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arch_prctl — set architecture-specific thread state
#include <asm/prctl.h> #include <sys/prctl.h>
int
arch_prctl( |
int code, |
unsigned long addr); |
int
arch_prctl( |
int code, |
unsigned long *addr); |
The arch_prctl() function
sets architecture-specific process or thread state.
code selects a
subfunction and passes argument addr to it; addr is interpreted as either
an unsigned long for the "set"
operations, or as an unsigned long
*, for the "get" operations.
Subfunctions for x86-64 are:
ARCH_SET_FSSet the 64-bit base for the FS register to addr.
ARCH_GET_FSReturn the 64-bit base value for the FS register of the current thread in
the unsigned long pointed to
by addr.
ARCH_SET_GSSet the 64-bit base for the GS register to addr.
ARCH_GET_GSReturn the 64-bit base value for the GS register of the current thread in
the unsigned long pointed to
by addr.
On success, arch_prctl()
returns 0; on error, −1 is returned, and errno is set to indicate the error.
addr points
to an unmapped address or is outside the process
address space.
code is not
a valid subcommand.
addr is
outside the process address space.
arch_prctl() is a
Linux/x86-64 extension and should not be used in programs
intended to be portable.
arch_prctl() is supported
only on Linux/x86-64 for 64-bit programs currently.
The 64-bit base changes when a new 32-bit segment selector is loaded.
ARCH_SET_GS is disabled in
some kernels.
Context switches for 64-bit segment bases are rather
expensive. It may be a faster alternative to set a 32-bit
base using a segment selector by setting up an LDT with
modify_ldt(2) or using the
set_thread_area(2) system
call in kernel 2.5 or later. arch_prctl() is needed only when you want
to set bases that are larger than 4GB. Memory in the first
2GB of address space can be allocated by using mmap(2) with the
MAP_32BIT flag.
As of version 2.7, glibc provides no prototype for
arch_prctl(). You have to
declare it yourself for now. This may be fixed in future
glibc versions.
FS may be already used by
the threading library.
This page is part of release 3.52 of the Linux man-pages project. A
description of the project, and information about reporting
bugs, can be found at
http://www.kernel.org/doc/man−pages/.
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Copyright (C) 2003 Andi Kleen %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END |