Merge branch 'lab8' into 310551038

lab6/c/include/oscos/mem/vm.h

@@ -55,6 +55,7 @@ void vm_drop_addr_space(vm_addr_space_t pgd);
 vm_map_page_result_t vm_map_page(vm_addr_space_t *addr_space, void *va);
 vm_map_page_result_t vm_handle_permission_fault(vm_addr_space_t *addr_space,
                                                 void *va, int access_mode);
+bool vm_remove_region(vm_addr_space_t *addr_space, void *start_va);
 void vm_switch_to_addr_space(const vm_addr_space_t *addr_space);
 
 void *vm_decide_mmap_addr(vm_addr_space_t addr_space, void *va, size_t len);

lab6/c/src/mem/vm.c

@@ -128,7 +128,7 @@ static void _vm_drop_page_table(page_table_entry_t *const page_table,
     for (size_t i = 0; i < 512; i++) {
       if (page_table[i].b0) {
         const pa_t next_level_pa = page_table[i].addr << PAGE_ORDER;
-        if (level == 1) {
+        if (level == 0) {
           shared_page_decref(pa_to_page_id(next_level_pa));
         } else {
           page_table_entry_t *const next_level_page_table =
@@ -511,6 +511,113 @@ vm_handle_permission_fault(vm_addr_space_t *const addr_space, void *const va,
   }
 }
 
+static page_table_entry_t *
+_vm_remove_region_from_pgd_rec(page_table_entry_t *const page_table,
+                               void *const start_va, void *const end_va,
+                               size_t level, void *const block_start,
+                               page_table_entry_t *const prev_level_entry) {
+  void *const block_end = (char *)block_start + (1 << (9 * level + PAGE_ORDER));
+
+  if (start_va == block_start && end_va == block_end) {
+    _vm_drop_page_table(page_table, level);
+    if (prev_level_entry) {
+      prev_level_entry->b0 = false;
+    }
+    return NULL;
+  } else {
+    page_table_entry_t *const new_page_table =
+        level == 0 ? _vm_clone_unshare_pte(page_table)
+                   : _vm_clone_unshare_page_table(page_table);
+    if (!new_page_table)
+      return NULL;
+
+    if (prev_level_entry) {
+      prev_level_entry->addr = kernel_va_to_pa(new_page_table) >> PAGE_ORDER;
+
+      // Since the page table is not shared, we can remove the read-only bit
+      // now.
+
+      union {
+        table_descriptor_upper_t s;
+        unsigned u;
+      } upper = {.u = prev_level_entry->upper};
+      upper.s.aptable = 0x0;
+      prev_level_entry->upper = upper.u;
+    }
+
+    size_t subblock_stride = 1 << (9 * (level - 1) + PAGE_ORDER);
+
+    for (size_t i = 0; i < 512; i++) {
+      if (new_page_table[i].b0) {
+        void *const subblock_start = (char *)block_start + i * subblock_stride,
+                    *const subblock_end =
+                        (char *)subblock_start + subblock_stride;
+
+        void *const max_start =
+                        start_va > subblock_start ? start_va : subblock_start,
+                    *const min_end =
+                        end_va < subblock_end ? end_va : subblock_end;
+
+        if (max_start < min_end) {
+          if (level == 0) {
+            const page_id_t page_id =
+                pa_to_page_id(new_page_table[i].addr << PAGE_ORDER);
+            shared_page_decref(page_id);
+          } else {
+            page_table_entry_t *const next_level_page_table =
+                pa_to_kernel_va(new_page_table[i].addr << PAGE_ORDER);
+            _vm_remove_region_from_pgd_rec(next_level_page_table, max_start,
+                                           min_end, level - 1, subblock_start,
+                                           &new_page_table[i]);
+          }
+        }
+      }
+    }
+
+    return new_page_table;
+  }
+}
+
+static page_table_entry_t *
+_vm_remove_region_from_pgd(page_table_entry_t *const pgd, void *const start_va,
+                           void *const end_va) {
+  return _vm_remove_region_from_pgd_rec(pgd, start_va, end_va, 3, (void *)0,
+                                        NULL);
+}
+
+bool vm_remove_region(vm_addr_space_t *const addr_space, void *const start_va) {
+  uint64_t daif_val;
+  CRITICAL_SECTION_ENTER(daif_val);
+
+  const mem_region_t *const mem_region = rb_search(
+      addr_space->mem_regions.root, start_va,
+      (int (*)(const void *, const void *, void *))_vm_cmp_va_and_mem_region,
+      NULL);
+  void *const end_va = (char *)start_va + mem_region->len;
+
+  rb_delete(
+      &addr_space->mem_regions.root, start_va,
+      (int (*)(const void *, const void *, void *))_vm_cmp_va_and_mem_region,
+      NULL);
+
+  page_table_entry_t *const new_pgd =
+      _vm_remove_region_from_pgd(addr_space->pgd, start_va, end_va);
+  // Note: `_vm_remove_region_from_pgd` returns NULL when the last region is
+  // removed, i.e., a new page table need not be allocated. However, in all
+  // places where `vm_remove_region` is used, the region to be removed is never
+  // the last one. Therefore, checking for an out-of-memory condition in this
+  // way is fine.
+  if (!new_pgd) {
+    CRITICAL_SECTION_LEAVE(daif_val);
+    return false;
+  }
+
+  addr_space->pgd = new_pgd;
+
+  CRITICAL_SECTION_LEAVE(daif_val);
+  return true;
+}
+
 void vm_switch_to_addr_space(const vm_addr_space_t *const addr_space) {
   const pa_t pgd_pa = kernel_va_to_pa(addr_space->pgd);
   __asm__ __volatile__(

