From de9678152db5a754830994d8a9c58a767d48b2be Mon Sep 17 00:00:00 2001
From: pbmpay3zt <2440255456@qq.com>
Date: Fri, 1 Jul 2022 23:47:00 +0800
Subject: [PATCH] =?UTF-8?q?sys=5Fmmap=20sys=5Fmunmap=E6=B7=BB=E5=8A=A0?=
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---
 memory1.c | 645 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 645 insertions(+)
 create mode 100644 memory1.c

diff --git a/memory1.c b/memory1.c
new file mode 100644
index 0000000..b92017d
--- /dev/null
+++ b/memory1.c
@@ -0,0 +1,645 @@
+/*
+ *  linux/mm/memory.c
+ *
+ *  (C) 1991  Linus Torvalds
+ */
+
+/*
+ * demand-loading started 01.12.91 - seems it is high on the list of
+ * things wanted, and it should be easy to implement. - Linus
+ */
+
+/*
+ * Ok, demand-loading was easy, shared pages a little bit tricker. Shared
+ * pages started 02.12.91, seems to work. - Linus.
+ *
+ * Tested sharing by executing about 30 /bin/sh: under the old kernel it
+ * would have taken more than the 6M I have free, but it worked well as
+ * far as I could see.
+ *
+ * Also corrected some "invalidate()"s - I wasn't doing enough of them.
+ */
+
+#include <signal.h>
+#include <asm/segment.h>
+#include <asm/system.h>
+#include <linux/sched.h>
+#include <linux/head.h>
+#include <linux/kernel.h>
+
+volatile void do_exit(long code);
+
+static inline volatile void oom(void)
+{
+	printk("out of memory\n\r");
+	do_exit(SIGSEGV);
+}
+
+#define invalidate() \
+__asm__("movl %%eax,%%cr3"::"a" (0))
+
+/* these are not to be changed without changing head.s etc */
+#define LOW_MEM 0x100000
+#define PAGING_MEMORY (15*1024*1024)
+#define PAGING_PAGES (PAGING_MEMORY>>12)
+#define MAP_NR(addr) (((addr)-LOW_MEM)>>12)
+#define USED 100
+
+#define CODE_SPACE(addr) ((((addr)+4095)&~4095) < \
+current->start_code + current->end_code)
+
+static long HIGH_MEMORY = 0;
+
+#define copy_page(from,to) \
+__asm__("cld ; rep ; movsl"::"S" (from),"D" (to),"c" (1024))
+
+static unsigned char mem_map [ PAGING_PAGES ] = {0,};
+
+/*
+ * Get physical address of first (actually last :-) free page, and mark it
+ * used. If no free pages left, return 0.
+ */
+unsigned long get_free_page(void)
+{
+register unsigned long __res asm("ax");
+
+__asm__("std ; repne ; scasb\n\t"
+	"jne 1f\n\t"
+	"movb $1,1(%%edi)\n\t"
+	"sall $12,%%ecx\n\t"
+	"addl %2,%%ecx\n\t"
+	"movl %%ecx,%%edx\n\t"
+	"movl $1024,%%ecx\n\t"
+	"leal 4092(%%edx),%%edi\n\t"
+	"rep ; stosl\n\t"
+	"movl %%edx,%%eax\n\t"
+	"1:"
+	"cld\n\t"       /* by wyj */
+	:"=a" (__res)
+	:"0" (0),"i" (LOW_MEM),"c" (PAGING_PAGES),
+	"D" (mem_map+PAGING_PAGES-1)
+	);
+return __res;
+}
+
+/*
+ * Free a page of memory at physical address 'addr'. Used by
+ * 'free_page_tables()'
+ */
+void free_page(unsigned long addr)
+{
+	if (addr < LOW_MEM) return;
+	if (addr >= HIGH_MEMORY)
+		panic("trying to free nonexistent page");
+	addr -= LOW_MEM;
+	addr >>= 12;
+	if (mem_map[addr]--) return;
+	mem_map[addr]=0;
+	panic("trying to free free page");
+}
+
+/*
+ * This function frees a continuos block of page tables, as needed
+ * by 'exit()'. As does copy_page_tables(), this handles only 4Mb blocks.
