diff options
Diffstat (limited to 'src/kernel/paging.c')
| -rw-r--r-- | src/kernel/paging.c | 130 |
1 files changed, 130 insertions, 0 deletions
diff --git a/src/kernel/paging.c b/src/kernel/paging.c new file mode 100644 index 0000000..b92e037 --- /dev/null +++ b/src/kernel/paging.c @@ -0,0 +1,130 @@ +#include <stdbool.h> +#include <stdint.h> +#include "pmap.h" +#include "paging.h" +#include "boot.h" +#include "panic.h" +#include "task.h" + +enum { + PE_ADDR_MASK = 0xfffff000, + + PT_GLOBAL = 0x100, + PD_LARGE = 0x080, + PT_DIRTY = 0x040, + PE_ACCESSED = 0x020, + PE_NO_CACHE = 0x010, + PE_WRTHCH = 0x008, + PE_USER = 0x004, + PE_WRITABLE = 0x002, + PE_PRESENT = 0x001 +}; + +//TODO: +// try_elf_run needs to call these new functions. + +void *new_pd() { + uint32_t *pd = allocate_kernel_pages(1); + for (uint16_t i = 0; i < 1024; ++i) + pd[i] = 0; + return pd; +} + +void free_pd(void *pd) { + uint32_t *pd_32 = pd; + for (uint16_t i = 0; i < 1024; ++i) + if (pd_32[i] & PE_PRESENT) + free_pages((void *)(pd_32[i] & PE_ADDR_MASK), 1); + free_pages(pd, 1); +} + +void pd_map(void *pd, uint32_t physical_addr, uint32_t virtual_addr, bool writable) { + uint32_t *ptp = (uint32_t *)pd + (virtual_addr >> 22); + if (!(*ptp & PE_PRESENT)) + *ptp = (uint32_t)allocate_kernel_pages(1) | PE_USER | PE_WRITABLE | PE_PRESENT; + ((uint32_t *)(*ptp & PE_ADDR_MASK))[(virtual_addr >> 12) % 1024] = physical_addr | PE_USER | PE_PRESENT | (PE_WRITABLE * writable); +} + +bool pd_is_mapped(void *pd, uint32_t vma) { + uint32_t pde = ((uint32_t *)pd)[vma >> 22]; + return (pde & PE_PRESENT) && (((uint32_t *)(pde & PE_ADDR_MASK))[(vma >> 12) % 1024] & PE_PRESENT); +} + +#define KERNEL_END (0x08000000) + +void free_task_pd(void *pd) { + uint32_t *pd_32 = pd; + for (uint16_t i = 0; i < 1024; ++i) + if (pd_32[i] & PE_PRESENT) { + uint32_t *pt_32 = (uint32_t *)(pd_32[i] & PE_ADDR_MASK); + if (i >= KERNEL_END >> 22) + for (uint16_t j = 0; j < 1024; ++j) + if (pt_32[j] & PE_PRESENT) + free_pages((void *)(pt_32[j] & PE_ADDR_MASK), 1); + free_pages(pt_32, 1); + } + free_pages(pd, 1); +} + +void *new_task_pd() { + uint32_t *pd = new_pd(); + for (uint32_t addr = 0; addr < KERNEL_END; addr += 4096) + pd_map(pd, addr, addr, false); + return pd; +} + +void *pd_user_allocate(void *pd, uint32_t vma, uint32_t pages, bool writable) { + void *pma = allocate_user_pages(pages); + if (!pma) + panic("Could not allocate user pages."); + for (uint32_t i = 0; i < pages; ++i) + pd_map(pd, (uint32_t)pma + (i << 12), vma + (i << 12), writable); + return pma; +} + +void *pd_user_allocate_anywhere_writable(void *pd, uint32_t pages) { + uint32_t run = 0; + for (void *vma = (void *)KERNEL_END; vma; vma += 4096) { + if (pd_is_mapped(pd, vma)) + run = 0; + else if (++run == pages) { + vma -= (pages - 1) * 4096; + for (uint32_t i = 0; i < pages; ++i) + pd_map(pd, (uint32_t)allocate_user_pages(1), (uint32_t)vma + 4096 * i, true); + return vma; + } + } +} + +#define KPAGE_DIR ((uint32_t *)0x00005000) +#define KPAGE_TABLE_0 ((uint32_t *)0x00400000) + +void init_paging() { + //TODO: use PAE if possible + + for (uint32_t i = 0; i < 1048576; ++i) + KPAGE_TABLE_0[i] = (i * 4096) | PE_WRITABLE | PE_PRESENT; + for (uint16_t i = 0; i < 1024; ++i) + KPAGE_DIR[i] = (uint32_t)(KPAGE_TABLE_0 + i * 1024) | PE_WRITABLE | PE_PRESENT; + + asm volatile ( + "mov $0x00005000, %%eax\n" + "mov %%eax, %%cr3\n" + "mov %%cr0, %%eax\n" + "or $0x80000000, %%eax\n" + "mov %%eax, %%cr0" + : : : "eax"); +} + +void switch_to_kernel_cr3() { + asm volatile ( + "mov $0x00005000, %%eax\n" + "mov %%eax, %%cr3" + : : : "eax"); +} + +void switch_to_task_cr3() { + asm volatile ( + "mov %0, %%cr3" + : : "a" (active_task->page_directory)); +}
\ No newline at end of file |