shm.c

嵌入式系统设计与实例开发实验教材二源码 多线程应用程序设计 串行端口程序设计 AD接口实验 CAN总线通信实验 GPS通信实验 Linux内核移植与编译实验 IC卡读写实验 SD驱动使

	struct shm_setbuf setbuf;
	struct shmid_kernel *shp;
	int err, version;

	if (cmd < 0 || shmid < 0)
		return -EINVAL;

	version = ipc_parse_version(&cmd);

	switch (cmd) { /* replace with proc interface ? */
	case IPC_INFO:
	{
		struct shminfo64 shminfo;

		memset(&shminfo,0,sizeof(shminfo));
		shminfo.shmmni = shminfo.shmseg = shm_ctlmni;
		shminfo.shmmax = shm_ctlmax;
		shminfo.shmall = shm_ctlall;

		shminfo.shmmin = SHMMIN;
		if(copy_shminfo_to_user (buf, &shminfo, version))
			return -EFAULT;
		/* reading a integer is always atomic */
		err= shm_ids.max_id;
		if(err<0)
			err = 0;
		return err;
	}
	case SHM_INFO:
	{
		struct shm_info shm_info;

		memset(&shm_info,0,sizeof(shm_info));
		down(&shm_ids.sem);
		shm_lockall();
		shm_info.used_ids = shm_ids.in_use;
		shm_get_stat (&shm_info.shm_rss, &shm_info.shm_swp);
		shm_info.shm_tot = shm_tot;
		shm_info.swap_attempts = 0;
		shm_info.swap_successes = 0;
		err = shm_ids.max_id;
		shm_unlockall();
		up(&shm_ids.sem);
		if(copy_to_user (buf, &shm_info, sizeof(shm_info)))
			return -EFAULT;

		return err < 0 ? 0 : err;
	}
	case SHM_STAT:
	case IPC_STAT:
	{
		struct shmid64_ds tbuf;
		int result;
		memset(&tbuf, 0, sizeof(tbuf));
		shp = shm_lock(shmid);
		if(shp==NULL)
			return -EINVAL;
		if(cmd==SHM_STAT) {
			err = -EINVAL;
			if (shmid > shm_ids.max_id)
				goto out_unlock;
			result = shm_buildid(shmid, shp->shm_perm.seq);
		} else {
			err = shm_checkid(shp,shmid);
			if(err)
				goto out_unlock;
			result = 0;
		}
		err=-EACCES;
		if (ipcperms (&shp->shm_perm, S_IRUGO))
			goto out_unlock;
		kernel_to_ipc64_perm(&shp->shm_perm, &tbuf.shm_perm);
		tbuf.shm_segsz	= shp->shm_segsz;
		tbuf.shm_atime	= shp->shm_atim;
		tbuf.shm_dtime	= shp->shm_dtim;
		tbuf.shm_ctime	= shp->shm_ctim;
		tbuf.shm_cpid	= shp->shm_cprid;
		tbuf.shm_lpid	= shp->shm_lprid;
		tbuf.shm_nattch	= shp->shm_nattch;
		shm_unlock(shmid);
		if(copy_shmid_to_user (buf, &tbuf, version))
			return -EFAULT;
		return result;
	}
	case SHM_LOCK:
	case SHM_UNLOCK:
	{
/* Allow superuser to lock segment in memory */
/* Should the pages be faulted in here or leave it to user? */
/* need to determine interaction with current->swappable */
		if (!capable(CAP_IPC_LOCK))
			return -EPERM;

