1 /* $NetBSD: msg_output.c,v 1.4 2022/10/08 16:12:50 christos Exp $ */
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 /* DESCRIPTION
25 /* This module implements low-level output management for the
26 /* msg(3) diagnostics interface.
27 /*
28 /* msg_output() registers an output handler for the diagnostics
29 /* interface. An application can register multiple output handlers.
30 /* Output handlers are called in the specified order.
31 /* An output handler takes as arguments a severity level (MSG_INFO,
32 /* MSG_WARN, MSG_ERROR, MSG_FATAL, MSG_PANIC, monotonically increasing
33 /* integer values ranging from 0 to MSG_LAST) and pre-formatted,
34 /* sanitized, text in the form of a null-terminated string.
35 /*
36 /* msg_printf() and msg_vprintf() format their arguments, sanitize the
37 /* result, and call the output handlers registered with msg_output().
38 /*
39 /* msg_text() copies a pre-formatted text, sanitizes the result, and
40 /* calls the output handlers registered with msg_output().
41 /* REENTRANCY
42 /* .ad
43 /* .fi
44 /* The above output routines are protected against ordinary
45 /* recursive calls and against re-entry by signal
46 /* handlers, with the following limitations:
47 /* .IP \(bu
48 /* The signal handlers must never return. In other words, the
49 /* signal handlers must do one or more of the following: call
50 /* _exit(), kill the process with a signal, and permanently
51 /* block the process.
52 /* .IP \(bu
53 /* The signal handlers must call the above output routines not
54 /* until after msg_output() completes initialization, and not
55 /* until after the first formatted output to a VSTRING or
56 /* VSTREAM.
57 /* .IP \(bu
58 /* Each msg_output() call-back function, and each Postfix or
59 /* system function called by that call-back function, either
60 /* must protect itself against recursive calls and re-entry
61 /* by a terminating signal handler, or it must be called
62 /* exclusively by functions in the msg_output(3) module.
63 /* .PP
64 /* When re-entrancy is detected, the requested output operation
65 /* is skipped. This prevents memory corruption of VSTREAM_ERR
66 /* data structures, and prevents deadlock on Linux releases
67 /* that use mutexes within system library routines such as
68 /* syslog(). This protection exists under the condition that
69 /* these specific resources are accessed exclusively via
70 /* msg_output() call-back functions.
71 /* LICENSE
72 /* .ad
73 /* .fi
74 /* The Secure Mailer license must be distributed with this software.
75 /* AUTHOR(S)
76 /* Wietse Venema
77 /* IBM T.J. Watson Research
78 /* P.O. Box 704
79 /* Yorktown Heights, NY 10598, USA
80 /*
81 /* Wietse Venema
82 /* Google, Inc.
83 /* 111 8th Avenue
84 /* New York, NY 10011, USA
85 /*--*/
86
87 /* System library. */
88
89 #include <sys_defs.h>
90 #include <stdarg.h>
91 #include <errno.h>
92
93 /* Utility library. */
94
95 #include <mymalloc.h>
96 #include <vstring.h>
97 #include <vstream.h>
98 #include <msg_vstream.h>
99 #include <stringops.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_level;
106
107 /*
108 * Private state. Allow one nested call, so that one logging error can be
109 * reported to stderr before bailing out.
110 */
111 #define MSG_OUT_NESTING_LIMIT 2
112 static MSG_OUTPUT_FN *msg_output_fn = 0;
113 static int msg_output_fn_count = 0;
114 static VSTRING *msg_buffers[MSG_OUT_NESTING_LIMIT];
115
116 /* msg_output - specify output handler */
117
msg_output(MSG_OUTPUT_FN output_fn)118 void msg_output(MSG_OUTPUT_FN output_fn)
119 {
120 int i;
121
122 /*
123 * Allocate all resources during initialization. This may result in a
124 * recursive call due to memory allocation error.
125 */
126 if (msg_buffers[MSG_OUT_NESTING_LIMIT - 1] == 0) {
127 for (i = 0; i < MSG_OUT_NESTING_LIMIT; i++)
128 msg_buffers[i] = vstring_alloc(100);
129 }
130
131 /*
132 * We're not doing this often, so avoid complexity and allocate memory
133 * for an exact fit.
134 */
135 if (msg_output_fn_count == 0)
136 msg_output_fn = (MSG_OUTPUT_FN *) mymalloc(sizeof(*msg_output_fn));
137 else
138 msg_output_fn = (MSG_OUTPUT_FN *) myrealloc((void *) msg_output_fn,
139 (msg_output_fn_count + 1) * sizeof(*msg_output_fn));
140 msg_output_fn[msg_output_fn_count++] = output_fn;
141 }
142
143 /* msg_printf - format text and log it */
144
msg_printf(int level,const char * format,...)145 void msg_printf(int level, const char *format,...)
146 {
147 va_list ap;
148
149 va_start(ap, format);
150 msg_vprintf(level, format, ap);
151 va_end(ap);
152 }
153
154 /* msg_vprintf - format text and log it */
155
msg_vprintf(int level,const char * format,va_list ap)156 void msg_vprintf(int level, const char *format, va_list ap)
157 {
158 int saved_errno = errno;
159 VSTRING *vp;
160 int i;
161
162 if (msg_vprintf_level < MSG_OUT_NESTING_LIMIT) {
163 msg_vprintf_level += 1;
164 /* On-the-fly initialization for test programs and startup errors. */
165 if (msg_output_fn_count == 0)
166 msg_vstream_init("unknown", VSTREAM_ERR);
167 vp = msg_buffers[msg_vprintf_level - 1];
168 /* OK if terminating signal handler hijacks control before next stmt. */
169 vstring_vsprintf(vp, format, ap);
170 printable(vstring_str(vp), '?');
171 for (i = 0; i < msg_output_fn_count; i++)
172 msg_output_fn[i] (level, vstring_str(vp));
173 msg_vprintf_level -= 1;
174 }
175 errno = saved_errno;
176 }
177