external/ibm-public/postfix/dist/src/util/msg_output.c

   1 /*      $NetBSD$        */
   2
   3 /*++
   4 /* NAME
   5 /*      msg_output 3
   6 /* SUMMARY
   7 /*      diagnostics output management
   8 /* SYNOPSIS
   9 /*      #include <msg_output.h>
  10 /*
  11 /*      typedef void (*MSG_OUTPUT_FN)(int level, char *text)
  12 /*
  13 /*      void    msg_output(output_fn)
  14 /*      MSG_OUTPUT_FN output_fn;
  15 /*
  16 /*      void    msg_printf(level, format, ...)
  17 /*      int     level;
  18 /*      const char *format;
  19 /*
  20 /*      void    msg_vprintf(level, format, ap)
  21 /*      int     level;
  22 /*      const char *format;
  23 /*      va_list ap;
  24 /*
  25 /*      void    msg_text(level, text)
  26 /*      int     level;
  27 /*      const char *text;
  28 /* DESCRIPTION
  29 /*      This module implements low-level output management for the
  30 /*      msg(3) diagnostics interface.
  31 /*
  32 /*      msg_output() registers an output handler for the diagnostics
  33 /*      interface. An application can register multiple output handlers.
  34 /*      Output handlers are called in the specified order.
  35 /*      An output handler takes as arguments a severity level (MSG_INFO,
  36 /*      MSG_WARN, MSG_ERROR, MSG_FATAL, MSG_PANIC, monotonically increasing
  37 /*      integer values ranging from 0 to MSG_LAST) and pre-formatted,
  38 /*      sanitized, text in the form of a null-terminated string.
  39 /*
  40 /*      msg_printf() and msg_vprintf() format their arguments, sanitize the
  41 /*      result, and call the output handlers registered with msg_output().
  42 /*
  43 /*      msg_text() copies a pre-formatted text, sanitizes the result, and
  44 /*      calls the output handlers registered with msg_output().
  45 /* REENTRANCY
  46 /* .ad
  47 /* .fi
  48 /*      The above output routines are protected against ordinary
  49 /*      recursive calls and against re-entry by signal
  50 /*      handlers, with the following limitations:
  51 /* .IP \(bu
  52 /*      The signal handlers must never return. In other words, the
  53 /*      signal handlers must do one or more of the following: call
  54 /*      _exit(), kill the process with a signal, and permanently
  55 /*      block the process.
  56 /* .IP \(bu
  57 /*      The signal handlers must call the above output routines not
  58 /*      until after msg_output() completes initialization, and not
  59 /*      until after the first formatted output to a VSTRING or
  60 /*      VSTREAM.
  61 /* .IP \(bu
  62 /*      Each msg_output() call-back function, and each Postfix or
  63 /*      system function called by that call-back function, either
  64 /*      must protect itself against recursive calls and re-entry
  65 /*      by a terminating signal handler, or it must be called
  66 /*      exclusively by functions in the msg_output(3) module.
  67 /* .PP
  68 /*      When re-entrancy is detected, the requested output operation
  69 /*      is skipped. This prevents memory corruption of VSTREAM_ERR
  70 /*      data structures, and prevents deadlock on Linux releases
  71 /*      that use mutexes within system library routines such as
  72 /*      syslog(). This protection exists under the condition that
  73 /*      these specific resources are accessed exclusively via
  74 /*      msg_output() call-back functions.
  75 /* LICENSE
  76 /* .ad
  77 /* .fi
  78 /*      The Secure Mailer license must be distributed with this software.
  79 /* AUTHOR(S)
  80 /*      Wietse Venema
  81 /*      IBM T.J. Watson Research
  82 /*      P.O. Box 704
  83 /*      Yorktown Heights, NY 10598, USA
  84 /*--*/
  85
  86 /* System library. */
  87
  88 #include <sys_defs.h>
  89 #include <stdarg.h>
  90 #include <errno.h>
  91
  92 /* Utility library. */
  93
  94 #include <mymalloc.h>
  95 #include <vstring.h>
  96 #include <vstream.h>
  97 #include <msg_vstream.h>
  98 #include <stringops.h>
  99 #include <percentm.h>
 100 #include <msg_output.h>
 101
 102  /*
 103   * Global scope, to discourage the compiler from doing smart things.
 104   */
 105 volatile int msg_vprintf_lock;
 106 volatile int msg_text_lock;
 107
 108  /*
 109   * Private state.
 110   */
 111 static MSG_OUTPUT_FN *msg_output_fn = 0;
 112 static int msg_output_fn_count = 0;
 113 static VSTRING *msg_buffer = 0;
 114
 115 /* msg_output - specify output handler */
 116
 117 void    msg_output(MSG_OUTPUT_FN output_fn)
 118 {
 119
 120     /*
 121      * Allocate all resources during initialization.
 122      */
 123     if (msg_buffer == 0)
 124         msg_buffer = vstring_alloc(100);
 125
 126     /*
 127      * We're not doing this often, so avoid complexity and allocate memory
 128      * for an exact fit.
 129      */
 130     if (msg_output_fn_count == 0)
 131         msg_output_fn = (MSG_OUTPUT_FN *) mymalloc(sizeof(*msg_output_fn));
 132     else
 133         msg_output_fn = (MSG_OUTPUT_FN *) myrealloc((char *) msg_output_fn,
 134                         (msg_output_fn_count + 1) * sizeof(*msg_output_fn));
 135     msg_output_fn[msg_output_fn_count++] = output_fn;
 136 }
 137
 138 /* msg_printf - format text and log it */
 139
 140 void    msg_printf(int level, const char *format,...)
 141 {
 142     va_list ap;
 143
 144     va_start(ap, format);
 145     msg_vprintf(level, format, ap);
 146     va_end(ap);
 147 }
 148
 149 /* msg_vprintf - format text and log it */
 150
 151 void    msg_vprintf(int level, const char *format, va_list ap)
 152 {
 153     if (msg_vprintf_lock == 0) {
 154         msg_vprintf_lock = 1;
 155         /* On-the-fly initialization for debugging test programs only. */
 156         if (msg_output_fn_count == 0)
 157             msg_vstream_init("unknown", VSTREAM_ERR);
 158         /* OK if terminating signal handler hijacks control before next stmt. */
 159         vstring_vsprintf(msg_buffer, percentm(format, errno), ap);
 160         msg_text(level, vstring_str(msg_buffer));
 161         msg_vprintf_lock = 0;
 162     }
 163 }
 164
 165 /* msg_text - sanitize and log pre-formatted text */
 166
 167 void    msg_text(int level, const char *text)
 168 {
 169     int     i;
 170
 171     /*
 172      * Sanitize the text. Use a private copy if necessary.
 173      */
 174     if (msg_text_lock == 0) {
 175         msg_text_lock = 1;
 176         /* OK if terminating signal handler hijacks control before next stmt. */
 177         if (text != vstring_str(msg_buffer))
 178             vstring_strcpy(msg_buffer, text);
 179         printable(vstring_str(msg_buffer), '?');
 180         /* On-the-fly initialization for debugging test programs only. */
 181         if (msg_output_fn_count == 0)
 182             msg_vstream_init("unknown", VSTREAM_ERR);
 183         for (i = 0; i < msg_output_fn_count; i++)
 184             msg_output_fn[i] (level, vstring_str(msg_buffer));
 185         msg_text_lock = 0;
 186     }
 187 }