src/find-rsdp.c

   1 #include <stdio.h>
   2 #include <fcntl.h>
   3 #include <unistd.h>
   4 #include <string.h>
   5
   6 #define VER "0.1"
   7
   8 int main( int argc, char **argv, char **env) {
   9         int ret = 0;
  10         unsigned char *device = "/dev/mem";
  11
  12  printf("\n"
  13         "find-RSDP version %s © 2007 TJ http://intuitivenipple.net\n"
  14         "Licensed on the terms of GPL version 3\n\n"
  15         "Finds ACPI Root System Descriptor Pointer (for supported BIOS's only).\n\n", VER);
  16
  17  if (ret == 0) {
  18         int fd;
  19         unsigned long i, len, address, byte_count;
  20         unsigned char checksum;
  21         off_t pos, extent;
  22         ssize_t qty;
  23         unsigned char buffer[256];
  24         unsigned char *sig = "RSD PTR ";
  25         unsigned int address_offset = 16, length_table = 20;
  26
  27         if ((fd = open(device, O_RDONLY)) > 0) {
  28                 /* get memory extent */
  29                 extent = lseek(fd, 0, SEEK_END);
  30                 printf("0x%0.16lX Memory size\n", extent);
  31                 len = strlen(sig);
  32                 for (pos = 0; pos < (unsigned)extent; pos+=0x10) {
  33                 pos = lseek(fd, pos, SEEK_SET);
  34                 if ((qty = read(fd, buffer, 20)) > 0) {
  35                          if (buffer[0] == sig[0]) {
  36                         // printf("= 0x%0.16lX\n", pos);
  37                                 if (strncmp(sig, buffer, len) == 0) {
  38                                         printf("0x%0.16lX \"%s\" ", pos, sig);
  39
  40                                 for (checksum = 0, i = 0; i < length_table; i++)
  41                                         // checksum += buffer[i];
  42                                  checksum += ((unsigned char *)(buffer))[i];
  43
  44                                 if (checksum == 0) {
  45                                 for (address = 0, i = 0; i < length_table; i++) {
  46                                                 // printf("%0.2X", buffer[i]);
  47                                          if (i >= address_offset && i <= address_offset+3)
  48                                                 address |= ((unsigned long)buffer[i]) << ((i-address_offset) * 8);
  49                                  }
  50                                 buffer[15] = 0; // make preceeding OEM_ID string zero-terminated, so we can print it easily
  51                                         printf(" RSDT @ %0.8lX OEM: \"%s\" sum: %u", address, &buffer[9], checksum);
  52                                 }
  53                                 printf("\n");
  54                                 }
  55                          }
  56                 }
  57                 else {
  58                         break;
  59                 }
  60                 }
  61                 close(fd);
  62         }
  63         else perror("Cannot open /dev/mem, need superuser privileges to access");
  64  }
  65         return ret;
  66 }