1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 /*
  22  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  23  * Use is subject to license terms.
  24  */
  25 
  26 #pragma ident   "%Z%%M% %I%     %E% SMI"
  27 
  28 #include <assert.h>
  29 #include <errno.h>
  30 #include <fcntl.h>
  31 #include <stdarg.h>
  32 #include <stdio.h>
  33 #include <stdlib.h>
  34 #include <strings.h>
  35 #include <thread.h>
  36 #include <unistd.h>
  37 
  38 #include <sys/modctl.h>
  39 #include <sys/stat.h>
  40 #include <sys/types.h>
  41 
  42 #include <sys/lx_brand.h>
  43 #include <sys/lx_debug.h>
  44 #include <sys/lx_misc.h>
  45 
  46 /* internal debugging state */
  47 static char     *lx_debug_path = NULL;          /* debug output file path */
  48 static char     lx_debug_path_buf[MAXPATHLEN];
  49 
  50 void
  51 lx_debug_enable(void)
  52 {
  53         /* send all debugging output to /dev/tty */
  54         lx_debug_path = "/dev/tty";
  55         lx_debug("lx_debug: debugging output enabled: %s", lx_debug_path);
  56 }
  57 
  58 void
  59 lx_debug_init(void)
  60 {
  61         if (getenv("LX_DEBUG") == NULL)
  62                 return;
  63 
  64         /*
  65          * It's OK to use this value without any locking, as all callers can
  66          * use the return value to decide whether extra work should be done
  67          * before calling lx_debug().
  68          *
  69          * If debugging is disabled after a routine calls this function it
  70          * doesn't really matter as lx_debug() will see debugging is disabled
  71          * and will not output anything.
  72          */
  73         lx_debug_enabled = 1;
  74 
  75         /* check if there's a debug log file specified */
  76         lx_debug_path = getenv("LX_DEBUG_FILE");
  77         if (lx_debug_path == NULL) {
  78                 /* send all debugging output to /dev/tty */
  79                 lx_debug_path = "/dev/tty";
  80         }
  81 
  82         (void) strlcpy(lx_debug_path_buf, lx_debug_path,
  83             sizeof (lx_debug_path_buf));
  84         lx_debug_path = lx_debug_path_buf;
  85 
  86         lx_debug("lx_debug: debugging output ENABLED to path: \"%s\"",
  87             lx_debug_path);
  88 }
  89 
  90 void
  91 lx_debug(const char *msg, ...)
  92 {
  93         va_list         ap;
  94         char            buf[LX_MSG_MAXLEN + 1];
  95         int             rv, fd, n;
  96         int             errno_backup;
  97 
  98         if (lx_debug_enabled == 0)
  99                 return;
 100 
 101         errno_backup = errno;
 102 
 103         /* prefix the message with pid/tid */
 104         if ((n = snprintf(buf, sizeof (buf), "%u/%u: ",
 105             getpid(), thr_self())) == -1) {
 106                 errno = errno_backup;
 107                 return;
 108         }
 109 
 110         /* format the message */
 111         va_start(ap, msg);
 112         rv = vsnprintf(&buf[n], sizeof (buf) - n, msg, ap);
 113         va_end(ap);
 114         if (rv == -1) {
 115                 errno = errno_backup;
 116                 return;
 117         }
 118 
 119         /* add a carrige return if there isn't one already */
 120         if ((buf[strlen(buf) - 1] != '\n') &&
 121             (strlcat(buf, "\n", sizeof (buf)) >= sizeof (buf))) {
 122                 errno = errno_backup;
 123                 return;
 124         }
 125 
 126         /*
 127          * Open the debugging output file.  note that we don't protect
 128          * ourselves against exec or fork1 here.  if an mt process were
 129          * to exec/fork1 while we're doing this they'd end up with an
 130          * extra open desciptor in their fd space.  a'well.  shouldn't
 131          * really matter.
 132          */
 133         if ((fd = open(lx_debug_path,
 134             O_WRONLY|O_APPEND|O_CREAT|O_NDELAY|O_NOCTTY, 0666)) == -1) {
 135                 return;
 136         }
 137         (void) fchmod(fd, 0666);
 138 
 139         /* we retry in case of EINTR */
 140         do {
 141                 rv = write(fd, buf, strlen(buf));
 142         } while ((rv == -1) && (errno == EINTR));
 143         (void) fsync(fd);
 144 
 145         (void) close(fd);
 146         errno = errno_backup;
 147 }