1IOPERM(2)                  Linux Programmer's Manual                 IOPERM(2)
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NAME

6       ioperm - set port input/output permissions
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SYNOPSIS

9       #include <sys/io.h>
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11       int ioperm(unsigned long from, unsigned long num, int turn_on);
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DESCRIPTION

14       ioperm()  sets  the  port access permission bits for the calling thread
15       for num bits starting from port address from.  If turn_on  is  nonzero,
16       then permission for the specified bits is enabled; otherwise it is dis‐
17       abled.  If turn_on is nonzero, the calling thread  must  be  privileged
18       (CAP_SYS_RAWIO).
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20       Before  Linux  2.6.8, only the first 0x3ff I/O ports could be specified
21       in this manner.  For more ports, the iopl(2) system call had to be used
22       (with  a level argument of 3).  Since Linux 2.6.8, 65,536 I/O ports can
23       be specified.
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25       Permissions are inherited by the child  created  by  fork(2)  (but  see
26       NOTES).  Permissions are preserved across execve(2); this is useful for
27       giving port access permissions to unprivileged programs.
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29       This call is mostly for the i386 architecture.  On many other architec‐
30       tures it does not exist or will always return an error.
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RETURN VALUE

33       On  success,  zero is returned.  On error, -1 is returned, and errno is
34       set to indicate the error.
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ERRORS

37       EINVAL Invalid values for from or num.
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39       EIO    (on PowerPC) This call is not supported.
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41       ENOMEM Out of memory.
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43       EPERM  The calling thread has insufficient privilege.
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CONFORMING TO

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

50       The /proc/ioports file shows the I/O ports that are currently allocated
51       on the system.
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53       Before Linux 2.4, permissions were not inherited by a child created  by
54       fork(2).
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56       Glibc has an ioperm() prototype both in <sys/io.h> and in <sys/perm.h>.
57       Avoid the latter, it is available on i386 only.
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SEE ALSO

60       iopl(2), outb(2), capabilities(7)
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COLOPHON

63       This page is part of release 5.13 of the Linux  man-pages  project.   A
64       description  of  the project, information about reporting bugs, and the
65       latest    version    of    this    page,    can     be     found     at
66       https://www.kernel.org/doc/man-pages/.
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70Linux                             2021-03-22                         IOPERM(2)
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