Welcome to The Fiwix Project
Your small UNIX-like kernel
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1 /* 2 * fiwix/kernel/syscalls.c 3 * 4 * Copyright 2018-2022, Jordi Sanfeliu. All rights reserved. 5 * Distributed under the terms of the Fiwix License. 6 */ 7 8 #include <fiwix/types.h> 9 #include <fiwix/syscalls.h> 10 #include <fiwix/mm.h> 11 #include <fiwix/stat.h> 12 #include <fiwix/errno.h> 13 #include <fiwix/string.h> 14 15 #ifdef __DEBUG__ 16 #include <fiwix/stdio.h> 17 #endif /*__DEBUG__ */ 18 19 static int verify_address(int type, const void *addr, unsigned int size) 20 { 21 #ifdef CONFIG_LAZY_USER_ADDR_CHECK 22 if(!addr) { 23 return -EFAULT; 24 } 25 #else 26 struct vma *vma; 27 unsigned int start; 28 29 /* 30 * Verifies if the 'vma' array of that process is not empty. It can 31 * only be empty during the initialization of INIT, when it calls to 32 * sys_execve and sys_open without having yet a proper setup. 33 */ 34 if(current->vma[0].s_type != 0) { 35 start = (unsigned int)addr; 36 if(!(vma = find_vma_region(start))) { 37 return -EFAULT; 38 } 39 40 for(;;) { 41 if(type == VERIFY_WRITE) { 42 if(!(vma->prot & PROT_WRITE)) { 43 return -EFAULT; 44 } 45 } else { 46 if(!(vma->prot & PROT_READ)) { 47 return -EFAULT; 48 } 49 } 50 if(start + size < vma->end) { 51 break; 52 } 53 if(!(vma = find_vma_region(vma->end))) { 54 return -EFAULT; 55 } 56 } 57 } 58 #endif /* CONFIG_LAZY_USER_ADDR_CHECK */ 59 60 return 0; 61 } 62 63 void free_name(const char *name) 64 { 65 kfree((unsigned int)name); 66 } 67 68 /* 69 * This function has two objectives: 70 * 71 * 1. verifies the memory address validity of the char pointer supplied by the 72 * user and, at the same time, limits its length to PAGE_SIZE (4096) bytes. 73 * 2. creates a copy of 'filename' in the kernel data space before using it. 74 */ 75 int malloc_name(const char *filename, char **name) 76 { 77 short int n, len; 78 char *b; 79 int errno; 80 81 /* verifies only the pointer address */ 82 if((errno = verify_address(PROT_READ, filename, 0))) { 83 return errno; 84 } 85 86 len = MIN(strlen(filename), PAGE_SIZE); 87 if(!(b = (char *)kmalloc())) { 88 return -ENOMEM; 89 } 90 *name = b; 91 for(n = 0; n < (len + 1); n++) { 92 if(!(*b = *filename)) { 93 return 0; 94 } 95 b++; 96 filename++; 97 } 98 99 free_name(*name); 100 return -ENAMETOOLONG; 101 } 102 103 int check_user_permission(struct inode *i) 104 { 105 if(!IS_SUPERUSER) { 106 if(current->euid != i->i_uid) { 107 return 1; 108 } 109 } 110 return 0; 111 } 112 113 int check_group(struct inode *i) 114 { 115 int n; 116 __gid_t gid; 117 118 if(current->flags & PF_USEREAL) { 119 gid = current->gid; 120 } else { 121 gid = current->egid; 122 } 123 124 if(i->i_gid == gid) { 125 return 0; 126 } 127 128 for(n = 0; n < NGROUPS_MAX; n++) { 129 if(current->groups[n] == -1) { 130 break; 131 } 132 if(current->groups[n] == i->i_gid) { 133 return 0; 134 } 135 } 136 return 1; 137 } 138 139 int check_user_area(int type, const void *addr, unsigned int size) 140 { 141 return verify_address(type, addr, size); 142 } 143 144 int check_permission(int mask, struct inode *i) 145 { 146 __uid_t uid; 147 148 if(current->flags & PF_USEREAL) { 149 uid = current->uid; 150 } else { 151 uid = current->euid; 152 } 153 154 if(mask & TO_EXEC) { 155 if(!