syscalls(2)
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 di-
rect 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 sys-
tem 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 wrap-
per function is provided.) Note: system calls indicate a failure by
returning a negative error number to the caller on architectures with-
out 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 trun-
cate64(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 prob-
ably 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 initi-
ated from a branch of kernel 1.0.6 via the 1.1.x unstable kernel se-
ries.)
* Where a system call is marked "2.0" this means the system call prob-
ably 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 initi-
ated 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 prob-
ably 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 initi-
ated 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 prob-
ably 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 initi-
ated from a branch of kernel 2.2.8 via the 2.3.x unstable kernel se-
ries.)
* Where a system call is marked "2.6" this means the system call prob-
ably 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 se-
ries.)
* 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 af-
ter 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 4.19 (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
bfin_spinlock(2) 2.6.22 Blackfin only (port removed
in Linux 4.17)
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
cmpxchg_badaddr(2) 2.6.36 Tile only (port removed
in Linux 4.17)
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
dma_memcpy(2) 2.6.22 Blackfin only (port removed
in Linux 4.17)
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
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
metag_get_tls(2) 3.9 Metag only (port removed
in Linux 4.17)
metag_set_fpu_flags(2) 3.9 Metag only (port removed
in Linux 4.17)
metag_set_tls(2) 3.9 Metag only (port removed
in Linux 4.17)
metag_setglobalbit(2) 3.9 Metag only (port removed
in Linux 4.17)
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
pread(2) Used for pread64(2) on AVR32
(port removed in Linux 4.12)
and Blackfin (port removed
in Linux 4.17)
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
pwrite(2) Used for pwrite64(2)
on AVR32 (port removed
in Linux 4.12) and Blackfin
(port removed in Linux 4.17)
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
sram_alloc(2) 2.6.22 Blackfin (port removed
in Linux 4.17)
sram_free(2) 2.6.22 Blackfin (port removed
in Linux 4.17)
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
swapcontext(2) 2.6.3 PowerPC 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 Sys-
tem V IPC calls are multiplexed through ipc(2).
Although slots are reserved for them in the system call table, the fol-
lowing 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 re-
moved in 2.6.16; this system call was never available to user space.
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 plat-
forms 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 bina-
ries.) 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 cur-
rent. A similar story applies for lstat(2) and fstat(2).
* Similarly, the defines __NR_oldolduname, __NR_olduname, and __NR_un-
ame refer to the routines sys_olduname(), sys_uname() and sys_newu-
name().
* 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)), su-
perseding 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, replace-
ments were required for system calls that deal with file offsets and
sizes. Thus the following system calls were added: fcntl64(2), get-
dents64(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 regis-
ter 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
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latest version of this page, can be found at
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