1// SPDX-License-Identifier: Apache-2.0
2// SPDX-FileCopyrightText: 2022 The Ebitengine Authors
3
4// TODO: remove s390x cgo dependency once golang/go#77449 is resolved
5//go:build darwin || freebsd || (linux && (386 || amd64 || arm || arm64 || loong64 || ppc64le || riscv64 || (cgo && s390x))) || netbsd
6
7package purego
8
9import (
10 "reflect"
11 "runtime"
12 "sync"
13 "unsafe"
14)
15
16var syscall15XABI0 uintptr
17
18func syscall_syscall15X(fn, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15 uintptr) (r1, r2, err uintptr) {
19 args := thePool.Get().(*syscall15Args)
20 defer thePool.Put(args)
21
22 *args = syscall15Args{
23 fn: fn,
24 a1: a1, a2: a2, a3: a3, a4: a4, a5: a5, a6: a6, a7: a7, a8: a8,
25 a9: a9, a10: a10, a11: a11, a12: a12, a13: a13, a14: a14, a15: a15,
26 f1: a1, f2: a2, f3: a3, f4: a4, f5: a5, f6: a6, f7: a7, f8: a8,
27 }
28
29 runtime_cgocall(syscall15XABI0, unsafe.Pointer(args))
30 return args.a1, args.a2, args.a3
31}
32
33// NewCallback converts a Go function to a function pointer conforming to the C calling convention.
34// This is useful when interoperating with C code requiring callbacks. The argument is expected to be a
35// function with zero or one uintptr-sized result. The function must not have arguments with size larger than the size
36// of uintptr. Only a limited number of callbacks may be created in a single Go process, and any memory allocated
37// for these callbacks is never released. At least 2000 callbacks can always be created. Although this function
38// provides similar functionality to windows.NewCallback it is distinct.
39func NewCallback(fn any) uintptr {
40 ty := reflect.TypeOf(fn)
41 for i := 0; i < ty.NumIn(); i++ {
42 in := ty.In(i)
43 if !in.AssignableTo(reflect.TypeOf(CDecl{})) {
44 continue
45 }
46 if i != 0 {
47 panic("purego: CDecl must be the first argument")
48 }
49 }
50 return compileCallback(fn)
51}
52
53// maxCb is the maximum number of callbacks
54// only increase this if you have added more to the callbackasm function
55const maxCB = 2000
56
57var cbs struct {
58 lock sync.Mutex
59 numFn int // the number of functions currently in cbs.funcs
60 funcs [maxCB]reflect.Value // the saved callbacks
61}
62
63func compileCallback(fn any) uintptr {
64 val := reflect.ValueOf(fn)
65 if val.Kind() != reflect.Func {
66 panic("purego: the type must be a function but was not")
67 }
68 if val.IsNil() {
69 panic("purego: function must not be nil")
70 }
71 ty := val.Type()
72 for i := 0; i < ty.NumIn(); i++ {
73 in := ty.In(i)
74 switch in.Kind() {
75 case reflect.Struct:
76 if i == 0 && in.AssignableTo(reflect.TypeOf(CDecl{})) {
77 continue
78 }
79 fallthrough
80 case reflect.Interface, reflect.Func, reflect.Slice,
81 reflect.Chan, reflect.Complex64, reflect.Complex128,
82 reflect.String, reflect.Map, reflect.Invalid:
83 panic("purego: unsupported argument type: " + in.Kind().String())
84 }
85 }
86output:
87 switch {
88 case ty.NumOut() == 1:
89 switch ty.Out(0).Kind() {
90 case reflect.Pointer, reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
91 reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr,
92 reflect.Bool, reflect.UnsafePointer:
93 break output
94 }
95 panic("purego: unsupported return type: " + ty.String())
96 case ty.NumOut() > 1:
97 panic("purego: callbacks can only have one return")
98 }
99 cbs.lock.Lock()
100 defer cbs.lock.Unlock()
101 if cbs.numFn >= maxCB {
102 panic("purego: the maximum number of callbacks has been reached")
103 }
104 cbs.funcs[cbs.numFn] = val
105 cbs.numFn++
106 return callbackasmAddr(cbs.numFn - 1)
107}
108
109const ptrSize = unsafe.Sizeof((*int)(nil))
110
111const callbackMaxFrame = 64 * ptrSize
112
113// callbackasm is implemented in zcallback_GOOS_GOARCH.s
114//
115//go:linkname __callbackasm callbackasm
116var __callbackasm byte
117var callbackasmABI0 = uintptr(unsafe.Pointer(&__callbackasm))
118
119// callbackWrap_call allows the calling of the ABIInternal wrapper
120// which is required for runtime.cgocallback without the
121// <ABIInternal> tag which is only allowed in the runtime.