(i->i_mode & (S_IXUSR | S_IXGRP | S_IXOTH))) { 156 return -EACCES; 157 } 158 } 159 if(uid == 0) { 160 return 0; 161 } 162 if(i->i_uid == uid) { 163 if((((i->i_mode >> 6) & 7) & mask) == mask) { 164 return 0; 165 } 166 } 167 if(!check_group(i)) { 168 if((((i->i_mode >> 3) & 7) & mask) == mask) { 169 return 0; 170 } 171 } 172 if(((i->i_mode & 7) & mask) == mask) { 173 return 0; 174 } 175 176 return -EACCES; 177 } 178 179 180 /* Linux 2.0 ABI system call (plus some from Linux 2.2) */ 181 void *syscall_table[] = { 182 NULL, /* 0 */ /* sys_setup (-ENOSYS) */ 183 sys_exit, 184 sys_fork, 185 sys_read, 186 sys_write, 187 sys_open, /* 5 */ 188 sys_close, 189 sys_waitpid, 190 sys_creat, 191 sys_link, 192 sys_unlink, /* 10 */ 193 sys_execve, 194 sys_chdir, 195 sys_time, 196 sys_mknod, 197 sys_chmod, /* 15 */ 198 sys_chown, 199 NULL, /* sys_break (-ENOSYS) */ 200 sys_stat, 201 sys_lseek, 202 sys_getpid, /* 20 */ 203 sys_mount, 204 sys_umount, 205 sys_setuid, 206 sys_getuid, 207 sys_stime, /* 25 */ 208 NULL, /* sys_ptrace */ 209 sys_alarm, 210 sys_fstat, 211 sys_pause, 212 sys_utime, /* 30 */ 213 NULL, /* sys_stty (-ENOSYS) */ 214 NULL, /* sys_gtty (-ENOSYS) */ 215 sys_access, 216 NULL, /* sys_nice */ 217 sys_ftime, /* 35 */ 218 sys_sync, 219 sys_kill, 220 sys_rename, 221 sys_mkdir, 222 sys_rmdir, /* 40 */ 223 sys_dup, 224 sys_pipe, 225 sys_times, 226 NULL, /* sys_prof */ 227 sys_brk, /* 45 */ 228 sys_setgid, 229 sys_getgid, 230 sys_signal, 231 sys_geteuid, 232 sys_getegid, /* 50 */ 233 NULL, /* sys_acct */ 234 sys_umount2, 235 NULL, /* sys_lock (-ENOSYS) */ 236 sys_ioctl, 237 sys_fcntl, /* 55 */ 238 NULL, /* sys_mpx (-ENOSYS) */ 239 sys_setpgid, 240 NULL, /* sys_ulimit (-ENOSYS) */ 241 sys_olduname, 242 sys_umask, /* 60 */ 243 sys_chroot, 244 sys_ustat, 245 sys_dup2, 246 sys_getppid, 247 sys_getpgrp, /* 65 */ 248 sys_setsid, 249 sys_sigaction, 250 sys_sgetmask, 251 sys_ssetmask, 252 sys_setreuid, /* 70 */ 253 sys_setregid, 254 sys_sigsuspend, 255 sys_sigpending, 256 sys_sethostname, 257 sys_setrlimit, /* 75 */ 258 sys_getrlimit, 259 sys_getrusage, 260 sys_gettimeofday, 261 sys_settimeofday, 262 sys_getgroups, /* 80 */ 263 sys_setgroups, 264 old_select, 265 sys_symlink, 266 sys_lstat, 267 sys_readlink, /* 85 */ 268 NULL, /* sys_uselib */ 269 NULL, /* sys_swapon */ 270 sys_reboot, 271 NULL, /* old_readdir */ 272 old_mmap, /* 90 */ 273 sys_munmap, 274 sys_truncate, 275 sys_ftruncate, 276 sys_fchmod, 277 sys_fchown, /* 95 */ 278 NULL, /* sys_getpriority */ 279 NULL, /* sys_setpriority */ 280 NULL, /* sys_profil (-ENOSYS) */ 281 sys_statfs, 282 sys_fstatfs, /* 100 */ 283 sys_ioperm, 284 sys_socketcall, /* sys_socketcall XXX */ 285 NULL, /* sys_syslog */ 286 sys_setitimer, 287 sys_getitimer, /* 105 */ 288 sys_newstat, 289 sys_newlstat, 290 sys_newfstat, 291 sys_uname, 292 sys_iopl, /* 110 */ 293 NULL, /* sys_vhangup */ 294 NULL, /* sys_idle (-ENOSYS) */ 295 NULL, /* sys_vm86old */ 296 sys_wait4, 297 NULL, /* sys_swapoff */ /* 