5 OSSL_trace_enabled, OSSL_trace_begin, OSSL_trace_end,
6 OSSL_TRACE_BEGIN, OSSL_TRACE_END, OSSL_TRACE_CANCEL,
7 OSSL_TRACE, OSSL_TRACE1, OSSL_TRACE2, OSSL_TRACE3, OSSL_TRACE4,
8 OSSL_TRACE5, OSSL_TRACE6, OSSL_TRACE7, OSSL_TRACE8, OSSL_TRACE9,
17 #include <openssl/trace.h>
19 int OSSL_trace_enabled(int category);
21 BIO *OSSL_trace_begin(int category);
22 void OSSL_trace_end(int category, BIO *channel);
24 /* trace group macros */
25 OSSL_TRACE_BEGIN(category) {
28 /* Leave trace group prematurely in case of an error */
29 OSSL_TRACE_CANCEL(category);
33 } OSSL_TRACE_END(category);
35 /* one-shot trace macros */
36 OSSL_TRACE1(category, format, arg1)
37 OSSL_TRACE2(category, format, arg1, arg2)
39 OSSL_TRACE9(category, format, arg1, ..., arg9)
41 /* check whether a trace category is enabled */
42 if (OSSL_TRACE_ENABLED(category)) {
48 The functions described here are mainly interesting for those who provide
49 OpenSSL functionality, either in OpenSSL itself or in engine modules
52 If the tracing facility is enabled (see L</Configure Tracing> below),
53 these functions are used to generate free text tracing output.
55 The tracing output is divided into types which are enabled
56 individually by the application.
57 The tracing types are described in detail in
58 L<OSSL_trace_set_callback(3)/Trace types>.
59 The fallback type B<OSSL_TRACE_CATEGORY_ALL> should I<not> be used
60 with the functions described here.
62 Tracing for a specific category is enabled at run-time if a so-called
63 I<trace channel> is attached to it. A trace channel is simply a
64 BIO object to which the application can write its trace output.
66 The application has two different ways of registering a trace channel,
67 either by directly providing a BIO object using L<OSSL_trace_set_channel(3)>,
68 or by providing a callback routine using L<OSSL_trace_set_callback(3)>.
69 The latter is wrapped internally by a dedicated BIO object, so for the
70 tracing code both channel types are effectively indistinguishable.
71 We call them a I<simple trace channel> and a I<callback trace channel>,
74 To produce trace output, it is necessary to obtain a pointer to the
75 trace channel (i.e., the BIO object) using OSSL_trace_begin(), write
76 to it using arbitrary BIO output routines, and finally releases the
77 channel using OSSL_trace_end(). The OSSL_trace_begin()/OSSL_trace_end()
78 calls surrounding the trace output create a group, which acts as a
79 critical section (guarded by a mutex) to ensure that the trace output
80 of different threads does not get mixed up.
82 The tracing code normally does not call OSSL_trace_{begin,end}() directly,
83 but rather uses a set of convenience macros, see the L</Macros> section below.
88 OSSL_trace_enabled() can be used to check if tracing for the given
89 I<category> is enabled, i.e., if the tracing facility has been statically
90 enabled (see L</Configure Tracing> below) and a trace channel has been
91 registered using L<OSSL_trace_set_channel(3)> or L<OSSL_trace_set_callback(3)>.
93 OSSL_trace_begin() is used to starts a tracing section, and get the
94 channel for the given I<category> in form of a BIO.
95 This BIO can only be used for output.
97 OSSL_trace_end() is used to end a tracing section.
99 Using OSSL_trace_begin() and OSSL_trace_end() to wrap tracing sections
101 The result of trying to produce tracing output outside of such
102 sections is undefined.
106 There are a number of convenience macros defined, to make tracing
109 OSSL_TRACE_BEGIN() and OSSL_TRACE_END() reserve the B<BIO> C<trc_out> and are
110 used as follows to wrap a trace section:
112 OSSL_TRACE_BEGIN(TLS) {
114 BIO_printf(trc_out, ... );
116 } OSSL_TRACE_END(TLS);
118 This will normally expand to:
121 BIO *trc_out = OSSL_trace_begin(OSSL_TRACE_CATEGORY_TLS);
122 if (trc_out != NULL) {
124 BIO_printf(trc_out, ...);
126 OSSL_trace_end(OSSL_TRACE_CATEGORY_TLS, trc_out);
129 OSSL_TRACE_CANCEL() must be used before returning from or jumping out of a
132 OSSL_TRACE_BEGIN(TLS) {
135 OSSL_TRACE_CANCEL(TLS);
138 BIO_printf(trc_out, ... );
140 } OSSL_TRACE_END(TLS);
142 This will normally expand to:
145 BIO *trc_out = OSSL_trace_begin(OSSL_TRACE_CATEGORY_TLS);
146 if (trc_out != NULL) {
148 OSSL_trace_end(OSSL_TRACE_CATEGORY_TLS, trc_out);
151 BIO_printf(trc_out, ... );
153 OSSL_trace_end(OSSL_TRACE_CATEGORY_TLS, trc_out);
157 OSSL_TRACE() and OSSL_TRACE1(), OSSL_TRACE2(), ... OSSL_TRACE9() are
158 so-called one-shot macros:
