Linux下将物理地址映射到用户空间

/************************************************************/
/* file name : memmap.c                                     */
/* linux /dev/mem mmap support func							*/
/* 															*/
/* 															*/
/* Copyright 2005 huawei com.                               */
/* Author :zhouaidi(42136)									*/
/* Create date: 2005-04-07									*/
/* Modify history											*/
/* 2005-06-12: 对映射成功空间建立管理链表，可以防止对重叠   */
/*             空间的重复映射                               */
/* 2005-12-21: 增加memunmap函数                             */
/************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>

typedef struct tag_MMAP_Node
{
unsigned int Start_P;
unsigned int Start_V;
unsigned int length;
unsigned int refcount;  /* map后的空间段的引用计数 */
struct tag_MMAP_Node * next;
}TMMAP_Node_t;

TMMAP_Node_t * pTMMAPNode = NULL;

#define PAGE_SIZE 0x1000
#define PAGE_SIZE_MASK 0xfffff000

static int fd = -1;
static const char dev[]="/dev/mem";

/* no need considering page_size of 4K */
void * memmap(unsigned int phy_addr, unsigned int size)
{
unsigned int phy_addr_in_page;
unsigned int page_diff;

unsigned int size_in_page;

TMMAP_Node_t * pTmp;
TMMAP_Node_t * pNew;

void *addr=NULL;

if(size == 0)
{
printf("memmap():size can't be zero!\n");
return NULL;
}

/* check if the physical memory space have been mmaped */
pTmp = pTMMAPNode;
while(pTmp != NULL)
{
if( (phy_addr >= pTmp->Start_P) &&
( (phy_addr + size) <= (pTmp->Start_P + pTmp->length) ) )
{
pTmp->refcount++;   /* referrence count increase by 1  */
return (void *)(pTmp->Start_V + phy_addr - pTmp->Start_P);
}

pTmp = pTmp->next;
}

/* not mmaped yet */
if(fd < 0)
{
/* dev not opened yet, so open it */
fd = open (dev, O_RDWR | O_SYNC);
if (fd < 0)
{
printf("memmap():open %s error!\n", dev);
return NULL;
}
}

/* addr align in page_size(4K) */
phy_addr_in_page = phy_addr & PAGE_SIZE_MASK;
page_diff = phy_addr - phy_addr_in_page;

/* size in page_size */
size_in_page =((size + page_diff - 1) & PAGE_SIZE_MASK) + PAGE_SIZE;

addr = mmap ((void *)0, size_in_page, PROT_READ|PROT_WRITE, MAP_SHARED, fd, phy_addr_in_page);
if (addr == MAP_FAILED)
{
printf("memmap():mmap @ 0x%x error!\n", phy_addr_in_page);
return NULL;
}

/* add this mmap to MMAP Node */
pNew = (TMMAP_Node_t *)malloc(sizeof(TMMAP_Node_t));
if(NULL == pNew)
{
printf("memmap():malloc new node failed!\n");
return NULL;
}
pNew->Start_P = phy_addr_in_page;
pNew->Start_V = (unsigned int)addr;
pNew->length = size_in_page;
pNew->refcount = 1;
pNew->next = NULL;

if(pTMMAPNode == NULL)
{
pTMMAPNode = pNew;
}
else
{
pTmp = pTMMAPNode;
while(pTmp->next != NULL)
{
pTmp = pTmp->next;
}

pTmp->next = pNew;
}

return (void *)(addr+page_diff);
}

/*****************************************************************************
Prototype    : memunmap
Description  :
Input        : void * addr_mapped
Output       : None
Return Value : On success, returns 0, on failure -1
Calls        :
Called By    :

History        :
1.Date         : 2005/12/21
Author       : Z42136
Modification : Created function

*****************************************************************************/
int memunmap(void * addr_mapped)
{
TMMAP_Node_t * pPre;
TMMAP_Node_t * pTmp;

if(pTMMAPNode == NULL)
{
printf("memunmap(): address have not been mmaped!\n");
return -1;
}

/* check if the physical memory space have been mmaped */
pTmp = pTMMAPNode;
pPre = pTMMAPNode;

do
{
if( ((unsigned int)addr_mapped >= pTmp->Start_V) &&
((unsigned int)addr_mapped <= (pTmp->Start_V + pTmp->length)) )
{
pTmp->refcount--;   /* referrence count decrease by 1  */
if(0 == pTmp->refcount)
{
/* 引用计数变为0, 被map的内存空间不再使用,此时需要进行munmap回收 */

//        printf("memunmap(): map node will be remove!\n");

/* delete this map node from pMMAPNode */
if(pTmp == pTMMAPNode)
{
pTMMAPNode = NULL;
}
else
{
pPre->next = pTmp->next;
}

/* munmap */
if(munmap((void *)pTmp->Start_V, pTmp->length) != 0 )
{
printf("memunmap(): munmap failed!\n");
}

free(pTmp);
}

return 0;
}

pPre = pTmp;
pTmp = pTmp->next;
}while(pTmp != NULL);

printf("memunmap(): address have not been mmaped!\n");
return -1;
}