minix/servers/avfs/open.c

/* This file contains the procedures for creating, opening, closing, and
 * seeking on files.
 *
 * The entry points into this file are
 *   do_creat:	perform the CREAT system call
 *   do_open:	perform the OPEN system call
 *   do_mknod:	perform the MKNOD system call
 *   do_mkdir:	perform the MKDIR system call
 *   do_close:	perform the CLOSE system call
 *   do_lseek:  perform the LSEEK system call
 *   do_llseek: perform the LLSEEK system call
 */

#include "fs.h"
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include <minix/callnr.h>
#include <minix/com.h>
#include <minix/u64.h>
#include "file.h"
#include "fproc.h"
#include "dmap.h"
#include "lock.h"
#include "param.h"
#include <dirent.h>
#include <assert.h>
#include <minix/vfsif.h>
#include "vnode.h"
#include "vmnt.h"
#include "path.h"

PUBLIC char mode_map[] = {R_BIT, W_BIT, R_BIT|W_BIT, 0};

FORWARD _PROTOTYPE( int common_open, (char path[PATH_MAX], int oflags,
				      mode_t omode)			);
FORWARD _PROTOTYPE( struct vnode *new_node, (struct lookup *resolve,
					     int oflags, mode_t bits)	);
FORWARD _PROTOTYPE( int pipe_open, (struct vnode *vp, mode_t bits,
				    int oflags)				);


/*===========================================================================*
 *				do_creat				     *
 *===========================================================================*/
PUBLIC int do_creat()
{
/* Perform the creat(name, mode) system call. */
  int r;
  char fullpath[PATH_MAX];

  if (fetch_name(m_in.name, m_in.name_length, M3, fullpath) != OK)
	return(err_code);
  r = common_open(fullpath, O_WRONLY | O_CREAT | O_TRUNC, (mode_t) m_in.mode);
  return(r);
}


/*===========================================================================*
 *				do_open					     *
 *===========================================================================*/
PUBLIC int do_open()
{
/* Perform the open(name, flags,...) system call. */
  int create_mode = 0;		/* is really mode_t but this gives problems */
  int r;
  char fullpath[PATH_MAX];

  /* If O_CREAT is set, open has three parameters, otherwise two. */
  if (m_in.mode & O_CREAT) {
	create_mode = m_in.c_mode;
	r = fetch_name(m_in.c_name, m_in.name1_length, M1, fullpath);
  } else {
	r = fetch_name(m_in.name, m_in.name_length, M3, fullpath);
  }

  if (r != OK) return(err_code); /* name was bad */
  r = common_open(fullpath, m_in.mode, create_mode);
  return(r);
}


/*===========================================================================*
 *				common_open				     *
 *===========================================================================*/
PRIVATE int common_open(char path[PATH_MAX], int oflags, mode_t omode)
{
/* Common code from do_creat and do_open. */
  int b, r, exist = TRUE, major_dev;
  dev_t dev;
  mode_t bits;
  struct filp *filp, *filp2;
  struct vnode *vp;
  struct vmnt *vmp;
  struct dmap *dp;
  struct lookup resolve;

  /* Remap the bottom two bits of oflags. */
  bits = (mode_t) mode_map[oflags & O_ACCMODE];
  if (!bits) return(EINVAL);

  /* See if file descriptor and filp slots are available. */
  if ((r = get_fd(0, bits, &m_in.fd, &filp)) != OK) return(r);

  lookup_init(&resolve, path, PATH_NOFLAGS, &vmp, &vp);

  /* If O_CREATE is set, try to make the file. */
  if (oflags & O_CREAT) {
        omode = I_REGULAR | (omode & ALL_MODES & fp->fp_umask);
	vp = new_node(&resolve, oflags, omode);
	r = err_code;
	if (r == OK) exist = FALSE;	/* We just created the file */
	else if (r != EEXIST) {		/* other error */
		if (vp) unlock_vnode(vp);
		unlock_filp(filp);
		return(r);
	}
	else exist = !(oflags & O_EXCL);/* file exists, if the O_EXCL
					   flag is set this is an error */
  } else {
	/* Scan path name */
	resolve.l_vmnt_lock = VMNT_READ;
	resolve.l_vnode_lock = VNODE_OPCL;
	if ((vp = eat_path(&resolve, fp)) == NULL) {
		unlock_filp(filp);
		return(err_code);
	}

	if (vmp != NULL) unlock_vmnt(vmp);
  }

  /* Claim the file descriptor and filp slot and fill them in. */
  fp->fp_filp[m_in.fd] = filp;
  FD_SET(m_in.fd, &fp->fp_filp_inuse);
  filp->filp_count = 1;
  filp->filp_vno = vp;
  filp->filp_flags = oflags;

