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 #include "compiler.h" 11 12 /* The struct returned by the stat() syscall, 32-bit only, the syscall returns 13 * exactly 56 bytes (stops before the unused array). 14 */ 15 struct sys_stat_struct { 16 unsigned long st_dev; 17 unsigned long st_ino; 18 unsigned short st_mode; 19 unsigned short st_nlink; 20 unsigned short st_uid; 21 unsigned short st_gid; 22 23 unsigned long st_rdev; 24 unsigned long st_size; 25 unsigned long st_blksize; 26 unsigned long st_blocks; 27 28 unsigned long st_atime; 29 unsigned long st_atime_nsec; 30 unsigned long st_mtime; 31 unsigned long st_mtime_nsec; 32 33 unsigned long st_ctime; 34 unsigned long st_ctime_nsec; 35 unsigned long __unused[2]; 36 }; 37 38 /* Syscalls for i386 : 39 * - mostly similar to x86_64 40 * - registers are 32-bit 41 * - syscall number is passed in eax 42 * - arguments are in ebx, ecx, edx, esi, edi, ebp respectively 43 * - all registers are preserved (except eax of course) 44 * - the system call is performed by calling int $0x80 45 * - syscall return comes in eax 46 * - the arguments are cast to long and assigned into the target registers 47 * which are then simply passed as registers to the asm code, so that we 48 * don't have to experience issues with register constraints. 49 * - the syscall number is always specified last in order to allow to force 50 * some registers before (gcc refuses a %-register at the last position). 51 * 52 * Also, i386 supports the old_select syscall if newselect is not available 53 */ 54 #define __ARCH_WANT_SYS_OLD_SELECT 55 56 #define my_syscall0(num) \ 57 ({ \ 58 long _ret; \ 59 register long _num __asm__ ("eax") = (num); \ 60 \ 61 __asm__ volatile ( \ 62 "int $0x80\n" \ 63 : "=a" (_ret) \ 64 : "0"(_num) \ 65 : "memory", "cc" \ 66 ); \ 67 _ret; \ 68 }) 69 70 #define my_syscall1(num, arg1) \ 71 ({ \ 72 long _ret; \ 73 register long _num __asm__ ("eax") = (num); \ 74 register long _arg1 __asm__ ("ebx") = (long)(arg1); \ 75 \ 76 __asm__ volatile ( \ 77 "int $0x80\n" \ 78 : "=a" (_ret) \ 79 : "r"(_arg1), \ 80 "0"(_num) \ 81 : "memory", "cc" \ 82 ); \ 83 _ret; \ 84 }) 85 86 #define my_syscall2(num, arg1, arg2) \ 87 ({ \ 88 long _ret; \ 89 register long _num __asm__ ("eax") = (num); \ 90 register long _arg1 __asm__ ("ebx") = (long)(arg1); \ 91 register long _arg2 __asm__ ("ecx") = (long)(arg2); \ 92 \ 93 __asm__ volatile ( \ 94 "int $0x80\n" \ 95 : "=a" (_ret) \ 96 : "r"(_arg1), "r"(_arg2), \ 97 "0"(_num) \ 98 : "memory", "cc" \ 99 ); \ 100 _ret; \ 101 }) 102 103 #define my_syscall3(num, arg1, arg2, arg3) \ 104 ({ \ 105 long _ret; \ 106 register long _num __asm__ ("eax") = (num); \ 107 register long _arg1 __asm__ ("ebx") = (long)(arg1); \ 108 register long _arg2 __asm__ ("ecx") = (long)(arg2); \ 109 register long _arg3 __asm__ ("edx") = (long)(arg3); \ 110 \ 111 __asm__ volatile ( \ 112 "int $0x80\n" \ 113 : "=a" (_ret) \ 114 : "r"(_arg1), "r"(_arg2), "r"(_arg3), \ 115 "0"(_num) \ 116 : "memory", "cc" \ 117 ); \ 118 _ret; \ 119 }) 120 121 #define my_syscall4(num, arg1, arg2, arg3, arg4) \ 122 ({ \ 123 long _ret; \ 124 register long _num __asm__ ("eax") = (num); \ 125 register long _arg1 __asm__ ("ebx") = (long)(arg1); \ 126 register long _arg2 __asm__ ("ecx") = (long)(arg2); \ 