1// SPDX-License-Identifier: Apache-2.0
2// SPDX-FileCopyrightText: 2026 The Ebitengine Authors
3
4//go:build linux
5
6#include "textflag.h"
7#include "go_asm.h"
8#include "funcdata.h"
9
10// Stack usage:
11// 0(SP) - 192(SP): stack args a9-a32 (24 * 8 bytes)
12// 192(SP) - 200(SP): saved RA (x1)
13// 200(SP) - 208(SP): saved X9 (s1)
14// 208(SP) - 216(SP): saved X18 (s2)
15// 216(SP) - 224(SP): saved args pointer (original X10)
16#define STACK_SIZE 224
17#define SAVE_RA 192
18#define SAVE_X9 200
19#define SAVE_X18 208
20#define SAVE_ARGP 216
21
22GLOBL ·syscallXABI0(SB), NOPTR|RODATA, $8
23DATA ·syscallXABI0(SB)/8, $syscallX(SB)
24
25TEXT syscallX(SB), NOSPLIT, $0
26 // Allocate stack frame (keeps 16-byte alignment)
27 SUB $STACK_SIZE, SP
28
29 // Save callee-saved regs we clobber + return address
30 MOV X1, SAVE_RA(SP)
31 MOV X9, SAVE_X9(SP)
32 MOV X18, SAVE_X18(SP)
33
34 // Save original args pointer (in a0/X10)
35 MOV X10, SAVE_ARGP(SP)
36
37 // X9 := args pointer (syscallArgs*)
38 MOV X10, X9
39
40 // Load float args into fa0-fa7 (F10-F17)
41 MOVD syscallArgs_f1(X9), F10
42 MOVD syscallArgs_f2(X9), F11
43 MOVD syscallArgs_f3(X9), F12
44 MOVD syscallArgs_f4(X9), F13
45 MOVD syscallArgs_f5(X9), F14
46 MOVD syscallArgs_f6(X9), F15
47 MOVD syscallArgs_f7(X9), F16
48 MOVD syscallArgs_f8(X9), F17
49
50 // Load integer args into a0-a7 (X10-X17)
51 MOV syscallArgs_a1(X9), X10
52 MOV syscallArgs_a2(X9), X11
53 MOV syscallArgs_a3(X9), X12
54 MOV syscallArgs_a4(X9), X13
55 MOV syscallArgs_a5(X9), X14
56 MOV syscallArgs_a6(X9), X15
57 MOV syscallArgs_a7(X9), X16
58 MOV syscallArgs_a8(X9), X17
59
60 // Spill a9-a32 onto the stack (C ABI)
61 MOV syscallArgs_a9(X9), X18
62 MOV X18, 0(SP)
63 MOV syscallArgs_a10(X9), X18
64 MOV X18, 8(SP)
65 MOV syscallArgs_a11(X9), X18
66 MOV X18, 16(SP)
67 MOV syscallArgs_a12(X9), X18
68 MOV X18, 24(SP)
69 MOV syscallArgs_a13(X9), X18
70 MOV X18, 32(SP)
71 MOV syscallArgs_a14(X9), X18
72 MOV X18, 40(SP)
73 MOV syscallArgs_a15(X9), X18
74 MOV X18, 48(SP)
75 MOV syscallArgs_a16(X9), X18
76 MOV X18, 56(SP)
77 MOV syscallArgs_a17(X9), X18
78 MOV X18, 64(SP)
79 MOV syscallArgs_a18(X9), X18
80 MOV X18, 72(SP)
81 MOV syscallArgs_a19(X9), X18
82 MOV X18, 80(SP)
83 MOV syscallArgs_a20(X9), X18
84 MOV X18, 88(SP)
85 MOV syscallArgs_a21(X9), X18
86 MOV X18, 96(SP)
87 MOV syscallArgs_a22(X9), X18
88 MOV X18, 104(SP)
89 MOV syscallArgs_a23(X9), X18
90 MOV X18, 112(SP)
91 MOV syscallArgs_a24(X9), X18
92 MOV X18, 120(SP)
93 MOV syscallArgs_a25(X9), X18
94 MOV X18, 128(SP)
95 MOV syscallArgs_a26(X9), X18
96 MOV X18, 136(SP)
97 MOV syscallArgs_a27(X9), X18
98 MOV X18, 144(SP)
99 MOV syscallArgs_a28(X9), X18
100 MOV X18, 152(SP)
101 MOV syscallArgs_a29(X9), X18
102 MOV X18, 160(SP)
103 MOV syscallArgs_a30(X9), X18
104 MOV X18, 168(SP)
105 MOV syscallArgs_a31(X9), X18
106 MOV X18, 176(SP)
107 MOV syscallArgs_a32(X9), X18
108 MOV X18, 184(SP)
109
110 // Call fn
111 // IMPORTANT: preserve RA across this call (we saved it above)
112 MOV syscallArgs_fn(X9), X18
113 CALL X18
114
115 // Restore args pointer (syscallArgs*) for storing results
116 MOV SAVE_ARGP(SP), X9
117
118 // Store results back
119 MOV X10, syscallArgs_a1(X9)
120 MOV X11, syscallArgs_a2(X9)
121 MOV X0, syscallArgs_a3(X9) // no errno here: clear the input argument
122
123 // Store back float return regs if used by your ABI contract
124 MOVD F10, syscallArgs_f1(X9)
125 MOVD F11, syscallArgs_f2(X9)
126 MOVD F12, syscallArgs_f3(X9)
127 MOVD F13, syscallArgs_f4(X9)
128
129 // Restore callee-saved regs and return address
130 MOV SAVE_X18(SP), X18
131 MOV SAVE_X9(SP), X9
132 MOV SAVE_RA(SP), X1
133
134 ADD $STACK_SIZE, SP
135 RET