Source File
stubs.go
Belonging Package
runtime
// Copyright 2014 The Go Authors. All rights reserved.// Use of this source code is governed by a BSD-style// license that can be found in the LICENSE file.package runtimeimport ()// Should be a built-in for unsafe.Pointer?////go:nosplitfunc ( unsafe.Pointer, uintptr) unsafe.Pointer {return unsafe.Pointer(uintptr() + )}// getg returns the pointer to the current g.// The compiler rewrites calls to this function into instructions// that fetch the g directly (from TLS or from the dedicated register).func () *g// mcall switches from the g to the g0 stack and invokes fn(g),// where g is the goroutine that made the call.// mcall saves g's current PC/SP in g->sched so that it can be restored later.// It is up to fn to arrange for that later execution, typically by recording// g in a data structure, causing something to call ready(g) later.// mcall returns to the original goroutine g later, when g has been rescheduled.// fn must not return at all; typically it ends by calling schedule, to let the m// run other goroutines.//// mcall can only be called from g stacks (not g0, not gsignal).//// This must NOT be go:noescape: if fn is a stack-allocated closure,// fn puts g on a run queue, and g executes before fn returns, the// closure will be invalidated while it is still executing.func ( func(*g))// systemstack runs fn on a system stack.// If systemstack is called from the per-OS-thread (g0) stack, or// if systemstack is called from the signal handling (gsignal) stack,// systemstack calls fn directly and returns.// Otherwise, systemstack is being called from the limited stack// of an ordinary goroutine. In this case, systemstack switches// to the per-OS-thread stack, calls fn, and switches back.// It is common to use a func literal as the argument, in order// to share inputs and outputs with the code around the call// to system stack://// ... set up y ...// systemstack(func() {// x = bigcall(y)// })// ... use x ...////go:noescapefunc ( func())//go:nosplit//go:nowritebarrierrecfunc () {writeErrStr("fatal: systemstack called from unexpected goroutine")}// memclrNoHeapPointers clears n bytes starting at ptr.//// Usually you should use typedmemclr. memclrNoHeapPointers should be// used only when the caller knows that *ptr contains no heap pointers// because either://// *ptr is initialized memory and its type is pointer-free, or//// *ptr is uninitialized memory (e.g., memory that's being reused// for a new allocation) and hence contains only "junk".//// memclrNoHeapPointers ensures that if ptr is pointer-aligned, and n// is a multiple of the pointer size, then any pointer-aligned,// pointer-sized portion is cleared atomically. Despite the function// name, this is necessary because this function is the underlying// implementation of typedmemclr and memclrHasPointers. See the doc of// memmove for more details.//// The (CPU-specific) implementations of this function are in memclr_*.s.////go:noescapefunc ( unsafe.Pointer, uintptr)//go:linkname reflect_memclrNoHeapPointers reflect.memclrNoHeapPointersfunc ( unsafe.Pointer, uintptr) {memclrNoHeapPointers(, )}// memmove copies n bytes from "from" to "to".//// memmove ensures that any pointer in "from" is written to "to" with// an indivisible write, so that racy reads cannot observe a// half-written pointer. This is necessary to prevent the garbage// collector from observing invalid pointers, and differs from memmove// in unmanaged languages. However, memmove is only required to do// this if "from" and "to" may contain pointers, which can only be the// case if "from", "to", and "n" are all be word-aligned.//// Implementations are in memmove_*.s.////go:noescapefunc (, unsafe.Pointer, uintptr)// Outside assembly calls memmove. Make sure it has ABI wrappers.////go:linkname memmove//go:linkname reflect_memmove reflect.memmovefunc (, unsafe.Pointer, uintptr) {memmove(, , )}// exported value for testingconst hashLoad = float32(loadFactorNum) / float32(loadFactorDen)//go:nosplitfunc () uint32 {:= getg().m// Implement wyrand: https://github.com/wangyi-fudan/wyhash// Only the platform that math.Mul64 can be lowered// by the compiler should be in this list.if goarch.IsAmd64|goarch.IsArm64|goarch.IsPpc64|goarch.IsPpc64le|goarch.IsMips64|goarch.IsMips64le|goarch.IsS390x|goarch.IsRiscv64|goarch.IsLoong64 == 1 {.fastrand += 0xa0761d6478bd642f, := math.Mul64(.fastrand, .fastrand^0xe7037ed1a0b428db)return uint32( ^ )}// Implement xorshift64+: 2 32-bit xorshift sequences added together.// Shift triplet [17,7,16] was calculated as indicated in Marsaglia's// Xorshift paper: https://www.jstatsoft.org/article/view/v008i14/xorshift.pdf// This generator passes the SmallCrush suite, part of TestU01 framework:// http://simul.iro.umontreal.ca/testu01/tu01.html:= (*[2]uint32)(unsafe.Pointer(&.fastrand)), := [0], [1]^= << 17= ^ ^ >>7 ^ >>16[0], [1] = ,return +}//go:nosplitfunc ( uint32) uint32 {// This is similar to fastrand() % n, but faster.