1// SPDX-License-Identifier: Apache-2.0
2// SPDX-FileCopyrightText: 2022 The Ebitengine Authors
3
4//go:build (386 || arm) && (freebsd || linux || netbsd || windows)
5
6package purego
7
8import (
9 "runtime"
10 "structs"
11 "unsafe"
12)
13
14const (
15 maxArgs = 32
16)
17
18// syscallArgs is the argument block handed to the syscall15 trampoline. On
19// platforms that go through internal/cgo it is passed to C as a
20// struct syscallArgs, so its layout must match the C ABI.
21type syscallArgs struct {
22 _ structs.HostLayout
23
24 fn, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15 uintptr
25 a16, a17, a18, a19, a20, a21, a22, a23, a24, a25, a26, a27, a28, a29, a30, a31, a32 uintptr
26 f1, f2, f3, f4, f5, f6, f7, f8, f9, f10, f11, f12, f13, f14, f15, f16 uintptr
27 arm64_r8 uintptr
28}
29
30func syscall_SyscallN(fn uintptr, sysargs []uintptr, floats []uintptr, r8 uintptr) *syscallArgs {
31 s := thePool.Get().(*syscallArgs)
32 *s = syscallArgs{
33 fn: fn,
34 a1: sysargs[0], a2: sysargs[1], a3: sysargs[2], a4: sysargs[3],
35 a5: sysargs[4], a6: sysargs[5], a7: sysargs[6], a8: sysargs[7],
36 a9: sysargs[8], a10: sysargs[9], a11: sysargs[10], a12: sysargs[11],
37 a13: sysargs[12], a14: sysargs[13], a15: sysargs[14], a16: sysargs[15],
38 a17: sysargs[16], a18: sysargs[17], a19: sysargs[18], a20: sysargs[19],
39 a21: sysargs[20], a22: sysargs[21], a23: sysargs[22], a24: sysargs[23],
40 a25: sysargs[24], a26: sysargs[25], a27: sysargs[26], a28: sysargs[27],
41 a29: sysargs[28], a30: sysargs[29], a31: sysargs[30], a32: sysargs[31],
42 f1: floats[0], f2: floats[1], f3: floats[2], f4: floats[3],
43 f5: floats[4], f6: floats[5], f7: floats[6], f8: floats[7],
44 f9: floats[8], f10: floats[9], f11: floats[10], f12: floats[11],
45 f13: floats[12], f14: floats[13], f15: floats[14], f16: floats[15],
46 arm64_r8: r8,
47 }
48 runtime_cgocall(syscallXABI0, unsafe.Pointer(s))
49 return s
50}
51
52// SyscallN takes fn, a C function pointer and a list of arguments as uintptr.
53// There is an internal maximum number of arguments that SyscallN can take. It panics
54// when the maximum is exceeded. It returns the result and the libc error code if there is one.
55//
56// In order to call this function properly make sure to follow all the rules specified in [unsafe.Pointer]
57// especially point 4.
58//
59// NOTE: SyscallN does not properly call functions that have both integer and float parameters.
60// See discussion comment https://github.com/ebiten/purego/pull/1#issuecomment-1128057607
61// for an explanation of why that is.
62//
63// On amd64, if there are more than 8 floats the 9th and so on will be placed incorrectly on the
64// stack.
65//
66// The pragma go:nosplit is not needed at this function declaration because it uses go:uintptrescapes
67// which forces all the objects that the uintptrs point to onto the heap where a stack split won't affect
68// their memory location.
69//
70//go:uintptrescapes
71func SyscallN(fn uintptr, args ...uintptr) (r1, r2, err uintptr) {
72 if fn == 0 {
73 panic("purego: fn is nil")
74 }
75 if len(args) > maxArgs {
76 panic("purego: too many arguments to SyscallN")
77 }
78
79 // Windows uses syscall.SyscallN in syscall_windows.go.
80 if runtime.GOOS == "windows" {
81 return syscall_syscallN(fn, args...)
82 }
83
84 // Add padding so there is no out-of-bounds slicing.
85 var tmp [maxArgs]uintptr
86 copy(tmp[:], args)
87 var floats [16]uintptr
88 copy(floats[:], tmp[:16])
89 s := syscall_SyscallN(fn, tmp[:], floats[:], 0)
90 defer thePool.Put(s)
91 return s.a1, s.a2, s.a3
92}