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 30 #define __nolibc_syscall0(num) \ 31 ({ \ 32 long _ret; \ 33 register long _num __asm__ ("eax") = (num); \ 34 \ 35 __asm__ volatile ( \ 36 "int $0x80\n" \ 37 : "=a" (_ret) \ 38 : "0"(_num) \ 39 : "memory", "cc" \ 40 ); \ 41 _ret; \ 42 }) 43 44 #define __nolibc_syscall1(num, arg1) \ 45 ({ \ 46 long _ret; \ 47 register long _num __asm__ ("eax") = (num); \ 48 register long _arg1 __asm__ ("ebx") = (long)(arg1); \ 49 \ 50 __asm__ volatile ( \ 51 "int $0x80\n" \ 52 : "=a" (_ret) \ 53 : "r"(_arg1), \ 54 "0"(_num) \ 55 : "memory", "cc" \ 56 ); \ 57 _ret; \ 58 }) 59 60 #define __nolibc_syscall2(num, arg1, arg2) \ 61 ({ \ 62 long _ret; \ 63 register long _num __asm__ ("eax") = (num); \ 64 register long _arg1 __asm__ ("ebx") = (long)(arg1); \ 65 register long _arg2 __asm__ ("ecx") = (long)(arg2); \ 66 \ 67 __asm__ volatile ( \ 68 "int $0x80\n" \ 69 : "=a" (_ret) \ 70 : "r"(_arg1), "r"(_arg2), \ 71 "0"(_num) \ 72 : "memory", "cc" \ 73 ); \ 74 _ret; \ 75 }) 76 77 #define __nolibc_syscall3(num, arg1, arg2, arg3) \ 78 ({ \ 79 long _ret; \ 80 register long _num __asm__ ("eax") = (num); \ 81 register long _arg1 __asm__ ("ebx") = (long)(arg1); \ 82 register long _arg2 __asm__ ("ecx") = (long)(arg2); \ 83 register long _arg3 __asm__ ("edx") = (long)(arg3); \ 84 \ 85 __asm__ volatile ( \ 86 "int $0x80\n" \ 87 : "=a" (_ret) \ 88 : "r"(_arg1), "r"(_arg2), "r"(_arg3), \ 89 "0"(_num) \ 90 : "memory", "cc" \ 91 ); \ 92 _ret; \ 93 }) 94 95 #define __nolibc_syscall4(num, arg1, arg2, arg3, arg4) \ 96 ({ \ 97 long _ret; \ 98 register long _num __asm__ ("eax") = (num); \ 99 register long _arg1 __asm__ ("ebx") = (long)(arg1); \ 100 register long _arg2 __asm__ ("ecx") = (long)(arg2); \ 101 register long _arg3 __asm__ ("edx") = (long)(arg3); \ 102 register long _arg4 __asm__ ("esi") = (long)(arg4); \ 103 \ 104 __asm__ volatile ( \ 105 "int $0x80\n" \ 106 : "=a" (_ret) \ 107 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), \ 108 "0"(_num) \ 109 : "memory", "cc" \ 110 ); \ 111 _ret; \ 112 }) 113 114 #define __nolibc_syscall5(num, arg1, arg2, arg3, arg4, arg5) \ 115 ({ \ 116 long _ret; \ 117 register long _num __asm__ ("eax") = (num); \ 118 register long _arg1 __asm__ ("ebx") = (long)(arg1); \ 119 register long _arg2 __asm__ ("ecx") = (long)(arg2); \ 120 register long _arg3 __asm__ ("edx") = (long)(arg3); \ 121 register long _arg4 __asm__ ("esi") = (long)(arg4); \ 122 register long _arg5 __asm__ ("edi") = (long)(arg5); \ 123 \ 124 __asm__ volatile ( \ 125 "int $0x80\n" \ 126 : "=a" (_ret) \ 127 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \ 128 "0"(_num) \ 129 : "memory", "cc" \ 130 ); \ 131 _ret; \ 132 }) 133 134 #define __nolibc_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \ 135 ({ \ 136 long _eax = (long)(num); \ 137 long _arg6 = (long)(arg6); /* Always in memory */ \ 138 __asm__ volatile ( \ 139 "pushl %[_arg6]\n\t" \ 140 "pushl %%ebp\n\t" \ 141 "movl 4(%%esp),%%ebp\n\t" \ 142 "int $0x80\n\t" \ 143 "popl %%ebp\n\t" \ 144 "addl $4,%%esp\n\t" \ 145 : "+a"(_eax) /* %eax */ \ 146 : "b"(arg1), /* %ebx */ \ 147 "c"(arg2), /* %ecx */ \ 148 "d"(arg3), /* %edx */ \ 149 "S"(arg4), /* %esi */ \ 150 "D"(arg5), /* %edi */ \ 151 [_arg6]"m"(_arg6) /* memory */ \ 152 : "memory", "cc" \ 153 ); \ 154 _eax; \ 155 }) 156 157 #ifndef NOLIBC_NO_RUNTIME 158 /* startup code */ 159 /* 160 * i386 System V ABI mandates: 161 * 1) last pushed argument must be 16-byte aligned. 