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IOPERM

Section: Linux Programmer's Manual (2)
Updated: 2004-05-27
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NAME

ioperm - set port input/output permissions  

SYNOPSIS

#include <unistd.h> /* for libc5 */
#include <sys/io.h> /* for glibc */

int ioperm(unsigned long from, unsigned long num, int turn_on);  

DESCRIPTION

ioperm() sets the port access permission bits for the process for num bytes starting from port address from to the value turn_on. If turn_on is non-zero, the calling process must be privileged (CAP_SYS_RAWIO).

Only the first 0x3ff I/O ports can be specified in this manner. For more ports, the iopl(2) system call must be used. Permissions are not inherited on fork(2), but on execve(2) they are. This is useful for giving port access permissions to non-privileged tasks.

This call is mostly for the i386 architecture. On many other architectures it does not exist or will always return an error.  

RETURN VALUE

On success, zero is returned. On error, -1 is returned, and errno is set appropriately.  

ERRORS

EINVAL
Invalid values for from or num.
EIO
(on ppc) This call is not supported.
ENOMEM
Out of memory.
EPERM
The calling process has insufficient privilege.
 

CONFORMING TO

ioperm() is Linux specific and should not be used in programs intended to be portable.  

NOTES

Libc5 treats it as a system call and has a prototype in <unistd.h>. Glibc1 does not have a prototype. Glibc2 has a prototype both in <sys/io.h> and in <sys/perm.h>. Avoid the latter, it is available on i386 only.  

SEE ALSO

iopl(2), capabilities(7)


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
CONFORMING TO
NOTES
SEE ALSO