ioperm
Section: System Calls (2)
Updated: 202-0-17
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NAME
ioperm - set port input/output permissions
LIBRARY
Standard C library
(
libc,~
-lc)
SYNOPSIS
#include <sys/io.h>
int ioperm(unsigned long from, unsigned long num, int turn_on);
DESCRIPTION
ioperm()
sets the port access permission bits for the calling thread for
num
bits starting from port address
from.
If
turn_on
is nonzero, then permission for the specified bits is enabled;
otherwise it is disabled.
If
turn_on
is nonzero, the calling thread must be privileged
(
CAP_SYS_RAWIO).
Before Linux 2.6.8,
only the first 0x3ff I/O ports could be specified in this manner.
For more ports, the
iopl(2)
system call had to be used (with a
level
argument of 3).
Since Linux 2.6.8, 65,536 I/O ports can be specified.
Permissions are inherited by the child created by
fork(2)
(but see HISTORY).
Permissions are preserved across
execve(2);
this is useful for giving port access permissions to unprivileged
programs.
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 to indicate the error.
ERRORS
- EINVAL
-
Invalid values for
from
or
num.
- EIO
-
(on PowerPC) This call is not supported.
- ENOMEM
-
Out of memory.
- EPERM
-
The calling thread has insufficient privilege.
VERSIONS
glibc has an
ioperm()
prototype both in
<sys/io.h>
and in
<sys/perm.h>.
Avoid the latter, it is available on i386 only.
STANDARDS
Linux.
HISTORY
Before Linux 2.4,
permissions were not inherited by a child created by
fork(2).
NOTES
The
/proc/ioports
file shows the I/O ports that are currently allocated on the system.
SEE ALSO
iopl(2),
outb(2),
capabilities(7)
Index
- NAME
-
- LIBRARY
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- VERSIONS
-
- STANDARDS
-
- HISTORY
-
- NOTES
-
- SEE ALSO
-
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