sanchayanmaity/minix
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity
minix/servers/vfs/open.c
Thomas Veerman ca9280e097 - Fix dangling symlink regression 
- Make open(2) more POSIX compliant
- Add a test case for dangling symlinks and open() syscall with O_CREAT and
  O_EXCL on a symlink.
- Update open(2) man page to reflect change.
2010-01-21 09:32:15 +00:00

735 lines
21 KiB
C
Raw Blame History

/* 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
*/
#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 "lock.h"
#include "param.h"
#include <dirent.h>
#include <assert.h>
#include <minix/vfsif.h>
#include "vnode.h"
#include "vmnt.h"
PRIVATE char mode_map[] = {R_BIT, W_BIT, R_BIT|W_BIT, 0};
FORWARD _PROTOTYPE( int common_open, (int oflags, mode_t omode) );
FORWARD _PROTOTYPE( struct vnode *new_node, (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;
if (fetch_name(m_in.name, m_in.name_length, M3) != OK) return(err_code);
r = common_open(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;
/* 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);
} else {
r = fetch_name(m_in.name, m_in.name_length, M3);
}
if (r != OK) return(err_code); /* name was bad */
r = common_open(m_in.mode, create_mode);
return(r);
}
/*===========================================================================*
* common_open *
*===========================================================================*/
PRIVATE int common_open(register int oflags, mode_t omode)
{
/* Common code from do_creat and do_open. */
int b, r, exist = TRUE;
dev_t dev;
mode_t bits;
struct filp *fil_ptr, *filp2;
struct vnode *vp;
struct vmnt *vmp;
struct dmap *dp;
/* 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, &fil_ptr)) != OK) return(r);
/* 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(oflags, omode);
r = err_code;
if (r == OK) exist = FALSE; /* We just created the file */
else if (r != EEXIST) return(r); /* other error */
else exist = !(oflags & O_EXCL); /* file exists, if the O_EXCL
flag is set this is an error */
} else {
/* Scan path name */
if ((vp = eat_path(PATH_NOFLAGS)) == NIL_VNODE) return(err_code);
}
/* Claim the file descriptor and filp slot and fill them in. */
fp->fp_filp[m_in.fd] = fil_ptr;
FD_SET(m_in.fd, &fp->fp_filp_inuse);
fil_ptr->filp_count = 1;
fil_ptr->filp_vno = vp;
fil_ptr->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;
r = dev_open(dev, who_e, bits | (oflags & ~O_ACCMODE));
if (r == SUSPEND) suspend(FP_BLOCKED_ON_DOPEN);
break;
case I_BLOCK_SPECIAL:
/* Invoke the driver for special processing. */
dev = (dev_t) vp->v_sdev;
r = dev_open(dev, who_e, bits | (oflags & ~O_ACCMODE));
/* 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)
vp->v_bfs_e = vmp->m_fs_e;
/* Get the driver endpoint of the block spec device */
dp = &dmap[(vp->v_sdev >> MAJOR) & BYTE];
if (dp->dmap_driver == NONE) {
printf("VFS: driver not found for device %d\n",
vp->v_sdev);
r = ENXIO;
break;
}
/* Send the driver endpoint (even when known already)*/
if ((r = req_newdriver(vp->v_bfs_e, vp->v_sdev,
dp->dmap_driver)) != OK) {
printf("VFS: error sending driver endpoint\n");
r = ENXIO;
}
break;
case I_NAMED_PIPE:
/* Create a mapped inode on PFS which handles reads
and writes to this named pipe. */
r = map_vnode(vp);
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 */
fil_ptr->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);
fil_ptr->filp_count = 0; /* don't find self */
if ((filp2 = find_filp(vp, b)) != NIL_FILP) {
/* 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.
*/
put_vnode(vp);
} else {
/* Nobody else found. Restore filp. */
fil_ptr->filp_count = 1;
}
}
break;
}
}
}
/* If error, release inode. */
if (r != OK) {
if (r == SUSPEND) return(r); /* Oops, just suspended */
fp->fp_filp[m_in.fd] = NIL_FILP;
FD_CLR(m_in.fd, &fp->fp_filp_inuse);
fil_ptr->filp_count= 0;
put_vnode(vp);
fil_ptr->filp_vno = NIL_VNODE;
return(r);
}
return(m_in.fd);
}
/*===========================================================================*
* new_node *
*===========================================================================*/
PRIVATE struct vnode *new_node(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.
