508 lines
15 KiB
C
508 lines
15 KiB
C
/* This file contains the procedures that manipulate file descriptors.
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*
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* The entry points into this file are
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* get_fd: look for free file descriptor and free filp slots
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* get_filp: look up the filp entry for a given file descriptor
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* find_filp: find a filp slot that points to a given vnode
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* inval_filp: invalidate a filp and associated fd's, only let close()
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* happen on it
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* do_copyfd: copies a file descriptor from or to another endpoint
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*/
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#include <sys/select.h>
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#include <minix/callnr.h>
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#include <minix/u64.h>
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#include <assert.h>
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#include <sys/stat.h>
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#include "fs.h"
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#include "file.h"
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#include "vnode.h"
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#if LOCK_DEBUG
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/*===========================================================================*
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* check_filp_locks *
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*===========================================================================*/
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void check_filp_locks_by_me(void)
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{
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/* Check whether this thread still has filp locks held */
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struct filp *f;
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int r;
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for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
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r = mutex_trylock(&f->filp_lock);
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if (r == -EDEADLK)
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panic("Thread %d still holds filp lock on filp %p call_nr=%d\n",
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mthread_self(), f, job_call_nr);
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else if (r == 0) {
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/* We just obtained the lock, release it */
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mutex_unlock(&f->filp_lock);
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}
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}
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}
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#endif
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/*===========================================================================*
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* check_filp_locks *
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*===========================================================================*/
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void check_filp_locks(void)
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{
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struct filp *f;
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int r, count = 0;
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for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
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r = mutex_trylock(&f->filp_lock);
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if (r == -EBUSY) {
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/* Mutex is still locked */
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count++;
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} else if (r == 0) {
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/* We just obtained a lock, don't want it */
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mutex_unlock(&f->filp_lock);
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} else
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panic("filp_lock weird state");
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}
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if (count) panic("locked filps");
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#if 0
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else printf("check_filp_locks OK\n");
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#endif
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}
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/*===========================================================================*
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* init_filps *
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*===========================================================================*/
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void init_filps(void)
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{
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/* Initialize filps */
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struct filp *f;
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for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
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if (mutex_init(&f->filp_lock, NULL) != 0)
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panic("Failed to initialize filp mutex");
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}
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}
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/*===========================================================================*
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* get_fd *
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*===========================================================================*/
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int get_fd(struct fproc *rfp, int start, mode_t bits, int *k, struct filp **fpt)
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{
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/* Look for a free file descriptor and a free filp slot. Fill in the mode word
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* in the latter, but don't claim either one yet, since the open() or creat()
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* may yet fail.
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*/
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register struct filp *f;
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register int i;
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/* Search the fproc fp_filp table for a free file descriptor. */
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for (i = start; i < OPEN_MAX; i++) {
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if (rfp->fp_filp[i] == NULL) {
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/* A file descriptor has been located. */
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*k = i;
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break;
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}
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}
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/* Check to see if a file descriptor has been found. */
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if (i >= OPEN_MAX) return(EMFILE);
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/* If we don't care about a filp, return now */
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if (fpt == NULL) return(OK);
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/* Now that a file descriptor has been found, look for a free filp slot. */
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for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
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assert(f->filp_count >= 0);
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if (f->filp_count == 0 && mutex_trylock(&f->filp_lock) == 0) {
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f->filp_mode = bits;
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f->filp_pos = 0;
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f->filp_selectors = 0;
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f->filp_select_ops = 0;
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f->filp_pipe_select_ops = 0;
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f->filp_char_select_dev = NO_DEV;
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f->filp_flags = 0;
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f->filp_select_flags = 0;
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f->filp_softlock = NULL;
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f->filp_ioctl_fp = NULL;
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*fpt = f;
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return(OK);
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}
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}
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/* If control passes here, the filp table must be full. Report that back. */
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return(ENFILE);
