syscalls

SYSCALLS(2)                 Linux Programmer's Manual                SYSCALLS(2)



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
          kernel 1.0 or earlier.

       *  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 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 kernel series.)

       *  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 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, via the 1.3.x
          unstable kernel series.)

       *  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 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 kernel
          series.)

       *  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 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 kernel
          series.)

       *  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 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 kernel series.)

       *  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, the
          exact version number where the system call appeared is shown.  This
          convention continues with the 3.x kernel series, which followed on
          from kernel 2.6.39; and the 4.x kernel series, which followed on from
          kernel 3.19; and the 5.x kernel series, which followed on from kernel
          4.20.

       *  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 2.6.x were also backported 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 series is listed.

       The list of system calls that are available as at kernel 5.9 (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
       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_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
       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
       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
       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_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
       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 kernel 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 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
       systems 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 kernel 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
       intro(2), syscall(2), unimplemented(2), errno(3), libc(7), vdso(7)

COLOPHON
       This page is part of release 5.09 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.



Linux                              2020-08-13                        SYSCALLS(2)