+ */
+int free_page_tables(unsigned long from,unsigned long size)
+{
+	unsigned long *pg_table;
+	unsigned long * dir, nr;
+
+	if (from & 0x3fffff)
+		panic("free_page_tables called with wrong alignment");
+	if (!from)
+		panic("Trying to free up swapper memory space");
+	size = (size + 0x3fffff) >> 22;
+	dir = (unsigned long *) ((from>>20) & 0xffc); /* _pg_dir = 0 */
+	for ( ; size-->0 ; dir++) {
+		if (!(1 & *dir))
+			continue;
+		pg_table = (unsigned long *) (0xfffff000 & *dir);
+		for (nr=0 ; nr<1024 ; nr++) {
+			if (1 & *pg_table)
+				free_page(0xfffff000 & *pg_table);
+			*pg_table = 0;
+			pg_table++;
+		}
+		free_page(0xfffff000 & *dir);
+		*dir = 0;
+	}
+	invalidate();
+	return 0;
+}
+
+/*
+ *  Well, here is one of the most complicated functions in mm. It
+ * copies a range of linerar addresses by copying only the pages.
+ * Let's hope this is bug-free, 'cause this one I don't want to debug :-)
+ *
+ * Note! We don't copy just any chunks of memory - addresses have to
+ * be divisible by 4Mb (one page-directory entry), as this makes the
+ * function easier. It's used only by fork anyway.
+ *
+ * NOTE 2!! When from==0 we are copying kernel space for the first
+ * fork(). Then we DONT want to copy a full page-directory entry, as
+ * that would lead to some serious memory waste - we just copy the
+ * first 160 pages - 640kB. Even that is more than we need, but it
+ * doesn't take any more memory - we don't copy-on-write in the low
+ * 1 Mb-range, so the pages can be shared with the kernel. Thus the
+ * special case for nr=xxxx.
+ */
+int copy_page_tables(unsigned long from,unsigned long to,long size)
+{
+	unsigned long * from_page_table;
+	unsigned long * to_page_table;
+	unsigned long this_page;
+	unsigned long * from_dir, * to_dir;
+	unsigned long nr;
+
+	if ((from&0x3fffff) || (to&0x3fffff))
+		panic("copy_page_tables called with wrong alignment");
+	from_dir = (unsigned long *) ((from>>20) & 0xffc); /* _pg_dir = 0 */
+	to_dir = (unsigned long *) ((to>>20) & 0xffc);
+	size = ((unsigned) (size+0x3fffff)) >> 22;
+	for( ; size-->0 ; from_dir++,to_dir++) {
+		if (1 & *to_dir)
+			panic("copy_page_tables: already exist");
+		if (!(1 & *from_dir))
+			continue;
+		from_page_table = (unsigned long *) (0xfffff000 & *from_dir);
+		if (!(to_page_table = (unsigned long *) get_free_page()))
+			return -1;	/* Out of memory, see freeing */
+		*to_dir = ((unsigned long) to_page_table) | 7;
+		nr = (from==0)?0xA0:1024;
+		for ( ; nr-- > 0 ; from_page_table++,to_page_table++) {
+			this_page = *from_page_table;
+			if (!(1 & this_page))
+				continue;
+			this_page &= ~2;
+			*to_page_table = this_page;
+			if (this_page > LOW_MEM) {
+				*from_page_table = this_page;
+				this_page -= LOW_MEM;
+				this_page >>= 12;
+				mem_map[this_page]++;
+			}
+		}
+	}
+	invalidate();
+	return 0;
+}
+
+/*
+ * This function puts a page in memory at the wanted address.
+ * It returns the physical address of the page gotten, 0 if
+ * out of memory (either when trying to access page-table or
+ * page.)
