1 // SPDX-License-Identifier: Apache-2.0
2 // SPDX-FileCopyrightText: 2022 The Ebitengine Authors
3 4 //go:build !cgo && (darwin || linux || freebsd)
5 6 /*
7 trampoline for emulating required C functions for cgo in go (see cgo.go)
8 (we convert cdecl calling convention to go and vice-versa)
9 10 Since we're called from go and call into C we can cheat a bit with the calling conventions:
11 - in go all the registers are caller saved
12 - in C we have a couple of callee saved registers
13 14 => we can use BX, R12, R13, R14, R15 instead of the stack
15 16 C Calling convention cdecl used here (we only need integer args):
17 1. arg: DI
18 2. arg: SI
19 3. arg: DX
20 4. arg: CX
21 5. arg: R8
22 6. arg: R9
23 We don't need floats with these functions -> AX=0
24 return value will be in AX
25 */
26 #include "textflag.h"
27 #include "go_asm.h"
28 29 // these trampolines map the gcc ABI to Go ABI and then calls into the Go equivalent functions.
30 31 TEXT x_cgo_init_trampoline(SB), NOSPLIT, $16
32 MOVQ DI, AX
33 MOVQ SI, BX
34 MOVQ ·x_cgo_init_call(SB), DX
35 MOVQ (DX), CX
36 CALL CX
37 RET
38 39 TEXT x_cgo_thread_start_trampoline(SB), NOSPLIT, $8
40 MOVQ DI, AX
41 MOVQ ·x_cgo_thread_start_call(SB), DX
42 MOVQ (DX), CX
43 CALL CX
44 RET
45 46 TEXT x_cgo_setenv_trampoline(SB), NOSPLIT, $8
47 MOVQ DI, AX
48 MOVQ ·x_cgo_setenv_call(SB), DX
49 MOVQ (DX), CX
50 CALL CX
51 RET
52 53 TEXT x_cgo_unsetenv_trampoline(SB), NOSPLIT, $8
54 MOVQ DI, AX
55 MOVQ ·x_cgo_unsetenv_call(SB), DX
56 MOVQ (DX), CX
57 CALL CX
58 RET
59 60 TEXT x_cgo_notify_runtime_init_done_trampoline(SB), NOSPLIT, $0
61 CALL ·x_cgo_notify_runtime_init_done(SB)
62 RET
63 64 TEXT x_cgo_bindm_trampoline(SB), NOSPLIT, $0
65 CALL ·x_cgo_bindm(SB)
66 RET
67 68 // func setg_trampoline(setg uintptr, g uintptr)
69 TEXT ·setg_trampoline(SB), NOSPLIT, $0-16
70 MOVQ G+8(FP), DI
71 MOVQ setg+0(FP), BX
72 XORL AX, AX
73 CALL BX
74 RET
75 76 TEXT threadentry_trampoline(SB), NOSPLIT, $16
77 MOVQ DI, AX
78 MOVQ ·threadentry_call(SB), DX
79 MOVQ (DX), CX
80 CALL CX
81 RET
82 83 TEXT ·call5(SB), NOSPLIT, $0-56
84 MOVQ fn+0(FP), BX
85 MOVQ a1+8(FP), DI
86 MOVQ a2+16(FP), SI
87 MOVQ a3+24(FP), DX
88 MOVQ a4+32(FP), CX
89 MOVQ a5+40(FP), R8
90 91 XORL AX, AX // no floats
92 93 PUSHQ BP // save BP
94 MOVQ SP, BP // save SP inside BP bc BP is callee-saved
95 SUBQ $16, SP // allocate space for alignment
96 ANDQ $-16, SP // align on 16 bytes for SSE
97 98 CALL BX
99 100 MOVQ BP, SP // get SP back
101 POPQ BP // restore BP
102 103 MOVQ AX, ret+48(FP)
104 RET
105