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 /* The struct returned by the stat() syscall, 32-bit only, the syscall returns
11 * exactly 56 bytes (stops before the unused array).
12 */
13 struct sys_stat_struct {
14 unsigned long st_dev;
15 unsigned long st_ino;
16 unsigned short st_mode;
17 unsigned short st_nlink;
18 unsigned short st_uid;
19 unsigned short st_gid;
20
21 unsigned long st_rdev;
22 unsigned long st_size;
23 unsigned long st_blksize;
24 unsigned long st_blocks;
25
26 unsigned long st_atime;
27 unsigned long st_atime_nsec;
28 unsigned long st_mtime;
29 unsigned long st_mtime_nsec;
30
31 unsigned long st_ctime;
32 unsigned long st_ctime_nsec;
33 unsigned long __unused[2];
34 };
35
36 /* Syscalls for i386 :
37 * - mostly similar to x86_64
38 * - registers are 32-bit
39 * - syscall number is passed in eax
40 * - arguments are in ebx, ecx, edx, esi, edi, ebp respectively
41 * - all registers are preserved (except eax of course)
42 * - the system call is performed by calling int $0x80
43 * - syscall return comes in eax
44 * - the arguments are cast to long and assigned into the target registers
45 * which are then simply passed as registers to the asm code, so that we
46 * don't have to experience issues with register constraints.
47 * - the syscall number is always specified last in order to allow to force
48 * some registers before (gcc refuses a %-register at the last position).
49 *
50 * Also, i386 supports the old_select syscall if newselect is not available
51 */
52 #define __ARCH_WANT_SYS_OLD_SELECT
53
54 #define my_syscall0(num) \
55 ({ \
56 long _ret; \
57 register long _num __asm__ ("eax") = (num); \
58 \
59 __asm__ volatile ( \
60 "int $0x80\n" \
61 : "=a" (_ret) \
62 : "0"(_num) \
63 : "memory", "cc" \
64 ); \
65 _ret; \
66 })
67
68 #define my_syscall1(num, arg1) \
69 ({ \
70 long _ret; \
71 register long _num __asm__ ("eax") = (num); \
72 register long _arg1 __asm__ ("ebx") = (long)(arg1); \
73 \
74 __asm__ volatile ( \
75 "int $0x80\n" \
76 : "=a" (_ret) \
77 : "r"(_arg1), \
78 "0"(_num) \
79 : "memory", "cc" \
80 ); \
81 _ret; \
82 })
83
84 #define my_syscall2(num, arg1, arg2) \
85 ({ \
86 long _ret; \
87 register long _num __asm__ ("eax") = (num); \
88 register long _arg1 __asm__ ("ebx") = (long)(arg1); \
89 register long _arg2 __asm__ ("ecx") = (long)(arg2); \
90 \
91 __asm__ volatile ( \
92 "int $0x80\n" \
93 : "=a" (_ret) \
94 : "r"(_arg1), "r"(_arg2), \
95 "0"(_num) \
96 : "memory", "cc" \
97 ); \
98 _ret; \
99 })
100
101 #define my_syscall3(num, arg1, arg2, arg3) \
102 ({ \
103 long _ret; \
104 register long _num __asm__ ("eax") = (num); \
105 register long _arg1 __asm__ ("ebx") = (long)(arg1); \
106 register long _arg2 __asm__ ("ecx") = (long)(arg2); \
107 register long _arg3 __asm__ ("edx") = (long)(arg3); \
108 \
109 __asm__ volatile ( \
110 "int $0x80\n" \
111 : "=a" (_ret) \
112 : "r"(_arg1), "r"(_arg2), "r"(_arg3), \
113 "0"(_num) \
114 : "memory", "cc" \
115 ); \
116 _ret; \
117 })
118
119 #define my_syscall4(num, arg1, arg2, arg3, arg4) \
120 ({ \
121 long _ret; \
122 register long _num __asm__ ("eax") = (num); \
123 register long _arg1 __asm__ ("ebx") = (long)(arg1); \
