system calls(系统调用)
1 [root@rockylinux tmp]# uname -a
2 Linux rockylinux 4.18.0-372.26.1.el8_6.x86_64 #1 SMP Tue Sep 13 18:09:48 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
3 [root@rockylinux tmp]#
4 [root@rockylinux tmp]# man syscalls
5 [root@rockylinux tmp]#
6
7
8 SYSCALLS(2) Linux Programmer's Manual SYSCALLS(2)
9
10 NAME
11 syscalls - Linux system calls
12
13 SYNOPSIS
14 Linux system calls.
15
16 DESCRIPTION
17 The system call is the fundamental interface between an application and the Linux kernel.
18
19 System calls and library wrapper functions
20 System calls are generally not invoked directly, but rather via wrapper functions in glibc (or perhaps some other library). For
21 details of direct invocation of a system call, see intro(2). Often, but not always, the name of the wrapper function is the same as
22 the name of the system call that it invokes. For example, glibc contains a function truncate() which invokes the underlying "trun‐
23 cate" system call.
24
25 Often the glibc wrapper function is quite thin, doing little work other than copying arguments to the right registers before invok‐
26 ing the system call, and then setting errno appropriately after the system call has returned. (These are the same steps that are
27 performed by syscall(2), which can be used to invoke system calls for which no wrapper function is provided.) Note: system calls
28 indicate a failure by returning a negative error number to the caller; when this happens, the wrapper function negates the returned
29 error number (to make it positive), copies it to errno, and returns -1 to the caller of the wrapper.
30
31 Sometimes, however, the wrapper function does some extra work before invoking the system call. For example, nowadays there are (for
32 reasons described below) two related system calls, truncate(2) and truncate64(2), and the glibc truncate() wrapper function checks
33 which of those system calls are provided by the kernel and determines which should be employed.
34
35 System call list
36 Below is a list of the Linux system calls. In the list, the Kernel column indicates the kernel version for those system calls that
37 were new in Linux 2.2, or have appeared since that kernel version. Note the following points:
38
39 * Where no kernel version is indicated, the system call appeared in kernel 1.0 or earlier.
40
41 * Where a system call is marked "1.2" this means the system call probably appeared in a 1.1.x kernel version, and first appeared in
42 a stable kernel with 1.2. (Development of the 1.2 kernel was initiated from a branch of kernel 1.0.6 via the 1.1.x unstable ker‐
43 nel series.)
44
45 * Where a system call is marked "2.0" this means the system call probably appeared in a 1.3.x kernel version, and first appeared in
46 a stable kernel with 2.0. (Development of the 2.0 kernel was initiated from a branch of kernel 1.2.x, somewhere around 1.2.10,
47 via the 1.3.x unstable kernel series.)
48
49 * Where a system call is marked "2.2" this means the system call probably appeared in a 2.1.x kernel version, and first appeared in
50 a stable kernel with 2.2.0. (Development of the 2.2 kernel was initiated from a branch of kernel 2.0.21 via the 2.1.x unstable
51 kernel series.)
52
53 * Where a system call is marked "2.4" this means the system call probably appeared in a 2.3.x kernel version, and first appeared in
54 a stable kernel with 2.4.0. (Development of the 2.4 kernel was initiated from a branch of kernel 2.2.8 via the 2.3.x unstable
55 kernel series.)
56
57 * Where a system call is marked "2.6" this means the system call probably appeared in a 2.5.x kernel version, and first appeared in
58 a stable kernel with 2.6.0. (Development of kernel 2.6 was initiated from a branch of kernel 2.4.15 via the 2.5.x unstable ker‐
59 nel series.)
60
61 * Starting with kernel 2.6.0, the development model changed, and new system calls may appear in each 2.6.x release. In this case,
62 the exact version number where the system call appeared is shown. This convention continues with the 3.x kernel series, which
63 followed on from kernel 2.6.39, and the 4.x kernel series, which followed on from kernel 3.19.
64
65 * In some cases, a system call was added to a stable kernel series after it branched from the previous stable kernel series, and
66 then backported into the earlier stable kernel series. For example some system calls that appeared in 2.6.x were also backported
67 into a 2.4.x release after 2.4.15. When this is so, the version where the system call appeared in both of the major kernel
68 series is listed.
