github.com/ebitengine/purego@v0.8.0-alpha.2.0.20240512170805-6cd12240d332/syscall.go (about) 1 // SPDX-License-Identifier: Apache-2.0 2 // SPDX-FileCopyrightText: 2022 The Ebitengine Authors 3 4 //go:build darwin || freebsd || linux || windows 5 6 package purego 7 8 // CDecl marks a function as being called using the __cdecl calling convention as defined in 9 // the [MSDocs] when passed to NewCallback. It must be the first argument to the function. 10 // This is only useful on 386 Windows, but it is safe to use on other platforms. 11 // 12 // [MSDocs]: https://learn.microsoft.com/en-us/cpp/cpp/cdecl?view=msvc-170 13 type CDecl struct{} 14 15 const ( 16 maxArgs = 15 17 numOfFloats = 8 // arm64 and amd64 both have 8 float registers 18 ) 19 20 type syscall15Args struct { 21 fn, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15 uintptr 22 f1, f2, f3, f4, f5, f6, f7, f8 uintptr 23 arm64_r8 uintptr 24 } 25 26 // SyscallN takes fn, a C function pointer and a list of arguments as uintptr. 27 // There is an internal maximum number of arguments that SyscallN can take. It panics 28 // when the maximum is exceeded. It returns the result and the libc error code if there is one. 29 // 30 // NOTE: SyscallN does not properly call functions that have both integer and float parameters. 31 // See discussion comment https://github.com/ebiten/purego/pull/1#issuecomment-1128057607 32 // for an explanation of why that is. 33 // 34 // On amd64, if there are more than 8 floats the 9th and so on will be placed incorrectly on the 35 // stack. 36 // 37 // The pragma go:nosplit is not needed at this function declaration because it uses go:uintptrescapes 38 // which forces all the objects that the uintptrs point to onto the heap where a stack split won't affect 39 // their memory location. 40 // 41 //go:uintptrescapes 42 func SyscallN(fn uintptr, args ...uintptr) (r1, r2, err uintptr) { 43 if fn == 0 { 44 panic("purego: fn is nil") 45 } 46 if len(args) > maxArgs { 47 panic("purego: too many arguments to SyscallN") 48 } 49 // add padding so there is no out-of-bounds slicing 50 var tmp [maxArgs]uintptr 51 copy(tmp[:], args) 52 return syscall_syscall15X(fn, tmp[0], tmp[1], tmp[2], tmp[3], tmp[4], tmp[5], tmp[6], tmp[7], tmp[8], tmp[9], tmp[10], tmp[11], tmp[12], tmp[13], tmp[14]) 53 }