1 /* SPDX-License-Identifier: LGPL-2.1 OR MIT */ 2 /* 3 * x86 specific definitions for NOLIBC (both 32- and 64-bit) 4 * Copyright (C) 2017-2025 Willy Tarreau <w@1wt.eu> 5 */ 6 7 #ifndef _NOLIBC_ARCH_X86_H 8 #define _NOLIBC_ARCH_X86_H 9 10 #include "compiler.h" 11 #include "crt.h" 12 13 #if !defined(__x86_64__) 14 15 /* Syscalls for i386 : 16 * - mostly similar to x86_64 17 * - registers are 32-bit 18 * - syscall number is passed in eax 19 * - arguments are in ebx, ecx, edx, esi, edi, ebp respectively 20 * - all registers are preserved (except eax of course) 21 * - the system call is performed by calling int $0x80 22 * - syscall return comes in eax 23 * - the arguments are cast to long and assigned into the target registers 24 * which are then simply passed as registers to the asm code, so that we 25 * don't have to experience issues with register constraints. 26 * - the syscall number is always specified last in order to allow to force 27 * some registers before (gcc refuses a %-register at the last position). 28 * 29 * Also, i386 supports the old_select syscall if newselect is not available 30 */ 31 #define __ARCH_WANT_SYS_OLD_SELECT 32 33 #define my_syscall0(num) \ 34 ({ \ 35 long _ret; \ 36 register long _num __asm__ ("eax") = (num); \ 37 \ 38 __asm__ volatile ( \ 39 "int $0x80\n" \ 40 : "=a" (_ret) \ 41 : "0"(_num) \ 42 : "memory", "cc" \ 43 ); \ 44 _ret; \ 45 }) 46 47 #define my_syscall1(num, arg1) \ 48 ({ \ 49 long _ret; \ 50 register long _num __asm__ ("eax") = (num); \ 51 register long _arg1 __asm__ ("ebx") = (long)(arg1); \ 52 \ 53 __asm__ volatile ( \ 54 "int $0x80\n" \ 55 : "=a" (_ret) \ 56 : "r"(_arg1), \ 57 "0"(_num) \ 58 : "memory", "cc" \ 59 ); \ 60 _ret; \ 61 }) 62 63 #define my_syscall2(num, arg1, arg2) \ 64 ({ \ 65 long _ret; \ 66 register long _num __asm__ ("eax") = (num); \ 67 register long _arg1 __asm__ ("ebx") = (long)(arg1); \ 68 register long _arg2 __asm__ ("ecx") = (long)(arg2); \ 69 \ 70 __asm__ volatile ( \ 71 "int $0x80\n" \ 72 : "=a" (_ret) \ 73 : "r"(_arg1), "r"(_arg2), \ 74 "0"(_num) \ 75 : "memory", "cc" \ 76 ); \ 77 _ret; \ 78 }) 79 80 #define my_syscall3(num, arg1, arg2, arg3) \ 81 ({ \ 82 long _ret; \ 83 register long _num __asm__ ("eax") = (num); \ 84 register long _arg1 __asm__ ("ebx") = (long)(arg1); \ 85 register long _arg2 __asm__ ("ecx") = (long)(arg2); \ 86 register long _arg3 __asm__ ("edx") = (long)(arg3); \ 87 \ 88 __asm__ volatile ( \ 89 "int $0x80\n" \ 90 : "=a" (_ret) \ 91 : "r"(_arg1), "r"(_arg2), "r"(_arg3), \ 92 "0"(_num) \ 93 : "memory", "cc" \ 94 ); \ 95 _ret; \ 96 }) 97 98 #define my_syscall4(num, arg1, arg2, arg3, arg4) \ 99 ({ \ 100 long _ret; \ 101 register long _num __asm__ ("eax") = (num); \ 102 register long _arg1 __asm__ ("ebx") = (long)(arg1); \ 103 register long _arg2 __asm__ ("ecx") = (long)(arg2); \ 104 register long _arg3 __asm__ ("edx") = (long)(arg3); \ 105 register long _arg4 __asm__ ("esi") = (long)(arg4); \ 106 \ 107 __asm__ volatile ( \ 108 "int $0x80\n" \ 109 : "=a" (_ret) \ 110 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), \ 111 "0"(_num) \ 112 : "memory", "cc" \ 113 ); \ 114 _ret; \ 115 }) 116 117 #define my_syscall5(num, arg1, arg2, arg3, arg4, arg5) \ 118 ({ \ 119 long _ret; \ 120 register long _num __asm__ ("eax") = (num); \ 121 register long _arg1 __asm__ ("ebx") = (long)(arg1); \ 122 register long _arg2 __asm__ ("ecx") = (long)(arg2); \ 123 register long _arg3 __asm__ ("edx") = (long)(arg3); \ 124 register long _arg4 __asm__ ("esi") = (long)(arg4); \ 125 register long _arg5 __asm__ ("edi") = (long)(arg5); \ 126 \ 127 __asm__ volatile ( \ 128 "int $0x80\n" \ 129 : "=a" (_ret) \ 130 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \ 131 "0"(_num) \ 132 : "memory", "cc" \ 133 ); \ 134 _ret; \ 135 }) 136 137 #define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \ 138 ({ \ 139 long _eax = (long)(num); \ 140 long _arg6 = (long)(arg6); /* Always in memory */ \ 141 __asm__ volatile ( \ 142 "pushl %[_arg6]\n\t" \ 143 "pushl %%ebp\n\t" \ 144 "movl 4(%%esp),%%ebp\n\t" \ 145 "int $0x80\n\t" \ 146 "popl %%ebp\n\t" \ 147 "addl $4,%%esp\n\t" \ 148 : "+a"(_eax) /* %eax */ \ 149 : "b"(arg1), /* %ebx */ \ 150 "c"(arg2), /* %ecx */ \ 151 "d"(arg3), /* %edx */ \ 152 "S"(arg4), /* %esi */ \ 153 "D"(arg5), /* %edi */ \ 154 [_arg6]"m"(_arg6) /* memory */ \ 155 : "memory", "cc" \ 156 ); \ 157 _eax; \ 158 }) 159 160 /* startup code */ 161 /* 162 * i386 System V ABI mandates: 163 * 1) last pushed argument must be 16-byte aligned. 164 * 2) The deepest stack frame should be set to zero 165 * 166 */ 167 void __attribute__((weak, noreturn)) __nolibc_entrypoint __no_stack_protector _start(void) 168 { 169 __asm__ volatile ( 170 "xor %ebp, %ebp\n" /* zero the stack frame */ 171 "mov %esp, %eax\n" /* save stack pointer to %eax, as arg1 of _start_c */ 172 "sub $12, %esp\n" /* sub 12 to keep it aligned after the push %eax */ 173 "push %eax\n" /* push arg1 on stack to support plain stack modes too */ 174 "call _start_c\n" /* transfer to c runtime */ 175 "hlt\n" /* ensure it does not return */ 176 ); 177 __nolibc_entrypoint_epilogue(); 178 } 179 180 #else /* !defined(__x86_64__) */ 181 182 /* Syscalls for x86_64 : 183 * - registers are 64-bit 184 * - syscall number is passed in rax 185 * - arguments are in rdi, rsi, rdx, r10, r8, r9 respectively 186 * - the system call is performed by calling the syscall instruction 187 * - syscall return comes in rax 188 * - rcx and r11 are clobbered, others are preserved. 189 * - the arguments are cast to long and assigned into the target registers 190 * which are then simply passed as registers to the asm code, so that we 191 * don't have to experience issues with register constraints. 