162 * 2) The deepest stack frame should be set to zero 163 * 164 */ 165 void __attribute__((weak, noreturn)) __nolibc_entrypoint __nolibc_no_stack_protector _start(void) 166 { 167 __asm__ volatile ( 168 "xor %ebp, %ebp\n" /* zero the stack frame */ 169 "mov %esp, %eax\n" /* save stack pointer to %eax, as arg1 of _start_c */ 170 "sub $12, %esp\n" /* sub 12 to keep it aligned after the push %eax */ 171 "push %eax\n" /* push arg1 on stack to support plain stack modes too */ 172 "call _start_c\n" /* transfer to c runtime */ 173 "hlt\n" /* ensure it does not return */ 174 ); 175 __nolibc_entrypoint_epilogue(); 176 } 177 #endif /* NOLIBC_NO_RUNTIME */ 178 179 #else /* !defined(__x86_64__) */ 180 181 /* Syscalls for x86_64 : 182 * - registers are 64-bit 183 * - syscall number is passed in rax 184 * - arguments are in rdi, rsi, rdx, r10, r8, r9 respectively 185 * - the system call is performed by calling the syscall instruction 186 * - syscall return comes in rax 187 * - rcx and r11 are clobbered, others are preserved. 188 * - the arguments are cast to long and assigned into the target registers 189 * which are then simply passed as registers to the asm code, so that we 190 * don't have to experience issues with register constraints. 191 * - the syscall number is always specified last in order to allow to force 192 * some registers before (gcc refuses a %-register at the last position). 193 * - see also x86-64 ABI section A.2 AMD64 Linux Kernel Conventions, A.2.1 194 * Calling Conventions. 195 * 196 * Link x86-64 ABI: https://gitlab.com/x86-psABIs/x86-64-ABI/-/wikis/home 197 * 198 */ 199 200 #define __nolibc_syscall0(num) \ 201 ({ \ 202 long long _ret; \ 203 register long long _num __asm__ ("rax") = (num); \ 204 \ 205 __asm__ volatile ( \ 206 "syscall\n" \ 207 : "=a"(_ret) \ 208 : "0"(_num) \ 209 : "rcx", "r11", "memory", "cc" \ 210 ); \ 211 _ret; \ 212 }) 213 214 #define __nolibc_syscall1(num, arg1) \ 215 ({ \ 216 long long _ret; \ 217 register long long _num __asm__ ("rax") = (num); \ 218 register long long _arg1 __asm__ ("rdi") = __nolibc_arg_to_reg(arg1); \ 219 \ 220 __asm__ volatile ( \ 221 "syscall\n" \ 222 : "=a"(_ret) \ 223 : "r"(_arg1), \ 224 "0"(_num) \ 225 : "rcx", "r11", "memory", "cc" \ 226 ); \ 227 _ret; \ 228 }) 229 230 #define __nolibc_syscall2(num, arg1, arg2) \ 231 ({ \ 232 long long _ret; \ 233 register long long _num __asm__ ("rax") = (num); \ 234 register long long _arg1 __asm__ ("rdi") = __nolibc_arg_to_reg(arg1); \ 235 register long long _arg2 __asm__ ("rsi") = __nolibc_arg_to_reg(arg2); \ 236 \ 237 __asm__ volatile ( \ 238 "syscall\n" \ 239 : "=a"(_ret) \ 240 : "r"(_arg1), "r"(_arg2), \ 241 "0"(_num) \ 242 : "rcx", "r11", "memory", "cc" \ 243 ); \ 244 _ret; \ 245 }) 246 247 #define __nolibc_syscall3(num, arg1, arg2, arg3) \ 248 ({ \ 249 long long _ret; \ 250 register long long _num __asm__ ("rax") = (num); \ 251 register long long _arg1 __asm__ ("rdi") = __nolibc_arg_to_reg(arg1); \ 252 register long long _arg2 __asm__ ("rsi") = __nolibc_arg_to_reg(arg2); \ 253 register long long _arg3 __asm__ ("rdx") = __nolibc_arg_to_reg(arg3); \ 254 \ 255 __asm__ volatile ( \ 256 "syscall\n" \ 257 : "=a"(_ret) \ 258 : "r"(_arg1), "r"(_arg2), "r"(_arg3), \ 259 "0"(_num) \ 260 : "rcx", "r11", "memory", "cc" \ 261 ); \ 262 _ret; \ 263 }) 264 265 #define __nolibc_syscall4(num, arg1, arg2, arg3, arg4) \ 266 ({ \ 267 long long _ret; \ 268 register