noble (2) syscalls.2.gz

Provided by: manpages-dev_6.7-2_all bug

NAME

       syscalls - Linux system calls

SYNOPSIS

       Linux system calls.

DESCRIPTION

       The system call is the fundamental interface between an application and the Linux kernel.

   System calls and library wrapper functions
       System  calls  are  generally not invoked directly, but rather via wrapper functions in glibc (or perhaps
       some other library).  For 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 the name of the system call that it invokes.  For
       example, glibc contains a function chdir() which invokes the underlying "chdir" system call.

       Often the glibc wrapper function is quite thin, doing little work other than  copying  arguments  to  the
       right  registers  before  invoking the system call, and then setting errno appropriately after the system
       call has returned.  (These are the same steps that are performed by syscall(2),  which  can  be  used  to
       invoke system calls for which no wrapper function is provided.)  Note: system calls indicate a failure by
       returning a negative error number to the caller on architectures without a separate error  register/flag,
       as  noted  in  syscall(2);  when this happens, the wrapper function negates the returned error number (to
       make it positive), copies it to errno, and returns -1 to the caller of the wrapper.

       Sometimes, however, the wrapper function does some extra work  before  invoking  the  system  call.   For
       example,  nowadays  there  are  (for  reasons  described below) two related system calls, truncate(2) and
       truncate64(2), and the glibc truncate() wrapper function checks which of those system calls are  provided
       by the kernel and determines which should be employed.

   System call list
       Below  is  a list of the Linux system calls.  In the list, the Kernel column indicates the kernel version
       for those system calls that were new in Linux 2.2, or have appeared since that kernel version.  Note  the
       following points:

       •  Where no kernel version is indicated, the system call appeared in Linux 1.0 or earlier.

       •  Where  a  system  call  is  marked "1.2" this means the system call probably appeared in a Linux 1.1.x
          kernel version, and first appeared in a stable kernel with 1.2.  (Development of the Linux 1.2  kernel
          was initiated from a branch of Linux 1.0.6 via the Linux 1.1.x unstable kernel series.)

       •  Where  a  system  call  is  marked "2.0" this means the system call probably appeared in a Linux 1.3.x
          kernel version, and first appeared in a stable kernel with Linux 2.0.  (Development of the  Linux  2.0
          kernel  was initiated from a branch of Linux 1.2.x, somewhere around Linux 1.2.10, via the Linux 1.3.x
          unstable kernel series.)

       •  Where a system call is marked "2.2" this means the system call probably  appeared  in  a  Linux  2.1.x
          kernel version, and first appeared in a stable kernel with Linux 2.2.0.  (Development of the Linux 2.2
          kernel was initiated from a branch of Linux 2.0.21 via the Linux 2.1.x unstable kernel series.)

       •  Where a system call is marked "2.4" this means the system call probably  appeared  in  a  Linux  2.3.x
          kernel version, and first appeared in a stable kernel with Linux 2.4.0.  (Development of the Linux 2.4
          kernel was initiated from a branch of Linux 2.2.8 via the Linux 2.3.x unstable kernel series.)

       •  Where a system call is marked "2.6" this means the system call probably  appeared  in  a  Linux  2.5.x
          kernel version, and first appeared in a stable kernel with Linux 2.6.0.  (Development of Linux 2.6 was
          initiated from a branch of Linux 2.4.15 via the Linux 2.5.x unstable kernel series.)

       •  Starting with Linux 2.6.0, the development model changed, and new system  calls  may  appear  in  each
          Linux  2.6.x release.  In this case, the exact version number where the system call appeared is shown.
          This convention continues with the Linux 3.x kernel series, which followed on from Linux  2.6.39;  and
          the Linux 4.x kernel series, which followed on from Linux 3.19; and the Linux 5.x kernel series, which
          followed on from Linux 4.20; and the Linux 6.x kernel series, which followed on from Linux 5.19.

