Originální popis anglicky:
arch_prctl - set architecture specific thread state
Návod, kniha: Linux Programmer's Manual
#include <asm/prctl.h>
#include <sys/prctl.h>
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.
Sub functions for x86-64 are:
- ARCH_SET_FS
- Set the 64bit base for the FS register to
addr.
- ARCH_GET_FS
- Return the 64bit base value for the FS register of
the current thread in the unsigned long pointed to by the
address parameter
- ARCH_SET_GS
- Set the 64bit base for the GS register to
addr.
- ARCH_GET_GS
- Return the 64bit base value for the GS register of
the current thread in the unsigned long pointed to by the
address parameter.
arch_prctl is only supported on Linux/x86-64 for 64bit programs
currently.
The 64bit base changes when a new 32bit segment selector is loaded.
ARCH_SET_GS is disabled in some kernels.
Context switches for 64bit segment bases are rather expensive. It may be a
faster alternative to set a 32bit base using a segment selector by setting up
an LDT with
modify_ldt(2) or using the
set_thread_area(2) system
call in a 2.5 kernel.
arch_prctl is only needed 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.
No prototype for
arch_prctl in glibc 2.2. You have to declare it yourself
for now. This will be fixed in future glibc versions.
FS may be already used by the threading library.
- 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.
Man page written by Andi Kleen.
arch_prctl is a Linux/x86-64 extension and should not be used in programs
intended to be portable.
mmap(2),
modify_ldt(2),
prctl(2),
set_thread_area(2)
AMD X86-64 Programmer's manual