		shp = shm_lock(shmid);
		if(shp==NULL)
			return -EINVAL;
		err = shm_checkid(shp,shmid);
		if(err)
			goto out_unlock;
		if(cmd==SHM_LOCK) {
			shmem_lock(shp->shm_file, 1);
			shp->shm_flags |= SHM_LOCKED;
		} else {
			shmem_lock(shp->shm_file, 0);
			shp->shm_flags &= ~SHM_LOCKED;
		}
		shm_unlock(shmid);
		return err;
	}
	case IPC_RMID:
	{
		/*
		 *	We cannot simply remove the file. The SVID states
		 *	that the block remains until the last person
		 *	detaches from it, then is deleted. A shmat() on
		 *	an RMID segment is legal in older Linux and if 
		 *	we change it apps break...
		 *
		 *	Instead we set a destroyed flag, and then blow
		 *	the name away when the usage hits zero.
		 */
		down(&shm_ids.sem);
		shp = shm_lock(shmid);
		err = -EINVAL;
		if (shp == NULL) 
			goto out_up;
		err = shm_checkid(shp, shmid);
		if(err)
			goto out_unlock_up;
		if (current->euid != shp->shm_perm.uid &&
		    current->euid != shp->shm_perm.cuid && 
		    !capable(CAP_SYS_ADMIN)) {
			err=-EPERM;
			goto out_unlock_up;
		}
		if (shp->shm_nattch){
			shp->shm_flags |= SHM_DEST;
			/* Do not find it any more */
			shp->shm_perm.key = IPC_PRIVATE;
		} else
			shm_destroy (shp);

		/* Unlock */
		shm_unlock(shmid);
		up(&shm_ids.sem);
		return err;
	}

	case IPC_SET:
	{
		if(copy_shmid_from_user (&setbuf, buf, version))
			return -EFAULT;
		down(&shm_ids.sem);
		shp = shm_lock(shmid);
		err=-EINVAL;
		if(shp==NULL)
			goto out_up;
		err = shm_checkid(shp,shmid);
		if(err)
			goto out_unlock_up;
		err=-EPERM;
		if (current->euid != shp->shm_perm.uid &&
		    current->euid != shp->shm_perm.cuid && 
		    !capable(CAP_SYS_ADMIN)) {
			goto out_unlock_up;
		}

		shp->shm_perm.uid = setbuf.uid;
		shp->shm_perm.gid = setbuf.gid;
		shp->shm_flags = (shp->shm_flags & ~S_IRWXUGO)
			| (setbuf.mode & S_IRWXUGO);
		shp->shm_ctim = CURRENT_TIME;
		break;
	}

	default:
		return -EINVAL;
	}

	err = 0;
out_unlock_up:
	shm_unlock(shmid);
out_up:
	up(&shm_ids.sem);
	return err;
out_unlock:
	shm_unlock(shmid);
	return err;
}

/*
 * Fix shmaddr, allocate descriptor, map shm, add attach descriptor to lists.
 */
asmlinkage long sys_shmat (int shmid, char *shmaddr, int shmflg, ulong *raddr)
{
	struct shmid_kernel *shp;
	unsigned long addr;
	unsigned long size;
	struct file * file;
	int    err;
	unsigned long flags;
	unsigned long prot;
	unsigned long o_flags;
	int acc_mode;
	void *user_addr;

	if (shmid < 0)
		return -EINVAL;

	if ((addr = (ulong)shmaddr)) {
		if (addr & (SHMLBA-1)) {
			if (shmflg & SHM_RND)
				addr &= ~(SHMLBA-1);	   /* round down */
			else
				return -EINVAL;
		}
		flags = MAP_SHARED | MAP_FIXED;
	} else {
		if ((shmflg & SHM_REMAP))
			return -EINVAL;

		flags = MAP_SHARED;
	}

	if (shmflg & SHM_RDONLY) {
		prot = PROT_READ;
		o_flags = O_RDONLY;
		acc_mode = S_IRUGO;
	} else {
		prot = PROT_READ | PROT_WRITE;
		o_flags = O_RDWR;
		acc_mode = S_IRUGO | S_IWUGO;
	}

