init commit of lab3_challenge3

Makefile

@@ -70,7 +70,7 @@ USER_OBJS  		:= $(addprefix $(OBJ_DIR)/, $(patsubst %.c,%.o,$(USER_CPPS)))
 
 
 
-USER_TARGET 	:= $(OBJ_DIR)/app_two_long_loops
+USER_TARGET 	:= $(OBJ_DIR)/app_cow
 #------------------------targets------------------------
 $(OBJ_DIR):
 	@-mkdir -p $(OBJ_DIR)	

kernel/process.c

@@ -196,31 +196,33 @@ int do_fork( process* parent)
 
         // convert free_pages_address into a filter to skip reclaimed blocks in the heap
         // when mapping the heap blocks
-        int free_block_filter[MAX_HEAP_PAGES];
-        memset(free_block_filter, 0, MAX_HEAP_PAGES);
-        uint64 heap_bottom = parent->user_heap.heap_bottom;
-        for (int i = 0; i < parent->user_heap.free_pages_count; i++) {
-          int index = (parent->user_heap.free_pages_address[i] - heap_bottom) / PGSIZE;
-          free_block_filter[index] = 1;
+        {
+          int free_block_filter[MAX_HEAP_PAGES];
+          memset(free_block_filter, 0, MAX_HEAP_PAGES);
+          uint64 heap_bottom = parent->user_heap.heap_bottom;
+          for (int i = 0; i < parent->user_heap.free_pages_count; i++) {
+            int index = (parent->user_heap.free_pages_address[i] - heap_bottom) / PGSIZE;
+            free_block_filter[index] = 1;
+          }
+
+          // copy and map the heap blocks
+          for (uint64 heap_block = current->user_heap.heap_bottom;
+              heap_block < current->user_heap.heap_top; heap_block += PGSIZE) {
+            if (free_block_filter[(heap_block - heap_bottom) / PGSIZE])  // skip free blocks
+              continue;
+
+            void* child_pa = alloc_page();
+            memcpy(child_pa, (void*)lookup_pa(parent->pagetable, heap_block), PGSIZE);
+            user_vm_map((pagetable_t)child->pagetable, heap_block, PGSIZE, (uint64)child_pa,
+                        prot_to_type(PROT_WRITE | PROT_READ, 1));
+          }
+
+          child->mapped_info[HEAP_SEGMENT].npages = parent->mapped_info[HEAP_SEGMENT].npages;
+
+          // copy the heap manager from parent to child
+          memcpy((void*)&child->user_heap, (void*)&parent->user_heap, sizeof(parent->user_heap));
+          break;
         }
-
-        // copy and map the heap blocks
-        for (uint64 heap_block = current->user_heap.heap_bottom;
-             heap_block < current->user_heap.heap_top; heap_block += PGSIZE) {
-          if (free_block_filter[(heap_block - heap_bottom) / PGSIZE])  // skip free blocks
-            continue;
-
-          void* child_pa = alloc_page();
-          memcpy(child_pa, (void*)lookup_pa(parent->pagetable, heap_block), PGSIZE);
-          user_vm_map((pagetable_t)child->pagetable, heap_block, PGSIZE, (uint64)child_pa,
-                      prot_to_type(PROT_WRITE | PROT_READ, 1));
-        }
-
-        child->mapped_info[HEAP_SEGMENT].npages = parent->mapped_info[HEAP_SEGMENT].npages;
-
-        // copy the heap manager from parent to child
-        memcpy((void*)&child->user_heap, (void*)&parent->user_heap, sizeof(parent->user_heap));
-        break;
       case CODE_SEGMENT:
         // TODO (lab3_1): implment the mapping of child code segment to parent's
         // code segment.

kernel/syscall.c

@@ -93,6 +93,12 @@ ssize_t sys_user_yield() {
 
   return 0;
 }
+ssize_t sys_user_printpa(uint64 va)
+{
+  uint64 pa = (uint64)user_va_to_pa((pagetable_t)(current->pagetable), (void*)va);
+  sprint("%lx\n", pa);
+  return 0;
+}
 
 //
 // [a0]: the syscall number; [a1] ... [a7]: arguments to the syscalls.
@@ -113,6 +119,8 @@ long do_syscall(long a0, long a1, long a2, long a3, long a4, long a5, long a6, l
       return sys_user_fork();
     case SYS_user_yield:
       return sys_user_yield();
+    case SYS_user_printpa:
+      return sys_user_printpa(a1);
     default:
       panic("Unknown syscall %ld \n", a0);
   }

kernel/syscall.h

@@ -14,7 +14,7 @@
 // added @lab3_1
 #define SYS_user_fork (SYS_user_base + 4)
 #define SYS_user_yield (SYS_user_base + 5)
-
+#define SYS_user_printpa (SYS_user_base + 6)
 long do_syscall(long a0, long a1, long a2, long a3, long a4, long a5, long a6, long a7);
 
 #endif

user/app_cow.c

@@ -0,0 +1,25 @@
+/*
+ * This app fork a child process to read and write the heap data from parent process.
+ * Because implemented copy on write, when child process only read the heap data,
+ * the physical address is the same as the parent process.
+ * But after writing, child process heap will have different physical address.              
+ */
+
+#include "user/user_lib.h"
+#include "util/types.h"
+
+int main(void) {
+  int *heap_data = naive_malloc();
+  printu("the physical address of parent process heap is: ");
+  printpa(heap_data);
+  int pid = fork();
+  if (pid == 0) {
+    printu("the physical address of child process heap before copy on write is: ");
+    printpa(heap_data);
+    heap_data[0] = 0;
+    printu("the physical address of child process heap after copy on write is: ");
+    printpa(heap_data);
+  }
+  exit(0);
+  return 0;
+}

user/app_two_long_loops.c

@@ -1,28 +0,0 @@
-/*
- * The application of lab3_3.
- * parent and child processes never give up their processor during execution.
- */
-
-#include "user/user_lib.h"
-#include "util/types.h"
-
-int main(void) {
-  uint64 pid = fork();
-  uint64 rounds = 100000000;
-  uint64 interval = 10000000;
-  uint64 a = 0;
-  if (pid == 0) {
-    printu("Child: Hello world! \n");
-    for (uint64 i = 0; i < rounds; ++i) {
-      if (i % interval == 0) printu("Child running %ld \n", i);
-    }
-  } else {
-    printu("Parent: Hello world! \n");
-    for (uint64 i = 0; i < rounds; ++i) {
-      if (i % interval == 0) printu("Parent running %ld \n", i);
-    }
-  }
-
-  exit(0);
-  return 0;
-}

user/user_lib.c

@@ -76,3 +76,8 @@ int fork() {
 void yield() {
   do_user_call(SYS_user_yield, 0, 0, 0, 0, 0, 0, 0);
 }
+
+void printpa(int* va)
+{
+  do_user_call(SYS_user_printpa, (uint64)va, 0, 0, 0, 0, 0, 0);
+}

user/user_lib.h

@@ -8,3 +8,4 @@ void* naive_malloc();
 void naive_free(void* va);
 int fork();
 void yield();
+void printpa(int* va);