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minix/servers/avfs/open.c
Thomas Veerman de5a9a3e8b AVFS: Use scratchpad instead of m_in to pass around file descriptors 
Some code relies on having the file descriptor in m_in.fd. Consequently,
m_in is not only used to provide syscall parameters from user space to
VFS, but also as a global variable to store temporary data within VFS.
This has the ugly side effect that m_in gets overwritten during core
dumping.*

To work around this problem VFS now uses a so called "scratchpad" to
store temporary data that has to be globally accessible. This is a simple
table indexed by process number, just like fproc. The scratchpad allows
us to store the buffer pointer and buffer size for suspended system calls
(i.e., read, write, open, lock) instead of using fproc. This makes fproc
a bit smaller and fproc iterators a bit faster. Moreover, suspension of
processes becomes simpler altogether and suspended operations on pipes
are now less of a special case.

* This patch fixes a bug where due to unexpected m_in overwriting a
coredump would fail, and consequently resources are leaked. The coredump
was triggered with:
$ a() { a; }
$ a
2011-12-21 10:52:51 +00:00

741 lines
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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_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 "scratchpad.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( 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 *
*===========================================================================*/
PUBLIC 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, &(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 & 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[scratch(fp).file.fd_nr] = filp;
FD_SET(scratch(fp).file.fd_nr, &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.
* 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 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[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;
FD_CLR(scratch(fp).file.fd_nr, &fp->fp_filp_inuse);
filp->filp_count = 0;
filp->filp_vno = NULL;
put_vnode(vp);
}
} else {
r = scratch(fp).file.fd_nr;
}
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] == '/') {
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.
* 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_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(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.
*/
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);
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 */
}
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