160 The macro call C<OSSL_TRACE(category, text)>, produces literal text trace output.
162 The macro call C<OSSL_TRACEn(category, format, arg1, ..., argn)> produces
163 printf-style trace output with n format field arguments (n=1,...,9).
166 OSSL_TRACE_BEGIN(category) {
167 BIO_printf(trc_out, format, arg1, ..., argN)
168 } OSSL_TRACE_END(category)
170 Internally, all one-shot macros are implemented using a generic OSSL_TRACEV()
171 macro, since C90 does not support variadic macros. This helper macro has a rather
172 weird synopsis and should not be used directly.
174 The OSSL_TRACE_ENABLED() macro can be used to conditionally execute some code
175 only if a specific trace category is enabled.
176 In some situations this is simpler than entering a trace section using
177 OSSL_TRACE_BEGIN() and OSSL_TRACE_END().
178 For example, the code
180 if (OSSL_TRACE_ENABLED(TLS)) {
186 if (OSSL_trace_enabled(OSSL_TRACE_CATEGORY_TLS) {
192 If producing the trace output requires carrying out auxiliary calculations,
193 this auxiliary code should be placed inside a conditional block which is
194 executed only if the trace category is enabled.
196 The most natural way to do this is to place the code inside the trace section
197 itself because it already introduces such a conditional block.
199 OSSL_TRACE_BEGIN(TLS) {
200 int var = do_some_auxiliary_calculation();
202 BIO_printf(trc_out, "var = %d\n", var);
204 } OSSL_TRACE_END(TLS);
206 In some cases it is more advantageous to use a simple conditional group instead
207 of a trace section. This is the case if calculations and tracing happen in
208 different locations of the code, or if the calculations are so time consuming
209 that placing them inside a (critical) trace section would create too much
212 if (OSSL_TRACE_ENABLED(TLS)) {
213 int var = do_some_auxiliary_calculation();
215 OSSL_TRACE1("var = %d\n", var);
218 Note however that premature optimization of tracing code is in general futile
219 and it's better to keep the tracing code as simple as possible.
220 Because most often the limiting factor for the application's speed is the time
221 it takes to print the trace output, not to calculate it.
223 =head2 Configure Tracing
225 By default, the OpenSSL library is built with tracing disabled. To
226 use the tracing functionality documented here, it is therefore
227 necessary to configure and build OpenSSL with the 'enable-trace' option.
229 When the library is built with tracing disabled:
235 The macro B<OPENSSL_NO_TRACE> is defined in F<< <openssl/opensslconf.h> >>.
239 all functions are still present, but OSSL_trace_enabled() will always
240 report the categories as disabled, and all other functions will do
245 the convenience macros are defined to produce dead code.
246 For example, take this example from L</Macros> section above:
248 OSSL_TRACE_BEGIN(TLS) {
251 OSSL_TRACE_CANCEL(TLS);
254 BIO_printf(trc_out, ... );
256 } OSSL_TRACE_END(TLS);
258 When the tracing API isn't operational, that will expand to:
267 BIO_printf(trc_out, ... );
275 OSSL_trace_enabled() returns 1 if tracing for the given I<type> is
276 operational and enabled, otherwise 0.
278 OSSL_trace_begin() returns a B<BIO> pointer if the given I<type> is enabled,
283 L<OSSL_trace_set_channel(3)>, L<OSSL_trace_set_callback(3)>
287 The OpenSSL Tracing API was added in OpenSSL 3.0.
291 Copyright 2019-2021 The OpenSSL Project Authors. All Rights Reserved.
293 Licensed under the Apache License 2.0 (the "License"). You may not use
294 this file except in compliance with the License. You can obtain a copy
295 in the file LICENSE in the source distribution or at
296 L<https://www.openssl.org/source/license.html>.