github.com/m10x/go/src@v0.0.0-20220112094212-ba61592315da/runtime/stubs.go (about) 1 // Copyright 2014 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 package runtime 6 7 import ( 8 "internal/abi" 9 "internal/goarch" 10 "internal/goexperiment" 11 "runtime/internal/math" 12 "unsafe" 13 ) 14 15 // Should be a built-in for unsafe.Pointer? 16 //go:nosplit 17 func add(p unsafe.Pointer, x uintptr) unsafe.Pointer { 18 return unsafe.Pointer(uintptr(p) + x) 19 } 20 21 // getg returns the pointer to the current g. 22 // The compiler rewrites calls to this function into instructions 23 // that fetch the g directly (from TLS or from the dedicated register). 24 func getg() *g 25 26 // mcall switches from the g to the g0 stack and invokes fn(g), 27 // where g is the goroutine that made the call. 28 // mcall saves g's current PC/SP in g->sched so that it can be restored later. 29 // It is up to fn to arrange for that later execution, typically by recording 30 // g in a data structure, causing something to call ready(g) later. 31 // mcall returns to the original goroutine g later, when g has been rescheduled. 32 // fn must not return at all; typically it ends by calling schedule, to let the m 33 // run other goroutines. 34 // 35 // mcall can only be called from g stacks (not g0, not gsignal). 36 // 37 // This must NOT be go:noescape: if fn is a stack-allocated closure, 38 // fn puts g on a run queue, and g executes before fn returns, the 39 // closure will be invalidated while it is still executing. 40 func mcall(fn func(*g)) 41 42 // systemstack runs fn on a system stack. 43 // If systemstack is called from the per-OS-thread (g0) stack, or 44 // if systemstack is called from the signal handling (gsignal) stack, 45 // systemstack calls fn directly and returns. 46 // Otherwise, systemstack is being called from the limited stack 47 // of an ordinary goroutine. In this case, systemstack switches 48 // to the per-OS-thread stack, calls fn, and switches back. 49 // It is common to use a func literal as the argument, in order 50 // to share inputs and outputs with the code around the call 51 // to system stack: 52 // 53 // ... set up y ... 54 // systemstack(func() { 55 // x = bigcall(y) 56 // }) 57 // ... use x ... 58 // 59 //go:noescape 60 func systemstack(fn func()) 61 62 var badsystemstackMsg = "fatal: systemstack called from unexpected goroutine" 63 64 //go:nosplit 65 //go:nowritebarrierrec 66 func badsystemstack() { 67 sp := stringStructOf(&badsystemstackMsg) 68 write(2, sp.str, int32(sp.len)) 69 } 70 71 // memclrNoHeapPointers clears n bytes starting at ptr. 72 // 73 // Usually you should use typedmemclr. memclrNoHeapPointers should be 74 // used only when the caller knows that *ptr contains no heap pointers 75 // because either: 76 // 77 // *ptr is initialized memory and its type is pointer-free, or 78 // 79 // *ptr is uninitialized memory (e.g., memory that's being reused 80 // for a new allocation) and hence contains only "junk". 81 // 82 // memclrNoHeapPointers ensures that if ptr is pointer-aligned, and n 83 // is a multiple of the pointer size, then any pointer-aligned, 84 // pointer-sized portion is cleared atomically. Despite the function 85 // name, this is necessary because this function is the underlying 86 // implementation of typedmemclr and memclrHasPointers. See the doc of 87 // memmove for more details. 88 // 89 // The (CPU-specific) implementations of this function are in memclr_*.s. 90 // 91 //go:noescape 92 func memclrNoHeapPointers(ptr unsafe.Pointer, n uintptr) 93 94 //go:linkname reflect_memclrNoHeapPointers reflect.memclrNoHeapPointers 95 func reflect_memclrNoHeapPointers(ptr unsafe.Pointer, n uintptr) { 96 memclrNoHeapPointers(ptr, n) 97 } 98 99 // memmove copies n bytes from "from" to "to". 100 // 101 // memmove ensures that any pointer in "from" is written to "to" with 102 // an indivisible write, so that racy reads cannot observe a 103 // half-written pointer. This is necessary to prevent the garbage 104 // collector from observing invalid pointers, and differs from memmove 105 // in unmanaged languages. However, memmove is only required to do 106 // this if "from" and "to" may contain pointers, which can only be the 107 // case if "from", "to", and "n" are all be word-aligned. 108 // 109 // Implementations are in memmove_*.s. 110 // 111 //go:noescape 112 func memmove(to, from unsafe.Pointer, n uintptr) 113 114 // Outside assembly calls memmove. Make sure it has ABI wrappers. 