is between start and end. 778 // 779 //go:nosplit 780 //go:nowritebarrierrec 781 func cgoInRange(p unsafe.Pointer, start, end uintptr) bool { 782 return start <= uintptr(p) && uintptr(p) < end 783 } 784 785 // cgoCheckResult is called to check the result parameter of an 786 // exported Go function. It panics if the result is or contains any 787 // other pointer into unpinned Go memory. 788 func cgoCheckResult(val any) { 789 if !goexperiment.CgoCheck2 && debug.cgocheck == 0 { 790 return 791 } 792 793 ep := efaceOf(&val) 794 t := ep._type 795 cgoCheckArg(t, ep.data, t.Kind_&abi.KindDirectIface == 0, false, cgoResultFail) 796 } 797