[MEMORY] Memory pages and paging management

2017-01-24 09:58:28 +01:00
parent 5dd42d26ae
commit 4bf5835dc4
10 changed files with 344 additions and 5 deletions
--- a/kernel/mem/vmm.c
+++ b/kernel/mem/vmm.c
@@ -0,0 +1,153 @@
+#include <mem.h>
+#include <string.h>
+#include <debug.h>
+#include <int.h>
+#include <registers.h>
+
+
+#define STRIP_FLAGS(addr) ((void *)(((uintptr_t)(addr)) & ~PAGE_FLAGS_MASK))
+#define ADD_FLAGS(addr, flags) ((void *)(((uintptr_t)(addr)) | ((flags) & PAGE_FLAGS_MASK)))
+
+
+extern page_table BootP4;
+
+page_table *vmm_new_P4()
+{
+  page_table *P4 = (page_table *)pmm_alloc();
+  memset(P2V(P4), 0, PAGE_SIZE);
+  ((page_table *)P2V(P4))[511] = ((page_table *)&BootP4)[511];
+  return P4;
+}
+
+void vmm_set_P4(page_table *P4)
+{
+  write_cr3((uint64_t)P4);
+}
+
+void vmm_free_P4(page_table *P4)
+{
+  P4 = P2V(P4);
+  for(int i4=0; i4 < (int)P4_OFFSET(KERNEL_OFFSET); i4++)
+  {
+    if(P4[i4])
+    {
+      page_table *P3 = P2V(STRIP_FLAGS(P4[i4]));
+      for(int i3=0; i3 < 0x200; i3++)
+      {
+        if(P3[i3])
+        {
+          page_table *P2 = P2V(STRIP_FLAGS(P3[i3]));
+          for(int i2=0; i2 < 0x200; i2++)
+          {
+            if(P2[i2])
+            {
+              page_table *P1 = P2V(STRIP_FLAGS(P2[i2]));
+              for(int i1=0; i1 < 0x200; i1++)
+              {
+                if(P1[i1])
+                {
+                  pmm_free((uintptr_t)STRIP_FLAGS(P1[i1]));
+                  P1[i1] = 0;
+                }
+              }
+              pmm_free((uintptr_t)STRIP_FLAGS(P2[i2]));
+              P2[i2] = 0;
+            }
+          }
+          pmm_free((uintptr_t)STRIP_FLAGS(P3[i3]));
+          P3[i3] = 0;
+        }
+      }
+      pmm_free((uintptr_t)STRIP_FLAGS(P4[i4]));
+      P4[i4] = 0;
+    }
+  }
+  pmm_free(V2P(P4));
+}
+
+void *vmm_find_page(page_table *P4, uintptr_t addr, uint32_t touch)
+{
+  addr &= ~PAGE_FLAGS_MASK;
+
+  page_table *P3, *P2, *P1;
+  P4 = P2V(P4);
+  if(!(P3 = P4[P4_OFFSET(addr)]))
+  {
+    if(!touch) return 0;
+    uintptr_t p = pmm_alloc();
+    memset(P2V(p), 0, PAGE_SIZE);
+    P4[P4_OFFSET(addr)] = P3 = ADD_FLAGS(p, PAGE_PRESENT | PAGE_WRITE | PAGE_USER);
+  }
+  P3 = P2V(STRIP_FLAGS(P3));
+
+  if(!(P2 = P3[P3_OFFSET(addr)]))
+  {
+    if(!touch) return 0;
+    uintptr_t p = pmm_alloc();
+    memset(P2V(p), 0, PAGE_SIZE);
+    P3[P3_OFFSET(addr)] = P2 = ADD_FLAGS(p, PAGE_PRESENT | PAGE_WRITE | PAGE_USER);
+  }
+  P2 = P2V(STRIP_FLAGS(P2));
+
+  if(!(P1 = P2[P2_OFFSET(addr)]))
+  {
+    if(!touch) return 0;
+    uintptr_t p = pmm_alloc();
+    memset(P2V(p), 0, PAGE_SIZE);
+    P2[P2_OFFSET(addr)] = P1 = ADD_FLAGS(p, PAGE_PRESENT | PAGE_WRITE | PAGE_USER);
+  }
+  return P2V(STRIP_FLAGS(P1));
+}
+
+uintptr_t vmm_get_page(page_table *P4, uintptr_t addr)
+{
+  page_table *P1;
+  if(!P4) P4=GET_P4();
+  if(!(P1 = vmm_find_page(P4, addr, 0))) return 0;
+  return (uintptr_t)(P1[P1_OFFSET(addr)]);
+}
+
+uintptr_t vmm_set_page(page_table *P4, uintptr_t addr, uintptr_t phys, uint32_t flags)
+{
+  page_table *P1;
+  if(!P4) P4=GET_P4();
+  if(!(P1 = vmm_find_page(P4, addr, 1))) return 0;
+  P1[P1_OFFSET(addr)] = ADD_FLAGS(phys, flags);
+  return (uintptr_t)P1[P1_OFFSET(addr)];
+}
+
+
+registers_t *page_fault_handler(registers_t *r)
+{
+  debug("\n ===== PAGE FAULT =====\n");
+  debug("Instruction at:%x tried to", r->rip);
+  if(r->err_code & 0x2)
+    debug(" read from");
+  else if(r->err_code & 0xE)
+    debug(" execute code from");
+  else
+    debug(" write to");
+  debug(" memory \nat:%x in",  read_cr2());
+  if(r->err_code & 0x8)
+    debug(" user mode");
+  else
+    debug(" kernel mode");
+  debug("\n");
+  debug("This caused a");
+  if(r->err_code & 0x1)
+    debug(" protection fault");
+  else
+    debug(" page miss");
+  debug(".\n ======================\n");
+  print_registers(r);
+
+#ifndef NDEBUG
+  asm("page_fault_breakpoint:");
+#endif
+  for(;;);
+}
+
+void vmm_init()
+{
+  register_int_handler(0xE, page_fault_handler);
+}