1 /* SPDX-License-Identifier: LGPL-2.1 OR MIT */
2 /*
3 * RISCV (32 and 64) specific definitions for NOLIBC
4 * Copyright (C) 2017-2022 Willy Tarreau <w@1wt.eu>
5 */
6
7 #ifndef _NOLIBC_ARCH_RISCV_H
8 #define _NOLIBC_ARCH_RISCV_H
9
10 #include "compiler.h"
11 #include "crt.h"
12
13 /* Syscalls for RISCV :
14 * - stack is 16-byte aligned
15 * - syscall number is passed in a7
16 * - arguments are in a0, a1, a2, a3, a4, a5
17 * - the system call is performed by calling ecall
18 * - syscall return comes in a0
19 * - the arguments are cast to long and assigned into the target
20 * registers which are then simply passed as registers to the asm code,
21 * so that we don't have to experience issues with register constraints.
22 *
23 * On riscv, select() is not implemented so we have to use pselect6().
24 */
25 #define __ARCH_WANT_SYS_PSELECT6
26
27 #define my_syscall0(num) \
28 ({ \
29 register long _num __asm__ ("a7") = (num); \
30 register long _arg1 __asm__ ("a0"); \
31 \
32 __asm__ volatile ( \
33 "ecall\n\t" \
34 : "=r"(_arg1) \
35 : "r"(_num) \
36 : "memory", "cc" \
37 ); \
38 _arg1; \
39 })
40
41 #define my_syscall1(num, arg1) \
42 ({ \
43 register long _num __asm__ ("a7") = (num); \
44 register long _arg1 __asm__ ("a0") = (long)(arg1); \
45 \
46 __asm__ volatile ( \
47 "ecall\n" \
48 : "+r"(_arg1) \
49 : "r"(_num) \
50 : "memory", "cc" \
51 ); \
52 _arg1; \
53 })
54
55 #define my_syscall2(num, arg1, arg2) \
56 ({ \
57 register long _num __asm__ ("a7") = (num); \
58 register long _arg1 __asm__ ("a0") = (long)(arg1); \
59 register long _arg2 __asm__ ("a1") = (long)(arg2); \
60 \
61 __asm__ volatile ( \
62 "ecall\n" \
63 : "+r"(_arg1) \
64 : "r"(_arg2), \
65 "r"(_num) \
66 : "memory", "cc" \
67 ); \
68 _arg1; \
69 })
70
71 #define my_syscall3(num, arg1, arg2, arg3) \
72 ({ \
73 register long _num __asm__ ("a7") = (num); \
74 register long _arg1 __asm__ ("a0") = (long)(arg1); \
75 register long _arg2 __asm__ ("a1") = (long)(arg2); \
76 register long _arg3 __asm__ ("a2") = (long)(arg3); \
77 \
78 __asm__ volatile ( \
79 "ecall\n\t" \
80 : "+r"(_arg1) \
81 : "r"(_arg2), "r"(_arg3), \
82 "r"(_num) \
83 : "memory", "cc" \
84 ); \
85 _arg1; \
86 })
87
88 #define my_syscall4(num, arg1, arg2, arg3, arg4) \
89 ({ \
90 register long _num __asm__ ("a7") = (num); \
91 register long _arg1 __asm__ ("a0") = (long)(arg1); \
92 register long _arg2 __asm__ ("a1") = (long)(arg2); \
93 register long _arg3 __asm__ ("a2") = (long)(arg3); \
94 register long _arg4 __asm__ ("a3") = (long)(arg4); \
95 \
96 __asm__ volatile ( \
97 "ecall\n" \
98 : "+r"(_arg1) \
99 : "r"(_arg2), "r"(_arg3), "r"(_arg4), \
100 "r"(_num) \
101 : "memory", "cc" \
102 ); \
103 _arg1; \
104 })
105
106 #define my_syscall5(num, arg1, arg2, arg3, arg4, arg5) \
107 ({ \
108 register long _num __asm__ ("a7") = (num); \
109 register long _arg1 __asm__ ("a0") = (long)(arg1); \
110 register long _arg2 __asm__ ("a1") = (long)(arg2); \
111 register long _arg3 __asm__ ("a2") = (long)(arg3); \
112 register long _arg4 __asm__ ("a3") = (long)(arg4); \
113 register long _arg5 __asm__ ("a4") = (long)(arg5); \
114 \
115 __asm__ volatile ( \
116 "ecall\n" \
117 : "+r"(_arg1) \
118 : "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
119 "r"(_num) \
120 : "memory", "cc" \
121 ); \
122 _arg1; \
123 })
124
125 #define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \
126 ({ \
127 register long _num __asm__ ("a7") = (num); \
128 register long _arg1 __asm__ ("a0") = (long)(arg1); \
129 register long _arg2 __asm__ ("a1") = (long)(arg2); \
130 register long _arg3 __asm__ ("a2") = (long)(arg3); \
131 register long _arg4 __asm__ ("a3") = (long)(arg4); \
132 register long _arg5 __asm__ ("a4") = (long)(arg5); \
133 register long _arg6 __asm__ ("a5") = (long)(arg6); \
134 \
135 __asm__ volatile ( \
136 "ecall\n" \
137 : "+r"(_arg1) \
138 : "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), "r"(_arg6), \
139 "r"(_num) \
140 : "memory", "cc" \
141 ); \
142 _arg1; \
143 })
144
145 /* startup code */
_start(void)146 void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)
147 {
148 __asm__ volatile (
149 ".option push\n"
150 ".option norelax\n"
151 "lla gp, __global_pointer$\n"
152 ".option pop\n"
153 "mv a0, sp\n" /* save stack pointer to a0, as arg1 of _start_c */
154 "andi sp, a0, -16\n" /* sp must be 16-byte aligned */
155 "call _start_c\n" /* transfer to c runtime */
156 );
157 __builtin_unreachable();
158 }
159
160 #endif /* _NOLIBC_ARCH_RISCV_H */
161