124 register long _arg2 __asm__ ("ecx") = (long)(arg2); \
125 register long _arg3 __asm__ ("edx") = (long)(arg3); \
126 register long _arg4 __asm__ ("esi") = (long)(arg4); \
127 \
128 __asm__ volatile ( \
129 "int $0x80\n" \
130 : "=a" (_ret) \
131 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), \
132 "0"(_num) \
133 : "memory", "cc" \
134 ); \
135 _ret; \
136 })
137
138 #define my_syscall5(num, arg1, arg2, arg3, arg4, arg5) \
139 ({ \
140 long _ret; \
141 register long _num __asm__ ("eax") = (num); \
142 register long _arg1 __asm__ ("ebx") = (long)(arg1); \
143 register long _arg2 __asm__ ("ecx") = (long)(arg2); \
144 register long _arg3 __asm__ ("edx") = (long)(arg3); \
145 register long _arg4 __asm__ ("esi") = (long)(arg4); \
146 register long _arg5 __asm__ ("edi") = (long)(arg5); \
147 \
148 __asm__ volatile ( \
149 "int $0x80\n" \
150 : "=a" (_ret) \
151 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
152 "0"(_num) \
153 : "memory", "cc" \
154 ); \
155 _ret; \
156 })
157
158 #define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \
159 ({ \
160 long _eax = (long)(num); \
161 long _arg6 = (long)(arg6); /* Always in memory */ \
162 __asm__ volatile ( \
163 "pushl %[_arg6]\n\t" \
164 "pushl %%ebp\n\t" \
165 "movl 4(%%esp),%%ebp\n\t" \
166 "int $0x80\n\t" \
167 "popl %%ebp\n\t" \
168 "addl $4,%%esp\n\t" \
169 : "+a"(_eax) /* %eax */ \
170 : "b"(arg1), /* %ebx */ \
171 "c"(arg2), /* %ecx */ \
172 "d"(arg3), /* %edx */ \
173 "S"(arg4), /* %esi */ \
174 "D"(arg5), /* %edi */ \
175 [_arg6]"m"(_arg6) /* memory */ \
176 : "memory", "cc" \
177 ); \
178 _eax; \
179 })
180
181 char **environ __attribute__((weak));
182 const unsigned long *_auxv __attribute__((weak));
183
184 /* startup code */
185 /*
186 * i386 System V ABI mandates:
187 * 1) last pushed argument must be 16-byte aligned.
188 * 2) The deepest stack frame should be set to zero
189 *
190 */
_start(void)191 void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) _start(void)
192 {
193 __asm__ volatile (
194 "pop %eax\n" // argc (first arg, %eax)
195 "mov %esp, %ebx\n" // argv[] (second arg, %ebx)
196 "lea 4(%ebx,%eax,4),%ecx\n" // then a NULL then envp (third arg, %ecx)
197 "mov %ecx, environ\n" // save environ
198 "xor %ebp, %ebp\n" // zero the stack frame
199 "mov %ecx, %edx\n" // search for auxv (follows NULL after last env)
200 "0:\n"
201 "add $4, %edx\n" // search for auxv using edx, it follows the
202 "cmp -4(%edx), %ebp\n" // ... NULL after last env (ebp is zero here)
203 "jnz 0b\n"
204 "mov %edx, _auxv\n" // save it into _auxv
205 "and $-16, %esp\n" // x86 ABI : esp must be 16-byte aligned before
206 "sub $4, %esp\n" // the call instruction (args are aligned)
207 "push %ecx\n" // push all registers on the stack so that we
208 "push %ebx\n" // support both regparm and plain stack modes
209 "push %eax\n"
210 "call main\n" // main() returns the status code in %eax
211 "mov %eax, %ebx\n" // retrieve exit code (32-bit int)
212 "movl $1, %eax\n" // NR_exit == 1
213 "int $0x80\n" // exit now
214 "hlt\n" // ensure it does not
215 );
216 __builtin_unreachable();
217 }
218
219 #endif // _NOLIBC_ARCH_I386_H
220