	/*
	 * We cannot rely on the fs check since SYSV IPC does have an
	 * additional creator id...
	 */
	shp = shm_lock(shmid);
	if(shp == NULL)
		return -EINVAL;
	err = shm_checkid(shp,shmid);
	if (err) {
		shm_unlock(shmid);
		return err;
	}
	if (ipcperms(&shp->shm_perm, acc_mode)) {
		shm_unlock(shmid);
		return -EACCES;
	}
	file = shp->shm_file;
	size = file->f_dentry->d_inode->i_size;
	shp->shm_nattch++;
	shm_unlock(shmid);

	down_write(&current->mm->mmap_sem);
	if (addr && !(shmflg & SHM_REMAP)) {
		user_addr = ERR_PTR(-EINVAL);
		if (find_vma_intersection(current->mm, addr, addr + size))
			goto invalid;
		/*
		 * If shm segment goes below stack, make sure there is some
		 * space left for the stack to grow (at least 4 pages).
		 */
		if (addr < current->mm->start_stack &&
		    addr > current->mm->start_stack - size - PAGE_SIZE * 5)
			goto invalid;
	}
		
	user_addr = (void*) do_mmap (file, addr, size, prot, flags, 0);

invalid:
	up_write(&current->mm->mmap_sem);

	down (&shm_ids.sem);
	if(!(shp = shm_lock(shmid)))
		BUG();
	shp->shm_nattch--;
	if(shp->shm_nattch == 0 &&
	   shp->shm_flags & SHM_DEST)
		shm_destroy (shp);
	shm_unlock(shmid);
	up (&shm_ids.sem);

	*raddr = (unsigned long) user_addr;
	err = 0;
	if (IS_ERR(user_addr))
		err = PTR_ERR(user_addr);
	return err;

}

/*
 * detach and kill segment if marked destroyed.
 * The work is done in shm_close.
 */
asmlinkage long sys_shmdt (char *shmaddr)
{
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *shmd, *shmdnext;

	down_write(&mm->mmap_sem);
	for (shmd = mm->mmap; shmd; shmd = shmdnext) {
		shmdnext = shmd->vm_next;
		if (shmd->vm_ops == &shm_vm_ops
		    && shmd->vm_start - (shmd->vm_pgoff << PAGE_SHIFT) == (ulong) shmaddr)
			do_munmap(mm, shmd->vm_start, shmd->vm_end - shmd->vm_start);
	}
	up_write(&mm->mmap_sem);
	return 0;
}

#ifdef CONFIG_PROC_FS
static int sysvipc_shm_read_proc(char *buffer, char **start, off_t offset, int length, int *eof, void *data)
{
	off_t pos = 0;
	off_t begin = 0;
	int i, len = 0;

	down(&shm_ids.sem);
	len += sprintf(buffer, "       key      shmid perms       size  cpid  lpid nattch   uid   gid  cuid  cgid      atime      dtime      ctime\n");

	for(i = 0; i <= shm_ids.max_id; i++) {
		struct shmid_kernel* shp;

		shp = shm_lock(i);
		if(shp!=NULL) {
#define SMALL_STRING "%10d %10d  %4o %10u %5u %5u  %5d %5u %5u %5u %5u %10lu %10lu %10lu\n"
#define BIG_STRING   "%10d %10d  %4o %21u %5u %5u  %5d %5u %5u %5u %5u %10lu %10lu %10lu\n"
			char *format;

			if (sizeof(size_t) <= sizeof(int))
				format = SMALL_STRING;
			else
				format = BIG_STRING;
			len += sprintf(buffer + len, format,
				shp->shm_perm.key,
				shm_buildid(i, shp->shm_perm.seq),
				shp->shm_flags,
				shp->shm_segsz,
				shp->shm_cprid,
				shp->shm_lprid,
				shp->shm_nattch,
				shp->shm_perm.uid,
				shp->shm_perm.gid,
				shp->shm_perm.cuid,
				shp->shm_perm.cgid,
				shp->shm_atim,
				shp->shm_dtim,
				shp->shm_ctim);
			shm_unlock(i);

			pos += len;
			if(pos < offset) {
				len = 0;
				begin = pos;
			}
			if(pos > offset + length)
				goto done;
		}
	}
	*eof = 1;
done:
	up(&shm_ids.sem);
	*start = buffer + (offset - begin);
	len -= (offset - begin);
	if(len > length)
		len = length;
	if(len < 0)
		len = 0;
	return len;
}
#endif