util/intelmetool/msr.c

   1 /* intelmetool */
   2 /* SPDX-License-Identifier: GPL-2.0-or-later */
   3
   4 #include <fcntl.h>
   5 #include <unistd.h>
   6 #include <stdio.h>
   7 #include <stdlib.h>
   8 #include <string.h>
   9 #include <errno.h>
  10
  11 #include "msr.h"
  12
  13 #ifndef __DARWIN__
  14 static int fd_msr = 0;
  15
  16 static int rdmsr(int addr, uint64_t *msr)
  17 {
  18         if (lseek(fd_msr, (off_t) addr, SEEK_SET) == -1) {
  19                 perror("Could not lseek() to MSR");
  20                 close(fd_msr);
  21                 return -1;
  22         }
  23
  24         if (read(fd_msr, msr, 8) == 8) {
  25                 close(fd_msr);
  26                 return 0;
  27         }
  28
  29         if (errno == EIO) {
  30                 perror("IO error couldn't read MSR.");
  31                 close(fd_msr);
  32                 /* On older platforms the MSR might not exists */
  33                 return -2;
  34         }
  35
  36         perror("Couldn't read() MSR");
  37         close(fd_msr);
  38         return -1;
  39 }
  40 #endif
  41
  42 int msr_bootguard(uint64_t *msr)
  43 {
  44
  45 #ifndef __DARWIN__
  46         fd_msr = open("/dev/cpu/0/msr", O_RDONLY);
  47         if (fd_msr < 0) {
  48                 perror("Error while opening /dev/cpu/0/msr");
  49                 printf("Did you run 'modprobe msr'?\n");
  50                 return -1;
  51         }
  52
  53         if (rdmsr(MSR_BOOTGUARD, msr) < 0)
  54                 return -1;
  55 #endif
  56
  57         return 0;
  58 }