69
70 The list of system calls that are available as at kernel 4.11 (or in a few cases only on older kernels) is as follows:
71
72 System call Kernel Notes
73 ───────────────────────────────────────────────────────────────────────────
74
75 _llseek(2) 1.2
76 _newselect(2) 2.0
77 _sysctl(2) 2.0
78 accept(2) 2.0 See notes on socketcall(2)
79 accept4(2) 2.6.28
80 access(2) 1.0
81 acct(2) 1.0
82 add_key(2) 2.6.10
83 adjtimex(2) 1.0
84 alarm(2) 1.0
85 alloc_hugepages(2) 2.5.36 Removed in 2.5.44
86 bdflush(2) 1.2 Deprecated (does nothing)
87 since 2.6
88 bind(2) 2.0 See notes on socketcall(2)
89 bpf(2) 3.18
90 brk(2) 1.0
91 cacheflush(2) 1.2 Not on x86
92 capget(2) 2.2
93 capset(2) 2.2
94 chdir(2) 1.0
95 chmod(2) 1.0
96 chown(2) 2.2 See chown(2) for
97 version details
98 chown32(2) 2.4
99 chroot(2) 1.0
100 clock_adjtime(2) 2.6.39
101 clock_getres(2) 2.6
102 clock_gettime(2) 2.6
103 clock_nanosleep(2) 2.6
104 clock_settime(2) 2.6
105 clone(2) 1.0
106 close(2) 1.0
107 connect(2) 2.0 See notes on socketcall(2)
108 copy_file_range(2) 4.5
109 creat(2) 1.0
110 create_module(2) 1.0 Removed in 2.6
111 delete_module(2) 1.0
112 dup(2) 1.0
113 dup2(2) 1.0
114 dup3(2) 2.6.27
115 epoll_create(2) 2.6
116 epoll_create1(2) 2.6.27
117 epoll_ctl(2) 2.6
118 epoll_pwait(2) 2.6.19
119 epoll_wait(2) 2.6
120 eventfd(2) 2.6.22
121 eventfd2(2) 2.6.27
122 execve(2) 1.0
123 execveat(2) 3.19
124 exit(2) 1.0
125 exit_group(2) 2.6
126 faccessat(2) 2.6.16
127 fadvise64(2) 2.6
128 fadvise64_64(2) 2.6
129 fallocate(2) 2.6.23
130 fanotify_init(2) 2.6.37
131 fanotify_mark(2) 2.6.37
132 fchdir(2) 1.0
133 fchmod(2) 1.0
134 fchmodat(2) 2.6.16
135 fchown(2) 1.0
136 fchown32(2) 2.4
137
138 fchownat(2) 2.6.16
139 fcntl(2) 1.0
140 fcntl64(2) 2.4
141 fdatasync(2) 2.0
142 fgetxattr(2) 2.6; 2.4.18
143 finit_module(2) 3.8
144 flistxattr(2) 2.6; 2.4.18
145 flock(2) 2.0
146 fork(2) 1.0
147 free_hugepages(2) 2.5.36 Removed in 2.5.44
148 fremovexattr(2) 2.6; 2.4.18
149 fsetxattr(2) 2.6; 2.4.18
150 fstat(2) 1.0
151 fstat64(2) 2.4
152 fstatat64(2) 2.6.16
153 fstatfs(2) 1.0
154 fstatfs64(2) 2.6
155 fsync(2) 1.0
156 ftruncate(2) 1.0
157 ftruncate64(2) 2.4
158 futex(2) 2.6
159 futimesat(2) 2.6.16
160 get_kernel_syms(2) 1.0 Removed in 2.6
161 get_mempolicy(2) 2.6.6
162 get_robust_list(2) 2.6.17
163 get_thread_area(2) 2.6
164 getcpu(2) 2.6.19
165 getcwd(2) 2.2
166 getdents(2) 2.0
167 getdents64(2) 2.4
168 getegid(2) 1.0
169 getegid32(2) 2.4
170 geteuid(2) 1.0
171 geteuid32(2) 2.4
172 getgid(2) 1.0
173 getgid32(2) 2.4
174 getgroups(2) 1.0
175 getgroups32(2) 2.4
176 getitimer(2) 1.0
177 getpeername(2) 2.0 See notes on socketcall(2)
178 getpagesize(2) 2.0 Not on x86
179 getpgid(2) 1.0
180 getpgrp(2) 1.0
181 getpid(2) 1.0
182 getppid(2) 1.0
183 getpriority(2) 1.0
184 getrandom(2) 3.17
185 getresgid(2) 2.2
186 getresgid32(2) 2.4
187 getresuid(2) 2.2