  /* Only do the normal open code if we didn't just create the file. */
  if (exist) {
	/* Check protections. */
	if ((r = forbidden(vp, bits)) == OK) {
		/* Opening reg. files, directories, and special files differ */
		switch (vp->v_mode & I_TYPE) {
		   case I_REGULAR:
			/* Truncate regular file if O_TRUNC. */
			if (oflags & O_TRUNC) {
				if ((r = forbidden(vp, W_BIT)) != OK)
					break;
				truncate_vnode(vp, 0);
			}
			break;
		   case I_DIRECTORY:
			/* Directories may be read but not written. */
			r = (bits & W_BIT ? EISDIR : OK);
			break;
		   case I_CHAR_SPECIAL:
			/* Invoke the driver for special processing. */
			dev = (dev_t) vp->v_sdev;
			/* TTY needs to know about the O_NOCTTY flag. */
			r = dev_open(dev, who_e, bits | (oflags & O_NOCTTY));
			if (r == SUSPEND) suspend(FP_BLOCKED_ON_DOPEN);
			else vp = filp->filp_vno; /* Might be updated by
						   * dev_open/clone_opcl */
			break;
		   case I_BLOCK_SPECIAL:

			lock_bsf();

			/* Invoke the driver for special processing. */
			dev = (dev_t) vp->v_sdev;
			r = bdev_open(dev, bits);
			if (r != OK) {
				unlock_bsf();
				break;
			}

			major_dev = major(vp->v_sdev);
			dp = &dmap[major_dev];
			if (dp->dmap_driver == NONE) {
				printf("VFS: block driver disappeared!\n");
				unlock_bsf();
				r = ENXIO;
				break;
			}

			/* Check whether the device is mounted or not. If so,
			 * then that FS is responsible for this device. Else
			 * we default to ROOT_FS. */
			vp->v_bfs_e = ROOT_FS_E; /* By default */
			for (vmp = &vmnt[0]; vmp < &vmnt[NR_MNTS]; ++vmp)
				if (vmp->m_dev == vp->v_sdev &&
				    !(vmp->m_flags & VMNT_FORCEROOTBSF)) {
					vp->v_bfs_e = vmp->m_fs_e;
				}

			/* Send the driver endpoint to the file system that
			 * will handle the block I/O requests (even when its
			 * endpoint is known already), but only when it is the
			 * root file system. Other file systems will already
			 * have it anyway.
			 */
			if (vp->v_bfs_e != ROOT_FS_E) {
				unlock_bsf();
				break;
			}

			if (req_newdriver(vp->v_bfs_e, vp->v_sdev,
					       dp->dmap_driver) != OK) {
				printf("VFS: error sending driver endpoint\n");
				bdev_close(dev);
				r = ENXIO;
			}
			unlock_bsf();
			break;

		   case I_NAMED_PIPE:
			/* Create a mapped inode on PFS which handles reads
			   and writes to this named pipe. */
			tll_upgrade(&vp->v_lock);
			r = map_vnode(vp, PFS_PROC_NR);
			if (r == OK) {
				vp->v_pipe = I_PIPE;
				if (vp->v_ref_count == 1) {
					vp->v_pipe_rd_pos = 0;
					vp->v_pipe_wr_pos = 0;
					if (vp->v_size != 0)
						r = truncate_vnode(vp, 0);
				}
				oflags |= O_APPEND;	/* force append mode */
				filp->filp_flags = oflags;
			}
			if (r == OK) {
				r = pipe_open(vp, bits, oflags);
			}
			if (r != ENXIO) {
				/* See if someone else is doing a rd or wt on
				 * the FIFO.  If so, use its filp entry so the
				 * file position will be automatically shared.
				 */
				b = (bits & R_BIT ? R_BIT : W_BIT);
				filp->filp_count = 0; /* don't find self */
				if ((filp2 = find_filp(vp, b)) != NULL) {
					/* Co-reader or writer found. Use it.*/
					fp->fp_filp[m_in.fd] = filp2;
					filp2->filp_count++;
					filp2->filp_vno = vp;
					filp2->filp_flags = oflags;

