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1/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
2/*
3 * MIPS specific definitions for NOLIBC
4 * Copyright (C) 2017-2022 Willy Tarreau <w@1wt.eu>
5 */
6
7#ifndef _NOLIBC_ARCH_MIPS_H
8#define _NOLIBC_ARCH_MIPS_H
9
10#include "compiler.h"
11#include "crt.h"
12
13#if !defined(_ABIO32)
14#error Unsupported MIPS ABI
15#endif
16
17/* Syscalls for MIPS ABI O32 :
18 * - WARNING! there's always a delayed slot!
19 * - WARNING again, the syntax is different, registers take a '$' and numbers
20 * do not.
21 * - registers are 32-bit
22 * - stack is 8-byte aligned
23 * - syscall number is passed in v0 (starts at 0xfa0).
24 * - arguments are in a0, a1, a2, a3, then the stack. The caller needs to
25 * leave some room in the stack for the callee to save a0..a3 if needed.
26 * - Many registers are clobbered, in fact only a0..a2 and s0..s8 are
27 * preserved. See: https://www.linux-mips.org/wiki/Syscall as well as
28 * scall32-o32.S in the kernel sources.
29 * - the system call is performed by calling "syscall"
30 * - syscall return comes in v0, and register a3 needs to be checked to know
31 * if an error occurred, in which case errno is in v0.
32 * - the arguments are cast to long and assigned into the target registers
33 * which are then simply passed as registers to the asm code, so that we
34 * don't have to experience issues with register constraints.
35 */
36
37#define _NOLIBC_SYSCALL_CLOBBERLIST \
38 "memory", "cc", "at", "v1", "hi", "lo", \
39 "t0", "t1", "t2", "t3", "t4", "t5", "t6", "t7", "t8", "t9"
40
41#define my_syscall0(num) \
42({ \
43 register long _num __asm__ ("v0") = (num); \
44 register long _arg4 __asm__ ("a3"); \
45 \
46 __asm__ volatile ( \
47 "addiu $sp, $sp, -32\n" \
48 "syscall\n" \
49 "addiu $sp, $sp, 32\n" \
50 : "=r"(_num), "=r"(_arg4) \
51 : "r"(_num) \
52 : _NOLIBC_SYSCALL_CLOBBERLIST \
53 ); \
54 _arg4 ? -_num : _num; \
55})
56
57#define my_syscall1(num, arg1) \
58({ \
59 register long _num __asm__ ("v0") = (num); \
60 register long _arg1 __asm__ ("a0") = (long)(arg1); \
61 register long _arg4 __asm__ ("a3"); \
62 \
63 __asm__ volatile ( \
64 "addiu $sp, $sp, -32\n" \
65 "syscall\n" \
66 "addiu $sp, $sp, 32\n" \
67 : "=r"(_num), "=r"(_arg4) \
68 : "0"(_num), \
69 "r"(_arg1) \
70 : _NOLIBC_SYSCALL_CLOBBERLIST \
71 ); \
72 _arg4 ? -_num : _num; \
73})
74
75#define my_syscall2(num, arg1, arg2) \
76({ \
77 register long _num __asm__ ("v0") = (num); \
78 register long _arg1 __asm__ ("a0") = (long)(arg1); \
79 register long _arg2 __asm__ ("a1") = (long)(arg2); \
80 register long _arg4 __asm__ ("a3"); \
81 \
82 __asm__ volatile ( \
83 "addiu $sp, $sp, -32\n" \
84 "syscall\n" \
85 "addiu $sp, $sp, 32\n" \
86 : "=r"(_num), "=r"(_arg4) \
87 : "0"(_num), \
88 "r"(_arg1), "r"(_arg2) \
89 : _NOLIBC_SYSCALL_CLOBBERLIST \
90 ); \
91 _arg4 ? -_num : _num; \
92})
93
94#define my_syscall3(num, arg1, arg2, arg3) \
95({ \
96 register long _num __asm__ ("v0") = (num); \
97 register long _arg1 __asm__ ("a0") = (long)(arg1); \
98 register long _arg2 __asm__ ("a1") = (long)(arg2); \
99 register long _arg3 __asm__ ("a2") = (long)(arg3); \
100 register long _arg4 __asm__ ("a3"); \
101 \
102 __asm__ volatile ( \