// See https://lemire.me/blog/2016/06/27/a-fast-alternative-to-the-modulo-reduction/return uint32(uint64(fastrand()) * uint64() >> 32)}func () uint64 {:= getg().m// Implement wyrand: https://github.com/wangyi-fudan/wyhash// Only the platform that math.Mul64 can be lowered// by the compiler should be in this list.if goarch.IsAmd64|goarch.IsArm64|goarch.IsPpc64|goarch.IsPpc64le|goarch.IsMips64|goarch.IsMips64le|goarch.IsS390x|goarch.IsRiscv64 == 1 {.fastrand += 0xa0761d6478bd642f, := math.Mul64(.fastrand, .fastrand^0xe7037ed1a0b428db)return ^}// Implement xorshift64+: 2 32-bit xorshift sequences added together.// Xorshift paper: https://www.jstatsoft.org/article/view/v008i14/xorshift.pdf// This generator passes the SmallCrush suite, part of TestU01 framework:// http://simul.iro.umontreal.ca/testu01/tu01.html:= (*[2]uint32)(unsafe.Pointer(&.fastrand)), := [0], [1]^= << 17= ^ ^ >>7 ^ >>16:= uint64( + ), = ,^= << 17= ^ ^ >>7 ^ >>16+= uint64(+) << 32[0], [1] = ,return}func () uint {if goarch.PtrSize == 4 {return uint(fastrand())}return uint(fastrand64())}//go:linkname rand_fastrand64 math/rand.fastrand64func () uint64 { return fastrand64() }//go:linkname sync_fastrandn sync.fastrandnfunc ( uint32) uint32 { return fastrandn() }//go:linkname net_fastrandu net.fastrandufunc () uint { return fastrandu() }//go:linkname os_fastrand os.fastrandfunc () uint32 { return fastrand() }// in internal/bytealg/equal_*.s////go:noescapefunc (, unsafe.Pointer, uintptr) bool// noescape hides a pointer from escape analysis. noescape is// the identity function but escape analysis doesn't think the// output depends on the input. noescape is inlined and currently// compiles down to zero instructions.// USE CAREFULLY!////go:nosplitfunc ( unsafe.Pointer) unsafe.Pointer {:= uintptr()return unsafe.Pointer( ^ 0)}// noEscapePtr hides a pointer from escape analysis. See noescape.// USE CAREFULLY!////go:nosplitfunc [ any]( *) * {:= uintptr(unsafe.Pointer())return (*)(unsafe.Pointer( ^ 0))}// Not all cgocallback frames are actually cgocallback,// so not all have these arguments. Mark them uintptr so that the GC// does not misinterpret memory when the arguments are not present.// cgocallback is not called from Go, only from crosscall2.// This in turn calls cgocallbackg, which is where we'll find// pointer-declared arguments.//// When fn is nil (frame is saved g), call dropm instead,// this is used when the C thread is exiting.func (, , uintptr)func ( *gobuf)func ()func ( *g)func ()// reflectcall calls fn with arguments described by stackArgs, stackArgsSize,// frameSize, and regArgs.//// Arguments passed on the stack and space for return values passed on the stack// must be laid out at the space pointed to by stackArgs (with total length// stackArgsSize) according to the ABI.//// stackRetOffset must be some value <= stackArgsSize that indicates the// offset within stackArgs where the return value space begins.//// frameSize is the total size of the argument frame at stackArgs and must// therefore be >= stackArgsSize. It must include additional space for spilling// register arguments for stack growth and preemption.//// TODO(mknyszek): Once we don't need the additional spill space, remove frameSize,// since frameSize will be redundant with stackArgsSize.//// Arguments passed in registers must be laid out in regArgs according to the ABI.// regArgs will hold any return values passed in registers after the call.//// reflectcall copies stack arguments from stackArgs to the goroutine stack, and// then copies back stackArgsSize-stackRetOffset bytes back to the return space// in stackArgs once fn has completed. It also "unspills" argument registers from// regArgs before calling fn, and spills them back into regArgs immediately// following the call to fn. If there are results being returned on the stack,// the caller should pass the argument frame type as stackArgsType so that// reflectcall can execute appropriate write barriers during the copy.//// reflectcall expects regArgs.ReturnIsPtr to be populated indicating which// registers on the return path will contain Go pointers. It will then store// these pointers in regArgs.Ptrs such that they are visible to the GC.//// Package reflect passes a frame type. In package runtime, there is only// one call that copies results back, in callbackWrap in syscall_windows.go, and it// does NOT pass a frame type, meaning there are no write barriers invoked. See that// call site for justification.//// Package reflect accesses this symbol through a linkname.//// Arguments passed through to reflectcall do not escape. The type is used// only in a very limited callee of reflectcall, the stackArgs are copied, and// regArgs is only used in the reflectcall frame.////go:noescapefunc ( *_type, , unsafe.Pointer, , , uint32, *abi.RegArgs)func ( uint32)type neverCallThisFunction struct{}// goexit is the return stub at the top of every goroutine call stack.// Each goroutine stack is constructed as if goexit called the// goroutine's entry point function, so that when the entry point// function returns, it will return to goexit, which will call goexit1// to perform the actual exit.//// This function must never be called directly. Call goexit1 instead.