					/* v_count was incremented after the
					 * vnode has been found. i_count was
					 * incremented incorrectly in FS, not
					 * knowing that we were going to use an
					 * existing filp entry.  Correct this
					 * error.
					 */
					unlock_vnode(vp);
					put_vnode(vp);
				} else {
					/* Nobody else found. Restore filp. */
					filp->filp_count = 1;
				}
			}
			break;
		}
	}
  }

  unlock_filp(filp);

  /* If error, release inode. */
  if (r != OK) {
	if (r != SUSPEND) {
		fp->fp_filp[m_in.fd] = NULL;
		FD_CLR(m_in.fd, &fp->fp_filp_inuse);
		filp->filp_count = 0;
		filp->filp_vno = NULL;
		put_vnode(vp);
	}
  } else {
	r = m_in.fd;
  }

  return(r);
}


/*===========================================================================*
 *				new_node				     *
 *===========================================================================*/
PRIVATE struct vnode *new_node(struct lookup *resolve, int oflags, mode_t bits)
{
/* Try to create a new inode and return a pointer to it. If the inode already
   exists, return a pointer to it as well, but set err_code accordingly.
   NULL is returned if the path cannot be resolved up to the last
   directory, or when the inode cannot be created due to permissions or
   otherwise. */
  struct vnode *dirp, *vp;
  struct vmnt *dir_vmp, *vp_vmp;
  int r;
  struct node_details res;
  struct lookup findnode;
  char *path;

  path = resolve->l_path;	/* For easy access */

  lookup_init(&findnode, path, resolve->l_flags, &dir_vmp, &dirp);
  findnode.l_vmnt_lock = VMNT_WRITE;
  findnode.l_vnode_lock = VNODE_WRITE; /* dir node */

  /* When O_CREAT and O_EXCL flags are set, the path may not be named by a
   * symbolic link. */
  if (oflags & O_EXCL) findnode.l_flags |= PATH_RET_SYMLINK;

  /* See if the path can be opened down to the last directory. */
  if ((dirp = last_dir(&findnode, fp)) == NULL) return(NULL);

  /* The final directory is accessible. Get final component of the path. */
  findnode.l_vmp = &vp_vmp;
  findnode.l_vnode = &vp;
  findnode.l_vnode_lock = (oflags & O_TRUNC) ? VNODE_WRITE : VNODE_OPCL;
  vp = advance(dirp, &findnode, fp);
  assert(vp_vmp == NULL);	/* Lookup to last dir should have yielded lock
				 * on vmp or final component does not exist. */

  /* The combination of a symlink with absolute path followed by a danglink
   * symlink results in a new path that needs to be re-resolved entirely. */
  if (path[0] == '/') {
printf("XXX: dangling symlink needs re-resolving\n");
	unlock_vnode(dirp);
	unlock_vmnt(dir_vmp);
	put_vnode(dirp);
	if (vp != NULL) {
		unlock_vnode(vp);
		put_vnode(vp);
	}
	return new_node(resolve, oflags, bits);
  }

  if (vp == NULL && err_code == ENOENT) {
	/* Last path component does not exist. Make a new directory entry. */
	if ((vp = get_free_vnode()) == NULL) {
		/* Can't create new entry: out of vnodes. */
		unlock_vnode(dirp);
		unlock_vmnt(dir_vmp);
		put_vnode(dirp);
		return(NULL);
	}

	lock_vnode(vp, VNODE_OPCL);

	if ((r = forbidden(dirp, W_BIT|X_BIT)) != OK ||
	    (r = req_create(dirp->v_fs_e, dirp->v_inode_nr,bits, fp->fp_effuid,
			    fp->fp_effgid, path, &res)) != OK ) {
		/* Can't create inode either due to permissions or some other
		 * problem. In case r is EEXIST, we might be dealing with a
		 * dangling symlink.*/
		if (r == EEXIST) {
			struct vnode *slp, *old_wd;

