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man page of ioperm

ioperm: set port input/output permissions


ioperm - set port input/output permissions


#include <unistd.h> /* for libc5 */ #include <sys/io.h> /* for glibc */ int ioperm(unsigned long from, unsigned long num, int turn_on);
ioperm() sets the port access permission bits for the calling process for num bytes starting from port address from to the value turn_on. If turn_on is nonzero, 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 by the child created by fork(2). 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.
On success, zero is returned. On error, -1 is returned, and errno is set appropriately.


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


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


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.


iopl(2), capabilities(7)
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at //www.kernel.org/doc/man-pages/. IOPERM(2)

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