Hi,
I am encountering problem while using copy_to_user in my program pasted
below. Can you tell me where I am going wrong?
My objective here is to pass the values of page_address(bvec->bv_page),
bvec->bv_len, bvec->bv_offset, bio_sectors(bio) to the user application
above. Right now I am just trying it with simple char *buffer. Once this is
successful , I have encapsulated the page_address etc in a structure and
will be using to pass onto the user application.
Need your help asap.
TIA.
My user -space application is
char *message = "How r u?"
char buffer[100];
int fd = open("/dev/sga",O_RDWR);
if (fd < 0)
{
printf("open failed\n");
exit(1);
}
memset(buffer,0,100);
write(fd, message, strlen(message) +1 );
bytes = read(fd,buffer,100);
write(1,buffer,100);
My kernel level function is :-
static int block_dev_random_transfer(struct block_dev *dev, struct bio *bio)
{
int segno;
struct bio_vec *bvec;
sector_t sector = bio->bi_sector;
bio_for_each_segment(bvec,bio,segno)
{
char *buffer = __bio_kmap_atomic(bio,segno,KM_USER0);
printk(KERN_ALERT " virtual address = %x ,bvec->bv_len = %u
, bvec->bv_offset = %d , data transferred in sectors = %u and segno = %d\n",
page_address(bvec->bv_page), bvec->bv_len, bvec->bv_offset,
bio_sectors(bio), segno);
block_transfer(dev,sector,bio_cur_sectors(bio),buffer,bio_data_dir(bio) ==
WRITE);
sector += bio_cur_sectors(bio);
__bio_kunmap_atomic(bio,KM_USER0);
bio->bi_private = vmalloc(strlen(buffer) +1);
if (copy_to_user((unsigned char *)bio->bi_private, (unsigned
char *)buffer, strlen(buffer)+1))
{
printk(KERN_ALERT "copy_to_user failed\n");
return -EFAULT;
}
}
return 0;
}
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