hi all:
I make a error:
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ring->buffer = mmap_addr + sizeof(RingBuffer);
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the codes in the userspace program will let the kernel module access the userspace virtual address.
2014-08-30 17:17 GMT+08:00 lx <lxlenovostar@xxxxxxxxx>:
hi all:I have a kernel module, it provide some functions:1. vmalloc a 4KB memory space (I built a ring buffer manage the 4KB memory space)2. provide the special mmap(), which can remap the memory space.3. write some data into the 4KB memory spaceAnd I have a userspace program, it provide some functions:1.mmap the kernel memory space into userspace2.read some data from that mmap spaceThe question is:When I first insmod the kernel module until the data have written in the space,I run the userspace program which read some data. This way is OK.If I insmod the kernel module and run the userspace program at the same time,the kernel will stop and computer will reboot. I think the kernel module iswriting the data and the userspace program is reading the data.How to fix it, thank you!the kernel module code is:######################################################include <linux/module.h>#include <linux/kernel.h>#include <linux/fs.h>#include <linux/errno.h>#include <linux/types.h>#include <linux/fcntl.h>#include <linux/cdev.h>#include <linux/version.h>#include <linux/vmalloc.h>#include <linux/ctype.h>#include <linux/pagemap.h>#include <linux/mm.h>#include <linux/slab.h>#include <linux/proc_fs.h>#include <asm/io.h>#include <asm/system.h>#include <linux/uaccess.h>#include <linux/timer.h>#include <linux/pid.h>#include <linux/sched.h>//#define USE_KMALLOC#define PAGE_ORDER 0#define PAGES_NUMBER 1static int MAJOR_DEVICE = 30;void * mmap_buf = 0;unsigned long mmap_size = 4*1024;static int ws_open(struct inode *inode, struct file *file){return 0;}#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,36)#define LIN_IOCTL_NAME .ioctlint ws_ioctl(struct inode *inode, struct file *file, u_int cmd, u_long data)#else#define LIN_IOCTL_NAME .unlocked_ioctllong ws_ioctl(struct file *file, u_int cmd, u_long data)#endif{//todoreturn 0;}int mmap_alloc(void){//struct page *page;int i;mmap_size = PAGE_ALIGN(mmap_size);#ifdef USE_KMALLOC //for kmallocmmap_buf = kzalloc(mmap_size, GFP_KERNEL);printk("kmalloc mmap_buf=%p\n", (void *)mmap_buf);if (!mmap_buf) {printk("kmalloc failed!\n");return -1;}for (page = virt_to_page(mmap_buf); page < virt_to_page(mmap_buf + mmap_size); page++) {SetPageReserved(page);strcpy((void *)mmap_buf, "Hello world!\n");}#else //for vmallocmmap_buf = vmalloc(mmap_size);printk("vmalloc mmap_buf=%p mmap_size=%ld\n", (void *)mmap_buf, mmap_size);if (!mmap_buf ) {printk("vmalloc failed!\n");return -1;}for (i = 0; i < mmap_size; i += PAGE_SIZE) {SetPageReserved(vmalloc_to_page(mmap_buf + i));}#endifreturn 0;}int mmap_free(void){#ifdef USE_KMALLOCstruct page *page;for (page = virt_to_page(mmap_buf); page < virt_to_page(mmap_buf + mmap_size); page++) {ClearPageReserved(page);}kfree((void *)mmap_buf);#elseint i;for (i = 0; i < mmap_size; i += PAGE_SIZE) {ClearPageReserved(vmalloc_to_page(mmap_buf + i));}vfree((void *)mmap_buf);#endifmmap_buf = NULL;return 0;}static int ws_mmap(struct file *f, struct vm_area_struct *vma){int ret;unsigned long pfn;unsigned long start = vma->vm_start;unsigned long size = PAGE_ALIGN(vma->vm_end - vma->vm_start);void * ptmp = mmap_buf;if (size > mmap_size || !mmap_buf) {return -EINVAL;}#ifdef USE_KMALLOCpfn = virt_to_phys(mmap_buf) >> PAGE_SHIFT;return remap_pfn_range(vma, start, pfn, size, PAGE_SHARED);#else/* loop over all pages, map it page individually */while (size > 0) {pfn = vmalloc_to_pfn(ptmp);if ((ret = remap_pfn_range(vma, start, pfn, PAGE_SIZE, PAGE_SHARED)) < 0) {return ret;}start += PAGE_SIZE;ptmp += PAGE_SIZE;size -= PAGE_SIZE;}#endifreturn 0;}static int ws_release(struct inode *inode, struct file *file){return 0;}static const struct file_operations ws_fops ={.owner = THIS_MODULE,//.write = ws_write,//.read = ws_read,.mmap = ws_mmap,//.ioctl = ws_ioctl,//.open = ws_open,//.release = ws_release,};static void wsmmap_exit(void){if( 0 != mmap_free( ))printk("mmap free failed!\n");unregister_chrdev(MAJOR_DEVICE,"wsmmap");printk("rmmod wsmmap module!\n");}/*manage data*/typedef struct {char *buffer;int length;volatile int start;volatile int end;} RingBuffer;RingBuffer * ring_buffer;RingBuffer *RingBuffer_create(void *start_malloc, int length){RingBuffer *buffer = (RingBuffer *)start_malloc;buffer->length = length + 1;buffer->start = 0;buffer->end = 0;buffer->buffer = (char *)start_malloc + sizeof(RingBuffer);return buffer;}#define RingBuffer_available_data(B) ((B)->end % (B)->length - (B)->start)#define RingBuffer_available_space(B) ((B)->length - (B)->end - 1)#define RingBuffer_commit_write(B, A) ((B)->end = ((B)->end + (A)) % (B)->length)#define RingBuffer_ends_at(B) ((B)->buffer + (B)->end)int RingBuffer_write(RingBuffer *buffer, char *data, int length){if(RingBuffer_available_data(buffer) == 0) {buffer->start = buffer->end = 0;}if (length > RingBuffer_available_space(buffer)){printk("Not enough space: %d request, %d available", RingBuffer_available_data(buffer), length);return -1;}void *result = memcpy(RingBuffer_ends_at(buffer), data, length);if (result != RingBuffer_ends_at(buffer)){printk("Failed to write data into buffer.");return -1;}RingBuffer_commit_write(buffer, length);