NIL_VNODE 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;
int r, flags;
struct node_details res;
struct vnode *rest;
/* When O_CREAT and O_EXCL flags are set, the path may not be named by a
* symbolic link. */
flags = PATH_NOFLAGS;
if (oflags & O_EXCL) flags |= PATH_RET_SYMLINK;
/* See if the path can be opened down to the last directory. */
if ((dirp = last_dir()) == NIL_VNODE) return(NIL_VNODE);
/* The final directory is accessible. Get final component of the path. */
vp = advance(dirp, flags);
/* 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 (user_fullpath[0] == '/') return new_node(oflags, bits);
if (vp == NIL_VNODE && err_code == ENOENT) {
/* Last path component does not exist. Make a new directory entry. */
if ((vp = get_free_vnode()) == NIL_VNODE) {
/* Can't create new vnode: out of vnodes. */
put_vnode(dirp);
return(NIL_VNODE);
}
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, user_fullpath, &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 */
slp = advance(dirp, PATH_RET_SYMLINK);
if (slp != NIL_VNODE) {
if (S_ISLNK(slp->v_mode)) {
/* Get contents of link */
int max_linklen;
max_linklen = sizeof(user_fullpath)-1;
r = req_rdlink(slp->v_fs_e,
slp->v_inode_nr,
VFS_PROC_NR,
user_fullpath,
max_linklen);
if (r < 0) {
/* Failed to read link */
put_vnode(slp);
put_vnode(dirp);
err_code = r;
return(NIL_VNODE);
}
user_fullpath[r] = '\0';/* Term. path*/
}
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(oflags, bits);
fp->fp_wd = old_wd; /* Restore */
if (vp != NIL_VNODE) {
put_vnode(dirp);
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;
put_vnode(dirp);
return(NIL_VNODE);
}
/* 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 != NIL_VNODE)
r = EEXIST; /* File exists or a symlink names a file while
* O_EXCL is set. */
else
r = err_code; /* Other problem. */
}
err_code = r;
put_vnode(dirp);
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);
if (find_filp(vp, bits & W_BIT ? R_BIT : W_BIT) == NIL_FILP) {
if (oflags & O_NONBLOCK) {
if (bits & W_BIT) return(ENXIO);
} else {
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;
/* 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)) 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) != OK) return(err_code);
if((vp = last_dir()) == NIL_VNODE) return(err_code);
/* Make sure that the object is a directory */
if((vp->v_mode & I_TYPE) != I_DIRECTORY) {
put_vnode(vp);
return(ENOTDIR);
}
if ((r = forbidden(vp, W_BIT|X_BIT)) == OK) {
r = req_mknod(vp->v_fs_e, vp->v_inode_nr, user_fullpath, fp->fp_effuid,
fp->fp_effgid, bits, m_in.mk_z0);
}
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;
if(fetch_name(m_in.name1, m_in.name1_length, M1) != OK) return(err_code);
bits = I_DIRECTORY | (m_in.mode & RWX_MODES & fp->fp_umask);
/* Request lookup */
if((vp = last_dir()) == NIL_VNODE) return(err_code);
/* Make sure that the object is a directory */
if ((vp->v_mode & I_TYPE) != I_DIRECTORY) {
put_vnode(vp);
return(ENOTDIR);
}
if ((r = forbidden(vp, W_BIT|X_BIT)) == OK) {
r = req_mkdir(vp->v_fs_e, vp->v_inode_nr, user_fullpath, fp->fp_effuid,
fp->fp_effgid, bits);
}
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;
long offset;
u64_t pos, newpos;
/* Check to see if the file descriptor is valid. */
if ( (rfilp = get_filp(m_in.ls_fd)) == NIL_FILP) return(err_code);
/* No lseek on pipes. */
if (rfilp->filp_vno->v_pipe == I_PIPE) 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: 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)
return(EINVAL);
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);
if (r != OK) return(r);
}
rfilp->filp_pos = newpos;
/* insert the new position into the output message */
m_out.reply_l1 = ex64lo(newpos);
return(OK);
}
/*===========================================================================*
* 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;
/* Check to see if the file descriptor is valid. */
if ( (rfilp = get_filp(m_in.ls_fd)) == NIL_FILP) return(err_code);
/* No lseek on pipes. */
if (rfilp->filp_vno->v_pipe == I_PIPE) 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: 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)
return(EINVAL);
if (((long)m_in.offset_high < 0) && cmp64(newpos, pos) > 0)
return(EINVAL);
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);
if (r != OK) return(r);
}
rfilp->filp_pos = newpos;
m_out.reply_l1 = ex64lo(newpos);
m_out.reply_l2 = ex64hi(newpos);
return(OK);
}
/*===========================================================================*
* 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)) == NIL_FILP) return(err_code);
vp = rfilp->filp_vno;
close_filp(rfilp);
FD_CLR(fd_nr, &rfp->fp_cloexec_set);
rfp->fp_filp[fd_nr] = NIL_FILP;
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) return(OK);
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(); /* lock released */
return(OK);
}
/*===========================================================================*
* close_filp *
*===========================================================================*/
PUBLIC void close_filp(fp)
struct filp *fp;
{
int mode_word, rw;
dev_t dev;
struct vnode *vp;
vp = fp->filp_vno;
if (fp->filp_count - 1 == 0 && fp->filp_mode != FILP_CLOSED) {
/* Check to see if the file is special. */
mode_word = vp->v_mode & I_TYPE;
if (mode_word == I_CHAR_SPECIAL || mode_word == I_BLOCK_SPECIAL) {
dev = (dev_t) vp->v_sdev;
if (mode_word == I_BLOCK_SPECIAL) {
if (vp->v_bfs_e == ROOT_FS_E) {
/* Invalidate the cache unless the special is
* mounted. Assume that the root filesystem's
* is open only for fsck.
