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int iopl(int level);
This call is necessary to allow 8514-compatible X servers to run under Linux. Since these X servers require access to all 65536 I/O ports, the ioperm() call is not sufficient.
In addition to granting unrestricted I/O port access, running at a higher I/O privilege level also allows the process to disable interrupts. This will probably crash the system, and is not recommended.
Permissions are inherited by fork() and exec().
The I/O privilege level for a normal process is 0.
This call is mostly for the i386 architecture. On many other architectures it does not exist or will always return an error.
Tag | Description |
---|---|
EINVAL | level is greater than 3. |
ENOSYS | This call is unimplemented. |
EPERM | The calling process has insufficient privilege to call iopl(); the CAP_SYS_RAWIO capability is required. |
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