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之所以想写这篇帖子，是有两个方面原因。其一是内核版有一个关于《内核可以从线性地址直接计算物理地址，用来做什么呢？》的讨论，偶说计算出物理地址可以共享给用户空间读写。dreamice兄说能否说一下详细的应用。其二是alb*版主提到wheelz曾经写过这样一个例程，拜读了一把，发现在传递物理地址和内存大小上，wheelz的例程还有些不够灵活。alb*版主提到可以通过文件的方式实现动态的传递。
因此，偶也写了这样一个例程，可以动态的将内核空间的物理地址和大小传给用户空间。
整个内核模块，在模块插入时建立proc文件，分配内存。卸载模块的时候将用户空间写入的内容打印出来。
以下是内核模块的代码和用户空间的测试代码。- /*This program is used to allocate memory in kernel
- and pass the physical address to userspace through proc file.*/
- #include <linux/version.h>
- #include <linux/module.h>
- #include <linux/proc_fs.h>
- #include <linux/mm.h>
- #define PROC_MEMSHARE_DIR "memshare"
- #define PROC_MEMSHARE_PHYADDR "phymem_addr"
- #define PROC_MEMSHARE_SIZE "phymem_size"
- /*alloc one page. 4096 bytes*/
- #define PAGE_ORDER 0
- /*this value can get from PAGE_ORDER*/
- #define PAGES_NUMBER 1
- struct proc_dir_entry *proc_memshare_dir ;
- unsigned long kernel_memaddr = 0;
- unsigned long kernel_memsize= 0;
- static int proc_read_phymem_addr(char *page, char **start, off_t off, int count)
- {
- return sprintf(page, "%08lx\n", __pa(kernel_memaddr));
- }
- static int proc_read_phymem_size(char *page, char **start, off_t off, int count)
- {
- return sprintf(page, "%lu\n", kernel_memsize);
- }
- static int __init init(void)
- {
- /*build proc dir "memshare"and two proc files: phymem_addr, phymem_size in the dir*/
- proc_memshare_dir = proc_mkdir(PROC_MEMSHARE_DIR, NULL);
- create_proc_info_entry(PROC_MEMSHARE_PHYADDR, 0, proc_memshare_dir, proc_read_phymem_addr);
- create_proc_info_entry(PROC_MEMSHARE_SIZE, 0, proc_memshare_dir, proc_read_phymem_size);
- /*alloc one page*/
- kernel_memaddr =__get_free_pages(GFP_KERNEL, PAGE_ORDER);
- if(!kernel_memaddr)
- {
- printk("Allocate memory failure!\n");
- }
- else
- {
- SetPageReserved(virt_to_page(kernel_memaddr));
- kernel_memsize = PAGES_NUMBER * PAGE_SIZE;
- printk("Allocate memory success!. The phy mem addr=%08lx, size=%lu\n", __pa(kernel_memaddr), kernel_memsize);
- }
- return 0;
- }
- static void __exit fini(void)
- {
- printk("The content written by user is: %s\n", (unsigned char *) kernel_memaddr);
- ClearPageReserved(virt_to_page(kernel_memaddr));
- free_pages(kernel_memaddr, PAGE_ORDER);
- remove_proc_entry(PROC_MEMSHARE_PHYADDR, proc_memshare_dir);
- remove_proc_entry(PROC_MEMSHARE_SIZE, proc_memshare_dir);
- remove_proc_entry(PROC_MEMSHARE_DIR, NULL);
- return;
- }
- module_init(init);
- module_exit(fini);
- MODULE_LICENSE("GPL");
- MODULE_AUTHOR("Godbach ([email]nylzhaowei@163.com[/email])");
- MODULE_DESCRIPTION("Kernel memory share module.");
- #include <stdio.h>
- #include <stdlib.h>
- #include <unistd.h>
- #include <string.h>
- #include <fcntl.h>
- #include <sys/stat.h>
- #include <sys/types.h>
- #include <sys/mman.h>
- int main(int argc, char* argv[])
- {
- if(argc != 2)
- {
- printf("Usage: %s string\n", argv[0]);
- return 0;
- }
-
- unsigned long phymem_addr, phymem_size;
- char *map_addr;
- char s[256];
- int fd;
-
- /*get the physical address of allocated memory in kernel*/
- fd = open("/proc/memshare/phymem_addr", O_RDONLY);
- if(fd < 0)
- {
- printf("cannot open file /proc/memshare/phymem_addr\n");
- return 0;
- }
- read(fd, s, sizeof(s));
- sscanf(s, "%lx", &phymem_addr);
- close(fd);
- /*get the size of allocated memory in kernel*/
- fd = open("/proc/memshare/phymem_size", O_RDONLY);
- if(fd < 0)
- {
- printf("cannot open file /proc/memshare/phymem_size\n");
- return 0;
- }
- read(fd, s, sizeof(s));
- sscanf(s, "%lu", &phymem_size);
- close(fd);
-
- printf("phymem_addr=%lx, phymem_size=%lu\n", phymem_addr, phymem_size);
- /*memory map*/
- int map_fd = open("/dev/mem", O_RDWR);
- if(map_fd < 0)
- {
- printf("cannot open file /dev/mem\n");
- return 0;
- }
-
- map_addr = mmap(0, phymem_size, PROT_READ|PROT_WRITE, MAP_SHARED, map_fd, phymem_addr);
- strcpy(map_addr, argv[1]);
- munmap(map_addr, phymem_size);
- close(map_fd);
- return 0;
-
- }
debian:/home/km/memshare# insmod memshare_kernel.ko
debian:/home/km/memshare# ./memshare_user 'hello,world!'
phymem_addr=e64e000, phymem_size=4096
debian:/home/km/memshare# cat /proc/memshare/phymem_addr
0e64e000
debian:/home/km/memshare# cat /proc/memshare/phymem_size
4096
debian:/home/km/memshare# rmmod memshare_kernel
debian:/home/km/memshare# tail /var/log/messages
Sep 27 18:14:24 debian kernel: [50527.567931] Allocate memory success!. The phy mem addr=0e64e000, size=4096
Sep 27 18:15:31 debian kernel: [50592.570986] The content written by user is: hello,world!
仓促之间，有些地方处理的还是比较简单。希望高手多多指正。需要了解这方面实现的可以参考一下，共同学习。
[ 本帖最后由 Godbach 于 2008-9-27 18:44 编辑 ] |
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发表于 2008-09-27 18:31
发表于 2008-09-27 18:51
恩，不错。