115 */ 298 sys_sysinfo, 299 #ifdef CONFIG_SYSVIPC 300 sys_ipc, 301 #else 302 NULL, /* sys_ipc */ 303 #endif /* CONFIG_SYSVIPC */ 304 sys_fsync, 305 sys_sigreturn, 306 NULL, /* sys_clone */ /* 120 */ 307 sys_setdomainname, 308 sys_newuname, 309 NULL, /* sys_modify_ldt */ 310 NULL, /* sys_adjtimex */ 311 sys_mprotect, /* 125 */ 312 sys_sigprocmask, 313 NULL, /* sys_create_module */ 314 NULL, /* sys_init_module */ 315 NULL, /* sys_delete_module */ 316 NULL, /* sys_get_kernel_syms */ /* 130 */ 317 NULL, /* sys_quotactl */ 318 sys_getpgid, 319 sys_fchdir, 320 NULL, /* sys_bdflush */ 321 NULL, /* sys_sysfs */ /* 135 */ 322 sys_personality, 323 NULL, /* afs_syscall (-ENOSYS) */ 324 sys_setfsuid, 325 sys_setfsgid, 326 sys_llseek, /* 140 */ 327 sys_getdents, 328 sys_select, 329 sys_flock, 330 NULL, /* sys_msync */ 331 NULL, /* sys_readv */ /* 145 */ 332 NULL, /* sys_writev */ 333 sys_getsid, 334 sys_fdatasync, 335 NULL, /* sys_sysctl */ 336 NULL, /* sys_mlock */ /* 150 */ 337 NULL, /* sys_munlock */ 338 NULL, /* sys_mlockall */ 339 NULL, /* sys_munlockall */ 340 NULL, /* sys_sched_setparam */ 341 NULL, /* sys_sched_getparam */ /* 155 */ 342 NULL, /* sys_sched_setscheduler */ 343 NULL, /* sys_sched_getscheduler */ 344 NULL, /* sys_sched_yield */ 345 NULL, /* sys_sched_get_priority_max */ 346 NULL, /* sys_sched_get_priority_min */ /* 160 */ 347 NULL, /* sys_sched_rr_get_interval */ 348 sys_nanosleep, 349 NULL, /* sys_mremap */ 350 NULL, 351 NULL, /* 165 */ 352 NULL, 353 NULL, 354 NULL, 355 NULL, 356 NULL, /* 170 */ 357 NULL, 358 NULL, 359 NULL, 360 NULL, 361 NULL, /* 175 */ 362 NULL, 363 NULL, 364 NULL, 365 NULL, 366 NULL, /* 180 */ 367 NULL, 368 sys_chown, 369 sys_getcwd, 370 NULL, 371 NULL, /* 185 */ 372 NULL, 373 NULL, 374 NULL, 375 NULL, 376 sys_fork, /* 190 (sys_vfork) */ 377 }; 378 379 static void do_bad_syscall(unsigned int num) 380 { 381 #ifdef __DEBUG__ 382 printk("***** (pid %d) system call %d not supported yet *****\n", current->pid, num); 383 #endif /*__DEBUG__ */ 384 } 385 386 /* 387 * The argument 'struct sigcontext' is needed because there are some system 388 * calls (such as sys_iopl and sys_fork) that need to get information from 389 * certain registers (EFLAGS and ESP). The rest of system calls will ignore 390 * such extra argument. 391 */ 392 #ifdef CONFIG_SYSCALL_6TH_ARG 393 int do_syscall(unsigned int num, int arg1, int arg2, int arg3, int arg4, int arg5, int arg6, struct sigcontext sc) 394 #else 395 int do_syscall(unsigned int num, int arg1, int arg2, int arg3, int arg4, int arg5, struct sigcontext sc) 396 #endif /* CONFIG_SYSCALL_6TH_ARG */ 397 { 398 int (*sys_func)(int, ...); 399 400 if(num > NR_SYSCALLS) { 401 do_bad_syscall(num); 402 return -ENOSYS; 403 } 404 sys_func = syscall_table[num]; 405 if(!sys_func) { 406 do_bad_syscall(num); 407 return -ENOSYS; 408 } 409 current->sp = (unsigned int)≻ 410 #ifdef CONFIG_SYSCALL_6TH_ARG 411 return sys_func(arg1, arg2, arg3, arg4, arg5, arg6, &sc); 412 #else 413 return sys_func(arg1, arg2, arg3, arg4, arg5, &sc); 414 #endif /* CONFIG_SYSCALL_6TH_ARG */ 415 }
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