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1 /* SPDX-License-Identifier: LGPL-2.1 OR MIT */
2 /*
3  * i386 specific definitions for NOLIBC
4  * Copyright (C) 2017-2022 Willy Tarreau <w@1wt.eu>
5  */
6 
7 #ifndef _NOLIBC_ARCH_I386_H
8 #define _NOLIBC_ARCH_I386_H
9 
10 /* O_* macros for fcntl/open are architecture-specific */
11 #define O_RDONLY            0
12 #define O_WRONLY            1
13 #define O_RDWR              2
14 #define O_CREAT          0x40
15 #define O_EXCL           0x80
16 #define O_NOCTTY        0x100
17 #define O_TRUNC         0x200
18 #define O_APPEND        0x400
19 #define O_NONBLOCK      0x800
20 #define O_DIRECTORY   0x10000
21 
22 /* The struct returned by the stat() syscall, 32-bit only, the syscall returns
23  * exactly 56 bytes (stops before the unused array).
24  */
25 struct sys_stat_struct {
26 	unsigned long  st_dev;
27 	unsigned long  st_ino;
28 	unsigned short st_mode;
29 	unsigned short st_nlink;
30 	unsigned short st_uid;
31 	unsigned short st_gid;
32 
33 	unsigned long  st_rdev;
34 	unsigned long  st_size;
35 	unsigned long  st_blksize;
36 	unsigned long  st_blocks;
37 
38 	unsigned long  st_atime;
39 	unsigned long  st_atime_nsec;
40 	unsigned long  st_mtime;
41 	unsigned long  st_mtime_nsec;
42 
43 	unsigned long  st_ctime;
44 	unsigned long  st_ctime_nsec;
45 	unsigned long  __unused[2];
46 };
47 
48 /* Syscalls for i386 :
49  *   - mostly similar to x86_64
50  *   - registers are 32-bit
51  *   - syscall number is passed in eax
52  *   - arguments are in ebx, ecx, edx, esi, edi, ebp respectively
53  *   - all registers are preserved (except eax of course)
54  *   - the system call is performed by calling int $0x80
55  *   - syscall return comes in eax
56  *   - the arguments are cast to long and assigned into the target registers
57  *     which are then simply passed as registers to the asm code, so that we
58  *     don't have to experience issues with register constraints.
59  *   - the syscall number is always specified last in order to allow to force
60  *     some registers before (gcc refuses a %-register at the last position).
61  *
62  * Also, i386 supports the old_select syscall if newselect is not available
63  */
64 #define __ARCH_WANT_SYS_OLD_SELECT
65 
66 #define my_syscall0(num)                                                      \
67 ({                                                                            \
68 	long _ret;                                                            \
69 	register long _num asm("eax") = (num);                                \
70 	                                                                      \
71 	asm volatile (                                                        \
72 		"int $0x80\n"                                                 \
73 		: "=a" (_ret)                                                 \
74 		: "0"(_num)                                                   \
75 		: "memory", "cc"                                              \
76 	);                                                                    \
77 	_ret;                                                                 \
78 })
79 
80 #define my_syscall1(num, arg1)                                                \
81 ({                                                                            \
82 	long _ret;                                                            \
83 	register long _num asm("eax") = (num);                                \
84 	register long _arg1 asm("ebx") = (long)(arg1);                        \
85 	                                                                      \
86 	asm volatile (                                                        \
87 		"int $0x80\n"                                                 \
88 		: "=a" (_ret)                                                 \
89 		: "r"(_arg1),                                                 \
90 		  "0"(_num)                                                   \
91 		: "memory", "cc"                                              \
92 	);                                                                    \
93 	_ret;                                                                 \
94 })
95 
96 #define my_syscall2(num, arg1, arg2)                                          \
97 ({                                                                            \
98 	long _ret;                                                            \
99 	register long _num asm("eax") = (num);                                \
100 	register long _arg1 asm("ebx") = (long)(arg1);                        \
101 	register long _arg2 asm("ecx") = (long)(arg2);                        \
102 	                                                                      \
103 	asm volatile (                                                        \
104 		"int $0x80\n"                                                 \
105 		: "=a" (_ret)                                                 \
106 		: "r"(_arg1), "r"(_arg2),                                     \
107 		  "0"(_num)                                                   \
108 		: "memory", "cc"                                              \
109 	);                                                                    \
