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/* Determine whether the current system is running under VirtualBox/KVM.
Copyright (C) 2021-2024 Free Software Foundation, Inc.
This file is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2.1 of the
License, or (at your option) any later version.
This file is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Bruno Haible <bruno@clisp.org>, 2024. */
#ifdef __linux__
# include <fcntl.h>
# include <string.h>
# include <unistd.h>
#endif
/* This function determines whether the current system is Linux and running
under the VirtualBox emulator. */
_GL_ATTRIBUTE_MAYBE_UNUSED static bool
is_running_under_virtualbox (void)
{
#ifdef __linux__
/* On distributions with systemd, this could be done through
test `systemd-detect-virt --vm` = oracle
More generally, it can be done through
test "`cat /sys/class/dmi/id/product_name`" = VirtualBox
This is what we do here. */
char buf[4096];
int fd = open ("/sys/class/dmi/id/product_name", O_RDONLY);
if (fd >= 0)
{
int n = read (fd, buf, sizeof (buf));
close (fd);
if (n == 10 + 1 && memcmp (buf, "VirtualBox\n", 10 + 1) == 0)
return true;
}
#endif
return false;
}
/* This function determines whether the current system is Linux and running
under the VirtualBox emulator, with paravirtualization acceleration set to
"Default" or "KVM". */
static bool
is_running_under_virtualbox_kvm (void)
{
#ifdef __linux__
if (is_running_under_virtualbox ())
{
/* As root, one can determine this paravirtualization mode through
dmesg | grep -i kvm
which produces output like this:
[ 0.000000] Hypervisor detected: KVM
[ 0.000000] kvm-clock: Using msrs 4b564d01 and 4b564d00
[ 0.000001] kvm-clock: using sched offset of 3736655524 cycles
[ 0.000004] clocksource: kvm-clock: mask: 0xffffffffffffffff max_cycles: 0x1cd42e4dffb, max_idle_ns: 881590591483 ns
[ 0.007355] Booting paravirtualized kernel on KVM
[ 0.213538] clocksource: Switched to clocksource kvm-clock
So, we test whether the file
/sys/devices/system/clocksource/clocksource0/available_clocksource
contains the word 'kvm-clock'. */
char buf[4096 + 1];
int fd = open ("/sys/devices/system/clocksource/clocksource0/available_clocksource", O_RDONLY);
if (fd >= 0)
{
int n = read (fd, buf, sizeof (buf) - 1);
close (fd);
if (n > 0)
{
buf[n] = '\0';
char *saveptr;
char *word;
for (word = strtok_r (buf, " \n", &saveptr);
word != NULL;
word = strtok_r (NULL, " \n", &saveptr))
{
if (strcmp (word, "kvm-clock") == 0)
return true;
}
}
}
}
#endif
return false;
}
/* This function returns the number of CPUs in the current system, assuming
it is Linux. */
static int
num_cpus (void)
{
#ifdef __linux__
/* We could use sysconf (_SC_NPROCESSORS_CONF), which on glibc and musl libc
is implemented through sched_getaffinity(). But there are some
complications; see nproc.c. It's simpler to parse /proc/cpuinfo.
More precisely, it's sufficient to count the number of blank lines in
/proc/cpuinfo. */
char buf[4096];
int fd = open ("/proc/cpuinfo", O_RDONLY);
if (fd >= 0)
{
unsigned int blank_lines = 0;
bool last_char_was_newline = false;
for (;;)
{
int n = read (fd, buf, sizeof (buf));
if (n <= 0)
break;
int i;
for (i = 0; i < n; i++)
{
if (last_char_was_newline && buf[i] == '\n')
blank_lines++;
last_char_was_newline = (buf[i] == '\n');
}
}
close (fd);
if (blank_lines > 0)
return blank_lines;
}
#endif
return 1;
}
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