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minix/servers/vfs/open.c
David van Moolenbroek 665198b4c2 Rewrite character driver protocol 
As a side effect, remove the clone style, as the normal device style
supports device cloning now.

Change-Id: Ie82d1ef0385514a04a8faa139129a617895780b5
2014-03-01 09:04:52 +01:00

703 lines
20 KiB
C
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/* This file contains the procedures for creating, opening, closing, and
* seeking on files.
*
* The entry points into this file are
* 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 "scratchpad.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"
static char mode_map[] = {R_BIT, W_BIT, R_BIT|W_BIT, 0};
static struct vnode *new_node(struct lookup *resolve, int oflags,
mode_t bits);
static int pipe_open(struct vnode *vp, mode_t bits, int oflags);
/*===========================================================================*
* do_open *
*===========================================================================*/
int do_open(message *UNUSED(m_out))
{
/* Perform the open(name, flags,...) system call.
* syscall might provide 'name' embedded in message when not creating file */
int create_mode; /* is really mode_t but this gives problems */
int open_mode = 0; /* is really mode_t but this gives problems */
int r = OK;
char fullpath[PATH_MAX];
vir_bytes vname;
size_t vname_length;
open_mode = (mode_t) job_m_in.mode;
create_mode = job_m_in.c_mode;
/* If O_CREAT is set, open has three parameters, otherwise two. */
if (open_mode & O_CREAT) {
vname = (vir_bytes) job_m_in.name1;
vname_length = (size_t) job_m_in.name1_length;
r = fetch_name(vname, vname_length, fullpath);
} else {
vname = (vir_bytes) job_m_in.name;
vname_length = (size_t) job_m_in.name_length;
create_mode = 0;
if (copy_name(vname_length, fullpath) != OK) {
/* Direct copy failed, try fetching from user space */
if (fetch_name(vname, vname_length, fullpath) != OK)
r = err_code;
}
}
if (r != OK) return(err_code); /* name was bad */
return common_open(fullpath, open_mode, create_mode);
}
/*===========================================================================*
* common_open *
*===========================================================================*/
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;
int start = 0;
/* 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(fp, start, bits, &(scratch(fp).file.fd_nr),
&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 & ALLPERMS & 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[scratch(fp).file.fd_nr] = filp;
filp->filp_count = 1;
filp->filp_vno = vp;
filp->filp_flags = oflags;
if (oflags & O_CLOEXEC)
FD_SET(scratch(fp).file.fd_nr, &fp->fp_cloexec_set);
/* Only do the normal open code if we didn't just create the file. */
if (exist) {
/* Check protections. */
if ((r = forbidden(fp, vp, bits)) == OK) {
/* Opening reg. files, directories, and special files differ */
switch (vp->v_mode & S_IFMT) {
case S_IFREG:
/* Truncate regular file if O_TRUNC. */
if (oflags & O_TRUNC) {
if ((r = forbidden(fp, vp, W_BIT)) != OK)
break;
upgrade_vnode_lock(vp);
truncate_vnode(vp, 0);
}
break;
case S_IFDIR:
/* Directories may be read but not written. */
r = (bits & W_BIT ? EISDIR : OK);
break;
case S_IFCHR:
/* Invoke the driver for special processing. */
dev = (dev_t) vp->v_sdev;
/* TTY needs to know about the O_NOCTTY flag. */
r = cdev_open(dev, bits | (oflags & O_NOCTTY));
vp = filp->filp_vno; /* Might be updated by
* cdev_open after cloning */
break;
case S_IFBLK:
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.
* Otherwise 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 label to the file system that will
* handle the block I/O requests (even when its label
* and endpoint are 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_label) != OK) {
printf("VFS: error sending driver label\n");
bdev_close(dev);
r = ENXIO;
}
unlock_bsf();
break;
case S_IFIFO:
/* Create a mapped inode on PFS which handles reads
and writes to this named pipe. */
upgrade_vnode_lock(vp);
r = map_vnode(vp, PFS_PROC_NR);
if (r == OK) {
if (vp->v_ref_count == 1) {
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[scratch(fp).file.fd_nr] = 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[scratch(fp).file.fd_nr] = NULL;
filp->filp_count = 0;
filp->filp_vno = NULL;
put_vnode(vp);
}
} else {
r = scratch(fp).file.fd_nr;
}
return(r);
}
/*===========================================================================*
* new_node *
*===========================================================================*/
static 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. */
lookup_init(&findnode, findnode.l_path, findnode.l_flags, &vp_vmp, &vp);
findnode.l_vmnt_lock = VMNT_WRITE;
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.
* Either way, vp_vmp ought to be not set.
*/
/* 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] == '/') {
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);
upgrade_vmnt_lock(dir_vmp); /* Creating file, need exclusive access */
if ((r = forbidden(fp, 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.*/
/* Downgrade lock to prevent deadlock during symlink resolving*/
downgrade_vmnt_lock(dir_vmp);
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,
(vir_bytes) 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.
* Unlock vnodes and vmnts as we're going to recurse.
