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 */ 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