lab6/c/src/sched/sched.c

@@ -286,29 +286,18 @@ void switch_vm(const thread_t *const thread) {
 }
 
 static void _exec_generic(const void *const text_start, const size_t text_len,
-                          const bool free_old_pages) {
+                          const bool remove_text_region) {
   thread_t *const curr_thread = current_thread();
   process_t *const curr_process = curr_thread->process;
 
-  // Allocate memory.
+  // Remove old text region.
 
-  vm_addr_space_t addr_space = {.pgd = NULL};
-  if (free_old_pages) {
-    addr_space = vm_new_addr_space();
-    if (!addr_space.pgd)
+  if (remove_text_region) {
+    if (!vm_remove_region(&curr_process->addr_space, (void *)0x0))
       return;
-  }
-
-  // Free old pages.
-
-  if (free_old_pages) {
-    vm_drop_addr_space(curr_process->addr_space);
-  }
-
-  // Set process data.
 
-  if (free_old_pages) {
-    curr_process->addr_space = addr_space;
+    // Set ttbr0_el1 again, as it might have changed.
+    vm_switch_to_addr_space(&curr_process->addr_space);
   }
 
   // We don't know exactly how large the .bss section of a user program is, so

lab7/c/include/oscos/mem/vm.h

@@ -55,6 +55,7 @@ void vm_drop_addr_space(vm_addr_space_t pgd);
 vm_map_page_result_t vm_map_page(vm_addr_space_t *addr_space, void *va);
 vm_map_page_result_t vm_handle_permission_fault(vm_addr_space_t *addr_space,
                                                 void *va, int access_mode);
+bool vm_remove_region(vm_addr_space_t *addr_space, void *start_va);
 void vm_switch_to_addr_space(const vm_addr_space_t *addr_space);
 
 void *vm_decide_mmap_addr(vm_addr_space_t addr_space, void *va, size_t len);

lab7/c/src/mem/vm.c

@@ -128,7 +128,7 @@ static void _vm_drop_page_table(page_table_entry_t *const page_table,
     for (size_t i = 0; i < 512; i++) {
       if (page_table[i].b0) {
         const pa_t next_level_pa = page_table[i].addr << PAGE_ORDER;
-        if (level == 1) {
+        if (level == 0) {
           shared_page_decref(pa_to_page_id(next_level_pa));
         } else {
           page_table_entry_t *const next_level_page_table =
@@ -511,6 +511,113 @@ vm_handle_permission_fault(vm_addr_space_t *const addr_space, void *const va,
   }
 }
 