*/
unlock_vnode(dirp);
unlock_vnode(vp);
unlock_vmnt(dir_vmp);
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) {
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_vmnt(dir_vmp);
unlock_vnode(dirp);
unlock_vnode(vp);
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 *
*===========================================================================*/
static int pipe_open(struct vnode *vp, mode_t bits, 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.
*/
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);
return(SUSPEND);
}
} else if (susp_count > 0) { /* revive blocked processes */
release(vp, OPEN, susp_count);
}
return(OK);
}
/*===========================================================================*
* do_mknod *
*===========================================================================*/
int do_mknod(message *UNUSED(m_out))
{
/* 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;
vir_bytes vname1;
size_t vname1_length;
dev_t dev;
vname1 = (vir_bytes) job_m_in.name1;
vname1_length = (size_t) job_m_in.name1_length;
mode_bits = (mode_t) job_m_in.mk_mode; /* mode of the inode */
dev = job_m_in.m1_i3;
lookup_init(&resolve, fullpath, PATH_NOFLAGS, &vmp, &vp);
resolve.l_vmnt_lock = VMNT_WRITE;
resolve.l_vnode_lock = VNODE_WRITE;
/* Only the super_user may make nodes other than fifos. */
if (!super_user && (!S_ISFIFO(mode_bits) && !S_ISSOCK(mode_bits))) {
return(EPERM);
}
bits = (mode_bits & S_IFMT) | (mode_bits & ACCESSPERMS & fp->fp_umask);
/* Open directory that's going to hold the new node. */
if (fetch_name(vname1, vname1_length, fullpath) != OK) return(err_code);
if ((vp = last_dir(&resolve, fp)) == NULL) return(err_code);
/* Make sure that the object is a directory */
if (!S_ISDIR(vp->v_mode)) {
r = ENOTDIR;
} else if ((r = forbidden(fp, 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, dev);
}
unlock_vnode(vp);
unlock_vmnt(vmp);
put_vnode(vp);
return(r);
}
/*===========================================================================*
* do_mkdir *
*===========================================================================*/
int do_mkdir(message *UNUSED(m_out))
{
/* 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;
vir_bytes vname1;
size_t vname1_length;
mode_t dirmode;
vname1 = (vir_bytes) job_m_in.name1;
vname1_length = (size_t) job_m_in.name1_length;
dirmode = (mode_t) job_m_in.mode;
lookup_init(&resolve, fullpath, PATH_NOFLAGS, &vmp, &vp);
resolve.l_vmnt_lock = VMNT_WRITE;
resolve.l_vnode_lock = VNODE_WRITE;
if (fetch_name(vname1, vname1_length, fullpath) != OK) return(err_code);
bits = I_DIRECTORY | (dirmode & RWX_MODES & fp->fp_umask);
if ((vp = last_dir(&resolve, fp)) == NULL) return(err_code);
/* Make sure that the object is a directory */
if (!S_ISDIR(vp->v_mode)) {
r = ENOTDIR;
} else if ((r = forbidden(fp, 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);
}
/*===========================================================================*
* actual_llseek *
*===========================================================================*/
int actual_llseek(struct fproc *rfp, message *m_out, int seekfd, int seekwhence,
off_t offset)
{
/* Perform the llseek(ls_fd, offset, whence) system call. */
register struct filp *rfilp;
int r = OK;
off_t pos, newpos;
/* Check to see if the file descriptor is valid. */
if ( (rfilp = get_filp2(rfp, seekfd, VNODE_READ)) == NULL) {
return(err_code);
}
/* No lseek on pipes. */
if (S_ISFIFO(rfilp->filp_vno->v_mode)) {
unlock_filp(rfilp);
return(ESPIPE);
}
/* The value of 'whence' determines the start position to use. */
switch(seekwhence) {
case SEEK_SET: pos = 0; break;
case SEEK_CUR: pos = rfilp->filp_pos; break;
case SEEK_END: pos = rfilp->filp_vno->v_size; break;
default: unlock_filp(rfilp); return(EINVAL);
}
newpos = pos + offset;
/* Check for overflow. */
if ((offset > 0) && (newpos <= pos)) {
r = EOVERFLOW;
} else if ((offset < 0) && (newpos >= pos)) {
r = EOVERFLOW;
} else {
/* insert the new position into the output message */
m_out->reply_l1 = ex64lo(newpos);
m_out->reply_l2 = ex64hi(newpos);
if (newpos != rfilp->filp_pos) {
rfilp->filp_pos = newpos;
/* 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_lseek *
*===========================================================================*/
int do_lseek(message *m_out)
{
return actual_llseek(fp, m_out, job_m_in.ls_fd, job_m_in.whence,
make64(job_m_in.offset_lo, job_m_in.offset_high));
}
/*===========================================================================*
* do_close *
*===========================================================================*/
int do_close(message *UNUSED(m_out))
{
/* Perform the close(fd) system call. */
int thefd = job_m_in.fd;
return close_fd(fp, thefd);
}
/*===========================================================================*
* close_fd *
*===========================================================================*/
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;
/* first, make all future get_filp2()'s fail; otherwise
* we might try to close the same fd in different threads
*/
rfp->fp_filp[fd_nr] = NULL;
close_filp(rfilp);
FD_CLR(fd_nr, &rfp->fp_cloexec_set);
/* 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);
}
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