/dev/fd driver

SCCS-vsn: sys/kern/kern_descrip.c 7.3

diff --git a/usr/src/sys/kern/kern_descrip.c b/usr/src/sys/kern/kern_descrip.c
index 3a8561d..b28c850 100644 (file)
--- a/usr/src/sys/kern/kern_descrip.c
+++ b/usr/src/sys/kern/kern_descrip.c
@@ -3,7 +3,7 @@
  * All rights reserved.  The Berkeley software License Agreement
  * specifies the terms and conditions for redistribution.
  *
  * All rights reserved.  The Berkeley software License Agreement
  * specifies the terms and conditions for redistribution.
  *

- *     @(#)kern_descrip.c      7.2 (Berkeley) %G%
+ *     @(#)kern_descrip.c      7.3 (Berkeley) %G%

  */
 
 #include "param.h"
  */
 
 #include "param.h"


@@ -410,3 +410,66 @@ flock()
                return;
        u.u_error = ino_lock(fp, uap->how);
 }
                return;
        u.u_error = ino_lock(fp, uap->how);
 }

+
+/*
+ * File Descriptor pseudo-device driver (/dev/fd/).
+ *
+ * Fred Blonder - U of Maryland        11-Sep-1984
+ *
+ * Opening minor device N dup()s the file (if any) connected to file
+ * descriptor N belonging to the calling process.  Note that this driver
+ * consists of only the ``open()'' routine, because all subsequent
+ * references to this file will be direct to the other driver.
+ */
+fdopen(dev, mode)
+       dev_t dev;
+       int mode;
+{
+       struct file *fp, *wfp;
+       struct inode *ip, *wip;
+       int rwmode;
+
+       /*
+        * Note the horrid kludge here: u.u_r.r_val1 contains the value
+        * of the new file descriptor, which has not been disturbed since
+        * it was allocated.
+        */
+       if ((fp = getf(u.u_r.r_val1)) == NULL)
+               return (u.u_error);
+       if ((wfp = getf(minor(dev))) == NULL)
+               return (u.u_error);
+       /*
+        * We must explicitly test for this case because ufalloc() may
+        * have allocated us the same file desriptor we are referring
+        * to, if the proccess referred to an invalid (closed) descriptor.
+        * Ordinarily this would be caught by getf(), but by the time we
+        * reach this routine u_pofile[minor(dev)] could already be set
+        * to point to our file struct.
+        */
+       if (fp == wfp)
+               return (EBADF);
+       /*
+        * Fake a ``dup()'' sys call.
+        * Check that the mode the file is being opened
+        * for is consistent with the mode of the existing
+        * descriptor. This isn't as clean as it should be,
+        * but this entire driver is a real kludge anyway.
+        */
+       rwmode = mode & (FREAD|FWRITE);
+       if ((fp->f_flag & rwmode) != rwmode)
+               return (EACCES);
+       /*
+        * Delete references to this pseudo-device.
+        * Note that fp->f_count is guaranteed == 1, and
+        * that fp references the inode for this driver.
+        */
+       if (fp->f_count != 1 || fp->f_type != DTYPE_INODE) 
+               panic("fdopen");
+       irele((struct inode *)fp->f_data);
+       fp->f_count = 0;
+       /* 
+        * Dup the file descriptor. 
+        */
+       dupit(u.u_r.r_val1, wfp, u.u_pofile[minor(dev)]);
+       return (0);
+}