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}
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/*===========================================================================*
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* get_filp *
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*===========================================================================*/
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struct filp *get_filp(fild, locktype)
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int fild; /* file descriptor */
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tll_access_t locktype;
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{
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/* See if 'fild' refers to a valid file descr. If so, return its filp ptr. */
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return get_filp2(fp, fild, locktype);
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}
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/*===========================================================================*
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* get_filp2 *
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*===========================================================================*/
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struct filp *get_filp2(rfp, fild, locktype)
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register struct fproc *rfp;
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int fild; /* file descriptor */
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tll_access_t locktype;
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{
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/* See if 'fild' refers to a valid file descr. If so, return its filp ptr. */
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struct filp *filp;
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filp = NULL;
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if (fild < 0 || fild >= OPEN_MAX)
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err_code = EBADF;
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else if (locktype != VNODE_OPCL && rfp->fp_filp[fild] != NULL &&
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rfp->fp_filp[fild]->filp_mode == FILP_CLOSED)
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err_code = EIO; /* disallow all use except close(2) */
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else if ((filp = rfp->fp_filp[fild]) == NULL)
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err_code = EBADF;
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else if (locktype != VNODE_NONE) /* Only lock the filp if requested */
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lock_filp(filp, locktype); /* All is fine */
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return(filp); /* may also be NULL */
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}
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/*===========================================================================*
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* find_filp *
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*===========================================================================*/
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struct filp *find_filp(struct vnode *vp, mode_t bits)
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{
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/* Find a filp slot that refers to the vnode 'vp' in a way as described
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* by the mode bit 'bits'. Used for determining whether somebody is still
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* interested in either end of a pipe. Also used when opening a FIFO to
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* find partners to share a filp field with (to shared the file position).
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* Like 'get_fd' it performs its job by linear search through the filp table.
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*/
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struct filp *f;
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for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
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if (f->filp_count != 0 && f->filp_vno == vp && (f->filp_mode & bits)) {
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return(f);
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}
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}
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/* If control passes here, the filp wasn't there. Report that back. */
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return(NULL);
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}
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/*===========================================================================*
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* invalidate_filp *
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*===========================================================================*/
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void invalidate_filp(struct filp *rfilp)
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{
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/* Invalidate filp. */
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rfilp->filp_mode = FILP_CLOSED;
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}
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/*===========================================================================*
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* invalidate_filp_by_char_major *
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*===========================================================================*/
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void invalidate_filp_by_char_major(devmajor_t major)
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{
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struct filp *f;
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for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
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if (f->filp_count != 0 && f->filp_vno != NULL) {
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if (major(f->filp_vno->v_sdev) == major &&
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S_ISCHR(f->filp_vno->v_mode)) {
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invalidate_filp(f);
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}
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}
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}
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}
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/*===========================================================================*
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* invalidate_filp_by_endpt *
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*===========================================================================*/
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void invalidate_filp_by_endpt(endpoint_t proc_e)
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{
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struct filp *f;
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for (f = &filp[0]; f < &filp[NR_FILPS]; f++) {
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if (f->filp_count != 0 && f->filp_vno != NULL) {
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if (f->filp_vno->v_fs_e == proc_e)
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invalidate_filp(f);
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}
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}
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}
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/*===========================================================================*
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* lock_filp *
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*===========================================================================*/
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void lock_filp(filp, locktype)
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struct filp *filp;
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tll_access_t locktype;
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{
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struct worker_thread *org_self;
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struct vnode *vp;
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assert(filp->filp_count > 0);
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vp = filp->filp_vno;
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assert(vp != NULL);
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/* Lock vnode only if we haven't already locked it. If already locked by us,
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* we're allowed to have one additional 'soft' lock. */
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if (tll_locked_by_me(&vp->v_lock)) {
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assert(filp->filp_softlock == NULL);
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filp->filp_softlock = fp;
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} else {
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/* We have to make an exception for vnodes belonging to pipes. Even
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* read(2) operations on pipes change the vnode and therefore require
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* exclusive access.
