|ioperm(2)||System Calls Manual||ioperm(2)|
ioperm - set port input/output permissions
Standard C library (libc, -lc)
int ioperm(unsigned long from, unsigned long num, int turn_on);
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.
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 to indicate the error.
glibc has an ioperm() prototype both in <sys/io.h> and in <sys/perm.h>. Avoid the latter, it is available on i386 only.
Before Linux 2.4, permissions were not inherited by a child created by fork(2).
The /proc/ioports file shows the I/O ports that are currently allocated on the system.
|2023-03-30||Linux man-pages 6.05.01|