long long _num __asm__ ("rax") = (num); \ 269 register long long _arg1 __asm__ ("rdi") = __nolibc_arg_to_reg(arg1); \ 270 register long long _arg2 __asm__ ("rsi") = __nolibc_arg_to_reg(arg2); \ 271 register long long _arg3 __asm__ ("rdx") = __nolibc_arg_to_reg(arg3); \ 272 register long long _arg4 __asm__ ("r10") = __nolibc_arg_to_reg(arg4); \ 273 \ 274 __asm__ volatile ( \ 275 "syscall\n" \ 276 : "=a"(_ret) \ 277 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), \ 278 "0"(_num) \ 279 : "rcx", "r11", "memory", "cc" \ 280 ); \ 281 _ret; \ 282 }) 283 284 #define __nolibc_syscall5(num, arg1, arg2, arg3, arg4, arg5) \ 285 ({ \ 286 long long _ret; \ 287 register long long _num __asm__ ("rax") = (num); \ 288 register long long _arg1 __asm__ ("rdi") = __nolibc_arg_to_reg(arg1); \ 289 register long long _arg2 __asm__ ("rsi") = __nolibc_arg_to_reg(arg2); \ 290 register long long _arg3 __asm__ ("rdx") = __nolibc_arg_to_reg(arg3); \ 291 register long long _arg4 __asm__ ("r10") = __nolibc_arg_to_reg(arg4); \ 292 register long long _arg5 __asm__ ("r8") = __nolibc_arg_to_reg(arg5); \ 293 \ 294 __asm__ volatile ( \ 295 "syscall\n" \ 296 : "=a"(_ret) \ 297 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \ 298 "0"(_num) \ 299 : "rcx", "r11", "memory", "cc" \ 300 ); \ 301 _ret; \ 302 }) 303 304 #define __nolibc_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \ 305 ({ \ 306 long long _ret; \ 307 register long long _num __asm__ ("rax") = (num); \ 308 register long long _arg1 __asm__ ("rdi") = __nolibc_arg_to_reg(arg1); \ 309 register long long _arg2 __asm__ ("rsi") = __nolibc_arg_to_reg(arg2); \ 310 register long long _arg3 __asm__ ("rdx") = __nolibc_arg_to_reg(arg3); \ 311 register long long _arg4 __asm__ ("r10") = __nolibc_arg_to_reg(arg4); \ 312 register long long _arg5 __asm__ ("r8") = __nolibc_arg_to_reg(arg5); \ 313 register long long _arg6 __asm__ ("r9") = __nolibc_arg_to_reg(arg6); \ 314 \ 315 __asm__ volatile ( \ 316 "syscall\n" \ 317 : "=a"(_ret) \ 318 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \ 319 "r"(_arg6), "0"(_num) \ 320 : "rcx", "r11", "memory", "cc" \ 321 ); \ 322 _ret; \ 323 }) 324 325 #ifndef NOLIBC_NO_RUNTIME 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 __nolibc_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 #endif /* NOLIBC_NO_RUNTIME */ 344 345 #define NOLIBC_ARCH_HAS_MEMMOVE 346 void *memmove(void *dst, const void *src, size_t len); 347 348 #define NOLIBC_ARCH_HAS_MEMCPY 349 void *memcpy(void *dst, const void *src, size_t len); 350 351 #define NOLIBC_ARCH_HAS_MEMSET 352 void *memset(void *dst, int c, size_t len); 353 354 __asm__ ( 355 ".pushsection .text.nolibc_memmove_memcpy\n" 356 ".weak memmove\n" 357 ".weak memcpy\n" 358 "memmove:\n" 359 "memcpy:\n" 360 "movq %rdx, %rcx\n\t" 361 "movq %rdi, %rax\n\t" 362 "movq %rdi, %rdx\n\t" 363 "subq %rsi, %rdx\n\t" 364 "cmpq %rcx, %rdx\n\t" 365 "jb 1f\n\t" 366 "rep movsb\n\t" 367 "retq\n" 368 "1:" /* backward copy */ 369 "leaq -1(%rdi, %rcx, 1), %rdi\n\t" 370 "leaq -1(%rsi, %rcx, 1), %rsi\n\t" 371 "std\n\t" 372 "rep movsb\n\t" 373 "cld\n\t" 374 "retq\n" 375 ".popsection\n" 376 377 ".pushsection .text.nolibc_memset\n" 378 ".weak memset\n" 379 "memset:\n" 380 "xchgl %eax, %esi\n\t" 381 "movq %rdx, %rcx\n\t" 382 "pushq %rdi\n\t" 383 "rep stosb\n\t" 384 "popq %rax\n\t" 385 "retq\n" 386 ".popsection\n" 387 ); 388 389 #endif /* !defined(__x86_64__) */ 390 #endif /* _NOLIBC_ARCH_X86_H */ 391