int main(int argc, char** argv, char** envp) {
/* Declare ourself as a real time task */
struct sched_param param;
param.sched_priority=MY_PRIORITY;
CHECK_NOT_M1(sched_setscheduler(0, SCHED_FIFO, ¶m));
/* Lock memory */
CHECK_NOT_M1(mlockall(MCL_CURRENT|MCL_FUTURE));
/* Pre-fault our stack - this is useless because of mlock(2) */
pthread_stack_prefault();
/* get the current time */
struct timespec t;
CHECK_NOT_M1(clock_gettime(CLOCK_MONOTONIC, &t));
/* start after one second */
timespec_add_nanos(&t, interval);
while(true) {
/* wait untill next shot */
CHECK_NOT_M1(clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &t, NULL));
/* do the stuff
* ...
* calculate next shot */
timespec_add_nanos(&t, interval);
}
return EXIT_SUCCESS;
}
int main(int argc, char** argv, char** envp) {
const char *str1="this is the content of str1";
const char *str2="this is the content of str2";
const char *str3="this is the content of str3";
proc_print_mmap_self_only();
printf("str1 is %p (%s)\n", str1, str1);
printf("str2 is %p (%s)\n", str2, str2);
printf("str3 is %p (%s)\n", str3, str3);
// this does NOT generate a compile error!
printf("doing assignment of one const char* to another\n");
str1=str3;
printf("str1 is %p (%s)\n", str1, str1);
printf("str2 is %p (%s)\n", str2, str2);
printf("str3 is %p (%s)\n", str3, str3);
// next line will cause the following compiled time error:
// --- char_pointer.c:15: error: assignment of read-only location ‘*(str1 + 2u)’
// str1[2]='y';
// --> This means const strings cannot be changed directly
// We should get a segmentation fault for trying the following...
// The casting is neccessary to avoid a compilation error.
printf("trying to change the value of the const char* buffer...\n");
if(signal_segfault_protect()) {
char *p=(char *)str1;
sprintf(p, "new content ovriding old");
}
// So lets relax the constraints of the mmu
char *p=(char *)str1;
CHECK_NOT_M1(mprotect(page_adr((void*)p), getpagesize(), PROT_READ|PROT_WRITE|PROT_EXEC));
proc_print_mmap_self_only();
sprintf(p, "new content ovriding old");
printf("str1 is %p (%s)\n", str1, str1);
printf("str2 is %p (%s)\n", str2, str2);
printf("str3 is %p (%s)\n", str3, str3);
return EXIT_SUCCESS;
}
