NAME
archprctl - set architecture-specific thread state SYNOPSIS
#include
#include
int archprctl(int code, unsigned long addr); int archprctl(int code, unsigned long *addr); DESCRIPTION The archprctl() 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: ARCHSETFS
Set the 64-bit base for the FS register to addr. ARCHGETFS
Return the 64-bit base value for the FS register of the current thread in the unsigned long pointed to by addr. ARCHSETGS
Set the 64-bit base for the GS register to addr. ARCHGETGS
Return the 64-bit base value for the GS register of the current thread in the unsigned long pointed to by addr. RETURN VALUE
On success, archprctl() returns 0; on error, -1 is returned, and errno is set to indicate the error. ERRORS EFAULT addr points to an unmapped address or is outside the process address space. EINVAL code is not a valid subcommand. EPERM addr is outside the process address space. CONFORMING TO
archprctl() is a Linux/x86-64 extension and should not be used in pro‐ grams intended to be portable. NOTES
archprctl() is supported only on Linux/x86-64 for 64-bit programs cur‐ rently.
The 64-bit base changes when a new 32-bit segment selector is loaded. ARCHSETGS 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 modifyldt(2) or using the setthreadarea(2) system call in kernel 2.5 or later. archprctl() 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 MAP32BIT flag. As of version 2.7, glibc provides no prototype for archprctl(). 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. SEE ALSO mmap(2), modifyldt(2), prctl(2), setthreadarea(2)
AMD X86-64 Programmer's manual COLOPHON
This page is part of release 3.53 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/.
Linux 2007-12-26 ARCHPRCTL(2)