127 register long _arg3 __asm__ ("edx") = (long)(arg3); \ 128 register long _arg4 __asm__ ("esi") = (long)(arg4); \ 129 \ 130 __asm__ volatile ( \ 131 "int $0x80\n" \ 132 : "=a" (_ret) \ 133 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), \ 134 "0"(_num) \ 135 : "memory", "cc" \ 136 ); \ 137 _ret; \ 138 }) 139 140 #define my_syscall5(num, arg1, arg2, arg3, arg4, arg5) \ 141 ({ \ 142 long _ret; \ 143 register long _num __asm__ ("eax") = (num); \ 144 register long _arg1 __asm__ ("ebx") = (long)(arg1); \ 145 register long _arg2 __asm__ ("ecx") = (long)(arg2); \ 146 register long _arg3 __asm__ ("edx") = (long)(arg3); \ 147 register long _arg4 __asm__ ("esi") = (long)(arg4); \ 148 register long _arg5 __asm__ ("edi") = (long)(arg5); \ 149 \ 150 __asm__ volatile ( \ 151 "int $0x80\n" \ 152 : "=a" (_ret) \ 153 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \ 154 "0"(_num) \ 155 : "memory", "cc" \ 156 ); \ 157 _ret; \ 158 }) 159 160 #define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \ 161 ({ \ 162 long _eax = (long)(num); \ 163 long _arg6 = (long)(arg6); /* Always in memory */ \ 164 __asm__ volatile ( \ 165 "pushl %[_arg6]\n\t" \ 166 "pushl %%ebp\n\t" \ 167 "movl 4(%%esp),%%ebp\n\t" \ 168 "int $0x80\n\t" \ 169 "popl %%ebp\n\t" \ 170 "addl $4,%%esp\n\t" \ 171 : "+a"(_eax) /* %eax */ \ 172 : "b"(arg1), /* %ebx */ \ 173 "c"(arg2), /* %ecx */ \ 174 "d"(arg3), /* %edx */ \ 175 "S"(arg4), /* %esi */ \ 176 "D"(arg5), /* %edi */ \ 177 [_arg6]"m"(_arg6) /* memory */ \ 178 : "memory", "cc" \ 179 ); \ 180 _eax; \ 181 }) 182 183 char **environ __attribute__((weak)); 184 const unsigned long *_auxv __attribute__((weak)); 185 186 /* startup code */ 187 /* 188 * i386 System V ABI mandates: 189 * 1) last pushed argument must be 16-byte aligned. 190 * 2) The deepest stack frame should be set to zero 191 * 192 */ 193 void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) __no_stack_protector _start(void) 194 { 195 __asm__ volatile ( 196 #ifdef _NOLIBC_STACKPROTECTOR 197 "call __stack_chk_init\n" /* initialize stack protector */ 198 #endif 199 "pop %eax\n" /* argc (first arg, %eax) */ 200 "mov %esp, %ebx\n" /* argv[] (second arg, %ebx) */ 201 "lea 4(%ebx,%eax,4),%ecx\n" /* then a NULL then envp (third arg, %ecx) */ 202 "mov %ecx, environ\n" /* save environ */ 203 "xor %ebp, %ebp\n" /* zero the stack frame */ 204 "mov %ecx, %edx\n" /* search for auxv (follows NULL after last env) */ 205 "0:\n" 206 "add $4, %edx\n" /* search for auxv using edx, it follows the */ 207 "cmp -4(%edx), %ebp\n" /* ... NULL after last env (ebp is zero here) */ 208 "jnz 0b\n" 209 "mov %edx, _auxv\n" /* save it into _auxv */ 210 "and $-16, %esp\n" /* x86 ABI : esp must be 16-byte aligned before */ 211 "sub $4, %esp\n" /* the call instruction (args are aligned) */ 212 "push %ecx\n" /* push all registers on the stack so that we */ 213 "push %ebx\n" /* support both regparm and plain stack modes */ 214 "push %eax\n" 215 "call main\n" /* main() returns the status code in %eax */ 216 "mov %eax, %ebx\n" /* retrieve exit code (32-bit int) */ 217 "movl $1, %eax\n" /* NR_exit == 1 */ 218 "int $0x80\n" /* exit now */ 219 "hlt\n" /* ensure it does not */ 220 ); 221 __builtin_unreachable(); 222 } 223 224 #endif /* _NOLIBC_ARCH_I386_H */ 225