// gentraceback assumes that goexit terminates the stack. A direct// call on the stack will cause gentraceback to stop walking the stack// prematurely and if there is leftover state it may panic.func (neverCallThisFunction)// publicationBarrier performs a store/store barrier (a "publication"// or "export" barrier). Some form of synchronization is required// between initializing an object and making that object accessible to// another processor. Without synchronization, the initialization// writes and the "publication" write may be reordered, allowing the// other processor to follow the pointer and observe an uninitialized// object. In general, higher-level synchronization should be used,// such as locking or an atomic pointer write. publicationBarrier is// for when those aren't an option, such as in the implementation of// the memory manager.//// There's no corresponding barrier for the read side because the read// side naturally has a data dependency order. All architectures that// Go supports or seems likely to ever support automatically enforce// data dependency ordering.func ()// getcallerpc returns the program counter (PC) of its caller's caller.// getcallersp returns the stack pointer (SP) of its caller's caller.// The implementation may be a compiler intrinsic; there is not// necessarily code implementing this on every platform.//// For example://// func f(arg1, arg2, arg3 int) {// pc := getcallerpc()// sp := getcallersp()// }//// These two lines find the PC and SP immediately following// the call to f (where f will return).//// The call to getcallerpc and getcallersp must be done in the// frame being asked about.//// The result of getcallersp is correct at the time of the return,// but it may be invalidated by any subsequent call to a function// that might relocate the stack in order to grow or shrink it.// A general rule is that the result of getcallersp should be used// immediately and can only be passed to nosplit functions.//go:noescapefunc () uintptr//go:noescapefunc () uintptr // implemented as an intrinsic on all platforms// getclosureptr returns the pointer to the current closure.// getclosureptr can only be used in an assignment statement// at the entry of a function. Moreover, go:nosplit directive// must be specified at the declaration of caller function,// so that the function prolog does not clobber the closure register.// for example://// //go:nosplit// func f(arg1, arg2, arg3 int) {// dx := getclosureptr()// }//// The compiler rewrites calls to this function into instructions that fetch the// pointer from a well-known register (DX on x86 architecture, etc.) directly.func () uintptr//go:noescapefunc (, unsafe.Pointer) int32func ()func ()func ()// return0 is a stub used to return 0 from deferproc.// It is called at the very end of deferproc to signal// the calling Go function that it should not jump// to deferreturn.// in asm_*.sfunc ()// in asm_*.s// not called directly; definitions here supply type information for traceback.// These must have the same signature (arg pointer map) as reflectcall.func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func (, , unsafe.Pointer, , , uint32, *abi.RegArgs)func ()// alignUp rounds n up to a multiple of a. a must be a power of 2.func (, uintptr) uintptr {return ( + - 1) &^ ( - 1)}// alignDown rounds n down to a multiple of a. a must be a power of 2.func (, uintptr) uintptr {return &^ ( - 1)}// divRoundUp returns ceil(n / a).func (, uintptr) uintptr {// a is generally a power of two. This will get inlined and// the compiler will optimize the division.return ( + - 1) /}// checkASM reports whether assembly runtime checks have passed.func () boolfunc (, unsafe.Pointer) bool// bool2int returns 0 if x is false or 1 if x is true.func ( bool) int {// Avoid branches. In the SSA compiler, this compiles to// exactly what you would want it to.return int(uint8(*(*uint8)(unsafe.Pointer(&))))}// abort crashes the runtime in situations where even throw might not// work. In general it should do something a debugger will recognize// (e.g., an INT3 on x86). A crash in abort is recognized by the// signal handler, which will attempt to tear down the runtime// immediately.func ()// Called from compiled code; declared for vet; do NOT call from Go.func ()func ()func ()func ()func ()func ()func ()func ()func ()func ()// Called from linker-generated .initarray; declared for go vet; do NOT call from Go.func ()// Injected by the signal handler for panicking signals.// Initializes any registers that have fixed meaning at calls but// are scratch in bodies and calls sigpanic.// On many platforms it just jumps to sigpanic.func ()// intArgRegs is used by the various register assignment// algorithm implementations in the runtime. These include:.// - Finalizers (mfinal.go)// - Windows callbacks (syscall_windows.go)//// Both are stripped-down versions of the algorithm since they// only have to deal with a subset of cases (finalizers only// take a pointer or interface argument, Go Windows callbacks// don't support floating point).//// It should be modified with care and are generally only// modified when testing this package.//// It should never be set higher than its internal/abi// constant counterparts, because the system relies on a// structure that is at least large enough to hold the// registers the system supports.//// Protected by finlock.var intArgRegs = abi.IntArgRegs
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