+ */
+unsigned long put_page(unsigned long page,unsigned long address)
+{
+	unsigned long tmp, *page_table;
+
+/* NOTE !!! This uses the fact that _pg_dir=0 */
+
+	if (page < LOW_MEM || page >= HIGH_MEMORY)
+		printk("Trying to put page %p at %p\n",page,address);
+	if (mem_map[(page-LOW_MEM)>>12] != 1)
+		printk("mem_map disagrees with %p at %p\n",page,address);
+	page_table = (unsigned long *) ((address>>20) & 0xffc);
+	if ((*page_table)&1)
+		page_table = (unsigned long *) (0xfffff000 & *page_table);
+	else {
+		if (!(tmp=get_free_page()))
+			return 0;
+		*page_table = tmp|7;
+		page_table = (unsigned long *) tmp;
+	}
+	page_table[(address>>12) & 0x3ff] = page | 7;
+/* no need for invalidate */
+	return page;
+}
+
+void un_wp_page(unsigned long * table_entry)
+{
+	unsigned long old_page,new_page;
+
+	old_page = 0xfffff000 & *table_entry;
+	if (old_page >= LOW_MEM && mem_map[MAP_NR(old_page)]==1) {
+		*table_entry |= 2;
+		invalidate();
+		return;
+	}
+	if (!(new_page=get_free_page()))
+		oom();
+	if (old_page >= LOW_MEM)
+		mem_map[MAP_NR(old_page)]--;
+	*table_entry = new_page | 7;
+	invalidate();
+	copy_page(old_page,new_page);
+}	
+
+/*
+ * This routine handles present pages, when users try to write
+ * to a shared page. It is done by copying the page to a new address
+ * and decrementing the shared-page counter for the old page.
+ *
+ * If it's in code space we exit with a segment error.
+ */
+void do_wp_page(unsigned long error_code,unsigned long address)
+{
+#if 0
+/* we cannot do this yet: the estdio library writes to code space */
+/* stupid, stupid. I really want the libc.a from GNU */
+	if (CODE_SPACE(address))
+		do_exit(SIGSEGV);
+#endif
+	un_wp_page((unsigned long *)
+		(((address>>10) & 0xffc) + (0xfffff000 &
+		*((unsigned long *) ((address>>20) &0xffc)))));
+
+}
+
+void write_verify(unsigned long address)
+{
+	unsigned long page;
+
+	if (!( (page = *((unsigned long *) ((address>>20) & 0xffc)) )&1))
+		return;
+	page &= 0xfffff000;
+	page += ((address>>10) & 0xffc);
+	if ((3 & *(unsigned long *) page) == 1)  /* non-writeable, present */
+		un_wp_page((unsigned long *) page);
+	return;
+}
+
+void get_empty_page(unsigned long address)
+{
+	unsigned long tmp;
+
+	if (!(tmp=get_free_page()) || !put_page(tmp,address)) {
+		free_page(tmp);		/* 0 is ok - ignored */
+		oom();
+	}
+}
+
+/*
+ * try_to_share() checks the page at address "address" in the task "p",
+ * to see if it exists, and if it is clean. If so, share it with the current
+ * task.
+ *
+ * NOTE! This assumes we have checked that p != current, and that they
+ * share the same executable.
+ */
+static int try_to_share(unsigned long address, struct task_struct * p)
+{
+	unsigned long from;
+	unsigned long to;
+	unsigned long from_page;
+	unsigned long to_page;
+	unsigned long phys_addr;
+
+	from_page = to_page = ((address>>20) & 0xffc);
+	from_page += ((p->start_code>>20) & 0xffc);
+	to_page += ((current->start_code>>20) & 0xffc);
+/* is there a page-directory at from? */
+	from = *(unsigned long *) from_page;
+	if (!(from & 1))
+		return 0;
+	from &= 0xfffff000;
+	from_page = from + ((address>>10) & 0xffc);
+	phys_addr = *(unsigned long *) from_page;
+/* is the page clean and present? */
+	if ((phys_addr & 0x41) != 0x01)
+		return 0;
+	phys_addr &= 0xfffff000;
+	if (phys_addr >= HIGH_MEMORY || phys_addr < LOW_MEM)
+		return 0;
+	to = *(unsigned long *) to_page;
+	if (!(to & 1))
+		if (to = get_free_page())
+			*(unsigned long *) to_page = to | 7;
+		else
+			oom();
+	to &= 0xfffff000;
+	to_page = to + ((address>>10) & 0xffc);
+	if (1 & *(unsigned long *) to_page)
+		panic("try_to_share: to_page already exists");
+/* share them: write-protect */
+	*(unsigned long *) from_page &= ~2;
+	*(unsigned long *) to_page = *(unsigned long *) from_page;
+	invalidate();
+	phys_addr -= LOW_MEM;
+	phys_addr >>= 12;
+	mem_map[phys_addr]++;
+	return 1;
+}
+
+/*
+ * share_page() tries to find a process that could share a page with
+ * the current one. Address is the address of the wanted page relative
+ * to the current data space.