188 getresuid32(2) 2.4
189 getrlimit(2) 1.0
190 getrusage(2) 1.0
191 getsid(2) 2.0
192 getsockname(2) 2.0 See notes on socketcall(2)
193 getsockopt(2) 2.0 See notes on socketcall(2)
194 gettid(2) 2.4.11
195 gettimeofday(2) 1.0
196 getuid(2) 1.0
197 getuid32(2) 2.4
198 getunwind(2) 2.4.8 ia64; deprecated
199 getxattr(2) 2.6; 2.4.18
200 init_module(2) 1.0
201 inotify_add_watch(2) 2.6.13
202 inotify_init(2) 2.6.13
203
204 inotify_init1(2) 2.6.27
205 inotify_rm_watch(2) 2.6.13
206 io_cancel(2) 2.6
207 io_destroy(2) 2.6
208 io_getevents(2) 2.6
209 io_setup(2) 2.6
210 io_submit(2) 2.6
211 ioctl(2) 1.0
212 ioperm(2) 1.0
213 iopl(2) 1.0
214 ioprio_get(2) 2.6.13
215 ioprio_set(2) 2.6.13
216 ipc(2) 1.0
217 kcmp(2) 3.5
218 kern_features(2) 3.7 Sparc64
219 kexec_file_load(2) 3.17
220 kexec_load(2) 2.6.13
221 keyctl(2) 2.6.10
222 kill(2) 1.0
223 lchown(2) 1.0 See chown(2) for
224 version details
225 lchown32(2) 2.4
226 lgetxattr(2) 2.6; 2.4.18
227 link(2) 1.0
228 linkat(2) 2.6.16
229 listen(2) 2.0 See notes on socketcall(2)
230 listxattr(2) 2.6; 2.4.18
231 llistxattr(2) 2.6; 2.4.18
232 lookup_dcookie(2) 2.6
233 lremovexattr(2) 2.6; 2.4.18
234 lseek(2) 1.0
235 lsetxattr(2) 2.6; 2.4.18
236 lstat(2) 1.0
237 lstat64(2) 2.4
238 madvise(2) 2.4
239 mbind(2) 2.6.6
240 membarrier(2) 3.17
241 memfd_create(2) 3.17
242 migrate_pages(2) 2.6.16
243 mincore(2) 2.4
244 mkdir(2) 1.0
245 mkdirat(2) 2.6.16
246 mknod(2) 1.0
247 mknodat(2) 2.6.16
248 mlock(2) 2.0
249 mlock2(2) 4.4
250 mlockall(2) 2.0
251 mmap(2) 1.0
252 mmap2(2) 2.4
253 modify_ldt(2) 1.0
254 mount(2) 1.0
255 move_pages(2) 2.6.18
256 mprotect(2) 1.0
257 mq_getsetattr(2) 2.6.6
258 mq_notify(2) 2.6.6
259 mq_open(2) 2.6.6
260 mq_timedreceive(2) 2.6.6
261 mq_timedsend(2) 2.6.6
262 mq_unlink(2) 2.6.6
263 mremap(2) 2.0
264 msgctl(2) 2.0 See notes on ipc(2)
265 msgget(2) 2.0 See notes on ipc(2)
266 msgrcv(2) 2.0 See notes on ipc(2)
267 msgsnd(2) 2.0 See notes on ipc(2)
268 msync(2) 2.0
269
270 munlock(2) 2.0
271 munlockall(2) 2.0
272 munmap(2) 1.0
273 name_to_handle_at(2) 2.6.39
274 nanosleep(2) 2.0
275 nfsservctl(2) 2.2 Removed in 3.1
276 nice(2) 1.0
277 oldfstat(2) 1.0
278 oldlstat(2) 1.0
279 oldolduname(2) 1.0
280 oldstat(2) 1.0
281 olduname(2) 1.0
282 open(2) 1.0
283 open_by_handle_at(2) 2.6.39
284 openat(2) 2.6.16
285 pause(2) 1.0
286 pciconfig_iobase(2) 2.2.15; 2.4 Not on x86
287 pciconfig_read(2) 2.0.26; 2.2 Not on x86
288 pciconfig_write(2) 2.0.26; 2.2 Not on x86
289 perf_event_open(2) 2.6.31 Was perf_counter_open() in
290 2.6.31; renamed in 2.6.32
291 personality(2) 1.2
292 perfctr(2) 2.2 Sparc; removed in 2.6.34
293 perfmonctl(2) 2.4 ia64
294 pipe(2) 1.0
295 pipe2(2) 2.6.27
296 pivot_root(2) 2.4
297 pkey_alloc(2) 4.8
298 pkey_free(2) 4.8
299 pkey_mprotect(2) 4.8
300 poll(2) 2.0.36; 2.2
301 ppc_rtas(2) 2.6.2 PowerPC only
302 ppc_swapcontext(2) 2.6.3 PowerPC only