			/* Resolve path up to symlink */
			findnode.l_flags = PATH_RET_SYMLINK;
			findnode.l_vnode_lock = VNODE_READ;
			findnode.l_vnode = &slp;
			slp = advance(dirp, &findnode, fp);
			if (slp != NULL) {
				if (S_ISLNK(slp->v_mode)) {
					/* Get contents of link */

					r = req_rdlink(slp->v_fs_e,
						       slp->v_inode_nr,
						       VFS_PROC_NR,
						       path,
						       PATH_MAX - 1, 0);
					if (r < 0) {
						/* Failed to read link */
						unlock_vnode(slp);
						unlock_vnode(dirp);
						unlock_vmnt(dir_vmp);
						put_vnode(slp);
						put_vnode(dirp);
						err_code = r;
						return(NULL);
					}
					path[r] = '\0'; /* Terminate path */
				}
				unlock_vnode(slp);
				put_vnode(slp);
			}

			/* Try to create the inode the dangling symlink was
			 * pointing to. We have to use dirp as starting point
			 * as there might be multiple successive symlinks
			 * crossing multiple mountpoints. */
			old_wd = fp->fp_wd; /* Save orig. working dirp */
			fp->fp_wd = dirp;
			vp = new_node(resolve, oflags, bits);
			fp->fp_wd = old_wd; /* Restore */

			if (vp != NULL) {
				unlock_vnode(dirp);
				unlock_vmnt(dir_vmp);
				put_vnode(dirp);
				*(resolve->l_vnode) = vp;
				return(vp);
			}
			r = err_code;
		}

		if (r == EEXIST)
			err_code = EIO; /* Impossible, we have verified that
					 * the last component doesn't exist and
					 * is not a dangling symlink. */
		else
			err_code = r;

		unlock_vnode(dirp);
		unlock_vnode(vp);
		unlock_vmnt(dir_vmp);
		put_vnode(dirp);
		return(NULL);
	}

	/* Store results and mark vnode in use */

	vp->v_fs_e = res.fs_e;
	vp->v_inode_nr = res.inode_nr;
	vp->v_mode = res.fmode;
	vp->v_size = res.fsize;
	vp->v_uid = res.uid;
	vp->v_gid = res.gid;
	vp->v_sdev = res.dev;
	vp->v_vmnt = dirp->v_vmnt;
	vp->v_dev = vp->v_vmnt->m_dev;
	vp->v_fs_count = 1;
	vp->v_ref_count = 1;
  } else {
	/* Either last component exists, or there is some other problem. */
	if (vp != NULL) {
		r = EEXIST;	/* File exists or a symlink names a file while
				 * O_EXCL is set. */
	} else
		r = err_code;	/* Other problem. */
  }

  err_code = r;
  /* When dirp equals vp, we shouldn't release the lock as a vp is locked only
   * once. Releasing the lock would cause the resulting vp not be locked and
   * cause mayhem later on. */
  if (dirp != vp) {
	unlock_vnode(dirp);
  }
  unlock_vmnt(dir_vmp);
  put_vnode(dirp);

  *(resolve->l_vnode) = vp;
  return(vp);
}


/*===========================================================================*
 *				pipe_open				     *
 *===========================================================================*/
PRIVATE int pipe_open(register struct vnode *vp, register mode_t bits,
	register int oflags)
{
/*  This function is called from common_open. It checks if
 *  there is at least one reader/writer pair for the pipe, if not
 *  it suspends the caller, otherwise it revives all other blocked
 *  processes hanging on the pipe.
 */

  vp->v_pipe = I_PIPE;

  if((bits & (R_BIT|W_BIT)) == (R_BIT|W_BIT)) return(ENXIO);

  /* Find the reader/writer at the other end of the pipe */
  if (find_filp(vp, bits & W_BIT ? R_BIT : W_BIT) == NULL) {
	/* Not found */
	if (oflags & O_NONBLOCK) {
		if (bits & W_BIT) return(ENXIO);
	} else {
		/* Let's wait for the other side to show up */
		suspend(FP_BLOCKED_ON_POPEN);	/* suspend caller */
		return(SUSPEND);
	}
  } else if (susp_count > 0) { /* revive blocked processes */
	release(vp, OPEN, susp_count);
	release(vp, CREAT, susp_count);
  }
  return(OK);
}