115 //go:linkname memmove 116 117 //go:linkname reflect_memmove reflect.memmove 118 func reflect_memmove(to, from unsafe.Pointer, n uintptr) { 119 memmove(to, from, n) 120 } 121 122 // exported value for testing 123 const hashLoad = float32(loadFactorNum) / float32(loadFactorDen) 124 125 //go:nosplit 126 func fastrand() uint32 { 127 mp := getg().m 128 // Implement wyrand: https://github.com/wangyi-fudan/wyhash 129 // Only the platform that math.Mul64 can be lowered 130 // by the compiler should be in this list. 131 if goarch.IsAmd64|goarch.IsArm64|goarch.IsPpc64| 132 goarch.IsPpc64le|goarch.IsMips64|goarch.IsMips64le| 133 goarch.IsS390x|goarch.IsRiscv64 == 1 { 134 mp.fastrand += 0xa0761d6478bd642f 135 hi, lo := math.Mul64(mp.fastrand, mp.fastrand^0xe7037ed1a0b428db) 136 return uint32(hi ^ lo) 137 } 138 139 // Implement xorshift64+: 2 32-bit xorshift sequences added together. 140 // Shift triplet [17,7,16] was calculated as indicated in Marsaglia's 141 // Xorshift paper: https://www.jstatsoft.org/article/view/v008i14/xorshift.pdf 142 // This generator passes the SmallCrush suite, part of TestU01 framework: 143 // http://simul.iro.umontreal.ca/testu01/tu01.html 144 t := (*[2]uint32)(unsafe.Pointer(&mp.fastrand)) 145 s1, s0 := t[0], t[1] 146 s1 ^= s1 << 17 147 s1 = s1 ^ s0 ^ s1>>7 ^ s0>>16 148 t[0], t[1] = s0, s1 149 return s0 + s1 150 } 151 152 //go:nosplit 153 func fastrandn(n uint32) uint32 { 154 // This is similar to fastrand() % n, but faster. 155 // See https://lemire.me/blog/2016/06/27/a-fast-alternative-to-the-modulo-reduction/ 156 return uint32(uint64(fastrand()) * uint64(n) >> 32) 157 } 158 159 //go:linkname sync_fastrandn sync.fastrandn 160 func sync_fastrandn(n uint32) uint32 { return fastrandn(n) } 161 162 //go:linkname net_fastrand net.fastrand 163 func net_fastrand() uint32 { return fastrand() } 164 165 //go:linkname os_fastrand os.fastrand 166 func os_fastrand() uint32 { return fastrand() } 167 168 // in internal/bytealg/equal_*.s 169 //go:noescape 170 func memequal(a, b unsafe.Pointer, size uintptr) bool 171 172 // noescape hides a pointer from escape analysis. noescape is 173 // the identity function but escape analysis doesn't think the 174 // output depends on the input. noescape is inlined and currently 175 // compiles down to zero instructions. 176 // USE CAREFULLY! 177 //go:nosplit 178 func noescape(p unsafe.Pointer) unsafe.Pointer { 179 x := uintptr(p) 180 return unsafe.Pointer(x ^ 0) 181 } 182 183 // Not all cgocallback frames are actually cgocallback, 184 // so not all have these arguments. Mark them uintptr so that the GC 185 // does not misinterpret memory when the arguments are not present. 186 // cgocallback is not called from Go, only from crosscall2. 187 // This in turn calls cgocallbackg, which is where we'll find 188 // pointer-declared arguments. 189 func cgocallback(fn, frame, ctxt uintptr) 190 191 func gogo(buf *gobuf) 192 193 func asminit() 194 func setg(gg *g) 195 func breakpoint() 196 197 // reflectcall calls fn with arguments described by stackArgs, stackArgsSize, 198 // frameSize, and regArgs. 199 // 200 // Arguments passed on the stack and space for return values passed on the stack 201 // must be laid out at the space pointed to by stackArgs (with total length 202 // stackArgsSize) according to the ABI. 203 // 204 // stackRetOffset must be some value <= stackArgsSize that indicates the 205 // offset within stackArgs where the return value space begins. 206 // 207 // frameSize is the total size of the argument frame at stackArgs and must 208 // therefore be >= stackArgsSize. It must include additional space for spilling 209 // register arguments for stack growth and preemption. 210 // 211 // TODO(mknyszek): Once we don't need the additional spill space, remove frameSize, 212 // since frameSize will be redundant with stackArgsSize. 213 // 214 // Arguments passed in registers must be laid out in regArgs according to the ABI. 215 // regArgs will hold any return values passed in registers after the call. 216 // 217 // reflectcall copies stack arguments from stackArgs to the goroutine stack, and 218 // then copies back stackArgsSize-stackRetOffset bytes back to the return space 219 // in stackArgs once fn has completed. It also "unspills" argument registers from 220 // regArgs before calling fn, and spills them back into regArgs immediately 221 // following the call to fn. If there are results being returned on the stack, 222 // the caller should pass the argument frame type as stackArgsType so that 223 // reflectcall can execute appropriate write barriers during the copy. 224 // 225 // reflectcall expects regArgs.ReturnIsPtr to be populated indicating which 226 // registers on the return path will contain Go pointers. It will then store 227 // these pointers in regArgs.Ptrs such that they are visible to the GC. 228 // 229 // Package reflect passes a frame type. In package runtime, there is only 230 // one call that copies results back, in callbackWrap in syscall_windows.go, and it 231 // does NOT pass a frame type, meaning there are no write barriers invoked. See that 232 // call site for justification. 