122// This closure is used inside sys_darwin_GOARCH.s
123var callbackWrap_call = callbackWrap
124
125// callbackWrap is called by assembly code which determines which Go function to call.
126// This function takes the arguments and passes them to the Go function and returns the result.
127func callbackWrap(a *callbackArgs) {
128 cbs.lock.Lock()
129 fn := cbs.funcs[a.index]
130 cbs.lock.Unlock()
131 fnType := fn.Type()
132 args := make([]reflect.Value, fnType.NumIn())
133 frame := (*[callbackMaxFrame]uintptr)(a.args)
134 // stackFrame points to stack-passed arguments. On most architectures this is
135 // contiguous with frame (after register args), but on ppc64le it's separate.
136 var stackFrame *[callbackMaxFrame]uintptr
137 if sf := a.stackFrame(); sf != nil {
138 // Only ppc64le uses separate stackArgs pointer due to NOSPLIT constraints
139 stackFrame = (*[callbackMaxFrame]uintptr)(sf)
140 }
141 // floatsN and intsN track the number of register slots used, not argument count.
142 // This distinction matters on ARM32 where float64 uses 2 slots (32-bit registers).
143 var floatsN int
144 var intsN int
145 // stackSlot points to the index into frame (or stackFrame) of the current stack element.
146 // When stackFrame is nil, stack begins after float and integer registers in frame.
147 // When stackFrame is not nil (ppc64le), stackSlot indexes into stackFrame starting at 0.
148 stackSlot := numOfIntegerRegisters() + numOfFloatRegisters()
149 if stackFrame != nil {
150 // ppc64le: stackArgs is a separate pointer, indices start at 0
151 stackSlot = 0
152 }
153 // stackByteOffset tracks the byte offset within the stack area for Darwin ARM64
154 // tight packing. On Darwin ARM64, C passes small types packed on the stack.
155 stackByteOffset := uintptr(0)
156 for i := range args {
157 // slots is the number of pointer-sized slots the argument takes
158 var slots int
159 inType := fnType.In(i)
160 switch inType.Kind() {
161 case reflect.Float32, reflect.Float64:
162 slots = int((fnType.In(i).Size() + ptrSize - 1) / ptrSize)
163 if floatsN+slots > numOfFloatRegisters() {
164 if runtime.GOOS == "darwin" && runtime.GOARCH == "arm64" {
165 // Darwin ARM64: read from packed stack with proper alignment
166 args[i] = callbackArgFromStack(a.args, stackSlot, &stackByteOffset, inType)
167 } else if stackFrame != nil {
168 // ppc64le/s390x: stack args are in separate stackFrame
169 if runtime.GOARCH == "s390x" {
170 // s390x big-endian: sub-8-byte values are right-justified
171 args[i] = callbackArgFromSlotBigEndian(unsafe.Pointer(&stackFrame[stackSlot]), inType)
172 } else {
173 args[i] = reflect.NewAt(inType, unsafe.Pointer(&stackFrame[stackSlot])).Elem()
174 }
175 stackSlot += slots
176 } else {
177 args[i] = reflect.NewAt(inType, unsafe.Pointer(&frame[stackSlot])).Elem()
178 stackSlot += slots
179 }
180 } else {
181 if runtime.GOARCH == "s390x" {
182 // s390x big-endian: float32 is right-justified in 8-byte FPR slot
183 args[i] = callbackArgFromSlotBigEndian(unsafe.Pointer(&frame[floatsN]), inType)
184 } else {
185 args[i] = reflect.NewAt(inType, unsafe.Pointer(&frame[floatsN])).Elem()
186 }
187 }
188 floatsN += slots
189 case reflect.Struct:
190 // This is the CDecl field
191 args[i] = reflect.Zero(inType)
192 default:
193 slots = int((inType.Size() + ptrSize - 1) / ptrSize)
194 if intsN+slots > numOfIntegerRegisters() {
195 if runtime.GOOS == "darwin" && runtime.GOARCH == "arm64" {
196 // Darwin ARM64: read from packed stack with proper alignment
197 args[i] = callbackArgFromStack(a.args, stackSlot, &stackByteOffset, inType)
198 } else if stackFrame != nil {
199 // ppc64le/s390x: stack args are in separate stackFrame
200 if runtime.GOARCH == "s390x" {
201 // s390x big-endian: sub-8-byte values are right-justified
202 args[i] = callbackArgFromSlotBigEndian(unsafe.Pointer(&stackFrame[stackSlot]), inType)
203 } else {
204 args[i] = reflect.NewAt(inType, unsafe.Pointer(&stackFrame[stackSlot])).Elem()
205 }
206 stackSlot += slots
207 } else {
208 args[i] = reflect.NewAt(inType, unsafe.Pointer(&frame[stackSlot])).Elem()
209 stackSlot += slots
210 }
211 } else {
212 // the integers begin after the floats in frame
213 pos := intsN + numOfFloatRegisters()
214 if runtime.GOARCH == "s390x" {
215 // s390x big-endian: sub-8-byte values are right-justified in GPR slot
216 args[i] = callbackArgFromSlotBigEndian(unsafe.Pointer(&frame[pos]), inType)
217 } else {
218 args[i] = reflect.NewAt(inType, unsafe.Pointer(&frame[pos])).Elem()
219 }
220 }
221 intsN += slots
222 }
223 }
224 ret := fn.Call(args)
225 if len(ret) > 0 {
226 switch k := ret[0].Kind(); k {
227 case reflect.Uint, reflect.Uint64, reflect.Uint32, reflect.Uint16, reflect.Uint8, reflect.Uintptr:
228 a.result = uintptr(ret[0].Uint())
229 case reflect.Int, reflect.Int64, reflect.Int32, reflect.Int16, reflect.Int8:
230 a.result = uintptr(ret[0].Int())
231 case reflect.Bool:
232 if ret[0].Bool() {
233 a.result = 1
234 } else {
235 a.result = 0
236 }
237 case reflect.Pointer:
238 a.result = ret[0].Pointer()
239 case reflect.UnsafePointer:
240 a.result = ret[0].Pointer()
241 default:
242 panic("purego: unsupported kind: " + k.String())
243 }
244 }
245}
246
247// callbackArgFromStack reads an argument from the tightly-packed stack area on Darwin ARM64.