+static page_table_entry_t *
+_vm_remove_region_from_pgd_rec(page_table_entry_t *const page_table,
+                               void *const start_va, void *const end_va,
+                               size_t level, void *const block_start,
+                               page_table_entry_t *const prev_level_entry) {
+  void *const block_end = (char *)block_start + (1 << (9 * level + PAGE_ORDER));
+
+  if (start_va == block_start && end_va == block_end) {
+    _vm_drop_page_table(page_table, level);
+    if (prev_level_entry) {
+      prev_level_entry->b0 = false;
+    }
+    return NULL;
+  } else {
+    page_table_entry_t *const new_page_table =
+        level == 0 ? _vm_clone_unshare_pte(page_table)
+                   : _vm_clone_unshare_page_table(page_table);
+    if (!new_page_table)
+      return NULL;
+
+    if (prev_level_entry) {
+      prev_level_entry->addr = kernel_va_to_pa(new_page_table) >> PAGE_ORDER;
+
+      // Since the page table is not shared, we can remove the read-only bit
+      // now.
+
+      union {
+        table_descriptor_upper_t s;
+        unsigned u;
+      } upper = {.u = prev_level_entry->upper};
+      upper.s.aptable = 0x0;
+      prev_level_entry->upper = upper.u;
+    }
+
+    size_t subblock_stride = 1 << (9 * (level - 1) + PAGE_ORDER);
+
+    for (size_t i = 0; i < 512; i++) {
+      if (new_page_table[i].b0) {
+        void *const subblock_start = (char *)block_start + i * subblock_stride,
+                    *const subblock_end =
+                        (char *)subblock_start + subblock_stride;
+
+        void *const max_start =
+                        start_va > subblock_start ? start_va : subblock_start,
+                    *const min_end =
+                        end_va < subblock_end ? end_va : subblock_end;
+
+        if (max_start < min_end) {
+          if (level == 0) {
+            const page_id_t page_id =
+                pa_to_page_id(new_page_table[i].addr << PAGE_ORDER);
+            shared_page_decref(page_id);
+          } else {
+            page_table_entry_t *const next_level_page_table =
+                pa_to_kernel_va(new_page_table[i].addr << PAGE_ORDER);
+            _vm_remove_region_from_pgd_rec(next_level_page_table, max_start,
+                                           min_end, level - 1, subblock_start,
+                                           &new_page_table[i]);
+          }
+        }
+      }
+    }
+
+    return new_page_table;
+  }
+}
+
+static page_table_entry_t *
+_vm_remove_region_from_pgd(page_table_entry_t *const pgd, void *const start_va,
+                           void *const end_va) {
+  return _vm_remove_region_from_pgd_rec(pgd, start_va, end_va, 3, (void *)0,
+                                        NULL);
+}
+
+bool vm_remove_region(vm_addr_space_t *const addr_space, void *const start_va) {
+  uint64_t daif_val;
+  CRITICAL_SECTION_ENTER(daif_val);
+
+  const mem_region_t *const mem_region = rb_search(
+      addr_space->mem_regions.root, start_va,
+      (int (*)(const void *, const void *, void *))_vm_cmp_va_and_mem_region,
+      NULL);
+  void *const end_va = (char *)start_va + mem_region->len;
+
+  rb_delete(
+      &addr_space->mem_regions.root, start_va,
+      (int (*)(const void *, const void *, void *))_vm_cmp_va_and_mem_region,
+      NULL);
+
+  page_table_entry_t *const new_pgd =
+      _vm_remove_region_from_pgd(addr_space->pgd, start_va, end_va);
+  // Note: `_vm_remove_region_from_pgd` returns NULL when the last region is
+  // removed, i.e., a new page table need not be allocated. However, in all
+  // places where `vm_remove_region` is used, the region to be removed is never
+  // the last one. Therefore, checking for an out-of-memory condition in this
+  // way is fine.
+  if (!new_pgd) {
+    CRITICAL_SECTION_LEAVE(daif_val);
+    return false;
+  }
+
+  addr_space->pgd = new_pgd;
+
+  CRITICAL_SECTION_LEAVE(daif_val);
+  return true;
+}
+
 void vm_switch_to_addr_space(const vm_addr_space_t *const addr_space) {
   const pa_t pgd_pa = kernel_va_to_pa(addr_space->pgd);
   __asm__ __volatile__(

lab7/c/src/sched/sched.c

@@ -290,29 +290,18 @@ void switch_vm(const thread_t *const thread) {
 }
 
 static void _exec_generic(const void *const text_start, const size_t text_len,
-                          const bool free_old_pages) {
+                          const bool remove_text_region) {
   thread_t *const curr_thread = current_thread();
   process_t *const curr_process = curr_thread->process;
 
-  // Allocate memory.
+  // Remove old text region.
 
-  vm_addr_space_t addr_space = {.pgd = NULL};
-  if (free_old_pages) {
-    addr_space = vm_new_addr_space();
-    if (!addr_space.pgd)
+  if (remove_text_region) {
+    if (!vm_remove_region(&curr_process->addr_space, (void *)0x0))
       return;
-  }
-
-  // Free old pages.
-
-  if (free_old_pages) {
-    vm_drop_addr_space(curr_process->addr_space);
-  }
-
-  // Set process data.
 
-  if (free_old_pages) {
-    curr_process->addr_space = addr_space;
+    // Set ttbr0_el1 again, as it might have changed.
+    vm_switch_to_addr_space(&curr_process->addr_space);
   }
 
   // We don't know exactly how large the .bss section of a user program is, so

lab8/c/include/oscos/mem/vm.h

@@ -55,6 +55,7 @@ void vm_drop_addr_space(vm_addr_space_t pgd);
 vm_map_page_result_t vm_map_page(vm_addr_space_t *addr_space, void *va);
 vm_map_page_result_t vm_handle_permission_fault(vm_addr_space_t *addr_space,
                                                 void *va, int access_mode);
+bool vm_remove_region(vm_addr_space_t *addr_space, void *start_va);
 void vm_switch_to_addr_space(const vm_addr_space_t *addr_space);
 
 void *vm_decide_mmap_addr(vm_addr_space_t addr_space, void *va, size_t len);