       •  In some cases, a system call was added to a stable kernel series after it branched from  the  previous
          stable  kernel  series,  and  then backported into the earlier stable kernel series.  For example some
          system calls that appeared in Linux 2.6.x were also backported into a Linux 2.4.x release after  Linux
          2.4.15.   When  this  is  so,  the  version where the system call appeared in both of the major kernel
          series is listed.

       The list of system calls that are available as at Linux 5.14 (or in a few cases only on older kernels) is
       as follows:

       System call                 Kernel        Notes
       ───────────────────────────────────────────────────────────────────────
       _llseek(2)                  1.2
       _newselect(2)               2.0
       _sysctl(2)                  2.0           Removed in 5.5
       accept(2)                   2.0           See notes on socketcall(2)
       accept4(2)                  2.6.28
       access(2)                   1.0
       acct(2)                     1.0
       add_key(2)                  2.6.10
       adjtimex(2)                 1.0
       alarm(2)                    1.0
       alloc_hugepages(2)          2.5.36        Removed in 2.5.44
       arc_gettls(2)               3.9           ARC only
       arc_settls(2)               3.9           ARC only
       arc_usr_cmpxchg(2)          4.9           ARC only
       arch_prctl(2)               2.6           x86_64, x86 since 4.12
       atomic_barrier(2)           2.6.34        m68k only
       atomic_cmpxchg_32(2)        2.6.34        m68k only
       bdflush(2)                  1.2           Deprecated   (does  nothing)
                                                 since 2.6
       bind(2)                     2.0           See notes on socketcall(2)
       bpf(2)                      3.18
       brk(2)                      1.0
       breakpoint(2)               2.2           ARM OABI only, defined  with
                                                 __ARM_NR prefix
       cacheflush(2)               1.2           Not on x86
       capget(2)                   2.2
       capset(2)                   2.2
       chdir(2)                    1.0
       chmod(2)                    1.0
       chown(2)                    2.2           See   chown(2)  for  version
                                                 details
       chown32(2)                  2.4
       chroot(2)                   1.0
       clock_adjtime(2)            2.6.39
       clock_getres(2)             2.6
       clock_gettime(2)            2.6
       clock_nanosleep(2)          2.6
       clock_settime(2)            2.6
       clone2(2)                   2.4           IA-64 only
       clone(2)                    1.0
       clone3(2)                   5.3
       close(2)                    1.0
       close_range(2)              5.9
       connect(2)                  2.0           See notes on socketcall(2)
       copy_file_range(2)          4.5
       creat(2)                    1.0
       create_module(2)            1.0           Removed in 2.6
       delete_module(2)            1.0
       dup(2)                      1.0
       dup2(2)                     1.0
       dup3(2)                     2.6.27
       epoll_create(2)             2.6
       epoll_create1(2)            2.6.27
       epoll_ctl(2)                2.6

