CoreMod

// coremod.c - CyrIng 2012
 
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>
 
// Intel® 64 and IA-32 Architectures Software Developer’s Manual
// Vol. 3C § 34-1
// Table 34-2. IA-32 Architectural MSRs
 
#define	IA32_PERF_STATUS	0x198
 
// System Management BIOS (SMBIOS) Reference Specification
// Version: 2.7.1 § 7.5
// Table 20 – Processor Information (Type 4) Structure
 
#define	SMBIOS_PROCINFO_STRUCTURE	4
#define	SMBIOS_PROCINFO_INSTANCE	0
#define	SMBIOS_PROCINFO_EXTCLK		0x12
 
 
int Read_MSR(int cpu, off_t offset, unsigned long long *msr) {
	ssize_t	retval=0;
	char	pathname[32]="";
	int		fd=0, rc=-1;
 
	sprintf(pathname, "/dev/cpu/%d/msr", cpu);
	if( (fd=open(pathname, O_RDONLY)) != -1 ) {
		retval=pread(fd, msr, sizeof *msr, offset);
		close(fd);
		rc=(retval != sizeof *msr) ? -1 : 0;
	}
	return(rc);
}
 
int Read_SMBIOS(int structure, int instance, off_t offset, void *buf, size_t nbyte) {
	ssize_t	retval=0;
	char	pathname[]="/sys/firmware/dmi/entries/999-99/raw";
	int		fd=0, rc=-1;
 
	sprintf(pathname, "/sys/firmware/dmi/entries/%d-%d/raw", structure, instance);
	if( (fd=open(pathname, O_RDONLY)) != -1 ) {
		retval=pread(fd, buf, nbyte, offset);
		close(fd);
		rc=(retval != nbyte) ? -1 : 0;
	}
	return(rc);
}
 
int	Get_Ratio(int target) {
	unsigned long long msr=0;
 
	if( Read_MSR(target, IA32_PERF_STATUS, &msr) != -1)
		return((int) msr);
	else
		return(0);
}
 
int External_Clock() {
	int	clock=0;
 
	if( Read_SMBIOS(SMBIOS_PROCINFO_STRUCTURE, SMBIOS_PROCINFO_INSTANCE, SMBIOS_PROCINFO_EXTCLK, &clock, 1) != -1)
		return(clock);
	else
		return(0);
}
 
int main(int argc, char *argv[]) {
	int	target=0, first=0, last=0, clock=0, ratio=0, rc=0;
 
	switch(argc) {
	  case 2:	first = atoi(argv[1]);
				last  = first;
	  break;
	  case 3:	first = atoi(argv[1]);
				last  = atoi(argv[2]);
	  break;
	}
	if((clock=External_Clock())!=0)
	  for(target=first; target<=last && (ratio=Get_Ratio(target)) != 0; target++)
		printf("Processor#%d : Ratio[%d] x Clock[%d] = %d Mhz\n", target, ratio, clock, ratio*clock);
	else
		rc=-1;
	return(rc);
}