233 // 234 // Package reflect accesses this symbol through a linkname. 235 // 236 // Arguments passed through to reflectcall do not escape. The type is used 237 // only in a very limited callee of reflectcall, the stackArgs are copied, and 238 // regArgs is only used in the reflectcall frame. 239 //go:noescape 240 func reflectcall(stackArgsType *_type, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 241 242 func procyield(cycles uint32) 243 244 type neverCallThisFunction struct{} 245 246 // goexit is the return stub at the top of every goroutine call stack. 247 // Each goroutine stack is constructed as if goexit called the 248 // goroutine's entry point function, so that when the entry point 249 // function returns, it will return to goexit, which will call goexit1 250 // to perform the actual exit. 251 // 252 // This function must never be called directly. Call goexit1 instead. 253 // gentraceback assumes that goexit terminates the stack. A direct 254 // call on the stack will cause gentraceback to stop walking the stack 255 // prematurely and if there is leftover state it may panic. 256 func goexit(neverCallThisFunction) 257 258 // publicationBarrier performs a store/store barrier (a "publication" 259 // or "export" barrier). Some form of synchronization is required 260 // between initializing an object and making that object accessible to 261 // another processor. Without synchronization, the initialization 262 // writes and the "publication" write may be reordered, allowing the 263 // other processor to follow the pointer and observe an uninitialized 264 // object. In general, higher-level synchronization should be used, 265 // such as locking or an atomic pointer write. publicationBarrier is 266 // for when those aren't an option, such as in the implementation of 267 // the memory manager. 268 // 269 // There's no corresponding barrier for the read side because the read 270 // side naturally has a data dependency order. All architectures that 271 // Go supports or seems likely to ever support automatically enforce 272 // data dependency ordering. 273 func publicationBarrier() 274 275 // getcallerpc returns the program counter (PC) of its caller's caller. 276 // getcallersp returns the stack pointer (SP) of its caller's caller. 277 // The implementation may be a compiler intrinsic; there is not 278 // necessarily code implementing this on every platform. 279 // 280 // For example: 281 // 282 // func f(arg1, arg2, arg3 int) { 283 // pc := getcallerpc() 284 // sp := getcallersp() 285 // } 286 // 287 // These two lines find the PC and SP immediately following 288 // the call to f (where f will return). 289 // 290 // The call to getcallerpc and getcallersp must be done in the 291 // frame being asked about. 292 // 293 // The result of getcallersp is correct at the time of the return, 294 // but it may be invalidated by any subsequent call to a function 295 // that might relocate the stack in order to grow or shrink it. 296 // A general rule is that the result of getcallersp should be used 297 // immediately and can only be passed to nosplit functions. 298 299 //go:noescape 300 func getcallerpc() uintptr 301 302 //go:noescape 303 func getcallersp() uintptr // implemented as an intrinsic on all platforms 304 305 // getclosureptr returns the pointer to the current closure. 306 // getclosureptr can only be used in an assignment statement 307 // at the entry of a function. Moreover, go:nosplit directive 308 // must be specified at the declaration of caller function, 309 // so that the function prolog does not clobber the closure register. 310 // for example: 311 // 312 // //go:nosplit 313 // func f(arg1, arg2, arg3 int) { 314 // dx := getclosureptr() 315 // } 316 // 317 // The compiler rewrites calls to this function into instructions that fetch the 318 // pointer from a well-known register (DX on x86 architecture, etc.) directly. 319 func getclosureptr() uintptr 320 321 //go:noescape 322 func asmcgocall(fn, arg unsafe.Pointer) int32 323 324 func morestack() 325 func morestack_noctxt() 326 func rt0_go() 327 328 // return0 is a stub used to return 0 from deferproc. 329 // It is called at the very end of deferproc to signal 330 // the calling Go function that it should not jump 331 // to deferreturn. 332 // in asm_*.s 333 func return0() 334 335 // in asm_*.s 336 // not called directly; definitions here supply type information for traceback. 337 // These must have the same signature (arg pointer map) as reflectcall. 