       epoll_pwait(2)              2.6.19
       epoll_pwait2(2)             5.11
       epoll_wait(2)               2.6
       eventfd(2)                  2.6.22
       eventfd2(2)                 2.6.27
       execv(2)                    2.0           SPARC/SPARC64   only,    for
                                                 compatibility with SunOS
       execve(2)                   1.0
       execveat(2)                 3.19
       exit(2)                     1.0
       exit_group(2)               2.6
       faccessat(2)                2.6.16
       faccessat2(2)               5.8
       fadvise64(2)                2.6
       fadvise64_64(2)             2.6
       fallocate(2)                2.6.23
       fanotify_init(2)            2.6.37
       fanotify_mark(2)            2.6.37
       fchdir(2)                   1.0
       fchmod(2)                   1.0
       fchmodat(2)                 2.6.16
       fchown(2)                   1.0
       fchown32(2)                 2.4
       fchownat(2)                 2.6.16
       fcntl(2)                    1.0
       fcntl64(2)                  2.4
       fdatasync(2)                2.0
       fgetxattr(2)                2.6; 2.4.18
       finit_module(2)             3.8
       flistxattr(2)               2.6; 2.4.18
       flock(2)                    2.0
       fork(2)                     1.0
       free_hugepages(2)           2.5.36        Removed in 2.5.44
       fremovexattr(2)             2.6; 2.4.18
       fsconfig(2)                 5.2
       fsetxattr(2)                2.6; 2.4.18
       fsmount(2)                  5.2
       fsopen(2)                   5.2
       fspick(2)                   5.2
       fstat(2)                    1.0
       fstat64(2)                  2.4
       fstatat64(2)                2.6.16
       fstatfs(2)                  1.0
       fstatfs64(2)                2.6
       fsync(2)                    1.0
       ftruncate(2)                1.0
       ftruncate64(2)              2.4
       futex(2)                    2.6
       futimesat(2)                2.6.16
       get_kernel_syms(2)          1.0           Removed in 2.6
       get_mempolicy(2)            2.6.6
       get_robust_list(2)          2.6.17
       get_thread_area(2)          2.6
       get_tls(2)                  4.15          ARM  OABI only, has __ARM_NR
                                                 prefix
       getcpu(2)                   2.6.19
       getcwd(2)                   2.2
       getdents(2)                 2.0
       getdents64(2)               2.4
       getdomainname(2)            2.2           SPARC, SPARC64; available as
                                                 osf_getdomainname(2)      on
                                                 Alpha since Linux 2.0
       getdtablesize(2)            2.0           SPARC (removed  in  2.6.26),
                                                 available    on   Alpha   as
                                                 osf_getdtablesize(2)

       getegid(2)                  1.0
       getegid32(2)                2.4
       geteuid(2)                  1.0
       geteuid32(2)                2.4
       getgid(2)                   1.0
       getgid32(2)                 2.4
       getgroups(2)                1.0
       getgroups32(2)              2.4
       gethostname(2)              2.0           Alpha,  was   available   on
                                                 SPARC up to Linux 2.6.26
       getitimer(2)                1.0
       getpeername(2)              2.0           See notes on socketcall(2)
       getpagesize(2)              2.0           Not on x86
       getpgid(2)                  1.0
       getpgrp(2)                  1.0
       getpid(2)                   1.0
       getppid(2)                  1.0
       getpriority(2)              1.0
       getrandom(2)                3.17
       getresgid(2)                2.2
       getresgid32(2)              2.4
       getresuid(2)                2.2
       getresuid32(2)              2.4
       getrlimit(2)                1.0
       getrusage(2)                1.0
       getsid(2)                   2.0
       getsockname(2)              2.0           See notes on socketcall(2)
       getsockopt(2)               2.0           See notes on socketcall(2)
       gettid(2)                   2.4.11
       gettimeofday(2)             1.0
       getuid(2)                   1.0
       getuid32(2)                 2.4
       getunwind(2)                2.4.8         IA-64 only; deprecated
       getxattr(2)                 2.6; 2.4.18
       getxgid(2)                  2.0           Alpha only; see NOTES
       getxpid(2)                  2.0           Alpha only; see NOTES
       getxuid(2)                  2.0           Alpha only; see NOTES
       init_module(2)              1.0
       inotify_add_watch(2)        2.6.13
       inotify_init(2)             2.6.13
       inotify_init1(2)            2.6.27
       inotify_rm_watch(2)         2.6.13
       io_cancel(2)                2.6
       io_destroy(2)               2.6
       io_getevents(2)             2.6
       io_pgetevents(2)            4.18
       io_setup(2)                 2.6
       io_submit(2)                2.6
       io_uring_enter(2)           5.1
       io_uring_register(2)        5.1
       io_uring_setup(2)           5.1
       ioctl(2)                    1.0
       ioperm(2)                   1.0
       iopl(2)                     1.0
       ioprio_get(2)               2.6.13
       ioprio_set(2)               2.6.13
       ipc(2)                      1.0
       kcmp(2)                     3.5
       kern_features(2)            3.7           SPARC64 only
       kexec_file_load(2)          3.17
       kexec_load(2)               2.6.13
       keyctl(2)                   2.6.10
       kill(2)                     1.0
       landlock_add_rule(2)        5.13
       landlock_create_ruleset(2)  5.13

