tests/virtualbox.h

   1 /* Determine whether the current system is running under VirtualBox/KVM.
   2    Copyright (C) 2021-2024 Free Software Foundation, Inc.
   3
   4    This file is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU Lesser General Public License as
   6    published by the Free Software Foundation; either version 2.1 of the
   7    License, or (at your option) any later version.
   8
   9    This file is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 /* Written by Bruno Haible <bruno@clisp.org>, 2024.  */
  18
  19 #ifdef __linux__
  20 # include <fcntl.h>
  21 # include <string.h>
  22 # include <unistd.h>
  23 #endif
  24
  25 /* This function determines whether the current system is Linux and running
  26    under the VirtualBox emulator.  */
  27 _GL_ATTRIBUTE_MAYBE_UNUSED static bool
  28 is_running_under_virtualbox (void)
  29 {
  30 #ifdef __linux__
  31   /* On distributions with systemd, this could be done through
  32        test `systemd-detect-virt --vm` = oracle
  33      More generally, it can be done through
  34        test "`cat /sys/class/dmi/id/product_name`" = VirtualBox
  35      This is what we do here.  */
  36   char buf[4096];
  37   int fd = open ("/sys/class/dmi/id/product_name", O_RDONLY);
  38   if (fd >= 0)
  39     {
  40       int n = read (fd, buf, sizeof (buf));
  41       close (fd);
  42       if (n == 10 + 1 && memcmp (buf, "VirtualBox\n", 10 + 1) == 0)
  43         return true;
  44     }
  45 #endif
  46
  47   return false;
  48 }
  49
  50 /* This function determines whether the current system is Linux and running
  51    under the VirtualBox emulator, with paravirtualization acceleration set to
  52    "Default" or "KVM".  */
  53 static bool
  54 is_running_under_virtualbox_kvm (void)
  55 {
  56 #ifdef __linux__
  57   if (is_running_under_virtualbox ())
  58     {
  59       /* As root, one can determine this paravirtualization mode through
  60            dmesg | grep -i kvm
  61          which produces output like this:
  62            [    0.000000] Hypervisor detected: KVM
  63            [    0.000000] kvm-clock: Using msrs 4b564d01 and 4b564d00
  64            [    0.000001] kvm-clock: using sched offset of 3736655524 cycles
  65            [    0.000004] clocksource: kvm-clock: mask: 0xffffffffffffffff max_cycles: 0x1cd42e4dffb, max_idle_ns: 881590591483 ns
  66            [    0.007355] Booting paravirtualized kernel on KVM
  67            [    0.213538] clocksource: Switched to clocksource kvm-clock
  68          So, we test whether the file
  69          /sys/devices/system/clocksource/clocksource0/available_clocksource
  70          contains the word 'kvm-clock'.  */
  71       char buf[4096 + 1];
  72       int fd = open ("/sys/devices/system/clocksource/clocksource0/available_clocksource", O_RDONLY);
  73       if (fd >= 0)
  74         {
  75           int n = read (fd, buf, sizeof (buf) - 1);
  76           close (fd);
  77           if (n > 0)
  78             {
  79               buf[n] = '\0';
  80               char *saveptr;
  81               char *word;
  82               for (word = strtok_r (buf, " \n", &saveptr);
  83                    word != NULL;
  84                    word = strtok_r (NULL, " \n", &saveptr))
  85                 {
  86                   if (strcmp (word, "kvm-clock") == 0)
  87                     return true;
  88                 }
  89             }
  90         }
  91     }
  92 #endif
  93
  94   return false;
  95 }
  96
  97 /* This function returns the number of CPUs in the current system, assuming
  98    it is Linux.  */
  99 static int
 100 num_cpus (void)
 101 {
 102 #ifdef __linux__
 103   /* We could use sysconf (_SC_NPROCESSORS_CONF), which on glibc and musl libc
 104      is implemented through sched_getaffinity().  But there are some
 105      complications; see nproc.c.  It's simpler to parse /proc/cpuinfo.
 106      More precisely, it's sufficient to count the number of blank lines in
 107      /proc/cpuinfo.  */
 108   char buf[4096];
 109   int fd = open ("/proc/cpuinfo", O_RDONLY);
 110   if (fd >= 0)
 111     {
 112       unsigned int blank_lines = 0;
 113       bool last_char_was_newline = false;
 114       for (;;)
 115         {
 116           int n = read (fd, buf, sizeof (buf));
 117           if (n <= 0)
 118             break;
 119           int i;
 120           for (i = 0; i < n; i++)
 121             {
 122               if (last_char_was_newline && buf[i] == '\n')
 123                 blank_lines++;
 124               last_char_was_newline = (buf[i] == '\n');
 125             }
 126         }
 127       close (fd);
 128       if (blank_lines > 0)
 129         return blank_lines;
 130     }
 131 #endif
 132
 133   return 1;
 134 }