return length;}int kernel_thread_write(void *argc){char *a = "aa";int num = 2038;while (num){RingBuffer_write(ring_buffer, a, 2);printk("write length is %d, start is %d, end is %d\n", ring_buffer->length, ring_buffer->start, ring_buffer->end);--num;msleep(10);}return 0;}int wsmmap_init(void){//int i;if(register_chrdev(MAJOR_DEVICE, "wsmmap", &ws_fops))printk("Cannot register mmap device as major device 0!\n");elseprintk("wsmmap device driver registed sucessfully!\n");printk("insmod wsmmap module successfully!\n");if(0 != mmap_alloc( ))printk("mmap alloc failed!\n");/** Initialization RingBuffer*/ring_buffer = RingBuffer_create(mmap_buf, mmap_size - sizeof(RingBuffer) - 1);kernel_thread(kernel_thread_write, NULL, CLONE_KERNEL);/*int i;for (i = 0; i < mmap_size; i += PAGE_SIZE){memset(mmap_buf + i, 'a', PAGE_SIZE);memset(mmap_buf + i + PAGE_SIZE - 1, '\0', 1);}*/return 0;}module_init(wsmmap_init);module_exit(wsmmap_exit);MODULE_LICENSE("GPL");MODULE_VERSION("1.0.0");MODULE_DESCRIPTION("wskmmap");MODULE_AUTHOR("wssys");#####################################################the userspace code is:######################################################include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <sys/mman.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <string.h>#include <unistd.h>#include <pthread.h>#include <unistd.h>#include <stdio.h>#include <execinfo.h>#include <signal.h>#include <stdlib.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <time.h>#include <string.h>void handler(int sig){#ifndef WIN32void *array[10];size_t size;size = backtrace(array, 10);int file_dump = open("/opt/dump.log", O_APPEND | O_RDWR);char message[7] = "BEGIN ";write(file_dump, message, 7);time_t now;struct tm *timenow;char strtemp[255];time(&now);timenow = localtime(&now);sprintf(strtemp, "recent time is : %s\n", asctime(timenow));int length=strlen(strtemp)+1;write(file_dump, strtemp, length);backtrace_symbols_fd(array, size, file_dump);close(file_dump);exit(1);#endif}unsigned long phymem_addr = 0;unsigned long phymem_size = 4*1024;/*manage data*/typedef struct {char *buffer;int length;volatile int start;volatile int end;} RingBuffer;RingBuffer *ring;int read_dump;#define RingBuffer_available_data(B) ((B)->end % (B)->length - (B)->start)#define RingBuffer_starts_at(B) ((B)->buffer + (B)->start)#define RingBuffer_commit_read(B, A) ((B)->start = ((B)->start + (A)) % (B)->length)#define RingBuffer_available_space(B) ((B)->length - (B)->end - 1)#define RingBuffer_commit_write(B, A) ((B)->end = ((B)->end + (A)) % (B)->length)#define RingBuffer_ends_at(B) ((B)->buffer + (B)->end)int RingBuffer_read(RingBuffer *buffer, char *target, int amount){if (amount > RingBuffer_available_data(buffer)){printf("Not enough in the buffer: has %d, needs %d", RingBuffer_available_data(buffer), amount);return -1;}void *result = memcpy(target, RingBuffer_starts_at(buffer), amount);if (result != target){printf("Failed to write buffer into data.");return -1;}RingBuffer_commit_read(buffer, amount);if(buffer->end == buffer->start) {buffer->start = buffer->end = 0;}return amount;}void *thread_read(void *arg){char mem_data[64];int num = 2038;
while (num){RingBuffer_read(ring, mem_data, 2);mem_data[2] = '\0';printf("read length is %d, start is %d, end is %d, data is %s\n", ring->length, ring->start, ring->end, mem_data);--num;sleep(1);}}int main(void){int fd;int i=0;void *mmap_addr = NULL;signal(SIGSEGV, handler); // install our handlerfd = open("/dev/wsmmap", O_RDWR);if(fd < 0) {perror("open");return 0;}mmap_addr = mmap(NULL, phymem_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);if(mmap_addr == MAP_FAILED) {perror("mmap");return 0;}ring = (RingBuffer *)mmap_addr;ring->buffer = mmap_addr + sizeof(RingBuffer);int res;pthread_t t_read;res = pthread_create(&t_read, NULL, thread_read, NULL);if (res != 0){perror("join failed");return -1;}void *thread_r_read;res = pthread_join(t_read, &thread_r_read);if (res != 0){perror("Thread join failed");return -1;}free(mmap_addr);mmap_addr=NULL;close(fd);return 0;}#####################################################
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