util/msrtool/linux.c

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2
   3 #include <sys/types.h>
   4 #include <sys/stat.h>
   5 #include <fcntl.h>
   6 #include <unistd.h>
   7 #include <string.h>
   8 #include <errno.h>
   9
  10 #include "msrtool.h"
  11
  12 static int msr_fd[MAX_CORES] = {-1, -1, -1, -1, -1, -1, -1, -1};
  13
  14 int linux_probe(const struct sysdef *system) {
  15         struct stat st;
  16         return 0 == stat("/dev/cpu/0/msr", &st);
  17 }
  18
  19 int linux_open(uint8_t cpu, enum SysModes mode) {
  20         int fmode;
  21         char fn[32];
  22         switch (mode) {
  23         case SYS_RDWR:
  24                 fmode = O_RDWR;
  25                 break;
  26         case SYS_WRONLY:
  27                 fmode = O_WRONLY;
  28                 break;
  29         case SYS_RDONLY:
  30         default:
  31                 fmode = O_RDONLY;
  32                 break;
  33         }
  34         if (cpu >= MAX_CORES) {
  35                 fprintf(stderr, "%s: only cores 0-%d are supported. requested=%d\n", __func__, MAX_CORES, cpu);
  36                 return 0;
  37         }
  38         if (snprintf(fn, sizeof(fn), "/dev/cpu/%d/msr", cpu) == -1) {
  39                 fprintf(stderr, "%s: snprintf: %s\n", __func__, strerror(errno));
  40                 return 0;
  41         }
  42         msr_fd[cpu] = open(fn, fmode);
  43         if (-1 == msr_fd[cpu]) {
  44                 fprintf(stderr, "open(%s): %s\n", fn, strerror(errno));
  45                 return 0;
  46         }
  47         return 1;
  48 }
  49
  50 int linux_close(uint8_t cpu) {
  51         int ret;
  52         if (cpu >= MAX_CORES) {
  53                 fprintf(stderr, "%s: only cores 0-%d are supported. requested=%d\n", __func__, MAX_CORES, cpu);
  54                 return 0;
  55         }
  56         ret = close(msr_fd[cpu]);
  57         msr_fd[cpu] = 0;
  58         return 0 == ret;
  59 }
  60
  61 int linux_rdmsr(uint8_t cpu, uint32_t addr, struct msr *val) {
  62         struct msr tmp;
  63         if (lseek(msr_fd[cpu], addr, SEEK_SET) == -1) {
  64                 SYSERROR(lseek, addr);
  65                 return 0;
  66         }
  67         if (read(msr_fd[cpu], &tmp, 8) != 8) {
  68                 SYSERROR(read, addr);
  69                 return 0;
  70         }
  71         val->hi = tmp.lo;
  72         val->lo = tmp.hi;
  73         return 1;
  74 }