diff options
Diffstat (limited to 'lib/libc/sys')
| -rw-r--r-- | lib/libc/sys/Makefile.inc | 7 | ||||
| -rw-r--r-- | lib/libc/sys/__get_tcb.2 | 64 |
2 files changed, 68 insertions, 3 deletions
diff --git a/lib/libc/sys/Makefile.inc b/lib/libc/sys/Makefile.inc index 4dfab7d3b9c..9c7618565ff 100644 --- a/lib/libc/sys/Makefile.inc +++ b/lib/libc/sys/Makefile.inc @@ -1,4 +1,4 @@ -# $OpenBSD: Makefile.inc,v 1.94 2011/07/18 23:04:40 matthew Exp $ +# $OpenBSD: Makefile.inc,v 1.95 2011/10/16 06:21:52 guenther Exp $ # $NetBSD: Makefile.inc,v 1.35 1995/10/16 23:49:07 jtc Exp $ # @(#)Makefile.inc 8.1 (Berkeley) 6/17/93 @@ -67,7 +67,7 @@ ASM= accept.o access.o acct.o adjfreq.o adjtime.o bind.o chdir.o chflags.o \ utimes.o wait4.o write.o writev.o nnpfspioctl.o __semctl.o \ __syscall.o __sysctl.o __getcwd.o sched_yield.o getthrid.o \ thrsleep.o thrwakeup.o threxit.o thrsigdivert.o \ - setrtable.o getrtable.o \ + setrtable.o getrtable.o __set_tcb.o __get_tcb.o \ openat.o fchmodat.o fstatat.o mkdirat.o mkfifoat.o mknodat.o \ faccessat.o fchownat.o linkat.o readlinkat.o renameat.o symlinkat.o \ unlinkat.o utimensat.o futimens.o @@ -222,7 +222,7 @@ MAN+= accept.2 access.2 acct.2 adjfreq.2 adjtime.2 bind.2 brk.2 chdir.2 \ dup.2 execve.2 _exit.2 fcntl.2 fhopen.2 \ flock.2 fork.2 fsync.2 getdirentries.2 \ getfh.2 getfsstat.2 getgid.2 getgroups.2 getitimer.2 getlogin.2 \ - getpeername.2 getpgrp.2 getrtable.2 \ + getpeername.2 getpgrp.2 getrtable.2 __get_tcb.2 \ getpid.2 getpriority.2 getrlimit.2 getrusage.2 getsid.2 getsockname.2 \ getsockopt.2 gettimeofday.2 getuid.2 intro.2 issetugid.2 ioctl.2 \ kill.2 kqueue.2 ktrace.2 link.2 \ @@ -266,6 +266,7 @@ MLINKS+=getpriority.2 setpriority.2 MLINKS+=getrlimit.2 setrlimit.2 MLINKS+=getsockopt.2 setsockopt.2 MLINKS+=getrtable.2 setrtable.2 +MLINKS+=__get_tcb.2 __set_tcb.2 MLINKS+=gettimeofday.2 settimeofday.2 MLINKS+=getuid.2 geteuid.2 MLINKS+=kqueue.2 kevent.2 kqueue.2 EV_SET.2 diff --git a/lib/libc/sys/__get_tcb.2 b/lib/libc/sys/__get_tcb.2 new file mode 100644 index 00000000000..6cd28d53fad --- /dev/null +++ b/lib/libc/sys/__get_tcb.2 @@ -0,0 +1,64 @@ +.\" $OpenBSD: __get_tcb.2,v 1.1 2011/10/16 06:21:52 guenther Exp $ +.\" +.\" Copyright (c) 2011 Philip Guenther <guenther@openbsd.org> +.\" +.\" Permission to use, copy, modify, and distribute this software for any +.\" purpose with or without fee is hereby granted, provided that the above +.\" copyright notice and this permission notice appear in all copies. +.\" +.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES +.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF +.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR +.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES +.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN +.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF +.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. +.\" +.Dd $Mdocdate: October 16 2011 $ +.Dt __GET_TCB 2 +.Os +.Sh NAME +.Nm __get_tcb , +.Nm __set_tcb +.Nd "get and set the address of the thread-control-block of the current thread" +.Sh SYNOPSIS +.Ft void * +.Fn __get_tcb "void" +.Ft void +.Fn __set_tcb "void *" +.Sh DESCRIPTION +The +.Fn __get_tcb +and +.Fn __set_tcb +are for use by librthread and other parts of the system runtime to +retrieve and set the address of the current thread's TCB +(thread-control-block). +This is used to locate per-thread data such as +.Va errno . +Each kernel-level thread in a process has a separate value for this +address which can be obtained and changed via these system calls. +New threads (including the first thread of a new process) created using +.Xr fork 2 , +.Xr vfork 2 , +or +.Xr rfork 2 , +start with this address set to zero. +Similarly, +.Xr execve 2 +resets it to zero. +.Pp +On some platforms, this address is also directly mapped to a CPU +register which can be accessed from userspace. +.Sh RETURN VALUES +.Fn __get_tcb +returns the address of the thread-control-block of the current thread. +.Sh SEE ALSO +.Xr rfork 2 +.Sh HISTORY +The +.Fn __get_tcb +and +.Fn __set_tcb +system calls appeared in +.Ox 5.1 . |