diff options
Diffstat (limited to 'src/paging.c')
| -rw-r--r-- | src/paging.c | 108 |
1 files changed, 105 insertions, 3 deletions
diff --git a/src/paging.c b/src/paging.c index ecbd647..9fdf6ea 100644 --- a/src/paging.c +++ b/src/paging.c @@ -2,6 +2,7 @@ #define MAX_REGIONS 1024 #define INVALID_PTR UINT64_MAX +#define PADDR_MASK 0x000FFFFFFFFFF000 struct region { @@ -21,6 +22,8 @@ struct region_map static struct region_map physical; static struct region_map virtual; +static uint64_t physbase; + static void init_map(struct region_map *, bool); static void mark_region(struct region_map *, uint64_t, uint64_t, bool); static uint64_t lookup(struct region_map *, uint64_t); @@ -28,11 +31,17 @@ static void delete_node(struct region_map *, uint64_t); static uint64_t add_node(struct region_map *, uint64_t, uint64_t, bool); static void debug_region_map(struct region_map *); static void print_size(uint64_t); +static uint64_t allocate_virtual(uint64_t); +static void update_pagetables(uint64_t, uint64_t, uint64_t, bool); +static uint64_t *table_ptr(uint64_t *, uint16_t); +static uint64_t encode_entry(uint64_t, bool); +static uint64_t get_physical_page(void); void setup_paging(struct boot_info *info) { print(u8"Setting up paging. All usable physical memory is mapped starting at %p\n", info->physbase); + physbase = info->physbase; init_map(&physical, false); init_map(&virtual, true); @@ -44,9 +53,7 @@ setup_paging(struct boot_info *info) /* TODO fill in the used regions of virtual memory, by inspection the page tables that was setup for us * by the bootloader. */ - - uint64_t cr3 = get_cr3(); - print(u8"CR3: %p\n", cr3); + mark_region(&virtual, 0, PAGE_SIZE, false); /* don't use the first page of virtual memory */ } bool @@ -60,6 +67,21 @@ page_fault_handler(uint32_t code) return false; /* We didn't actually handle it */ } +uint64_t +map_page(uint64_t paddr, uint64_t pagecount, bool cacheable) +{ + /* Find a region of virtual memory which isn't in use yet, and which is large enough */ + uint64_t offset = paddr % PAGE_SIZE; + if(offset != 0){ + pagecount++; + paddr -= offset; + } + + uint64_t vaddr = allocate_virtual(pagecount); + update_pagetables(paddr, vaddr, pagecount, cacheable); + return vaddr + offset; +} + static void init_map(struct region_map *map, bool available) { @@ -203,3 +225,83 @@ print_size(uint64_t size) P(kb, "KB", 0); P(b, "B", 1); } + +static uint64_t +allocate_virtual(uint64_t pagecount) +{ + uint64_t size = PAGE_SIZE * pagecount; + + for(uint64_t p = virtual.used; p != INVALID_PTR; p = virtual.regions[p].next){ + struct region *r = &virtual.regions[p]; + if(r->available && r->size >= size){ + uint64_t vaddr = r->start; + mark_region(&virtual, vaddr, size, false); + return vaddr; + } + } + panic(); +} + +static void +update_pagetables(uint64_t paddr, uint64_t vaddr, uint64_t pagecount, bool cacheable) +{ + uint64_t cr3 = get_cr3(); + uint64_t *pml4 = table_ptr(&cr3, 0); + + for(uint64_t i = 0; i < pagecount; i++){ + uint16_t pml4o = (vaddr >> 39) & 0x1F; + uint16_t pdpo = (vaddr >> 30) & 0x1F; + uint16_t pdeo = (vaddr >> 21) & 0x1F; + uint16_t pteo = (vaddr >> 12) & 0x1F; + + uint64_t *pdp = table_ptr(pml4, pml4o); + uint64_t *pde = table_ptr(pdp, pdpo); + uint64_t *pte = table_ptr(pde, pdeo); + + pte[pteo] = encode_entry(paddr, cacheable); + + paddr += PAGE_SIZE; + vaddr += PAGE_SIZE; + } +} + +static uint64_t * +table_ptr(uint64_t *table, uint16_t index) +{ + uint64_t v = table[index]; + if(v == 0){ + v = get_physical_page(); + memset((void*)(v + physbase), 0, PAGE_SIZE); + table[index] = encode_entry(v, true); + }else + v &= PADDR_MASK; + + return (uint64_t *)(v + physbase); +} + +static uint64_t +encode_entry(uint64_t paddr, bool cacheable) +{ + uint64_t v = 0; + v |= (paddr & PADDR_MASK); + v |= 0x3; /* Present + RW */ + if(!cacheable) + v |= 0x10; /* Cache disable */ + return v; +} + +static uint64_t +get_physical_page(void) +{ + /* Almost identical to allocate_virtual. merge them. */ + + for(uint64_t p = physical.used; p != INVALID_PTR; p = physical.regions[p].next){ + struct region *r = &physical.regions[p]; + if(r->available && r->size >= PAGE_SIZE){ + uint64_t paddr = r->start; + mark_region(&physical, paddr, PAGE_SIZE, false); + return paddr; + } + } + panic(); +} |