/*===========================================================================*
 *				do_mknod				     *
 *===========================================================================*/
PUBLIC int do_mknod()
{
/* Perform the mknod(name, mode, addr) system call. */
  register mode_t bits, mode_bits;
  int r;
  struct vnode *vp;
  struct vmnt *vmp;
  char fullpath[PATH_MAX];
  struct lookup resolve;

  lookup_init(&resolve, fullpath, PATH_NOFLAGS, &vmp, &vp);
  resolve.l_vmnt_lock = VMNT_WRITE;
  resolve.l_vnode_lock = VNODE_READ;

  /* Only the super_user may make nodes other than fifos. */
  mode_bits = (mode_t) m_in.mk_mode;		/* mode of the inode */
  if (!super_user && (((mode_bits & I_TYPE) != I_NAMED_PIPE) &&
      ((mode_bits & I_TYPE) != I_UNIX_SOCKET))) {
	return(EPERM);
  }
  bits = (mode_bits & I_TYPE) | (mode_bits & ALL_MODES & fp->fp_umask);

  /* Open directory that's going to hold the new node. */
  if (fetch_name(m_in.name1, m_in.name1_length, M1, fullpath) != OK)
	return(err_code);
  if ((vp = last_dir(&resolve, fp)) == NULL) return(err_code);

  /* Make sure that the object is a directory */
  if ((vp->v_mode & I_TYPE) != I_DIRECTORY) {
	r = ENOTDIR;
  } else if ((r = forbidden(vp, W_BIT|X_BIT)) == OK) {
	r = req_mknod(vp->v_fs_e, vp->v_inode_nr, fullpath, fp->fp_effuid,
		      fp->fp_effgid, bits, m_in.mk_z0);
  }

  unlock_vnode(vp);
  unlock_vmnt(vmp);
  put_vnode(vp);
  return(r);
}

/*===========================================================================*
 *				do_mkdir				     *
 *===========================================================================*/
PUBLIC int do_mkdir()
{
/* Perform the mkdir(name, mode) system call. */
  mode_t bits;			/* mode bits for the new inode */
  int r;
  struct vnode *vp;
  struct vmnt *vmp;
  char fullpath[PATH_MAX];
  struct lookup resolve;

  lookup_init(&resolve, fullpath, PATH_NOFLAGS, &vmp, &vp);
  resolve.l_vmnt_lock = VMNT_WRITE;
  resolve.l_vnode_lock = VNODE_READ;

  if (fetch_name(m_in.name1, m_in.name1_length, M1, fullpath) != OK)
	return(err_code);
  bits = I_DIRECTORY | (m_in.mode & RWX_MODES & fp->fp_umask);
  if ((vp = last_dir(&resolve, fp)) == NULL) return(err_code);

  /* Make sure that the object is a directory */
  if ((vp->v_mode & I_TYPE) != I_DIRECTORY) {
	r = ENOTDIR;
  } else if ((r = forbidden(vp, W_BIT|X_BIT)) == OK) {
	r = req_mkdir(vp->v_fs_e, vp->v_inode_nr, fullpath, fp->fp_effuid,
		      fp->fp_effgid, bits);
  }

  unlock_vnode(vp);
  unlock_vmnt(vmp);
  put_vnode(vp);
  return(r);
}

/*===========================================================================*
 *				do_lseek				     *
 *===========================================================================*/
PUBLIC int do_lseek()
{
/* Perform the lseek(ls_fd, offset, whence) system call. */
  register struct filp *rfilp;
  int r = OK;
  long offset;
  u64_t pos, newpos;

  /* Check to see if the file descriptor is valid. */
  if ( (rfilp = get_filp(m_in.ls_fd, VNODE_READ)) == NULL) return(err_code);

  /* No lseek on pipes. */
  if (rfilp->filp_vno->v_pipe == I_PIPE) {
	unlock_filp(rfilp);
	return(ESPIPE);
  }

  /* The value of 'whence' determines the start position to use. */
  switch(m_in.whence) {
    case SEEK_SET: pos = cvu64(0);	break;
    case SEEK_CUR: pos = rfilp->filp_pos;	break;
    case SEEK_END: pos = cvul64(rfilp->filp_vno->v_size);	break;
    default: unlock_filp(rfilp); return(EINVAL);
  }

  offset = m_in.offset_lo;
  if (offset >= 0)
	newpos = add64ul(pos, offset);
  else
	newpos = sub64ul(pos, -offset);

