Kernel/MMU: Dellocate pagedirectory when process exits.

5 files changed, 67 insertions, 12 deletions

diff --git a/kernel/arch/i386/mmu.c b/kernel/arch/i386/mmu.c
index 53b2156..2c05fb6 100644
--- a/kernel/arch/i386/mmu.c
+++ b/kernel/arch/i386/mmu.c
@@ -9,9 +9,6 @@
 #define INDEX_FROM_BIT(a) (a / (32))
 #define OFFSET_FROM_BIT(a) (a % (32))
 
-#define PAGE_ALLOCATE 1
-#define PAGE_NO_ALLOCATE 0
-
 PageDirectory *kernel_directory;
 PageDirectory real_kernel_directory;
 PageDirectory *active_directory = 0;
@@ -92,7 +89,7 @@ Page *get_page(void *ptr, PageDirectory *directory, int create_new_page,
 
     u32 physical;
     directory->tables[table_index] =
-        (PageTable *)ksbrk_physical(sizeof(PageTable), (void **)&physical);
+        (PageTable *)kmalloc_align(sizeof(PageTable), (void **)&physical);
     memset(directory->tables[table_index], 0, sizeof(PageTable));
     directory->physical_tables[table_index] =
         (u32)physical | ((set_user) ? 0x7 : 0x3);
@@ -157,7 +154,7 @@ PageDirectory *get_active_pagedirectory(void) {
 PageTable *clone_table(u32 src_index, PageDirectory *src_directory,
                        u32 *physical_address) {
   PageTable *new_table =
-      ksbrk_physical(sizeof(PageTable), (void **)physical_address);
+      kmalloc_align(sizeof(PageTable), (void **)physical_address);
   PageTable *src = src_directory->tables[src_index];
 
   // Copy all the pages
@@ -214,7 +211,7 @@ PageTable *clone_table(u32 src_index, PageDirectory *src_directory,
 
 PageTable *copy_table(PageTable *src, u32 *physical_address) {
   PageTable *new_table =
-      ksbrk_physical(sizeof(PageTable), (void **)physical_address);
+      kmalloc_align(sizeof(PageTable), (void **)physical_address);
 
   // copy all the pages
   for (u16 i = 0; i < 1024; i++) {
@@ -239,7 +236,7 @@ PageDirectory *clone_directory(PageDirectory *original) {
 
   u32 physical_address;
   PageDirectory *new_directory =
-      ksbrk_physical(sizeof(PageDirectory), (void **)&physical_address);
+      kmalloc_align(sizeof(PageDirectory), (void **)&physical_address);
   u32 offset = (u32)new_directory->physical_tables - (u32)new_directory;
   new_directory->physical_address = physical_address + offset;
 
@@ -388,6 +385,34 @@ void *allocate_frame(Page *page, int rw, int is_kernel) {
   return (void *)(frame_address * 0x1000);
 }
 
+void mmu_free_pagedirectory(PageDirectory *pd) {
+  for (int i = 0; i < 1024; i++) {
+    if (!pd->tables[i]) {
+      continue;
+    }
+    if (pd->tables[i] == kernel_directory->tables[i]) {
+      continue;
+    }
+
+    for (int j = 0; j < 1024; j++) {
+      Page *page = &(pd->tables[i]->pages[j]);
+      if (!page) {
+        continue;
+      }
+      if (!page->present) {
+        continue;
+      }
+      if (!page->frame) {
+        continue;
+      }
+      write_to_frame(((u32)page->frame) * 0x1000, 0);
+    }
+    kmalloc_align_free(pd->tables[i], sizeof(PageTable));
+    pd->tables[i] = NULL;
+  }
+  kmalloc_align_free(pd, sizeof(PageDirectory));
+}
+
 void mmu_free_address_range(void *ptr, size_t length, PageDirectory *pd) {
   size_t num_pages = (size_t)align_page((void *)length) / PAGE_SIZE;
   for (size_t i = 0; i < num_pages; i++, ptr += PAGE_SIZE) {
@@ -581,7 +606,7 @@ void create_table(int table_index) {
   u32 physical;
   kernel_directory->tables[table_index] = (PageTable *)0xDEADBEEF;
   kernel_directory->tables[table_index] =
-      (PageTable *)ksbrk_physical(sizeof(PageTable), (void **)&physical);
+      (PageTable *)kmalloc_align(sizeof(PageTable), (void **)&physical);
   memset(kernel_directory->tables[table_index], 0, sizeof(PageTable));
   kernel_directory->physical_tables[table_index] = (u32)physical | 0x3;
 }
diff --git a/kernel/includes/mmu.h b/kernel/includes/mmu.h
index 43814d5..211a950 100644
--- a/kernel/includes/mmu.h
+++ b/kernel/includes/mmu.h
@@ -9,6 +9,9 @@ typedef u8 mmu_flags;
 #define MMU_FLAG_RW (1 << 0)
 #define MMU_FLAG_KERNEL (1 << 1)
 
