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/******************************************************************************
* xen_detect.c
*
* Simple GNU C / POSIX application to detect execution on Xen VMM platform.
*
* Copyright (c) 2007, XenSource Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
static int pv_context;
static void cpuid(uint32_t idx,
uint32_t *eax,
uint32_t *ebx,
uint32_t *ecx,
uint32_t *edx)
{
asm volatile (
"test %1,%1 ; jz 1f ; ud2a ; .ascii \"xen\" ; 1: cpuid"
: "=a" (*eax), "=b" (*ebx), "=c" (*ecx), "=d" (*edx)
: "0" (idx), "1" (pv_context) );
}
static int check_for_xen(void)
{
uint32_t eax, ebx, ecx, edx;
char signature[13];
uint32_t base;
for ( base = 0x40000000; base < 0x40001000; base += 0x100 )
{
cpuid(base, &eax, &ebx, &ecx, &edx);
*(uint32_t *)(signature + 0) = ebx;
*(uint32_t *)(signature + 4) = ecx;
*(uint32_t *)(signature + 8) = edx;
signature[12] = '\0';
if ( !strcmp("XenVMMXenVMM", signature) && (eax >= (base + 2)) )
goto found;
}
return 0;
found:
cpuid(base + 1, &eax, &ebx, &ecx, &edx);
printf("Running in %s context on Xen v%d.%d.\n",
pv_context ? "PV" : "HVM", (uint16_t)(eax >> 16), (uint16_t)eax);
return 1;
}
int main(void)
{
pid_t pid;
int status;
uint32_t dummy;
/* Check for execution in HVM context. */
if ( check_for_xen() )
return 0;
/* Now we check for execution in PV context. */
pv_context = 1;
/*
* Fork a child to test the paravirtualised CPUID instruction.
* If executed outside Xen PV context, the extended opcode will fault.
*/
pid = fork();
switch ( pid )
{
case 0:
/* Child: test paravirtualised CPUID opcode and then exit cleanly. */
cpuid(0x40000000, &dummy, &dummy, &dummy, &dummy);
exit(0);
case -1:
fprintf(stderr, "Fork failed.\n");
return 0;
}
/*
* Parent waits for child to terminate and checks for clean exit.
* Only if the exit is clean is it safe for us to try the extended CPUID.
*/
waitpid(pid, &status, 0);
if ( WIFEXITED(status) && check_for_xen() )
return 0;
printf("Not running on Xen.\n");
return 0;
}
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