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