#include <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>
#include <errno.h>
#include <sys/ptrace.h>
#include <signal.h>
#include <sched.h>

static inline void clear_icache(void *p)
{
    asm volatile ("dcbst 0,%0;
                   sync;
                   icbi 0,%0;
                   sync;
                   isync" : : "r" (p));
}


int main( int argc, char** argv ) {
    long* loc;
    int (*init)(void);
    long returninstr0 = 0x38600009; // li r3,4
    long returninstr1 = 0x4e800020; // blr
    int returned;
    int fd;
    char zero;
    char tempfile[20] = { "test-XXXXXX" };

    printf( "start of test\n" );


    fd = mkstemp( tempfile );
    printf( "memfile name test-XXXXXX, fd %d\n", fd );
    if (fchmod(fd, 0777) < 0){
	perror("fchmod");
	exit(1);
    }
    if( lseek( fd, 32768*1024, SEEK_SET ) != 32768*1024 ){ //32M
	perror("lseek");
	exit(1);
    }
    zero = 0;
    if( write(fd, &zero, 1 ) != 1){
	perror("write");
	exit(1);
    }
    if( fcntl(fd, F_SETFD, FD_CLOEXEC ) != 0)
	perror("Setting FD_CLOEXEC failed");


    loc = mmap( (void *) 0x62800000, 12288,
	        PROT_READ | PROT_WRITE | PROT_EXEC,
	        MAP_SHARED | MAP_FIXED,
	        fd, 0x3a0000);

    printf( "memory allocated at addr %x\n", loc );
    printf( "data %x\n", loc[0] );

    // random behaviour, sometimes works, sometimes illegal instruction
    //loc = (long*)0x62800000; // set the address
    //loc = (long*)0x62802000; // set the address
    // always illegal instruction
    loc = (long*)0x62801b44;
    //loc = (long*)0x62801000;
    loc[0] = returninstr0;
    loc[1] = returninstr1;

    printf( "new code: addr %x, %x\n", loc, loc[0] );

    clear_icache( loc );

    init = (int (*)(void))loc;
    returned = init();

    printf( "function returned %d\n", returned );

}