       landlock_restrict_self(2)   5.13
       lchown(2)                   1.0           See   chown(2)  for  version
                                                 details
       lchown32(2)                 2.4
       lgetxattr(2)                2.6; 2.4.18
       link(2)                     1.0
       linkat(2)                   2.6.16
       listen(2)                   2.0           See notes on socketcall(2)
       listxattr(2)                2.6; 2.4.18
       llistxattr(2)               2.6; 2.4.18
       lookup_dcookie(2)           2.6
       lremovexattr(2)             2.6; 2.4.18
       lseek(2)                    1.0
       lsetxattr(2)                2.6; 2.4.18
       lstat(2)                    1.0
       lstat64(2)                  2.4
       madvise(2)                  2.4
       mbind(2)                    2.6.6
       memory_ordering(2)          2.2           SPARC64 only
       membarrier(2)               3.17
       memfd_create(2)             3.17
       memfd_secret(2)             5.14
       migrate_pages(2)            2.6.16
       mincore(2)                  2.4
       mkdir(2)                    1.0
       mkdirat(2)                  2.6.16
       mknod(2)                    1.0
       mknodat(2)                  2.6.16
       mlock(2)                    2.0
       mlock2(2)                   4.4
       mlockall(2)                 2.0
       mmap(2)                     1.0
       mmap2(2)                    2.4
       modify_ldt(2)               1.0
       mount(2)                    1.0
       move_mount(2)               5.2
       move_pages(2)               2.6.18
       mprotect(2)                 1.0
       mq_getsetattr(2)            2.6.6
       mq_notify(2)                2.6.6
       mq_open(2)                  2.6.6
       mq_timedreceive(2)          2.6.6
       mq_timedsend(2)             2.6.6
       mq_unlink(2)                2.6.6
       mremap(2)                   2.0
       msgctl(2)                   2.0           See notes on ipc(2)
       msgget(2)                   2.0           See notes on ipc(2)
       msgrcv(2)                   2.0           See notes on ipc(2)
       msgsnd(2)                   2.0           See notes on ipc(2)
       msync(2)                    2.0
       munlock(2)                  2.0
       munlockall(2)               2.0
       munmap(2)                   1.0
       name_to_handle_at(2)        2.6.39
       nanosleep(2)                2.0
       newfstatat(2)               2.6.16        See stat(2)
       nfsservctl(2)               2.2           Removed in 3.1
       nice(2)                     1.0
       old_adjtimex(2)             2.0           Alpha only; see NOTES
       old_getrlimit(2)            2.4           Old variant of  getrlimit(2)
                                                 that  used a different value
                                                 for RLIM_INFINITY
       oldfstat(2)                 1.0
       oldlstat(2)                 1.0
       oldolduname(2)              1.0