303 ppoll(2) 2.6.16
304 prctl(2) 2.2
305 pread64(2) Added as "pread" in 2.2;
306 renamed "pread64" in 2.6
307 preadv(2) 2.6.30
308 preadv2(2) 4.6
309 prlimit64(2) 2.6.36
310 process_vm_readv(2) 3.2
311 process_vm_writev(2) 3.2
312 pselect6(2) 2.6.16
313 ptrace(2) 1.0
314 pwrite64(2) Added as "pwrite" in 2.2;
315 renamed "pwrite64" in 2.6
316 pwritev(2) 2.6.30
317 pwritev2(2) 4.6
318 query_module(2) 2.2 Removed in 2.6
319 quotactl(2) 1.0
320 read(2) 1.0
321 readahead(2) 2.4.13
322 readdir(2) 1.0
323 readlink(2) 1.0
324 readlinkat(2) 2.6.16
325 readv(2) 2.0
326 reboot(2) 1.0
327 recv(2) 2.0 See notes on socketcall(2)
328 recvfrom(2) 2.0 See notes on socketcall(2)
329 recvmsg(2) 2.0 See notes on socketcall(2)
330 recvmmsg(2) 2.6.33
331 remap_file_pages(2) 2.6 Deprecated since 3.16
332 removexattr(2) 2.6; 2.4.18
333 rename(2) 1.0
334 renameat(2) 2.6.16
335
336 renameat2(2) 3.15
337 request_key(2) 2.6.10
338 restart_syscall(2) 2.6
339 rmdir(2) 1.0
340 rt_sigaction(2) 2.2
341 rt_sigpending(2) 2.2
342 rt_sigprocmask(2) 2.2
343 rt_sigqueueinfo(2) 2.2
344 rt_sigreturn(2) 2.2
345 rt_sigsuspend(2) 2.2
346 rt_sigtimedwait(2) 2.2
347 rt_tgsigqueueinfo(2) 2.6.31
348 s390_runtime_instr(2) 3.7 s390 only
349 s390_pci_mmio_read(2) 3.19 s390 only
350 s390_pci_mmio_write(2) 3.19 s390 only
351 s390_sthyi(2) 4.15 s390 only
352 sched_get_priority_max(2) 2.0
353 sched_get_priority_min(2) 2.0
354 sched_getaffinity(2) 2.6
355 sched_getattr(2) 3.14
356 sched_getparam(2) 2.0
357 sched_getscheduler(2) 2.0
358 sched_rr_get_interval(2) 2.0
359 sched_setaffinity(2) 2.6
360 sched_setattr(2) 3.14
361 sched_setparam(2) 2.0
362 sched_setscheduler(2) 2.0
363 sched_yield(2) 2.0
364 seccomp(2) 3.17
365 select(2) 1.0
366 semctl(2) 2.0 See notes on ipc(2)
367 semget(2) 2.0 See notes on ipc(2)
368 semop(2) 2.0 See notes on ipc(2)
369 semtimedop(2) 2.6; 2.4.22
370 send(2) 2.0 See notes on socketcall(2)
371 sendfile(2) 2.2
372 sendfile64(2) 2.6; 2.4.19
373 sendmmsg(2) 3.0
374 sendmsg(2) 2.0 See notes on socketcall(2)
375 sendto(2) 2.0 See notes on socketcall(2)
376 set_mempolicy(2) 2.6.6
377 set_robust_list(2) 2.6.17
378 set_thread_area(2) 2.6
379 set_tid_address(2) 2.6
380 setdomainname(2) 1.0
381 setfsgid(2) 1.2
382 setfsgid32(2) 2.4
383 setfsuid(2) 1.2
384 setfsuid32(2) 2.4
385 setgid(2) 1.0
386 setgid32(2) 2.4
387 setgroups(2) 1.0
388 setgroups32(2) 2.4
389 sethostname(2) 1.0
390 setitimer(2) 1.0
391 setns(2) 3.0
392 setpgid(2) 1.0
393 setpriority(2) 1.0
394 setregid(2) 1.0
395 setregid32(2) 2.4
396 setresgid(2) 2.2
397 setresgid32(2) 2.4
398 setresuid(2) 2.2
399 setresuid32(2) 2.4
400 setreuid(2) 1.0
401
402 setreuid32(2) 2.4
403 setrlimit(2) 1.0
404 setsid(2) 1.0
405 setsockopt(2) 2.0 See notes on socketcall(2)
406 settimeofday(2) 1.0
407 setuid(2) 1.0
408 setuid32(2) 2.4
409 setup(2) 1.0 Removed in 2.2
