github.com/jwijenbergh/purego@v0.0.0-20240126093400-70ff3a61df13/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 const ( 9 maxArgs = 15 10 numOfFloats = 8 // arm64 and amd64 both have 8 float registers 11 ) 12 13 // SyscallN takes fn, a C function pointer and a list of arguments as uintptr. 14 // There is an internal maximum number of arguments that SyscallN can take. It panics 15 // when the maximum is exceeded. It returns the result and the libc error code if there is one. 16 // 17 // NOTE: SyscallN does not properly call functions that have both integer and float parameters. 18 // See discussion comment https://github.com/ebiten/purego/pull/1#issuecomment-1128057607 19 // for an explanation of why that is. 20 // 21 // On amd64, if there are more than 8 floats the 9th and so on will be placed incorrectly on the 22 // stack. 23 // 24 // The pragma go:nosplit is not needed at this function declaration because it uses go:uintptrescapes 25 // which forces all the objects that the uintptrs point to onto the heap where a stack split won't affect 26 // their memory location. 27 // 28 //go:uintptrescapes 29 func SyscallN(fn uintptr, args ...uintptr) (r1, r2, err uintptr) { 30 if fn == 0 { 31 panic("purego: fn is nil") 32 } 33 if len(args) > maxArgs { 34 panic("purego: too many arguments to SyscallN") 35 } 36 // add padding so there is no out-of-bounds slicing 37 var tmp [maxArgs]uintptr 38 copy(tmp[:], args) 39 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]) 40 }