lab 2 (probably working)

kern/arch/mips/syscall/syscall.c

@@ -110,6 +110,25 @@ syscall(struct trapframe *tf)
 		break;
 
 	    /* Add stuff here */
+			case SYS_read:
+		err = sys_read(
+			(int)tf->tf_a0,
+			(userptr_t)tf->tf_a1,
+			(size_t)tf->tf_a2
+		);
+		break;
+
+			case SYS_write:
+		err = sys_write(
+			(int)tf->tf_a0,
+			(userptr_t)tf->tf_a1,
+			(size_t)tf->tf_a2
+		);
+		break;
+
+			case SYS__exit:
+		sys__exit((int)tf->tf_a0);
+		break;
 
 	    default:
 		kprintf("Unknown syscall %d\n", callno);

kern/arch/mips/vm/dumbvm.c

@@ -55,6 +55,15 @@
  * it's cutting (there are many) and why, and more importantly, how.
  */
 
+
+/*
+ * Bitmap utils
+ */
+#define setBit(A,k)     ( A[(k/32)] |= (1 << (k%32)) )
+#define resetBit(A,k)   ( A[(k/32)] &= ~(1 << (k%32)) )
+#define checkBit(A,k)    ( A[(k/32)] & (1 << (k%32)) )
+
+
 /* under dumbvm, always have 72k of user stack */
 /* (this must be > 64K so argument blocks of size ARG_MAX will fit) */
 #define DUMBVM_STACKPAGES    18
@@ -63,11 +72,35 @@
  * Wrap ram_stealmem in a spinlock.
  */
 static struct spinlock stealmem_lock = SPINLOCK_INITIALIZER;
+static struct spinlock freemem_lock = SPINLOCK_INITIALIZER;
+
+static uint32_t *freeRamFrames = NULL;
+static unsigned long *allocSize = NULL;
+static int nRamFrames = 0;
+static int allocTableActive = 0;
 
 void
 vm_bootstrap(void)
 {
-	/* Do nothing. */
+	int i;
+  nRamFrames = ((int)ram_getsize())/PAGE_SIZE;
+  /* alloc freeRamFrame and allocSize */
+  freeRamFrames = kmalloc(sizeof(uint32_t)*(nRamFrames/32 + 1));
+  if (freeRamFrames==NULL) return;
+  allocSize     = kmalloc(sizeof(unsigned long)*nRamFrames);
+  if (allocSize==NULL) {
+    /* reset to disable this vm management */
+    freeRamFrames = NULL; return;
+  }
+  for (i=0; i<nRamFrames; i++) {
+		if (i<(nRamFrames/32 + 1)) {
+	    freeRamFrames[i] = (uint32_t)0;
+		}
+    allocSize[i]     = 0;
+  }
+  spinlock_acquire(&freemem_lock);
+  allocTableActive = 1;
+  spinlock_release(&freemem_lock);
 }
 
 /*
@@ -90,17 +123,88 @@ dumbvm_can_sleep(void)
 	}
 }
 
-static
-paddr_t
+static paddr_t
+getfreeppages(unsigned long npages) {
+  paddr_t addr;
+  long i, first, found, np = (long)npages;
+
+  spinlock_acquire(&freemem_lock);
+	if (!allocTableActive) {
+		spinlock_release(&freemem_lock);
+		return 0;
+	}
+  for (i=0,first=found=-1; i<nRamFrames; i++) {
+    if (checkBit(freeRamFrames, i)) {
+      if (i==0 || !checkBit(freeRamFrames, i-1))
+        first = i; /* set first free in an interval */
+      if (i-first+1 >= np) {
+        found = first;
+        break;
+      }
+    }
+  }
+
+  if (found>=0) {
+    for (i=found; i<found+np; i++) {
+			resetBit(freeRamFrames, i);
+    }
+    allocSize[found] = np;
+    addr = (paddr_t) found*PAGE_SIZE;
+  }
+  else {
+    addr = 0;
+  }
+
+  spinlock_release(&freemem_lock);
+
+  return addr;
+}
+
+static int 
+freeppages(paddr_t addr, unsigned long npages){
+  long i, first, np=(long)npages;	
+
+	spinlock_acquire(&freemem_lock);
+	if (!allocTableActive) {
+		spinlock_release(&freemem_lock);
+		return 0;
+	}
+
+  first = addr/PAGE_SIZE;
+  KASSERT(allocSize!=NULL);
+  KASSERT(nRamFrames>first);
+
+  for (i=first; i<first+np; i++) {
+		setBit(freeRamFrames, i);
+  }
+  spinlock_release(&freemem_lock);
+
+  return 1;
+}
+
+static paddr_t
 getppages(unsigned long npages)
 {
-	paddr_t addr;
+  paddr_t addr;
 
-	spinlock_acquire(&stealmem_lock);
+  /* try freed pages first */
+  addr = getfreeppages(npages);
+  if (addr == 0) {
+    /* call stealmem */
+    spinlock_acquire(&stealmem_lock);
+    addr = ram_stealmem(npages);
+    spinlock_release(&stealmem_lock);
+  }
+	if (addr!=0) {
+    spinlock_acquire(&freemem_lock);
+		if (!allocTableActive) {
+			spinlock_release(&freemem_lock);
+			return addr;
+		}
+		allocSize[addr/PAGE_SIZE] = npages;
+    spinlock_release(&freemem_lock);
+	}
 
-	addr = ram_stealmem(npages);
-
-	spinlock_release(&stealmem_lock);
 	return addr;
 }
 
@@ -121,9 +225,17 @@ alloc_kpages(unsigned npages)
 void
 free_kpages(vaddr_t addr)
 {
-	/* nothing - leak the memory. */
-
-	(void)addr;
+	spinlock_acquire(&freemem_lock);
+	if (!allocTableActive) {
+		spinlock_release(&freemem_lock);
+		return;
+	}
+	spinlock_release(&freemem_lock);
+	paddr_t paddr = addr - MIPS_KSEG0;
+	long first = paddr/PAGE_SIZE;	
+	KASSERT(allocSize!=NULL);
+	KASSERT(nRamFrames>first);
+	freeppages(paddr, allocSize[first]);	
 }
 
 void