forkbomb 2W

inc/kern/kmalloc.h

@@ -5,6 +5,7 @@
 
 void		phy_free_4k(phyaddr_t v);
 phyaddr_t	phy_malloc_4k(void);
+void		phy_init_4k();
 
 void		kfree(void *v);
 void *		kmalloc(size_t n);

kern/main.c

@@ -6,6 +6,7 @@
 #include <kern/protect.h>
 #include <kern/process.h>
 #include <kern/trap.h>
+#include <kern/kmalloc.h>
 
 // 标志着内核是否处理完成
 bool init_kernel;
@@ -22,7 +23,7 @@ PROCESS	proc_table[PCB_SIZE];
 void kernel_main(void)
 {
 	kprintf("---start kernel main---\n");
-
+	phy_init_4k(); // init phy_malloc/free_4k management
 	p_proc_ready = proc_table;
 
 	PROCESS_0 *p_proc = &p_proc_ready->pcb;

lib/kern/kmalloc.c

@@ -10,6 +10,32 @@
 static u32 phy_malloc_4k_lock;
 static phyaddr_t phy_malloc_4k_p = 96 * MB;
 
+// 96MB~128MB = 0x0600_0000 ~ 0x0800_0000
+// 32MB = 32 * 1024 / 4 = 8192 PAGES
+#define PHY_START (96 * MB)
+#define PHY_END	(128 * MB)
+#define PHY_PAGENUM ((PHY_END - PHY_START) / PGSIZE)
+// map them to 8192 slots
+#define PHY_INDEX(paddr) ((paddr - PHY_START) >> 12)
+#define PHY_PADDR(idx) ((idx << 12) + PHY_START)
+// we have a head index point to the lowest free slot
+// if slot[i] is free, slot[i] = the index of the next free slot
+// else, slot[i] = -1
+// when initialize, slots are initialized to {1, 2, 3, ...}
+// when alloc, head mov to slot[i], then set slot[i] = 0
+// when free, set slot[i]=head, head = i
+
+static int phy_free_head;
+static int phy_free_table[PHY_PAGENUM];
+
+void phy_init_4k() {
+	for (int i = 0; i < PHY_PAGENUM - 1; ++ i) {
+		phy_free_table[i] = i + 1;
+	}
+	phy_free_table[PHY_PAGENUM-1] = -1;
+	phy_free_head = 0;
+}
+
 /*
  * 释放物理页面，这里并没有为你实现好free_4k的代码，
  * 你需要自己实现一个数据结构用于维护释放的页面，
@@ -19,6 +45,12 @@ void
 phy_free_4k(phyaddr_t paddr)
 {
 	assert(paddr % PGSIZE == 0);
+	assert(96 * MB <= paddr && paddr < 128 * MB);
+	while(xchg(&phy_malloc_4k_lock, 1) == 1)
+		schedule();
+	phy_free_table[PHY_INDEX(paddr)] = phy_free_head;
+	phy_free_head = PHY_INDEX(paddr);
+	xchg(&phy_malloc_4k_lock, 0);
 }
 /*
  * 分配物理页面，每次分配4kb，一页
@@ -29,10 +61,13 @@ phy_malloc_4k(void)
 {
 	while(xchg(&phy_malloc_4k_lock, 1) == 1)
 		schedule();
-	
+	assert(0 <= phy_free_head && phy_free_head < PHY_PAGENUM);
-	assert(phy_malloc_4k_p < 128 * MB);
+	phyaddr_t paddr = PHY_PADDR(phy_free_head);
-	phyaddr_t paddr = phy_malloc_4k_p;
+	phy_free_head = phy_free_table[phy_free_head];
-	phy_malloc_4k_p += PGSIZE;
+	phy_free_table[PHY_INDEX(paddr)] = -1;
+	// assert(phy_malloc_4k_p < 128 * MB);
+	// phyaddr_t paddr = phy_malloc_4k_p;
+	// phy_malloc_4k_p += PGSIZE;
 free:
 	xchg(&phy_malloc_4k_lock, 0);
 	return paddr;