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*/
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if (S_ISFIFO(vp->v_mode) && locktype == VNODE_READ)
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locktype = VNODE_WRITE;
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lock_vnode(vp, locktype);
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}
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assert(vp->v_ref_count > 0); /* vnode still in use? */
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assert(filp->filp_vno == vp); /* vnode still what we think it is? */
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/* First try to get filp lock right off the bat */
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if (mutex_trylock(&filp->filp_lock) != 0) {
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/* Already in use, let's wait for our turn */
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org_self = worker_suspend();
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if (mutex_lock(&filp->filp_lock) != 0)
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panic("unable to obtain lock on filp");
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worker_resume(org_self);
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}
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}
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/*===========================================================================*
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* unlock_filp *
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*===========================================================================*/
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void unlock_filp(filp)
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struct filp *filp;
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{
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/* If this filp holds a soft lock on the vnode, we must be the owner */
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if (filp->filp_softlock != NULL)
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assert(filp->filp_softlock == fp);
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if (filp->filp_count > 0) {
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/* Only unlock vnode if filp is still in use */
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/* and if we don't hold a soft lock */
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if (filp->filp_softlock == NULL) {
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assert(tll_islocked(&(filp->filp_vno->v_lock)));
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unlock_vnode(filp->filp_vno);
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}
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}
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filp->filp_softlock = NULL;
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if (mutex_unlock(&filp->filp_lock) != 0)
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panic("unable to release lock on filp");
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}
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/*===========================================================================*
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* unlock_filps *
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*===========================================================================*/
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void unlock_filps(filp1, filp2)
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struct filp *filp1;
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struct filp *filp2;
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{
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/* Unlock two filps that are tied to the same vnode. As a thread can lock a
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* vnode only once, unlocking the vnode twice would result in an error. */
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/* No NULL pointers and not equal */
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assert(filp1);
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assert(filp2);
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assert(filp1 != filp2);
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/* Must be tied to the same vnode and not NULL */
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assert(filp1->filp_vno == filp2->filp_vno);
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assert(filp1->filp_vno != NULL);
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if (filp1->filp_count > 0 && filp2->filp_count > 0) {
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/* Only unlock vnode if filps are still in use */
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unlock_vnode(filp1->filp_vno);
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}
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filp1->filp_softlock = NULL;
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filp2->filp_softlock = NULL;
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if (mutex_unlock(&filp2->filp_lock) != 0)
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panic("unable to release filp lock on filp2");
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if (mutex_unlock(&filp1->filp_lock) != 0)
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panic("unable to release filp lock on filp1");
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}
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/*===========================================================================*
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* close_filp *
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*===========================================================================*/
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void close_filp(f)
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struct filp *f;
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{
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/* Close a file. Will also unlock filp when done */
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int rw;
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dev_t dev;
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struct vnode *vp;
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/* Must be locked */
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assert(mutex_trylock(&f->filp_lock) == -EDEADLK);
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assert(tll_islocked(&f->filp_vno->v_lock));
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vp = f->filp_vno;
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if (f->filp_count - 1 == 0 && f->filp_mode != FILP_CLOSED) {
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/* Check to see if the file is special. */
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if (S_ISCHR(vp->v_mode) || S_ISBLK(vp->v_mode)) {
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dev = vp->v_sdev;
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if (S_ISBLK(vp->v_mode)) {
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lock_bsf();
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if (vp->v_bfs_e == ROOT_FS_E) {
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/* Invalidate the cache unless the special is
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* mounted. Assume that the root filesystem's
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* is open only for fsck.
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*/
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req_flush(vp->v_bfs_e, dev);
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}
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unlock_bsf();
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(void) bdev_close(dev); /* Ignore errors */
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} else {
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(void) cdev_close(dev); /* Ignore errors */
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}
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f->filp_mode = FILP_CLOSED;
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}
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}
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/* If the inode being closed is a pipe, release everyone hanging on it. */
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if (S_ISFIFO(vp->v_mode)) {
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rw = (f->filp_mode & R_BIT ? VFS_WRITE : VFS_READ);
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release(vp, rw, susp_count);
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}
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if (--f->filp_count == 0) {
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if (S_ISFIFO(vp->v_mode)) {
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/* Last reader or writer is going. Tell PFS about latest
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* pipe size.