192 * - the syscall number is always specified last in order to allow to force 193 * some registers before (gcc refuses a %-register at the last position). 194 * - see also x86-64 ABI section A.2 AMD64 Linux Kernel Conventions, A.2.1 195 * Calling Conventions. 196 * 197 * Link x86-64 ABI: https://gitlab.com/x86-psABIs/x86-64-ABI/-/wikis/home 198 * 199 */ 200 201 #define my_syscall0(num) \ 202 ({ \ 203 long _ret; \ 204 register long _num __asm__ ("rax") = (num); \ 205 \ 206 __asm__ volatile ( \ 207 "syscall\n" \ 208 : "=a"(_ret) \ 209 : "0"(_num) \ 210 : "rcx", "r11", "memory", "cc" \ 211 ); \ 212 _ret; \ 213 }) 214 215 #define my_syscall1(num, arg1) \ 216 ({ \ 217 long _ret; \ 218 register long _num __asm__ ("rax") = (num); \ 219 register long _arg1 __asm__ ("rdi") = (long)(arg1); \ 220 \ 221 __asm__ volatile ( \ 222 "syscall\n" \ 223 : "=a"(_ret) \ 224 : "r"(_arg1), \ 225 "0"(_num) \ 226 : "rcx", "r11", "memory", "cc" \ 227 ); \ 228 _ret; \ 229 }) 230 231 #define my_syscall2(num, arg1, arg2) \ 232 ({ \ 233 long _ret; \ 234 register long _num __asm__ ("rax") = (num); \ 235 register long _arg1 __asm__ ("rdi") = (long)(arg1); \ 236 register long _arg2 __asm__ ("rsi") = (long)(arg2); \ 237 \ 238 __asm__ volatile ( \ 239 "syscall\n" \ 240 : "=a"(_ret) \ 241 : "r"(_arg1), "r"(_arg2), \ 242 "0"(_num) \ 243 : "rcx", "r11", "memory", "cc" \ 244 ); \ 245 _ret; \ 246 }) 247 248 #define my_syscall3(num, arg1, arg2, arg3) \ 249 ({ \ 250 long _ret; \ 251 register long _num __asm__ ("rax") = (num); \ 252 register long _arg1 __asm__ ("rdi") = (long)(arg1); \ 253 register long _arg2 __asm__ ("rsi") = (long)(arg2); \ 254 register long _arg3 __asm__ ("rdx") = (long)(arg3); \ 255 \ 256 __asm__ volatile ( \ 257 "syscall\n" \ 258 : "=a"(_ret) \ 259 : "r"(_arg1), "r"(_arg2), "r"(_arg3), \ 260 "0"(_num) \ 261 : "rcx", "r11", "memory", "cc" \ 262 ); \ 263 _ret; \ 264 }) 265 266 #define my_syscall4(num, arg1, arg2, arg3, arg4) \ 267 ({ \ 268 long _ret; \ 269 register long _num __asm__ ("rax") = (num); \ 270 register long _arg1 __asm__ ("rdi") = (long)(arg1); \ 271 register long _arg2 __asm__ ("rsi") = (long)(arg2); \ 272 register long _arg3 __asm__ ("rdx") = (long)(arg3); \ 273 register long _arg4 __asm__ ("r10") = (long)(arg4); \ 274 \ 275 __asm__ volatile ( \ 276 "syscall\n" \ 277 : "=a"(_ret) \ 278 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), \ 279 "0"(_num) \ 280 : "rcx", "r11", "memory", "cc" \ 281 ); \ 282 _ret; \ 283 }) 284 285 #define my_syscall5(num, arg1, arg2, arg3, arg4, arg5) \ 286 ({ \ 287 long _ret; \ 288 register long _num __asm__ ("rax") = (num); \ 289 register long _arg1 __asm__ ("rdi") = (long)(arg1); \ 290 register long _arg2 __asm__ ("rsi") = (long)(arg2); \ 291 register long _arg3 __asm__ ("rdx") = (long)(arg3); \ 292 register long _arg4 __asm__ ("r10") = (long)(arg4); \ 293 register long _arg5 __asm__ ("r8") = (long)(arg5); \ 294 \ 295 __asm__ volatile ( \ 296 "syscall\n" \ 297 : "=a"(_ret) \ 298 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \ 299 "0"(_num) \ 300 : "rcx", "r11", "memory", "cc" \ 301 ); \ 302 _ret; \ 303 }) 304 305 #define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \ 306 ({ \ 307 long _ret; \ 308 register long _num __asm__ ("rax") = (num); \ 309 register long _arg1 __asm__ ("rdi") = (long)(arg1); \ 310 register long _arg2 __asm__ ("rsi") = (long)(arg2); \ 311 register long _arg3 __asm__ ("rdx") = (long)(arg3); \ 312 register long _arg4 __asm__ ("r10") = (long)(arg4); \ 313 register long _arg5 __asm__ ("r8") = (long)(arg5); \ 314 register long _arg6 __asm__ ("r9") = (long)(arg6); \ 315 \ 316 __asm__ volatile ( \ 317 "syscall\n" \ 318 : "=a"(_ret) \ 319 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \ 320 "r"(_arg6), "0"(_num) \ 321 : "rcx", "r11", "memory", "cc" \ 322 ); \ 323 _ret; \ 324 }) 325 326 /* startup code */ 327 /* 328 * x86-64 System V ABI mandates: 329 * 1) %rsp must be 16-byte aligned right before the function call. 330 * 2) The deepest stack frame should be zero (the %rbp). 331 * 332 */ 333 void __attribute__((weak, noreturn)) __nolibc_entrypoint __no_stack_protector _start(void) 334 { 335 __asm__ volatile ( 336 "xor %ebp, %ebp\n" /* zero the stack frame */ 337 "mov %rsp, %rdi\n" /* save stack pointer to %rdi, as arg1 of _start_c */ 338 "call _start_c\n" /* transfer to c runtime */ 339 "hlt\n" /* ensure it does not return */ 340 ); 341 __nolibc_entrypoint_epilogue(); 342 } 343 344 #define NOLIBC_ARCH_HAS_MEMMOVE 345 void *memmove(void *dst, const void *src, size_t len); 346 347 #define NOLIBC_ARCH_HAS_MEMCPY 348 void *memcpy(void *dst, const void *src, size_t len); 349 350 #define NOLIBC_ARCH_HAS_MEMSET 351 void *memset(void *dst, int c, size_t len); 352 353 __asm__ ( 354 ".section .text.nolibc_memmove_memcpy\n" 355 ".weak memmove\n" 356 ".weak memcpy\n" 357 "memmove:\n" 358 "memcpy:\n" 359 "movq %rdx, %rcx\n\t" 360 "movq %rdi, %rax\n\t" 361 "movq %rdi, %rdx\n\t" 362 "subq %rsi, %rdx\n\t" 363 "cmpq %rcx, %rdx\n\t" 364 "jb 1f\n\t" 365 "rep movsb\n\t" 366 "retq\n" 367 "1:" /* backward copy */ 368 "leaq -1(%rdi, %rcx, 1), %rdi\n\t" 369 "leaq -1(%rsi, %rcx, 1), %rsi\n\t" 370 "std\n\t" 371 "rep movsb\n\t" 372 "cld\n\t" 373 "retq\n" 374 375 ".section .text.nolibc_memset\n" 376 ".weak memset\n" 377 "memset:\n" 378 "xchgl %eax, %esi\n\t" 379 "movq %rdx, %rcx\n\t" 380 "pushq %rdi\n\t" 381 "rep stosb\n\t" 382 "popq %rax\n\t" 383 "retq\n" 384 ); 385 386 #endif /* !defined(__x86_64__) */ 387 #endif /* _NOLIBC_ARCH_X86_H */ 388