338 func call16(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 339 func call32(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 340 func call64(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 341 func call128(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 342 func call256(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 343 func call512(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 344 func call1024(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 345 func call2048(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 346 func call4096(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 347 func call8192(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 348 func call16384(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 349 func call32768(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 350 func call65536(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 351 func call131072(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 352 func call262144(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 353 func call524288(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 354 func call1048576(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 355 func call2097152(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 356 func call4194304(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 357 func call8388608(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 358 func call16777216(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 359 func call33554432(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 360 func call67108864(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 361 func call134217728(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 362 func call268435456(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 363 func call536870912(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 364 func call1073741824(typ, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) 365 366 func systemstack_switch() 367 368 // alignUp rounds n up to a multiple of a. a must be a power of 2. 369 func alignUp(n, a uintptr) uintptr { 370 return (n + a - 1) &^ (a - 1) 371 } 372 373 // alignDown rounds n down to a multiple of a. a must be a power of 2. 374 func alignDown(n, a uintptr) uintptr { 375 return n &^ (a - 1) 376 } 377 378 // divRoundUp returns ceil(n / a). 379 func divRoundUp(n, a uintptr) uintptr { 380 // a is generally a power of two. This will get inlined and 381 // the compiler will optimize the division. 382 return (n + a - 1) / a 383 } 384 385 // checkASM reports whether assembly runtime checks have passed. 386 func checkASM() bool 387 388 func memequal_varlen(a, b unsafe.Pointer) bool 389 390 // bool2int returns 0 if x is false or 1 if x is true. 391 func bool2int(x bool) int { 392 // Avoid branches. In the SSA compiler, this compiles to 393 // exactly what you would want it to. 394 return int(uint8(*(*uint8)(unsafe.Pointer(&x)))) 395 } 396 397 // abort crashes the runtime in situations where even throw might not 398 // work. In general it should do something a debugger will recognize 399 // (e.g., an INT3 on x86). A crash in abort is recognized by the 400 // signal handler, which will attempt to tear down the runtime 401 // immediately. 402 func abort() 403 404 // Called from compiled code; declared for vet; do NOT call from Go. 405 func gcWriteBarrier() 406 func duffzero() 407 func duffcopy() 408 409 // Called from linker-generated .initarray; declared for go vet; do NOT call from Go. 410 func addmoduledata() 411 412 // Injected by the signal handler for panicking signals. 413 // Initializes any registers that have fixed meaning at calls but 414 // are scratch in bodies and calls sigpanic. 415 // On many platforms it just jumps to sigpanic. 416 func sigpanic0() 417 418 // intArgRegs is used by the various register assignment 419 // algorithm implementations in the runtime. These include:. 420 // - Finalizers (mfinal.go) 421 // - Windows callbacks (syscall_windows.go) 422 // 423 // Both are stripped-down versions of the algorithm since they 424 // only have to deal with a subset of cases (finalizers only 425 // take a pointer or interface argument, Go Windows callbacks 426 // don't support floating point). 427 // 428 // It should be modified with care and are generally only 429 // modified when testing this package. 430 // 431 // It should never be set higher than its internal/abi 432 // constant counterparts, because the system relies on a 433 // structure that is at least large enough to hold the 434 // registers the system supports. 435 // 436 // Protected by finlock. 437 var intArgRegs = abi.IntArgRegs * (goexperiment.RegabiArgsInt | goarch.IsAmd64)