       oldstat(2)                  1.0
       oldumount(2)                2.4.116       Name of  the  old  umount(2)
                                                 syscall on Alpha
       olduname(2)                 1.0
       open(2)                     1.0
       open_by_handle_at(2)        2.6.39
       open_tree(2)                5.2
       openat(2)                   2.6.16
       openat2(2)                  5.6
       or1k_atomic(2)              3.1           OpenRISC 1000 only
       pause(2)                    1.0
       pciconfig_iobase(2)         2.2.15; 2.4   Not on x86
       pciconfig_read(2)           2.0.26; 2.2   Not on x86
       pciconfig_write(2)          2.0.26; 2.2   Not on x86
       perf_event_open(2)          2.6.31        Was  perf_counter_open()  in
                                                 2.6.31; renamed in 2.6.32
       personality(2)              1.2
       perfctr(2)                  2.2           SPARC   only;   removed   in
                                                 2.6.34
       perfmonctl(2)               2.4           IA-64 only; removed in 5.10
       pidfd_getfd(2)              5.6
       pidfd_send_signal(2)        5.1
       pidfd_open(2)               5.3
       pipe(2)                     1.0
       pipe2(2)                    2.6.27
       pivot_root(2)               2.4
       pkey_alloc(2)               4.8
       pkey_free(2)                4.8
       pkey_mprotect(2)            4.8
       poll(2)                     2.0.36; 2.2
       ppoll(2)                    2.6.16
       prctl(2)                    2.2
       pread64(2)                                Added  as  "pread"  in  2.2;
                                                 renamed "pread64" in 2.6
       preadv(2)                   2.6.30
       preadv2(2)                  4.6
       prlimit64(2)                2.6.36
       process_madvise(2)          5.10
       process_vm_readv(2)         3.2
       process_vm_writev(2)        3.2
       pselect6(2)                 2.6.16
       ptrace(2)                   1.0
       pwrite64(2)                               Added as  "pwrite"  in  2.2;
                                                 renamed "pwrite64" in 2.6
       pwritev(2)                  2.6.30
       pwritev2(2)                 4.6
       query_module(2)             2.2           Removed in 2.6
       quotactl(2)                 1.0
       quotactl_fd(2)              5.14
       read(2)                     1.0
       readahead(2)                2.4.13
       readdir(2)                  1.0
       readlink(2)                 1.0
       readlinkat(2)               2.6.16
       readv(2)                    2.0
       reboot(2)                   1.0
       recv(2)                     2.0           See notes on socketcall(2)
       recvfrom(2)                 2.0           See notes on socketcall(2)
       recvmsg(2)                  2.0           See notes on socketcall(2)
       recvmmsg(2)                 2.6.33
       remap_file_pages(2)         2.6           Deprecated since 3.16
       removexattr(2)              2.6; 2.4.18
       rename(2)                   1.0
       renameat(2)                 2.6.16
       renameat2(2)                3.15

       request_key(2)              2.6.10
       restart_syscall(2)          2.6
       riscv_flush_icache(2)       4.15          RISC-V only
       rmdir(2)                    1.0
       rseq(2)                     4.18
       rt_sigaction(2)             2.2
       rt_sigpending(2)            2.2
       rt_sigprocmask(2)           2.2
       rt_sigqueueinfo(2)          2.2
       rt_sigreturn(2)             2.2
       rt_sigsuspend(2)            2.2
       rt_sigtimedwait(2)          2.2
       rt_tgsigqueueinfo(2)        2.6.31
       rtas(2)                     2.6.2         PowerPC/PowerPC64 only
       s390_runtime_instr(2)       3.7           s390 only
       s390_pci_mmio_read(2)       3.19          s390 only
       s390_pci_mmio_write(2)      3.19          s390 only
       s390_sthyi(2)               4.15          s390 only
       s390_guarded_storage(2)     4.12          s390 only
       sched_get_affinity(2)       2.6           Name of sched_getaffinity(2)
                                                 on SPARC and SPARC64
       sched_get_priority_max(2)   2.0
       sched_get_priority_min(2)   2.0
       sched_getaffinity(2)        2.6
       sched_getattr(2)            3.14
       sched_getparam(2)           2.0
       sched_getscheduler(2)       2.0
       sched_rr_get_interval(2)    2.0
       sched_set_affinity(2)       2.6           Name of sched_setaffinity(2)
                                                 on SPARC and SPARC64
       sched_setaffinity(2)        2.6
       sched_setattr(2)            3.14
       sched_setparam(2)           2.0
       sched_setscheduler(2)       2.0
       sched_yield(2)              2.0
       seccomp(2)                  3.17
       select(2)                   1.0
       semctl(2)                   2.0           See notes on ipc(2)
       semget(2)                   2.0           See notes on ipc(2)
       semop(2)                    2.0           See notes on ipc(2)
       semtimedop(2)               2.6; 2.4.22
       send(2)                     2.0           See notes on socketcall(2)
       sendfile(2)                 2.2
       sendfile64(2)               2.6; 2.4.19
       sendmmsg(2)                 3.0
       sendmsg(2)                  2.0           See notes on socketcall(2)
       sendto(2)                   2.0           See notes on socketcall(2)
       set_mempolicy(2)            2.6.6
       set_robust_list(2)          2.6.17
       set_thread_area(2)          2.6
       set_tid_address(2)          2.6
       set_tls(2)                  2.6.11        ARM OABI/EABI only (constant
                                                 has __ARM_NR prefix)
       setdomainname(2)            1.0
       setfsgid(2)                 1.2
       setfsgid32(2)               2.4
       setfsuid(2)                 1.2
       setfsuid32(2)               2.4
       setgid(2)                   1.0
       setgid32(2)                 2.4
       setgroups(2)                1.0
       setgroups32(2)              2.4
       sethae(2)                   2.0           Alpha only; see NOTES
       sethostname(2)              1.0
       setitimer(2)                1.0