+ *
+ * We first check if it is at all feasible by checking executable->i_count.
+ * It should be >1 if there are other tasks sharing this inode.
+ */
+static int share_page(unsigned long address)
+{
+	struct task_struct ** p;
+
+	if (!current->executable)
+		return 0;
+	if (current->executable->i_count < 2)
+		return 0;
+	for (p = &LAST_TASK ; p > &FIRST_TASK ; --p) {
+		if (!*p)
+			continue;
+		if (current == *p)
+			continue;
+		if ((*p)->executable != current->executable)
+			continue;
+		if (try_to_share(address,*p))
+			return 1;
+	}
+	return 0;
+}
+
+void do_no_page(unsigned long error_code,unsigned long address)
+{
+	int nr[4];
+	unsigned long tmp;
+	unsigned long page;
+	int block,i;
+
+	if (current->pid > 5)
+		printk(" --do_no_page: address=%x, pid=%d\n", address, current->pid);
+		
+	address &= 0xfffff000;
+	tmp = address - current->start_code;
+	if (!current->executable || tmp >= current->end_data) {
+		get_empty_page(address);
+		return;
+	}
+	if (share_page(tmp))
+		return;
+	if (!(page = get_free_page()))
+		oom();
+/* remember that 1 block is used for header */
+	block = 1 + tmp/BLOCK_SIZE;
+	for (i=0 ; i<4 ; block++,i++)
+		nr[i] = bmap(current->executable,block);
+	bread_page(page,current->executable->i_dev,nr);
+	i = tmp + 4096 - current->end_data;
+	tmp = page + 4096;
+	while (i-- > 0) {
+		tmp--;
+		*(char *)tmp = 0;
+	}
+	if (put_page(page,address))
+		return;
+	free_page(page);
+	oom();
+}
+void do_no_page1(unsigned long address)
+{
+	int nr[4];
+	unsigned long tmp;
+	unsigned long page;
+	int block,i;
+	address &= 0xfffff000;
+	tmp = address - current->start_code;
+	if (!current->executable || tmp >= current->end_data) {
+		get_empty_page(address);
+		return;
+	}
+	if (share_page(tmp))
+		return;
+	if (!(page = get_free_page()))
+		oom();
+	block = 1 + tmp/BLOCK_SIZE;
+	for (i=0 ; i<4 ; block++,i++)
+		nr[i] = bmap(current->executable,block);
+	bread_page(page,current->executable->i_dev,nr);
+	i = tmp + 4096 - current->end_data;
+	tmp = page + 4096;
+	while (i-- > 0) {
+		tmp--;
+		*(char *)tmp = 0;
+	}
+	if (put_page(page,address))
+		return;
+	free_page(page);
+	oom();
+}
+void mem_init(long start_mem, long end_mem)
+{
+	int i;
+
+	HIGH_MEMORY = end_mem;
+	for (i=0 ; i<PAGING_PAGES ; i++)
+		mem_map[i] = USED;
+	i = MAP_NR(start_mem);
+	end_mem -= start_mem;
+	end_mem >>= 12;
+	while (end_mem-->0)
+		mem_map[i++]=0;
+}
+
+void calc_mem(void)
+{
+	int i,j,k,free=0;
+	long * pg_tbl;
+
+	for(i=0 ; i<PAGING_PAGES ; i++)
+		if (!mem_map[i]) free++;
+	printk("%d pages free (of %d)\n\r",free,PAGING_PAGES);
