Ioperm-set Port permissions in Windows

There are two system calls for setting Port permissions in Windows: ioperm and iopl functions.

1. ioperm FunctionFunction Description:
Set the I/O port access capability for the calling process. Ioperm requires Super User Permissions. Only the low-end [0-0x3ff] I/O port can be set. to specify more port capabilities, you can use the iopl function. This call can only be used on the i386 platform.

Usage:

#include  <ioperm.h>/* for libc5 */#include  <sys/io.h>/* for glibc */int ioperm(unsigned long from, unsigned long num, int turn_on);

Parameters:
From: Start port address.
Num: the number of ports that need to be modified.
Turn_on: The New Power bit of the port. 1 is enabled, 0 is disabled.
Return description:
0 is returned when execution is successful. -1 is returned for failure, and errno is set to one of the following values
Einval: the parameter is invalid.
EIO: This call is not supported
Eperm: unable to call the process.2. iopl Functions
Function Description: This call is used to modify the operation Port permissions of the current process. It can be used for permissions on all 65536 ports. Therefore, ioperm is equivalent to a subset of the call. Like ioperm, this call is only applicable to the i386 platform.

Usage:

#include <ioperm.h>int iopl(int level);

Parameters:
Level: the port permission level. The read/write port is 3. The default capability level is 0, and the user space cannot be read or written.
Return Description: 0 is returned when execution is successful. -1 is returned for failure, and errno is set to one of the following values
Einval: The level value is greater than 3.
Enosys: The call is not implemented.
Eperm: unable to call the process.

Currently, the main part has been changed to support GCC compilation. Supports GCC inline assembly.
The Code is as follows (the C compiler of Windows is used by default ):

/** function: read cmos data using rtc port(0x70 -- port, 0x71 -- data)*/#include <stdio.h>#include <stdlib.h>#include <string.h>#include <windows.h>extern int install( int  );extern int uninstall(int );extern ioperm( unsigned long from, unsigned long num, int turn_on );#ifdef _GCCvoid outp(unsigned short addr, unsigned short data){__asm__ ("mov %1,   %%al;""mov %0,   %%dx;""out %%al, %%dx;": /* no output */        :"m" (addr), "m" (data) /* input addr and data */        :"ax", "dx");}unsigned char inp( unsigned short addr){unsigned char cha;__asm__ (    "mov %1,   %%dx;""in  %%dx, %%al;""mov %%al, %0;":"=r" (cha) /* output to var(cha) */:"m" (addr) /* input addr */: "ax", "dx");return cha;}#else /* using windows asm */void outp(unsigned short addr , unsigned short data){asm {mov al,datamov dx,addrout dx,al}}unsigned char inp( unsigned short addr){unsigned char cha;asm{mov dx,addrin al,dxmov cha ,al}return cha;}#endifint main( void ){int i;unsigned char c;install(0);Sleep(500);if (ioperm(0x70, 2, 1 )) {fprintf( stderr, "Error: ioperm() failed. Please install ioperm.sys driver.\n" );}else{        for (i=0; i<260; i++)        {//Sleep(100);            outp(0x70, i);c = inp(0x71);            printf("%02x ", c);    if ((i+1)%20 == 0)    printf("\n");            }}uninstall(0);return 0;}