       setns(2)                    3.0
       setpgid(2)                  1.0
       setpgrp(2)                  2.0           Alternative     name     for
                                                 setpgid(2) on Alpha
       setpriority(2)              1.0
       setregid(2)                 1.0
       setregid32(2)               2.4
       setresgid(2)                2.2
       setresgid32(2)              2.4
       setresuid(2)                2.2
       setresuid32(2)              2.4
       setreuid(2)                 1.0
       setreuid32(2)               2.4
       setrlimit(2)                1.0
       setsid(2)                   1.0
       setsockopt(2)               2.0           See notes on socketcall(2)
       settimeofday(2)             1.0
       setuid(2)                   1.0
       setuid32(2)                 2.4
       setup(2)                    1.0           Removed in 2.2
       setxattr(2)                 2.6; 2.4.18
       sgetmask(2)                 1.0
       shmat(2)                    2.0           See notes on ipc(2)
       shmctl(2)                   2.0           See notes on ipc(2)
       shmdt(2)                    2.0           See notes on ipc(2)
       shmget(2)                   2.0           See notes on ipc(2)
       shutdown(2)                 2.0           See notes on socketcall(2)
       sigaction(2)                1.0
       sigaltstack(2)              2.2
       signal(2)                   1.0
       signalfd(2)                 2.6.22
       signalfd4(2)                2.6.27
       sigpending(2)               1.0
       sigprocmask(2)              1.0
       sigreturn(2)                1.0
       sigsuspend(2)               1.0
       socket(2)                   2.0           See notes on socketcall(2)
       socketcall(2)               1.0
       socketpair(2)               2.0           See notes on socketcall(2)
       spill(2)                    2.6.13        Xtensa only
       splice(2)                   2.6.17
       spu_create(2)               2.6.16        PowerPC/PowerPC64 only
       spu_run(2)                  2.6.16        PowerPC/PowerPC64 only
       ssetmask(2)                 1.0
       stat(2)                     1.0
       stat64(2)                   2.4
       statfs(2)                   1.0
       statfs64(2)                 2.6
       statx(2)                    4.11
       stime(2)                    1.0
       subpage_prot(2)             2.6.25        PowerPC/PowerPC64 only
       swapcontext(2)              2.6.3         PowerPC/PowerPC64 only
       switch_endian(2)            4.1           PowerPC64 only
       swapoff(2)                  1.0
       swapon(2)                   1.0
       symlink(2)                  1.0
       symlinkat(2)                2.6.16
       sync(2)                     1.0
       sync_file_range(2)          2.6.17
       sync_file_range2(2)         2.6.22
       syncfs(2)                   2.6.39
       sys_debug_setcontext(2)     2.6.11        PowerPC only
       syscall(2)                  1.0           Still  available on ARM OABI
                                                 and MIPS O32 ABI
       sysfs(2)                    1.2