+	for(i=2 ; i<1024 ; i++) {
+		if (1&pg_dir[i]) {
+			pg_tbl=(long *) (0xfffff000 & pg_dir[i]);
+			for(j=k=0 ; j<1024 ; j++)
+				if (pg_tbl[j]&1)
+					k++;
+			printk("Pg-dir[%d] uses %d pages\n",i,k);
+		}
+	}
+}
+//long sys_mmap(void *start,size_t len,int prot,int flags,int fd,off_t off){
+long sys_mmap(void *start,size_t len,...){
+	int prot = 3,flags=2,fd=3,off = 0;
+	int block;
+	size_t l=len;
+	struct buffer_head * bh;
+	void * buf=start;
+	int tempprot=0;
+	struct m_inode *dir = current->filp[fd]->f_inode;
+	size_t size=len;
+	if (size%PAGE_SIZE)	size = size/4096*4096+4096;
+	printk("Size is %ld \n",size);
+	//必须要有读权限 如果没有 直接返回-1
+	if(prot&PROT_READ){
+		printk(" Permission denied \n");
+		return -1;
+	}
+	//如果是空的 由其自己分配内存
+	if(start==NULL){
+		//需要由程序分配合适的地址空间
+		//由于是借助链表实现 所以需要搜索来找到合适的地址进行使用
+		if(current->mmap==NULL)	buf = 0x2000000;//直接从中间
+		else if(current->mmap->next==NULL)	buf = current->mmap->vm_end;
+	}
+	//初始化
+	struct vmarea_struct *m1 = (struct vmarea_struct *)malloc(sizeof(struct vmarea_struct));
+	m1->mode = prot;
+	m1->flag = flags;
+	m1->next = NULL;
+	m1->size = size;
+	m1->vm_start = buf;
+	m1->vm_end  = (unsigned long)buf+size;
+	if(current->mmap==NULL)	current->mmap->next = m1;
+	else{//插到最后一个位置
+		struct vmarea_struct *m2=current->mmap;
+		for(m2;m2->next;m2=m2->next)
+			;
+		m2->next = m1;
+	}
+	printk("buf is %ld  \n",buf);
+	//接下来进行映射等操作
+	//参考了try_to_share的实现
+	unsigned long from;
+	unsigned long to;
+	unsigned long from_page;
+	unsigned long to_page;
+	unsigned long phys_addr;
+	unsigned long page;
+	unsigned long tmp;
+	unsigned long vm_address=m1->vm_start;
+	while(vm_address<m1->vm_end){
+		from_page = to_page = ((vm_address>>20)&0xffc);//逻辑的页目录项偏移
+		from_page +=((current->start_code>>20)&0xffc);//该进程目录项地址 
+		//from处是否存在页目录项 否则进行申请
+		from = *(unsigned long *) from_page;
+		from &=0xfffff000;
+		from_page = from +((vm_address>>10)&0xffc);//页表项指针
+		phys_addr = *(unsigned long *) from_page;//页表项内容
+		if(!(phys_addr & 0x1)){
+			if(page = get_free_page())
+				phys_addr = page |0x7,mem_map[(page-LOW_MEM)>>12]++;
+			else
+				oom();
+		}
+		//对页面分配权限
+		*(unsigned long *)from_page &= (prot&PROT_WRITE)?0xffffffff:0xfffffffd;
+		//对flags进行处理,重点处理的是MAP_SHARE,私有的话不需要进行多余的处理
+		//需要将所有进程共享同一页面
+		if(flags&MAP_SHARED){
+			struct task_struct ** task;
+			for (task = &LAST_TASK ; task>&FIRST_TASK;--task){
+				if (!*task)
+					continue;
+				else if (current == *task)
+					continue;
+				else if(!try_to_share(vm_address,*task))
+					printk("current pid %d cann't share memory\n",(*task)->pid);