103 "addiu $sp, $sp, -32\n" \
104 "syscall\n" \
105 "addiu $sp, $sp, 32\n" \
106 : "=r"(_num), "=r"(_arg4) \
107 : "0"(_num), \
108 "r"(_arg1), "r"(_arg2), "r"(_arg3) \
109 : _NOLIBC_SYSCALL_CLOBBERLIST \
110 ); \
111 _arg4 ? -_num : _num; \
112})
113
114#define my_syscall4(num, arg1, arg2, arg3, arg4) \
115({ \
116 register long _num __asm__ ("v0") = (num); \
117 register long _arg1 __asm__ ("a0") = (long)(arg1); \
118 register long _arg2 __asm__ ("a1") = (long)(arg2); \
119 register long _arg3 __asm__ ("a2") = (long)(arg3); \
120 register long _arg4 __asm__ ("a3") = (long)(arg4); \
121 \
122 __asm__ volatile ( \
123 "addiu $sp, $sp, -32\n" \
124 "syscall\n" \
125 "addiu $sp, $sp, 32\n" \
126 : "=r" (_num), "=r"(_arg4) \
127 : "0"(_num), \
128 "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4) \
129 : _NOLIBC_SYSCALL_CLOBBERLIST \
130 ); \
131 _arg4 ? -_num : _num; \
132})
133
134#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5) \
135({ \
136 register long _num __asm__ ("v0") = (num); \
137 register long _arg1 __asm__ ("a0") = (long)(arg1); \
138 register long _arg2 __asm__ ("a1") = (long)(arg2); \
139 register long _arg3 __asm__ ("a2") = (long)(arg3); \
140 register long _arg4 __asm__ ("a3") = (long)(arg4); \
141 register long _arg5 = (long)(arg5); \
142 \
143 __asm__ volatile ( \
144 "addiu $sp, $sp, -32\n" \
145 "sw %7, 16($sp)\n" \
146 "syscall\n" \
147 "addiu $sp, $sp, 32\n" \
148 : "=r" (_num), "=r"(_arg4) \
149 : "0"(_num), \
150 "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5) \
151 : _NOLIBC_SYSCALL_CLOBBERLIST \
152 ); \
153 _arg4 ? -_num : _num; \
154})
155
156#define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \
157({ \
158 register long _num __asm__ ("v0") = (num); \
159 register long _arg1 __asm__ ("a0") = (long)(arg1); \
160 register long _arg2 __asm__ ("a1") = (long)(arg2); \
161 register long _arg3 __asm__ ("a2") = (long)(arg3); \
162 register long _arg4 __asm__ ("a3") = (long)(arg4); \
163 register long _arg5 = (long)(arg5); \
164 register long _arg6 = (long)(arg6); \
165 \
166 __asm__ volatile ( \
167 "addiu $sp, $sp, -32\n" \
168 "sw %7, 16($sp)\n" \
169 "sw %8, 20($sp)\n" \
170 "syscall\n" \
171 "addiu $sp, $sp, 32\n" \
172 : "=r" (_num), "=r"(_arg4) \
173 : "0"(_num), \
174 "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
175 "r"(_arg6) \
176 : _NOLIBC_SYSCALL_CLOBBERLIST \
177 ); \
178 _arg4 ? -_num : _num; \
179})
180
181/* startup code, note that it's called __start on MIPS */
182void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector __start(void)
183{
184 __asm__ volatile (
185 ".set push\n"
186 ".set noreorder\n"
187 "bal 1f\n" /* prime $ra for .cpload */
188 "nop\n"
189 "1:\n"
190 ".cpload $ra\n"
191 "move $a0, $sp\n" /* save stack pointer to $a0, as arg1 of _start_c */
192 "addiu $sp, $sp, -4\n" /* space for .cprestore to store $gp */
193 ".cprestore 0\n"
194 "li $t0, -8\n"
195 "and $sp, $sp, $t0\n" /* $sp must be 8-byte aligned */
196 "addiu $sp, $sp, -16\n" /* the callee expects to save a0..a3 there */
197 "jal _start_c\n" /* transfer to c runtime */
198 " nop\n" /* delayed slot */
199 ".set pop\n"
200 );
201 __builtin_unreachable();
202}
203
204#endif /* _NOLIBC_ARCH_MIPS_H */