110 	_ret;                                                                 \
111 })
112 
113 #define my_syscall3(num, arg1, arg2, arg3)                                    \
114 ({                                                                            \
115 	long _ret;                                                            \
116 	register long _num asm("eax") = (num);                                \
117 	register long _arg1 asm("ebx") = (long)(arg1);                        \
118 	register long _arg2 asm("ecx") = (long)(arg2);                        \
119 	register long _arg3 asm("edx") = (long)(arg3);                        \
120 	                                                                      \
121 	asm volatile (                                                        \
122 		"int $0x80\n"                                                 \
123 		: "=a" (_ret)                                                 \
124 		: "r"(_arg1), "r"(_arg2), "r"(_arg3),                         \
125 		  "0"(_num)                                                   \
126 		: "memory", "cc"                                              \
127 	);                                                                    \
128 	_ret;                                                                 \
129 })
130 
131 #define my_syscall4(num, arg1, arg2, arg3, arg4)                              \
132 ({                                                                            \
133 	long _ret;                                                            \
134 	register long _num asm("eax") = (num);                                \
135 	register long _arg1 asm("ebx") = (long)(arg1);                        \
136 	register long _arg2 asm("ecx") = (long)(arg2);                        \
137 	register long _arg3 asm("edx") = (long)(arg3);                        \
138 	register long _arg4 asm("esi") = (long)(arg4);                        \
139 	                                                                      \
140 	asm volatile (                                                        \
141 		"int $0x80\n"                                                 \
142 		: "=a" (_ret)                                                 \
143 		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4),             \
144 		  "0"(_num)                                                   \
145 		: "memory", "cc"                                              \
146 	);                                                                    \
147 	_ret;                                                                 \
148 })
149 
150 #define my_syscall5(num, arg1, arg2, arg3, arg4, arg5)                        \
151 ({                                                                            \
152 	long _ret;                                                            \
153 	register long _num asm("eax") = (num);                                \
154 	register long _arg1 asm("ebx") = (long)(arg1);                        \
155 	register long _arg2 asm("ecx") = (long)(arg2);                        \
156 	register long _arg3 asm("edx") = (long)(arg3);                        \
157 	register long _arg4 asm("esi") = (long)(arg4);                        \
158 	register long _arg5 asm("edi") = (long)(arg5);                        \
159 	                                                                      \
160 	asm volatile (                                                        \
161 		"int $0x80\n"                                                 \
162 		: "=a" (_ret)                                                 \
163 		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
164 		  "0"(_num)                                                   \
165 		: "memory", "cc"                                              \
166 	);                                                                    \
167 	_ret;                                                                 \
168 })
169 
170 /* startup code */
171 /*
172  * i386 System V ABI mandates:
173  * 1) last pushed argument must be 16-byte aligned.
174  * 2) The deepest stack frame should be set to zero
175  *
176  */
177 asm(".section .text\n"
178     ".weak _start\n"
179     "_start:\n"
180     "pop %eax\n"                // argc   (first arg, %eax)
181     "mov %esp, %ebx\n"          // argv[] (second arg, %ebx)
182     "lea 4(%ebx,%eax,4),%ecx\n" // then a NULL then envp (third arg, %ecx)
183     "xor %ebp, %ebp\n"          // zero the stack frame
184     "and $-16, %esp\n"          // x86 ABI : esp must be 16-byte aligned before
185     "sub $4, %esp\n"            // the call instruction (args are aligned)
186     "push %ecx\n"               // push all registers on the stack so that we
187     "push %ebx\n"               // support both regparm and plain stack modes
188     "push %eax\n"
189     "call main\n"               // main() returns the status code in %eax
190     "mov %eax, %ebx\n"          // retrieve exit code (32-bit int)
191     "movl $1, %eax\n"           // NR_exit == 1
192     "int $0x80\n"               // exit now
193     "hlt\n"                     // ensure it does not
194     "");
195 
196 #endif // _NOLIBC_ARCH_I386_H
197