Section: Linux Programmer's Manual (2)
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ioperm - set port input/output permissions
/* for glibc */
int ioperm(unsigned long from, unsigned long num, int turn_on);
sets the port access permission bits for the calling thread for
bits starting from port address
is nonzero, then permission for the specified bits is enabled;
otherwise it is disabled.
is nonzero, the calling thread must be privileged
Before Linux 2.6.8,
only the first 0x3ff I/O ports could be specified in this manner.
For more ports, the
system call had to be used (with a
argument of 3).
Since Linux 2.6.8, 65,536 I/O ports can be specified.
Permissions are inherited by the child created by
(but see NOTES).
Permissions are preserved across
this is useful for giving port access permissions to unprivileged
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
is set appropriately.
Invalid values for
(on PowerPC) This call is not supported.
Out of memory.
The calling thread has insufficient privilege.
is Linux-specific and should not be used in programs
intended to be portable.
file shows the I/O ports that are currently allocated on the system.
Before Linux 2.4,
permissions were not inherited by a child created by
Glibc has an
prototype both in
Avoid the latter, it is available on i386 only.
This page is part of release 4.16 of the Linux
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