+#define PAGE_ALLOCATE 1
+#define PAGE_NO_ALLOCATE 0
+
 #define PAGE_SIZE ((uintptr_t)0x1000)
 #define next_page(_ptr)                                                        \
   ((_ptr) + (PAGE_SIZE - (((uintptr_t)_ptr) & (PAGE_SIZE - 1))))
@@ -37,6 +40,7 @@ typedef struct PageDirectory {
 
 int mmu_allocate_region(void *ptr, size_t n, mmu_flags flags,
                         PageDirectory *pd);
+void mmu_free_pagedirectory(PageDirectory *pd);
 void mmu_allocate_shared_kernel_region(void *rc, size_t n);
 void *mmu_find_unallocated_virtual_range(void *addr, size_t length);
 void mmu_remove_virtual_physical_address_mapping(void *ptr, size_t length);
diff --git a/kernel/kmalloc.c b/kernel/kmalloc.c
index 7138d61..59cc93d 100644
--- a/kernel/kmalloc.c
+++ b/kernel/kmalloc.c
@@ -2,12 +2,36 @@
 #include <kmalloc.h>
 #include <ksbrk.h>
 #include <math.h>
+#include <mmu.h>
 #include <random.h>
 #define NEW_ALLOC_SIZE 0x5000
 
 #define IS_FREE (1 << 0)
 #define IS_FINAL (1 << 1)
 
+void *kmalloc_align(size_t s, void **physical) {
+  // TODO: It should reuse virtual regions so that it does not run out
+  // of address space.
+  return ksbrk_physical(s, physical);
+}
+
+void kmalloc_align_free(void *p, size_t s) {
+  for (int i = 0; i < s; i += 0x1000) {
+    Page *page = get_page((char *)p + i, NULL, PAGE_NO_ALLOCATE, 0);
+    if (!page) {
+      continue;
+    }
+    if (!page->present) {
+      continue;
+    }
+    if (!page->frame) {
+      continue;
+    }
+    write_to_frame(((u32)page->frame) * 0x1000, 0);
+    page->present = 0;
+  }
+}
+
 typedef struct MallocHeader {
   u64 magic;
   u32 size;
diff --git a/kernel/kmalloc.h b/kernel/kmalloc.h
index 8c55cb4..8b9d59d 100644
--- a/kernel/kmalloc.h
+++ b/kernel/kmalloc.h
@@ -4,10 +4,12 @@
 #include <string.h>
 #include <typedefs.h>
 
+void *kmalloc_align(size_t s, void **physical);
+void kmalloc_align_free(void *p, size_t s);
+
 void kmalloc_allocate_heap(void);
 
 void *kmalloc(size_t s);
-void *kmalloc_align(size_t s);
 void *krealloc(void *ptr, size_t size);
 void *kreallocarray(void *ptr, size_t nmemb, size_t size);
 void *kallocarray(size_t nmemb, size_t size);
diff --git a/kernel/sched/scheduler.c b/kernel/sched/scheduler.c
index 52e4848..45969b0 100644
--- a/kernel/sched/scheduler.c
+++ b/kernel/sched/scheduler.c
@@ -191,9 +191,6 @@ void free_process(process_t *p) {
     mmu_remove_virtual_physical_address_mapping(m->u_address, m->length);
   }
 
-  // NOTE: Kernel stuff begins at 0x90000000
-  mmu_free_address_range((void *)0x1000, 0x90000000, p->cr3);
-
   list_free(&p->read_list);
   list_free(&p->write_list);
   list_free(&p->disconnect_list);
@@ -202,9 +199,12 @@ void free_process(process_t *p) {
   list_free(&p->event_queue);
   list_free(&p->file_descriptors);
   kfree(p->tcb);
+
+  mmu_free_pagedirectory(p->cr3);
 }
 
 void exit_process(process_t *p, int status) {
+  disable_interrupts();
   assert(p->pid != 1);
   if (p->parent) {
     p->parent->halts[WAIT_CHILD_HALT] = 0;