[root@localhost kernel]# cat a.c
#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;
}
[root@localhost kernel]# cat main.c
#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, int *eof, void *data)
{
return sprintf(page, "%08lx\n", __pa(kernel_memaddr));
}
static int proc_read_phymem_size(char *page, char **start, off_t off, int count, int *eof, void *data)
{
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_read_entry(PROC_MEMSHARE_PHYADDR, 0, proc_memshare_dir, proc_read_phymem_addr, NULL);
create_proc_read_entry(PROC_MEMSHARE_SIZE, 0, proc_memshare_dir, proc_read_phymem_size, NULL);
/*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.");
[root@localhost kernel]#
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