410 setxattr(2) 2.6; 2.4.18
411 sgetmask(2) 1.0
412 shmat(2) 2.0 See notes on ipc(2)
413 shmctl(2) 2.0 See notes on ipc(2)
414 shmdt(2) 2.0 See notes on ipc(2)
415 shmget(2) 2.0 See notes on ipc(2)
416 shutdown(2) 2.0 See notes on socketcall(2)
417 sigaction(2) 1.0
418 sigaltstack(2) 2.2
419 signal(2) 1.0
420 signalfd(2) 2.6.22
421 signalfd4(2) 2.6.27
422 sigpending(2) 1.0
423 sigprocmask(2) 1.0
424 sigreturn(2) 1.0
425 sigsuspend(2) 1.0
426 socket(2) 2.0 See notes on socketcall(2)
427 socketcall(2) 1.0
428 socketpair(2) 2.0 See notes on socketcall(2)
429 splice(2) 2.6.17
430 spu_create(2) 2.6.16 PowerPC only
431 spu_run(2) 2.6.16 PowerPC only
432 ssetmask(2) 1.0
433 stat(2) 1.0
434 stat64(2) 2.4
435 statfs(2) 1.0
436 statfs64(2) 2.6
437 statx(2) 4.11
438 stime(2) 1.0
439 subpage_prot(2) 2.6.25 PowerPC only
440 swapoff(2) 1.0
441 swapon(2) 1.0
442 symlink(2) 1.0
443 symlinkat(2) 2.6.16
444 sync(2) 1.0
445 sync_file_range(2) 2.6.17
446 sync_file_range2(2) 2.6.22
447 syncfs(2) 2.6.39
448 sysfs(2) 1.2
449 sysinfo(2) 1.0
450 syslog(2) 1.0
451 tee(2) 2.6.17
452 tgkill(2) 2.6
453 time(2) 1.0
454 timer_create(2) 2.6
455 timer_delete(2) 2.6
456 timer_getoverrun(2) 2.6
457 timer_gettime(2) 2.6
458 timer_settime(2) 2.6
459 timerfd_create(2) 2.6.25
460 timerfd_gettime(2) 2.6.25
461 timerfd_settime(2) 2.6.25
462 times(2) 1.0
463 tkill(2) 2.6; 2.4.22
464 truncate(2) 1.0
465 truncate64(2) 2.4
466 ugetrlimit(2) 2.4
467
468 umask(2) 1.0
469 umount(2) 1.0
470 umount2(2) 2.2
471 uname(2) 1.0
472 unlink(2) 1.0
473 unlinkat(2) 2.6.16
474 unshare(2) 2.6.16
475 uselib(2) 1.0
476 ustat(2) 1.0
477 userfaultfd(2) 4.3
478 utime(2) 1.0
479 utimensat(2) 2.6.22
480 utimes(2) 2.2
481 utrap_install(2) 2.2 Sparc only
482 vfork(2) 2.2
483 vhangup(2) 1.0
484 vm86old(2) 1.0 Was "vm86"; renamed in 2.0.28/2.2
485 vm86(2) 2.0.28; 2.2
486 vmsplice(2) 2.6.17
487 wait4(2) 1.0
488 waitid(2) 2.6.10
489 waitpid(2) 1.0
490 write(2) 1.0
491 writev(2) 2.0
492
493 On many platforms, including x86-32, socket calls are all multiplexed (via glibc wrapper functions) through socketcall(2) and simi‐
494 larly System V IPC calls are multiplexed through ipc(2).
495
496 Although slots are reserved for them in the system call table, the following system calls are not implemented in the standard ker‐
497 nel: afs_syscall(2), break(2), ftime(2), getpmsg(2), gtty(2), idle(2), lock(2), madvise1(2), mpx(2), phys(2), prof(2), profil(2),
498 putpmsg(2), security(2), stty(2), tuxcall(2), ulimit(2), and vserver(2) (see also unimplemented(2)). However, ftime(3), profil(3),
499 and ulimit(3) exist as library routines. The slot for phys(2) is in use since kernel 2.1.116 for umount(2); phys(2) will never be
500 implemented. The getpmsg(2) and putpmsg(2) calls are for kernels patched to support STREAMS, and may never be in the standard ker‐
501 nel.
