1// SPDX-License-Identifier: Apache-2.0
2// SPDX-FileCopyrightText: 2022 The Ebitengine Authors
3
4//go:build linux
5
6package purego
7
8import (
9 "unsafe"
10)
11
12const (
13 maxArgs = 15
14)
15
16type syscallArgs struct {
17 fn, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15 uintptr
18 f1, f2, f3, f4, f5, f6, f7, f8 uintptr
19 arm64_r8 uintptr
20}
21
22func syscall_SyscallN(fn uintptr, sysargs []uintptr, floats []uintptr, r8 uintptr) *syscallArgs {
23 s := &syscallArgs{
24 fn: fn,
25 a1: sysargs[0], a2: sysargs[1], a3: sysargs[2], a4: sysargs[3],
26 a5: sysargs[4], a6: sysargs[5], a7: sysargs[6], a8: sysargs[7],
27 a9: sysargs[8], a10: sysargs[9], a11: sysargs[10], a12: sysargs[11],
28 a13: sysargs[12], a14: sysargs[13], a15: sysargs[14],
29 f1: floats[0], f2: floats[1], f3: floats[2], f4: floats[3],
30 f5: floats[4], f6: floats[5], f7: floats[6], f8: floats[7],
31 arm64_r8: r8,
32 }
33 runtime_cgocall(syscallXABI0, unsafe.Pointer(s))
34 return s
35}
36
37// SyscallN takes fn, a C function pointer and a list of arguments as uintptr.
38// There is an internal maximum number of arguments that SyscallN can take. It panics
39// when the maximum is exceeded. It returns the result and the libc error code if there is one.
40//
41// In order to call this function properly make sure to follow all the rules specified in [unsafe.Pointer]
42// especially point 4.
43//
44// NOTE: SyscallN does not properly call functions that have both integer and float parameters.
45// See discussion comment https://github.com/ebiten/purego/pull/1#issuecomment-1128057607
46// for an explanation of why that is.
47//
48// On amd64, if there are more than 8 floats the 9th and so on will be placed incorrectly on the
49// stack.
50//
51// The pragma go:nosplit is not needed at this function declaration because it uses go:uintptrescapes
52// which forces all the objects that the uintptrs point to onto the heap where a stack split won't affect
53// their memory location.
54//
55//go:uintptrescapes
56func SyscallN(fn uintptr, args ...uintptr) (r1, r2, err uintptr) {
57 if fn == 0 {
58 panic("purego: fn is nil")
59 }
60 if len(args) > maxArgs {
61 panic("purego: too many arguments to SyscallN")
62 }
63
64 var tmp [maxArgs]uintptr
65 copy(tmp[:], args)
66 var floats [maxArgs]uintptr
67 copy(floats[:], tmp[:])
68 s := syscall_SyscallN(fn, tmp[:], floats[:], 0)
69 return s.a1, s.a2, s.a3
70}