Linux cli command iopl

➡ A Linux man page (short for manual page) is a form of software documentation found on Linux and Unix-like operating systems. This man-page explains the command iopl and provides detailed information about the command iopl, system calls, library functions, and other aspects of the system, including usage, options, and examples of _. You can access this man page by typing man followed by the iopl.

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NAME 🖥️ iopl 🖥️

change I/O privilege level

LIBRARY

Standard C library (libc, -lc)

SYNOPSIS

#include <sys/io.h>
[[deprecated]] int iopl(int level);

DESCRIPTION

iopl() changes the I/O privilege level of the calling thread, as specified by the two least significant bits in level.

The I/O privilege level for a normal thread is 0. Permissions are inherited from parents to children.

This call is deprecated, is significantly slower than ioperm(2), and is only provided for older X servers which require access to all 65536 I/O ports. It 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
level is greater than 3.

ENOSYS
This call is unimplemented.

EPERM
The calling thread has insufficient privilege to call iopl(); the CAP_SYS_RAWIO capability is required to raise the I/O privilege level above its current value.

VERSIONS

glibc2 has a prototype both in <sys/io.h> and in <sys/perm.h>. Avoid the latter, it is available on i386 only.

STANDARDS

Linux.

HISTORY

Prior to Linux 5.5 iopl() allowed the thread to disable interrupts while running at a higher I/O privilege level. This will probably crash the system, and is not recommended.

Prior to Linux 3.7, on some architectures (such as i386), permissions were inherited by the child produced by fork(2) and were preserved across execve(2). This behavior was inadvertently changed in Linux 3.7, and won’t be reinstated.

SEE ALSO

ioperm(2), outb(2), capabilities(7)

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