Add fallback in Linux in case we cant get the freq from cpuid, using udev (welcome back, udev...)

src/udev.c

@@ -0,0 +1,71 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include "global.h"
+#include "standart.h"
+
+#define _PATH_SYS_SYSTEM    "/sys/devices/system"
+#define _PATH_SYS_CPU       _PATH_SYS_SYSTEM"/cpu"
+#define _PATH_ONE_CPU       _PATH_SYS_CPU"/cpu0"
+
+#define _PATH_FREQUENCY     _PATH_ONE_CPU"/cpufreq"
+#define _PATH_FREQUENCY_MAX _PATH_FREQUENCY"/cpuinfo_max_freq"
+#define _PATH_FREQUENCY_MIN _PATH_FREQUENCY"/cpuinfo_min_freq"
+
+#define DEFAULT_FILE_SIZE 4096
+
+long get_freq_from_file(char* path) {
+  FILE *file = fopen(path, "r");
+
+  if(file == NULL) {
+    perror("fopen");
+    printBug("Could not open '%s'", path);
+    return UNKNOWN;
+  }
+
+  //File exists, read it
+  int fd = fileno(file);
+  int bytes_read = 0;
+  int offset = 0;
+  int block = 1;
+  char* buf = malloc(sizeof(char)*DEFAULT_FILE_SIZE);
+  memset(buf, 0, sizeof(char)*DEFAULT_FILE_SIZE);
+
+  while (  (bytes_read = read(fd, buf+offset, block)) > 0 ) {
+    offset += bytes_read;
+  }
+
+  char* end;
+  errno = 0;
+  long ret = strtol(buf, &end, 10);
+  if(errno != 0) {
+    perror("strtol");
+    printBug("Failed parsing '%s' file. Read data was: '%s'", path, buf);
+    free(buf);
+    return UNKNOWN;
+  }
+  
+  // We will be getting the frequency in KHz
+  // We consider it is an error if frequency is
+  // greater than 10 GHz or less than 100 MHz
+  if(ret > 10000 * 1000 || ret <  100 * 1000) {
+    printBug("Invalid data was read from file '%s': %ld\n", path, ret);
+    return UNKNOWN;
+  }
+  
+  free(buf);
+  fclose(file);
+  
+  return ret/1000;
+}
+
+long get_max_freq_from_file() {
+  return get_freq_from_file(_PATH_FREQUENCY_MAX);
+}
+
+long get_min_freq_from_file() {
+  return get_freq_from_file(_PATH_FREQUENCY_MIN);
+}