RockOS/kernel/lib/memory.c

#include "lib/memory.h"
#include "memory/mm.h"

#define KHEAP_START 0xE0000000

typedef struct __attribute__((packed)) {
    uint8_t free;
    uint32_t next_blk;
} alloc_header_t;

void memcpy(const void* src, void* dst, size_t sz) {
    for (size_t i = 0; i < sz; i++) {
        ((uint8_t*)dst)[i] = ((uint8_t*)src)[i];
    }
}

void memset(const uint8_t* dst, uint8_t val, size_t sz) {
    for (size_t i = 0; i < sz; i++) {
        ((uint8_t*)dst)[i] = val;
    }
}

int strcmp(const char* s1, const char* s2) {
    while (*s1 && (*s1 == *s2)) {
        s1++;
        s2++;
    }
    return *(const uint8_t*)s1 - *(const uint8_t*)s2;
}

int strlen(const char* str) {
    int len = 0;
    while(*str != 0) {
        str++;
        len++;
    }
    return len;
}

static void* kernel_heap_start = (void*)KHEAP_START;
static void* kernel_heap_end = (void*)KHEAP_START;
alloc_header_t* blk_list = NULL;

void kgrow(size_t pages) {
    if (kernel_heap_end == kernel_heap_start) {
        // probaably not great, but if we don't have a heap yet, allocate the first (or only) frame requested.
        // Then initialize the first block header for the allocator
        void* frame = p_alloc_frame();
        map_page((uint32_t)kernel_heap_end, (uint32_t)frame, PAGE_PRESENT | PAGE_WRITABLE);
        kernel_heap_end = (void*)((uint32_t)kernel_heap_end + PAGE_SIZE);
        pages--;
        blk_list = kernel_heap_start;
        blk_list->free = 1;
        blk_list->next_blk = 0;
    }

    for (size_t p = 0; p < pages; p++) {
        void* frame = p_alloc_frame();
        map_page((uint32_t)kernel_heap_end, (uint32_t)frame, PAGE_PRESENT | PAGE_WRITABLE);
        kernel_heap_end = (void*)((uint32_t)kernel_heap_end + PAGE_SIZE); 
    }
}

void* kalloc(size_t sz) {
    if (sz == 0) {
        return NULL;
    }

    alloc_header_t* header = blk_list;
    while (!header->free) {
        if (header->next_blk == 0) {
            return NULL;
        }
        header = (alloc_header_t*)header->next_blk;
    }

    uint32_t data_ptr = (uint32_t)header + sizeof(alloc_header_t);
    if (data_ptr >= (uint32_t)kernel_heap_end) {
        return NULL;
    } // if the start of the data is already at the end, we don't have room

    uint32_t end_of_blk = data_ptr + sz;
    if (end_of_blk > (uint32_t)kernel_heap_end) {
        return NULL;
    } // if the end of the data is past the end, we don't have room

    if (end_of_blk != header->next_blk && end_of_blk < ((uint32_t)kernel_heap_end - sizeof(alloc_header_t))) {
        header->next_blk = end_of_blk;
        alloc_header_t* next_header = (alloc_header_t*)header->next_blk;
        next_header->f
    } // see if we have room to place the next header and at least 1 byte of data

    return (void*)data_ptr;
}