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