502
503 There was briefly set_zone_reclaim(2), added in Linux 2.6.13, and removed in 2.6.16; this system call was never available to user
504 space.
505
506 NOTES
507 Roughly speaking, the code belonging to the system call with number __NR_xxx defined in /usr/include/asm/unistd.h can be found in
508 the Linux kernel source in the routine sys_xxx(). (The dispatch table for i386 can be found in /usr/src/linux/arch/i386/ker‐
509 nel/entry.S.) There are many exceptions, however, mostly because older system calls were superseded by newer ones, and this has
510 been treated somewhat unsystematically. On platforms with proprietary operating-system emulation, such as parisc, sparc, sparc64,
511 and alpha, there are many additional system calls; mips64 also contains a full set of 32-bit system calls.
512
513 Over time, changes to the interfaces of some system calls have been necessary. One reason for such changes was the need to increase
514 the size of structures or scalar values passed to the system call. Because of these changes, certain architectures (notably, long‐
515 standing 32-bit architectures such as i386) now have various groups of related system calls (e.g., truncate(2) and truncate64(2))
516 which perform similar tasks, but which vary in details such as the size of their arguments. (As noted earlier, applications are
517 generally unaware of this: the glibc wrapper functions do some work to ensure that the right system call is invoked, and that ABI
518 compatibility is preserved for old binaries.) Examples of systems calls that exist in multiple versions are the following:
519
520 * By now there are three different versions of stat(2): sys_stat() (slot __NR_oldstat), sys_newstat() (slot __NR_stat), and
521 sys_stat64() (slot __NR_stat64), with the last being the most current. A similar story applies for lstat(2) and fstat(2).
522
523 * Similarly, the defines __NR_oldolduname, __NR_olduname, and __NR_uname refer to the routines sys_olduname(), sys_uname() and
524 sys_newuname().
525
526 * In Linux 2.0, a new version of vm86(2) appeared, with the old and the new kernel routines being named sys_vm86old() and
527 sys_vm86().
528
529 * In Linux 2.4, a new version of getrlimit(2) appeared, with the old and the new kernel routines being named sys_old_getrlimit()
530 (slot __NR_getrlimit) and sys_getrlimit() (slot __NR_ugetrlimit).
531
532 * Linux 2.4 increased the size of user and group IDs from 16 to 32 bits. To support this change, a range of system calls were
533 added (e.g., chown32(2), getuid32(2), getgroups32(2), setresuid32(2)), superseding earlier calls of the same name without the
534 "32" suffix.
535
536 * Linux 2.4 added support for applications on 32-bit architectures to access large files (i.e., files for which the sizes and file
537 offsets can't be represented in 32 bits.) To support this change, replacements were required for system calls that deal with
538 file offsets and sizes. Thus the following system calls were added: fcntl64(2), getdents64(2), stat64(2), statfs64(2), trun‐
539 cate64(2), and their analogs that work with file descriptors or symbolic links. These system calls supersede the older system
540 calls which, except in the case of the "stat" calls, have the same name without the "64" suffix.
541
542 On newer platforms that only have 64-bit file access and 32-bit UIDs/GIDs (e.g., alpha, ia64, s390x, x86-64), there is just a
543 single version of the UID/GID and file access system calls. On platforms (typically, 32-bit platforms) where the *64 and *32
544 calls exist, the other versions are obsolete.
545
546 * The rt_sig* calls were added in kernel 2.2 to support the addition of real-time signals (see signal(7)). These system calls
547 supersede the older system calls of the same name without the "rt_" prefix.
548
549 * The select(2) and mmap(2) system calls use five or more arguments, which caused problems in the way argument passing on the i386
550 used to be set up. Thus, while other architectures have sys_select() and sys_mmap() corresponding to __NR_select and __NR_mmap,
551 on i386 one finds old_select() and old_mmap() (routines that use a pointer to an argument block) instead. These days passing
552 five arguments is not a problem any more, and there is a __NR__newselect that corresponds directly to sys_select() and similarly
553 __NR_mmap2.
554
555 SEE ALSO
556 intro(2), syscall(2), unimplemented(2), errno(3), libc(7), vdso(7)
557
558 COLOPHON
559 This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs,
560 and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.
561
562 Linux 2018-02-02 SYSCALLS(2)