1 files changed, 155 insertions, 0 deletions
diff --git a/loader/paging_efi.c b/loader/paging_efi.c
new file mode 100644
index 0000000..5f65213
--- /dev/null
+++ b/loader/paging_efi.c
@@ -0,0 +1,155 @@
+#include "loader_efi.h"
+
+#include <kernel/memory/paging.h>
+
+#define KERNEL_SPACE_LOWER (void *)0xffffffff80000000
+#define KERNEL_SPACE_UPPER (void *)0xffffffffc0000000
+
+static uint64_t *new_page_table(void);
+static uint64_t *get_page_table(void *vaddr, int level);
+static uint64_t *get_page_entry(void *vaddr);
+
+static uint64_t *get_page_map(void);
+static void set_page_map(uint64_t *map);
+
+static uint64_t *efi_page_map = NULL;
+static uint64_t *system_page_map = NULL;
+
+void paging_init(void)
+{
+    efi_page_map = get_page_map();
+    system_page_map = new_page_table();
+    
+    if (!system_page_map)
+    {
+        Print(L"error creating page map: %r\r\n", e_last_error);
+        efi_exit(e_last_error);
+    }
+    
+    // copy the identity mappings from the EFI PML4.
+    system_page_map[0] = efi_page_map[0];
+    
+    // create kernel fractal mappings
+    // TODO: move this into the kernel instead?
+    uint64_t *lower_pm2 = get_page_table(KERNEL_SPACE_LOWER, 2);
+    uint64_t *upper_pm2 = get_page_table(KERNEL_SPACE_UPPER, 2);
+    
+    upper_pm2[PAGE_TABLE_INDEX_MASK - 1] = (phys_addr_t)lower_pm2|DATA_PAGE_TYPE;
+    upper_pm2[PAGE_TABLE_INDEX_MASK] = (phys_addr_t)upper_pm2|DATA_PAGE_TYPE;
+}
+
+void paging_enter(void)
+{
+    // use the system_page_map instead of efi_page_map
+    set_page_map(system_page_map);
+}
+
+void *paging_map_page(void *vaddr, phys_addr_t paddr, enum page_type type)
+{
+    uint64_t *entry = get_page_entry(vaddr);
+    
+    if (entry)
+    {
+        *entry = paddr | type;
+        return vaddr;
+    }
+    
+    return NULL;
+}
+
+void *paging_map_pages(void *vaddr,
+                       phys_addr_t paddr,
+                       enum page_type type,
+                       size_t size)
+{
+    for (size_t offset = 0; offset < size; offset += page_size(1))
+    {
+        if (!paging_map_page((char *)vaddr + offset, paddr + offset, type))
+        {
+            return NULL;
+        }
+    }
+    
+    return vaddr;
+}
+
+void *paging_map_range(void *vaddr,
+                       struct memory_range *range,
+                       enum page_type type)
+{
+    return paging_map_pages(vaddr, range->base, type, range->size);
+}
+
+static uint64_t *new_page_table(void)
+{
+    struct memory_range table = system_allocate(page_size(1));
+    
+    if (table.type == SYSTEM_MEMORY)
+    {
+        e_bs->SetMem((void *)table.base, table.size, 0);
+        return (uint64_t *)table.base;
+    }
+
+    return NULL;
+}
+
+static uint64_t *get_page_table(void *vaddr, int level)
+{
+    // don't try to do anything if there's no page map.
+    if (!system_page_map)
+    {
+        return NULL;
+    }
+    
+    // don't try to do anything outside of the page map
+    if ((level < 1) || (level > PAGE_MAP_LEVELS))
+    {
+        return NULL;
+    }
+    
+    // don't use a non-canonical address
+    
+    uint64_t *map = system_page_map;
+
+    for (int i = PAGE_MAP_LEVELS; i > level; i--)
+    {
+        if (!map[pte_index(vaddr, i)])
+        {
+            uint64_t *next_map = new_page_table();
+            map[pte_index(vaddr, i)] = (phys_addr_t)next_map|PAGE_PR|PAGE_WR;
+            map = next_map;
+        }
+        else
+        {
+            map = (uint64_t *)page_address(map[pte_index(vaddr, i)], 1);
+        }
+    }
+
+    return map;
+}
+
+static uint64_t *get_page_entry(void *vaddr)
+{
+    uint64_t *table = get_page_table(vaddr, 1);
+    return &table[pte_index(vaddr, 1)];
+}
+
+static uint64_t *get_page_map(void)
+{
+    uint64_t map;
+    __asm__("mov %%cr3, %0" : "=r"(map));
+    return (uint64_t *)(page_address(map, 1));
+}
+
+static void set_page_map(uint64_t *map)
+{
+    __asm__
+    (
+        "pushf\r\n"
+        "cli\r\n"
+        "mov %0, %%cr3\r\n"
+        "popf"
+        :
+        : "r"(map)
+    );
+}