+			}
+			
+		}
+		vm_address += PAGE_SIZE; 
+	}
+	if (!(block = dir->i_zone[0]))
+		return NULL;
+	if (!(bh = bread(dir->i_dev,block)))
+		return NULL;
+	char *s = (char *) bh->b_data;
+	char *p1=(char *)s;
+	char *p2=(char *)buf;
+	while(len--)
+		put_fs_byte(*(p1++),p2++);
+	return buf;
+}
+/*取消映射
+取消映射分为以下几步：
+	1.从当前进程的虚拟地址结构出发，找到要取消映射的虚拟地址
+	2.判断权限 若是具有可写权限 需要将内容写入到对应的文件之中 可参考sys_wirte的实现
+	3.判断该虚拟地址是否是所有共享
+	4.清空该页面的内容
+	5.取消该进程/所有进程的读写权限
+要注意的是：
+	该结构是一个单向链表 所以链表删除的时候需要谨慎一些
+	
+*/
+//取消进程p的共享 与try_share很类似 只是少了几步
+static int cancle_share(unsigned long address, struct task_struct * p)
+{
+	unsigned long to;
+	unsigned long to_page;
+	unsigned long phys_addr;
+	to_page = ((address>>20) & 0xffc);
+	to_page += ((p->start_code>>20) & 0xffc);
+	to = *(unsigned long *) to_page;
+	to &= 0xfffff000;
+	to_page = to + ((address>>10) & 0xffc);
+	*(unsigned long *) to_page&=~1;
+	phys_addr -= LOW_MEM;
+	phys_addr >>= 12;
+	mem_map[phys_addr]--;
+	return 1;
+}
+//将page页面的内容保存到对应的文件
+int sys_munmap(void *address,size_t len){
+	struct vmarea_struct *m1 = current->mmap;
+	struct vmarea_struct *pre = NULL;
+	//寻找对应的虚拟地址结构
+	if(!m1){
+		printk("address is wrong \n");
+		return 0;
+	}
+	//b遍历所有的结构来进行U型你找
+	for(m1;m1;m1=m1->next)
+		if(m1->vm_start=address){
+			pre = m1;
+			break;
+		}
+	//需要判断一下是否是真的找到了
+	if(m1->vm_start!=m1){
+		printk("address is wrong \n");
+		return 0;
+	}
+	//进行页面的删除 其实很简单 只需要pre只能m1->next即可
+	pre->next = m1->next;
+	//首先释放掉当前页面
+	unsigned long from;
+	unsigned long to;
+	unsigned long from_page;
+	unsigned long to_page;
+	unsigned long phys_addr;
+	unsigned long tpage;
+	unsigned long address=m1->vm_start;
+	if(len%PAGE_SIZE)	len = len/4096*4096+PAGE_SIZE;
+	while(address<len+m1->vm_start&&address<m1->vm_end){
+		from_page = to_page = ((address>>20)&0xffc);//逻辑的页目录项偏移
+		from_page +=((current->start_code>>20)&0xffc);//该进程目录项地址
+		from = *(unsigned long *) from_page;
+		from &=0xfffff000;
+		from_page = from +((address>>10)&0xffc);//页表项指针
+		phys_addr = *(unsigned long *) from_page;//页表项内容 
+		//主要是针对页表项进行修改
+		*(unsigned long *)from_page &= ~1;
+		address += PAGE_SIZE;
+	}
+	//接下来对共享进行处理
+	//如果是共享的话
+	//当前进程已经处理过了 着重处理的是对应页面的进程
+	address = m1->address;
+	if(m1->flag&MAP_SHARED){
+		//其实与mmap设置共享内存类似,如何设置出来的就如何取消掉
+		//仍旧是参照try_to_share的实现
+		struct task_struct **p;
+		for (p = &LAST_TASK ; p > &FIRST_TASK ; --p)
+		{
+			//当前进程已经处理过了 就没必要再处理了
+			if(current == *p)
+				continue;
+			cancle_share(address,*p);
+		}
+	}
+	free(m1);//释放掉结构体占用的内存
+	return 0;
+}
\ No newline at end of file