struct cache_line *get_line_to_use(struct set *set_to_observe) {
/*
Main function for choosing a line that will be used for storing
another portion of data
*/
int number_of_lines = set_to_observe->number_of_lines;
int *line_age = calloc(number_of_lines, sizeof(int));
int i;
struct cache_line *current_line;
struct cache_line *result_line;
for (i = 0; i < number_of_lines; i++) {
current_line = &(set_to_observe->lines[i]);
if (is_usable(current_line)) {
return current_line;
}
line_age[i] = current_line->age;
}
/* If we are here no usable line was found.
We will be using the "LRU" cache policy. */
result_line = get_lru_line(set_to_observe->lines, number_of_lines, line_age);
free(line_age);
return result_line;
}
/**
* The initialization function for the allocation table AT.
* It contains two major parts:
* 1. Calculate the actual physical memory of the machine, and sets the number of physical pages (NUM_PAGES).
* 2. Initializes the physical allocation table (AT) implemented in MATIntro layer, based on the
* information available in the physical memory map table.
* Review import.h in the current directory for the list of avaiable getter and setter functions.
*/
void
pmem_init(unsigned int mbi_addr)
{
unsigned int nps;
// TODO: Define your local variables here.
// number of rows
unsigned int rows;
unsigned int h_addr;
unsigned int i;
unsigned int first_row, tmp_row;
//Calls the lower layer initializatin primitives.
//The parameter mbi_addr shell not be used in the further code.
devinit(mbi_addr);
/**
* Calculate the number of actual number of avaiable physical pages and store it into the local varaible nps.
* Hint: Think of it as the highest address possible in the ranges of the memory map table,
* divided by the page size.
*/
// TODO
rows = get_size();
h_addr = get_mms(rows - 1) + get_mml(rows - 1);
dprintf("h_addr: %u\n", h_addr);
nps = h_addr / PAGESIZE;
set_nps(nps); // Setting the value computed above to NUM_PAGES.
/**
* Initialization of the physical allocation table (AT).
*
* In CertiKOS, the entire addresses < VM_USERLO or >= VM_USERHI are reserved by the kernel.
* That corresponds to the physical pages from 0 to VM_USERLO_PI-1, and from VM_USERHI_PI to NUM_PAGES-1.
* The rest of pages that correspond to addresses [VM_USERLO, VM_USERHI), can be used freely ONLY IF
* the entire page falls into one of the ranges in the memory map table with the permission marked as usable.
*
* Hint:
* 1. You have to initialize AT for all the page indices from 0 to NPS - 1.
* 2. For the pages that are reserved by the kernel, simply set its permission to 1.
* Recall that the setter at_set_perm also marks the page as unallocated.
* Thus, you don't have to call another function to set the allocation flag.
* 3. For the rest of the pages, explore the memory map table to set its permission accordingly.
* The permission should be set to 2 only if there is a range containing the entire page that
* is marked as available in the memory map table. O.w., it should be set to 0.
* Note that the ranges in the memory map are not aligned by pages.
* So it may be possible that for some pages, only part of the addresses are in the ranges.
* Currently, we do not utilize partial pages, so in that case, you should consider those pages as unavailble.
* 4. Every page in the allocation table shold be initialized.
* But the ranges in the momory map table may not cover the entire available address space.
* That means there may be some gaps between the ranges.
* You should still set the permission of those pages in allocation table to 0.
*/
// TODO
for (i = 0; i < VM_USERLO_PI; i++) {
// check if one page occupies two rows
at_set_perm(i, 1);
}
for (first_row = 0; first_row < rows - 1; first_row++) {
if (get_mms(first_row) + get_mml(first_row) < i * PAGESIZE && get_mms(first_row + 1) < (i + 1) * PAGESIZE) {
first_row ++;
break;
}
}
for (i = VM_USERLO_PI; i < VM_USERHI_PI; i++) {
if (i * PAGESIZE <= get_mms(first_row) + get_mml(first_row) && (i + 1) * PAGESIZE > get_mms(first_row) + get_mml(first_row)) {
first_row ++ ;
at_set_perm(i, 0);
} else if (is_usable(i)) {
at_set_perm(i, 2);
} else {
at_set_perm(i, 0);
}
}
for (i = VM_USERHI; i < nps; i++) {
at_set_perm(i, 1);
}
}