*/
req_flush(vp->v_bfs_e, dev);
}
}
/* Do any special processing on device close. */
(void) dev_close(dev, fp-filp);
/* Ignore any errors, even SUSPEND. */
}
}
/* If the inode being closed is a pipe, release everyone hanging on it. */
if (vp->v_pipe == I_PIPE) {
rw = (fp->filp_mode & R_BIT ? WRITE : READ);
release(vp, rw, NR_PROCS);
}
/* If a write has been done, the inode is already marked as DIRTY. */
if (--fp->filp_count == 0) {
if (vp->v_pipe == I_PIPE) {
/* Last reader or writer is going. Tell MFS about latest
* pipe size.
*/
truncate_vnode(vp, vp->v_size);
}
put_vnode(fp->filp_vno);
}
}
/*===========================================================================*
* close_reply *
*===========================================================================*/
PUBLIC void close_reply()
{
/* No need to do anything */
}
/*===========================================================================*
* do_vm_open *
*===========================================================================*/
PUBLIC int do_vm_open()
{
int len, r, n;
endpoint_t ep;
len = m_in.VMVO_NAME_LENGTH;
m_out.VMV_ENDPOINT = ep = m_in.VMVO_ENDPOINT;
/* Do open() call on behalf of any process, performed by VM. */
if(len < 2 || len > sizeof(user_fullpath)) {
printf("do_vm_open: strange length %d\n", len);
m_out.VMVRO_FD = EINVAL;
return(VM_VFS_REPLY_OPEN);
}
/* Do open on behalf of which process? */
if(isokendpt(ep, &n) != OK) {
printf("do_vm_open: strange endpoint %d\n", ep);
m_out.VMVRO_FD = EINVAL;
return(VM_VFS_REPLY_OPEN);
}
/* XXX - do open on behalf of this process */
fp = &fproc[n];
/* Get path name from VM address space. */
if((r=sys_safecopyfrom(VM_PROC_NR, m_in.VMVO_NAME_GRANT, 0,
(vir_bytes) user_fullpath, len, D)) != OK) {
printf("do_vm_open: sys_safecopyfrom failed: %d\n", r);
m_out.VMVRO_FD = EPERM;
return(VM_VFS_REPLY_OPEN);
}
/* Check if path is null-terminated. */
if(user_fullpath[len-1] != '\0') {
printf("do_vm_open: name (len %d) not 0-terminated\n", len);
m_out.VMVRO_FD = EINVAL;
return(VM_VFS_REPLY_OPEN);
}
/* Perform open(). */
m_out.VMVRO_FD = common_open(m_in.VMVO_FLAGS, m_in.VMVO_MODE);
m_out.VMV_ENDPOINT = ep;
/* Send open() reply. */
return(VM_VFS_REPLY_OPEN);
}
/*===========================================================================*
* do_vm_close *
*===========================================================================*/
PUBLIC int do_vm_close()
{
int len, r, n;
endpoint_t ep;
len = m_in.VMVO_NAME_LENGTH;
/* Do close() call on behalf of any process, performed by VM. */
m_out.VMV_ENDPOINT = ep = m_in.VMVC_ENDPOINT;
if(isokendpt(ep, &n) != OK) {
printf("do_vm_close: strange endpoint %d\n", ep);
return(VM_VFS_REPLY_CLOSE);
}
/* Perform close(). */
r = close_fd(&fproc[n], m_in.VMVC_FD);
return(VM_VFS_REPLY_CLOSE);
}
Reference in a new issue View git blame Copy permalink