limine/common/mm/pmm.c

#include <mm/pmm.h>
#include <lib/rand.h>
#include <lib/print.h>

void pmm_randomise_memory(void) {
    print("pmm: Randomising memory contents...");

    for (size_t i = 0; i < memmap_entries; i++) {
        if (memmap[i].type != MEMMAP_USABLE)
            continue;

#if bios == 1
        // We're not going to randomise memory above 4GiB from protected mode,
        // are we?
        if (memmap[i].base >= 0x100000000) {
            continue;
        }
#endif

        uint8_t *ptr = (void *)(uintptr_t)memmap[i].base;
        size_t len = memmap[i].length;

        for (size_t j = 0;;) {
            uint32_t random = rand32();
            uint8_t *rnd_data = (void *)&random;
            if (j >= len)
                break;
            ptr[j++] = rnd_data[0];
            if (j >= len)
                break;
            ptr[j++] = rnd_data[1];
            if (j >= len)
                break;
            ptr[j++] = rnd_data[2];
            if (j >= len)
                break;
            ptr[j++] = rnd_data[3];
        }
    }

    print("\n");
}