       sysinfo(2)                  1.0
       syslog(2)                   1.0
       sysmips(2)                  2.6.0         MIPS only
       tee(2)                      2.6.17
       tgkill(2)                   2.6
       time(2)                     1.0
       timer_create(2)             2.6
       timer_delete(2)             2.6
       timer_getoverrun(2)         2.6
       timer_gettime(2)            2.6
       timer_settime(2)            2.6
       timerfd_create(2)           2.6.25
       timerfd_gettime(2)          2.6.25
       timerfd_settime(2)          2.6.25
       times(2)                    1.0
       tkill(2)                    2.6; 2.4.22
       truncate(2)                 1.0
       truncate64(2)               2.4
       ugetrlimit(2)               2.4
       umask(2)                    1.0
       umount(2)                   1.0
       umount2(2)                  2.2
       uname(2)                    1.0
       unlink(2)                   1.0
       unlinkat(2)                 2.6.16
       unshare(2)                  2.6.16
       uselib(2)                   1.0
       ustat(2)                    1.0
       userfaultfd(2)              4.3
       usr26(2)                    2.4.8.1       ARM OABI only
       usr32(2)                    2.4.8.1       ARM OABI only
       utime(2)                    1.0
       utimensat(2)                2.6.22
       utimes(2)                   2.2
       utrap_install(2)            2.2           SPARC64 only
       vfork(2)                    2.2
       vhangup(2)                  1.0
       vm86old(2)                  1.0           Was   "vm86";   renamed   in
                                                 2.0.28/2.2
       vm86(2)                     2.0.28; 2.2
       vmsplice(2)                 2.6.17
       wait4(2)                    1.0
       waitid(2)                   2.6.10
       waitpid(2)                  1.0
       write(2)                    1.0
       writev(2)                   2.0
       xtensa(2)                   2.6.13        Xtensa only

       On  many  platforms,  including  x86-32,  socket  calls are all multiplexed (via glibc wrapper functions)
       through socketcall(2) and similarly System V IPC calls are multiplexed through ipc(2).

       Although slots are reserved for them in the system  call  table,  the  following  system  calls  are  not
       implemented  in  the  standard  kernel: 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), putpmsg(2), security(2), stty(2),  tuxcall(2),
       ulimit(2), and vserver(2) (see also unimplemented(2)).  However, ftime(3), profil(3), and ulimit(3) exist
       as library routines.  The slot for phys(2) is in use since Linux  2.1.116  for  umount(2);  phys(2)  will
       never  be  implemented.   The getpmsg(2) and putpmsg(2) calls are for kernels patched to support STREAMS,
       and may never be in the standard kernel.

       There was briefly set_zone_reclaim(2), added in Linux 2.6.13, and removed in Linux  2.6.16;  this  system
       call was never available to user space.

   System calls on removed ports
       Some system calls only ever existed on Linux architectures that have since been removed from the kernel:

       AVR32 (port removed in Linux 4.12)
              •  pread(2)
              •  pwrite(2)

       Blackfin (port removed in Linux 4.17)
              •  bfin_spinlock(2) (added in Linux 2.6.22)
              •  dma_memcpy(2) (added in Linux 2.6.22)
              •  pread(2) (added in Linux 2.6.22)
              •  pwrite(2) (added in Linux 2.6.22)
              •  sram_alloc(2) (added in Linux 2.6.22)
              •  sram_free(2) (added in Linux 2.6.22)

       Metag (port removed in Linux 4.17)
              •  metag_get_tls(2) (add in Linux 3.9)
              •  metag_set_fpu_flags(2) (add in Linux 3.9)
              •  metag_set_tls(2) (add in Linux 3.9)
              •  metag_setglobalbit(2) (add in Linux 3.9)

       Tile (port removed in Linux 4.17)
              •  cmpxchg_badaddr(2) (added in Linux 2.6.36)

NOTES

       Roughly   speaking,   the   code   belonging   to  the  system  call  with  number  __NR_xxx  defined  in
       /usr/include/asm/unistd.h can be found in the Linux kernel source in the routine  sys_xxx().   There  are
       many  exceptions,  however, mostly because older system calls were superseded by newer ones, and this has
       been treated somewhat unsystematically.  On platforms with proprietary operating-system  emulation,  such
       as  sparc, sparc64, and alpha, there are many additional system calls; mips64 also contains a full set of
       32-bit system calls.