  /* Check for overflow. */
  if (ex64hi(newpos) != 0)
	r = EINVAL;
  else {
	rfilp->filp_pos = newpos;

	/* insert the new position into the output message */
	m_out.reply_l1 = ex64lo(newpos);

	if (cmp64(newpos, rfilp->filp_pos) != 0) {
		/* Inhibit read ahead request */
		r = req_inhibread(rfilp->filp_vno->v_fs_e,
				  rfilp->filp_vno->v_inode_nr);
	}
  }

  unlock_filp(rfilp);
  return(r);
}

/*===========================================================================*
 *				do_llseek				     *
 *===========================================================================*/
PUBLIC int do_llseek()
{
/* Perform the llseek(ls_fd, offset, whence) system call. */
  register struct filp *rfilp;
  u64_t pos, newpos;
  int r = OK;

  /* Check to see if the file descriptor is valid. */
  if ( (rfilp = get_filp(m_in.ls_fd, VNODE_READ)) == NULL) return(err_code);

  /* No lseek on pipes. */
  if (rfilp->filp_vno->v_pipe == I_PIPE) {
	unlock_filp(rfilp);
	return(ESPIPE);
  }

  /* The value of 'whence' determines the start position to use. */
  switch(m_in.whence) {
    case SEEK_SET: pos = cvu64(0);	break;
    case SEEK_CUR: pos = rfilp->filp_pos;	break;
    case SEEK_END: pos = cvul64(rfilp->filp_vno->v_size);	break;
    default: unlock_filp(rfilp); return(EINVAL);
  }

  newpos = add64(pos, make64(m_in.offset_lo, m_in.offset_high));

  /* Check for overflow. */
  if (( (long) m_in.offset_high > 0) && cmp64(newpos, pos) < 0)
      r = EINVAL;
  else if (( (long) m_in.offset_high < 0) && cmp64(newpos, pos) > 0)
      r = EINVAL;
  else {
	rfilp->filp_pos = newpos;

	/* insert the new position into the output message */
	m_out.reply_l1 = ex64lo(newpos);
	m_out.reply_l2 = ex64hi(newpos);

	if (cmp64(newpos, rfilp->filp_pos) != 0) {
		/* Inhibit read ahead request */
		r = req_inhibread(rfilp->filp_vno->v_fs_e,
				  rfilp->filp_vno->v_inode_nr);
	}
  }

  unlock_filp(rfilp);
  return(r);
}

/*===========================================================================*
 *				do_close				     *
 *===========================================================================*/
PUBLIC int do_close()
{
/* Perform the close(fd) system call. */

  return close_fd(fp, m_in.fd);
}


/*===========================================================================*
 *				close_fd				     *
 *===========================================================================*/
PUBLIC int close_fd(rfp, fd_nr)
struct fproc *rfp;
int fd_nr;
{
/* Perform the close(fd) system call. */
  register struct filp *rfilp;
  register struct vnode *vp;
  struct file_lock *flp;
  int lock_count;

  /* First locate the vnode that belongs to the file descriptor. */
  if ( (rfilp = get_filp2(rfp, fd_nr, VNODE_OPCL)) == NULL) return(err_code);
  vp = rfilp->filp_vno;

  close_filp(rfilp);
  rfp->fp_filp[fd_nr] = NULL;
  FD_CLR(fd_nr, &rfp->fp_cloexec_set);
  FD_CLR(fd_nr, &rfp->fp_filp_inuse);

  /* Check to see if the file is locked.  If so, release all locks. */
  if (nr_locks > 0) {
	lock_count = nr_locks;	/* save count of locks */
	for (flp = &file_lock[0]; flp < &file_lock[NR_LOCKS]; flp++) {
		if (flp->lock_type == 0) continue;	/* slot not in use */
		if (flp->lock_vnode == vp && flp->lock_pid == rfp->fp_pid) {
			flp->lock_type = 0;
			nr_locks--;
		}
	}
	if (nr_locks < lock_count)
		lock_revive();	/* one or more locks released */
  }

  return(OK);
}

/*===========================================================================*
 *				close_reply				     *
 *===========================================================================*/
PUBLIC void close_reply()
{
	/* No need to do anything */
}