diff options
Diffstat (limited to 'src/kernel/memory/paging.c')
| -rw-r--r-- | src/kernel/memory/paging.c | 203 |
1 files changed, 203 insertions, 0 deletions
diff --git a/src/kernel/memory/paging.c b/src/kernel/memory/paging.c new file mode 100644 index 0000000..e050861 --- /dev/null +++ b/src/kernel/memory/paging.c @@ -0,0 +1,203 @@ +#include <kernel/memory/paging.h> +#include <kernel/memory/kheap.h> +#include <kernel/lib/lib.h> +#include <kernel/system.h> + +int paging_enabled = 0; + +page_directory_t *kernel_directory = 0; +page_directory_t *current_directory = 0; + +uint32_t *frames; +uint32_t nframes; + +extern uint32_t placement_address; +extern heap_t *kheap; + +extern void copy_page_physical(); + +#define INDEX_FROM_BIT(a) (a/(8*4)) +#define OFFSET_FROM_BIT(a) (a%(8*4)) + +static void set_frame(uint32_t frame_addr) +{ + uint32_t frame = frame_addr / 0x1000; + uint32_t idx = INDEX_FROM_BIT(frame); + uint32_t off = OFFSET_FROM_BIT(frame); + frames[idx] |= (0x1 << off); +} + +static void clear_frame(uint32_t frame_addr) +{ + uint32_t frame = frame_addr / 0x1000; + uint32_t idx = INDEX_FROM_BIT(frame); + uint32_t off = OFFSET_FROM_BIT(frame); + frames[idx] &= ~(0x1 << off); +} + +static uint32_t first_frame() +{ + uint32_t i, j; + for (i = 0; i < INDEX_FROM_BIT(nframes); i++) { + if (frames[i] != 0xFFFFFFFF) { + for (j = 0; j < 32; j++) { + uint32_t toTest = (0x1 << j); + if (!(frames[i] & toTest)) { + return i * 4 * 8 + j; + } + } + } + } + return 0; +} + +void alloc_frame(page_t *page, int is_kernel, int is_writeable) +{ + if (page->frame != 0) { + return; + } else { + uint32_t idx = first_frame(); + if (idx == (uint32_t) -1) + panic("No free frames!"); + set_frame(idx * 0x1000); + page->present = 1; + page->rw = (is_writeable == 1) ? 1 : 0; + page->user = (is_kernel == 1) ? 0 : 1; + page->frame = idx; + } +} + +void free_frame(page_t *page) +{ + uint32_t frame; + if (!(frame = page->frame)) { + return; + } else { + clear_frame(frame); + page->frame = 0x0; + } +} + +void paging_install() +{ + uint32_t mem_end_page = memory_get_all() << 10; + + nframes = mem_end_page / 0x1000; + frames = (uint32_t *) kmalloc(INDEX_FROM_BIT(nframes)); + memset(frames, 0, INDEX_FROM_BIT(nframes)); + + kernel_directory = (page_directory_t *) kmalloc_a(sizeof(page_directory_t)); + memset(kernel_directory, 0, sizeof(page_directory_t)); + kernel_directory->physicalAddr = (uint32_t) kernel_directory->tablesPhysical; + + for (uint32_t i = KHEAP_START; i < KHEAP_START + KHEAP_INITIAL_SIZE; i += 0x1000) + get_page((uint32_t) i, 1, kernel_directory); + + int i = 0; + while (i < 0x400000) { + alloc_frame(get_page((uint32_t) i, 1, kernel_directory), 0, 0); + i += 0x1000; + } + + for (i = KHEAP_START; i < (int) (KHEAP_START + KHEAP_INITIAL_SIZE); i += 0x1000) + alloc_frame(get_page((uint32_t) i, 1, kernel_directory), 0, 0); + + switch_page_directory(kernel_directory); + + kheap = create_heap(KHEAP_START, KHEAP_START + KHEAP_INITIAL_SIZE, 0xCFFFF000, 0, 0); + + current_directory = clone_directory(kernel_directory); + switch_page_directory(current_directory); + vga_log("Installed Paging"); +} + +void switch_page_directory(page_directory_t *dir) +{ + current_directory = dir; + asm volatile("mov %0, %%cr3"::"r"(dir->physicalAddr)); + uint32_t cr0; + asm volatile("mov %%cr0, %0": "=r"(cr0)); + cr0 |= 0x80000000; // Enable paging! + asm volatile("mov %0, %%cr0"::"r"(cr0)); +} + +void paging_enable() +{ + switch_page_directory(kernel_directory); + paging_enabled = 1; +} + +void paging_disable() +{ + uint32_t cr0; + asm ("mov %%cr0, %0": "=r"(cr0)); + cr0 &= 0x7fffffff; + asm ("mov %0, %%cr0"::"r"(cr0)); + paging_enabled = 0; +} + +page_t *get_page(uint32_t address, int make, page_directory_t *dir) +{ + address /= 0x1000; + uint32_t table_idx = address / 1024; + + if (dir->tables[table_idx]) { + return &dir->tables[table_idx]->pages[address % 1024]; + } else if (make) { + uint32_t tmp; + dir->tables[table_idx] = (page_table_t *) kmalloc_ap(sizeof(page_table_t), &tmp); + memset(dir->tables[table_idx], 0, 0x1000); + dir->tablesPhysical[table_idx] = tmp | 0x7; // PRESENT, RW, US + return &dir->tables[table_idx]->pages[address % 1024]; + } else { + return 0; + } +} + +static page_table_t *clone_table(page_table_t *src, uint32_t *physAddr) +{ + page_table_t *table = (page_table_t *) kmalloc_ap(sizeof(page_table_t), physAddr); + memset(table, 0, sizeof(page_directory_t)); + + for (int i = 0; i < 1024; i++) { + if (!src->pages[i].frame) + continue; + + alloc_frame(&table->pages[i], 0, 0); + + if (src->pages[i].present) table->pages[i].present = 1; + if (src->pages[i].rw) table->pages[i].rw = 1; + if (src->pages[i].user) table->pages[i].user = 1; + if (src->pages[i].accessed)table->pages[i].accessed = 1; + if (src->pages[i].dirty) table->pages[i].dirty = 1; + + copy_page_physical(src->pages[i].frame * 0x1000, table->pages[i].frame * 0x1000); + } + return table; +} + +page_directory_t *clone_directory(page_directory_t *src) +{ + uint32_t phys; + page_directory_t *dir = (page_directory_t *) kmalloc_ap(sizeof(page_directory_t), &phys); + memset(dir, 0, sizeof(page_directory_t)); + + uint32_t offset = (uint32_t) dir->tablesPhysical - (uint32_t) dir; + + dir->physicalAddr = phys + offset; + + for (int i = 0; i < 1024; i++) { + if (!src->tables[i]) + continue; + + if (kernel_directory->tables[i] == src->tables[i]) { + dir->tables[i] = src->tables[i]; + dir->tablesPhysical[i] = src->tablesPhysical[i]; + } else { + uint32_t phys; + dir->tables[i] = clone_table(src->tables[i], &phys); + dir->tablesPhysical[i] = phys | 0x07; + } + } + return dir; +}
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