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*/
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truncate_vnode(vp, vp->v_size);
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}
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unlock_vnode(f->filp_vno);
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put_vnode(f->filp_vno);
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f->filp_vno = NULL;
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f->filp_mode = FILP_CLOSED;
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f->filp_count = 0;
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} else if (f->filp_count < 0) {
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panic("VFS: invalid filp count: %d ino %llx/%llu", f->filp_count,
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vp->v_dev, vp->v_inode_nr);
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} else {
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unlock_vnode(f->filp_vno);
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}
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mutex_unlock(&f->filp_lock);
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}
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/*===========================================================================*
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* do_copyfd *
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*===========================================================================*/
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int do_copyfd(void)
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{
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/* Copy a file descriptor between processes, or close a remote file descriptor.
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* This call is used as back-call by device drivers (UDS, VND), and is expected
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* to be used in response to an IOCTL to such device drivers.
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*/
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struct fproc *rfp;
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struct filp *rfilp;
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endpoint_t endpt;
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int r, fd, what, slot;
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/* This should be replaced with an ACL check. */
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if (!super_user) return(EPERM);
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endpt = job_m_in.m_lsys_vfs_copyfd.endpt;
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fd = job_m_in.m_lsys_vfs_copyfd.fd;
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what = job_m_in.m_lsys_vfs_copyfd.what;
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if (isokendpt(endpt, &slot) != OK) return(EINVAL);
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rfp = &fproc[slot];
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/* FIXME: we should now check that the user process is indeed blocked on an
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* IOCTL call, so that we can safely mess with its file descriptors. We
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* currently do not have the necessary state to verify this, so we assume
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* that the call is always used in the right way.
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*/
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/* Depending on the operation, get the file descriptor from the caller or the
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* user process. Do not lock the filp yet: we first need to make sure that
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* locking it will not result in a deadlock.
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*/
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rfilp = get_filp2((what == COPYFD_TO) ? fp : rfp, fd, VNODE_NONE);
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if (rfilp == NULL)
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return(err_code);
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/* If the filp is involved in an IOCTL by the user process, locking the filp
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* here would result in a deadlock. This would happen if a user process
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* passes in the file descriptor to the device node on which it is performing
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* the IOCTL. We do not allow manipulation of such device nodes. In
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* practice, this only applies to block-special files (and thus VND), because
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* character-special files (as used by UDS) are unlocked during the IOCTL.
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*/
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if (rfilp->filp_ioctl_fp == rfp)
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return(EBADF);
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/* Now we can safely lock the filp, copy or close it, and unlock it again. */
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lock_filp(rfilp, VNODE_READ);
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switch (what) {
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case COPYFD_FROM:
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rfp = fp;
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/* FALLTHROUGH */
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case COPYFD_TO:
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/* Find a free file descriptor slot in the local or remote process. */
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for (fd = 0; fd < OPEN_MAX; fd++)
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if (rfp->fp_filp[fd] == NULL)
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break;
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/* If found, fill the slot and return the slot number. */
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if (fd < OPEN_MAX) {
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rfp->fp_filp[fd] = rfilp;
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rfilp->filp_count++;
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r = fd;
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} else
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r = EMFILE;
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break;
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case COPYFD_CLOSE:
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/* This should be used ONLY to revert a successful copy-to operation,
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* and assumes that the filp is still in use by the caller as well.
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*/
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if (rfilp->filp_count > 1) {
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rfilp->filp_count--;
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rfp->fp_filp[fd] = NULL;
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r = OK;
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} else
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r = EBADF;
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break;
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default:
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r = EINVAL;
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}
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unlock_filp(rfilp);
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return(r);
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}
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