       Over time, changes to the interfaces of some system calls have  been  necessary.   One  reason  for  such
       changes  was  the  need  to  increase  the size of structures or scalar values passed to the system call.
       Because of these changes, certain architectures (notably, longstanding 32-bit architectures such as i386)
       now  have  various  groups  of  related  system calls (e.g., truncate(2) and truncate64(2)) which perform
       similar tasks, but which vary in details such as  the  size  of  their  arguments.   (As  noted  earlier,
       applications  are  generally unaware of this: the glibc wrapper functions do some work to ensure that the
       right system call is invoked, and that ABI compatibility is preserved for  old  binaries.)   Examples  of
       system calls that exist in multiple versions are the following:

       •  By  now  there  are three different versions of stat(2): sys_stat() (slot __NR_oldstat), sys_newstat()
          (slot __NR_stat), and sys_stat64() (slot __NR_stat64), with  the  last  being  the  most  current.   A
          similar story applies for lstat(2) and fstat(2).

       •  Similarly,  the  defines  __NR_oldolduname,  __NR_olduname,  and  __NR_uname  refer  to  the  routines
          sys_olduname(), sys_uname(), and sys_newuname().

       •  In Linux 2.0, a new version of vm86(2) appeared, with the old and the new kernel routines being  named
          sys_vm86old() and sys_vm86().

       •  In  Linux  2.4, a new version of getrlimit(2) appeared, with the old and the new kernel routines being
          named sys_old_getrlimit() (slot __NR_getrlimit) and sys_getrlimit() (slot __NR_ugetrlimit).

       •  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  added (e.g., chown32(2), getuid32(2), getgroups32(2), setresuid32(2)),
          superseding earlier calls of the same name without the "32" suffix.

       •  Linux 2.4 added support for applications on 32-bit architectures to access large  files  (i.e.,  files
          for  which  the  sizes  and  file  offsets  can't be represented in 32 bits.)  To support this change,
          replacements were required for system calls that deal with file offsets and sizes.  Thus the following
          system  calls  were added: fcntl64(2), getdents64(2), stat64(2), statfs64(2), truncate64(2), and their
          analogs that work with file descriptors or symbolic links.  These system  calls  supersede  the  older
          system  calls  which,  except  in  the  case  of the "stat" calls, have the same name without the "64"
          suffix.

          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 single version of the UID/GID and file access system calls.  On platforms
          (typically, 32-bit platforms) where the *64 and *32 calls exist, the other versions are obsolete.

       •  The rt_sig* calls were added  in  Linux  2.2  to  support  the  addition  of  real-time  signals  (see
          signal(7)).   These  system  calls supersede the older system calls of the same name without the "rt_"
          prefix.

       •  The select(2) and mmap(2) system calls use five or more arguments, which caused problems  in  the  way
          argument passing on the i386 used to be set up.  Thus, while other architectures have sys_select() and
          sys_mmap() corresponding to __NR_select and __NR_mmap, on i386 one finds old_select()  and  old_mmap()
          (routines  that use a pointer to an argument block) instead.  These days passing five arguments is not
          a problem any more, and there is a __NR__newselect  that  corresponds  directly  to  sys_select()  and
          similarly __NR_mmap2.  s390x is the only 64-bit architecture that has old_mmap().

   Architecture-specific details: Alpha
       getxgid(2)
              returns  a  pair  of  GID  and  effective  GID via registers r0 and r20; it is provided instead of
              getgid(2) and getegid(2).

       getxpid(2)
              returns a pair of PID and parent PID via registers r0 and r20; it is provided instead of getpid(2)
              and getppid(2).

       old_adjtimex(2)
              is a variant of adjtimex(2) that uses struct timeval32, for compatibility with OSF/1.

       getxuid(2)
              returns  a  pair  of  GID  and  effective  GID via registers r0 and r20; it is provided instead of
              getuid(2) and geteuid(2).

       sethae(2)
              is used for configuring the Host Address Extension register on low-cost Alphas in order to  access
              address space beyond first 27 bits.

SEE ALSO

       ausyscall(1), intro(2), syscall(2), unimplemented(2), errno(3), libc(7), vdso(7)