248// The C ABI on Darwin ARM64 packs small types on the stack without padding to 8 bytes.
249// This function handles proper alignment and advances stackByteOffset accordingly.
250func callbackArgFromStack(argsBase unsafe.Pointer, stackSlot int, stackByteOffset *uintptr, inType reflect.Type) reflect.Value {
251 // Calculate base address of stack area (after float and int registers)
252 stackBase := unsafe.Add(argsBase, stackSlot*int(ptrSize))
253
254 // Get type's natural alignment
255 align := uintptr(inType.Align())
256 size := inType.Size()
257
258 // Align the offset
259 if *stackByteOffset%align != 0 {
260 *stackByteOffset = (*stackByteOffset + align - 1) &^ (align - 1)
261 }
262
263 // Read value at aligned offset
264 ptr := unsafe.Add(stackBase, *stackByteOffset)
265 *stackByteOffset += size
266
267 return reflect.NewAt(inType, ptr).Elem()
268}
269
270// callbackArgFromSlotBigEndian reads an argument from an 8-byte slot on big-endian architectures.
271// On s390x:
272// - Integer types are right-justified in GPRs: sub-8-byte values are at offset (8 - size)
273// - Float32 in FPRs is left-justified: stored in upper 32 bits, so at offset 0
274// - Float64 occupies the full 8-byte slot
275func callbackArgFromSlotBigEndian(slotPtr unsafe.Pointer, inType reflect.Type) reflect.Value {
276 size := inType.Size()
277 if size >= 8 {
278 // 8-byte values occupy the entire slot
279 return reflect.NewAt(inType, slotPtr).Elem()
280 }
281 // Float32 is left-justified in FPRs (upper 32 bits), so offset is 0
282 if inType.Kind() == reflect.Float32 {
283 return reflect.NewAt(inType, slotPtr).Elem()
284 }
285 // Integer types are right-justified: offset = 8 - size
286 offset := 8 - size
287 ptr := unsafe.Add(slotPtr, offset)
288 return reflect.NewAt(inType, ptr).Elem()
289}
290
291// callbackasmAddr returns address of runtime.callbackasm
292// function adjusted by i.
293// On x86 and amd64, runtime.callbackasm is a series of CALL instructions,
294// and we want callback to arrive at
295// correspondent call instruction instead of start of
296// runtime.callbackasm.
297// On ARM, runtime.callbackasm is a series of mov and branch instructions.
298// R12 is loaded with the callback index. Each entry is two instructions,
299// hence 8 bytes.
300func callbackasmAddr(i int) uintptr {
301 var entrySize int
302 switch runtime.GOARCH {
303 default:
304 panic("purego: unsupported architecture")
305 case "amd64":
306 // On amd64, each callback entry is just a CALL instruction (5 bytes)
307 entrySize = 5
308 case "386":
309 // On 386, each callback entry is MOVL $imm, CX (5 bytes) + JMP (5 bytes)
310 entrySize = 10
311 case "arm", "arm64", "loong64", "ppc64le", "riscv64":
312 // On ARM, ARM64, Loong64, PPC64LE and RISCV64, each entry is a MOV instruction
313 // followed by a branch instruction
314 entrySize = 8
315 case "s390x":
316 // On S390X, each entry is LGHI (4 bytes) + JG (6 bytes)
317 entrySize = 10
318 }
319 return callbackasmABI0 + uintptr(i*entrySize)
320}