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_TRACE(category, text)
37 OSSL_TRACE1(category, format, arg1)
38 OSSL_TRACE2(category, format, arg1, arg2)
40 OSSL_TRACE9(category, format, arg1, ..., arg9)
42 /* check whether a trace category is enabled */
43 if (OSSL_TRACE_ENABLED(category)) {
49 The functions described here are mainly interesting for those who provide
50 OpenSSL functionality, either in OpenSSL itself or in engine modules
53 If the tracing facility is enabled (see L</Configure Tracing> below),
54 these functions are used to generate free text tracing output.
56 The tracing output is divided into types which are enabled
57 individually by the application.
58 The tracing types are described in detail in
59 L<OSSL_trace_set_callback(3)/Trace types>.
60 The fallback type B<OSSL_TRACE_CATEGORY_ALL> should I<not> be used
61 with the functions described here.
63 Tracing for a specific category is enabled at run-time if a so-called
64 I<trace channel> is attached to it. A trace channel is simply a
65 BIO object to which the application can write its trace output.
67 The application has two different ways of registering a trace channel,
68 either by directly providing a BIO object using L<OSSL_trace_set_channel(3)>,
69 or by providing a callback routine using L<OSSL_trace_set_callback(3)>.
70 The latter is wrapped internally by a dedicated BIO object, so for the
71 tracing code both channel types are effectively indistinguishable.
72 We call them a I<simple trace channel> and a I<callback trace channel>,
75 To produce trace output, it is necessary to obtain a pointer to the
76 trace channel (i.e., the BIO object) using OSSL_trace_begin(), write
77 to it using arbitrary BIO output routines, and finally releases the
78 channel using OSSL_trace_end(). The OSSL_trace_begin()/OSSL_trace_end()
79 calls surrounding the trace output create a group, which acts as a
80 critical section (guarded by a mutex) to ensure that the trace output
81 of different threads does not get mixed up.
83 The tracing code normally does not call OSSL_trace_{begin,end}() directly,
84 but rather uses a set of convenience macros, see the L</Macros> section below.
89 OSSL_trace_enabled() can be used to check if tracing for the given
90 I<category> is enabled, i.e., if the tracing facility has been statically
91 enabled (see L</Configure Tracing> below) and a trace channel has been
92 registered using L<OSSL_trace_set_channel(3)> or L<OSSL_trace_set_callback(3)>.
94 OSSL_trace_begin() is used to starts a tracing section, and get the
95 channel for the given I<category> in form of a BIO.
96 This BIO can only be used for output.
98 OSSL_trace_end() is used to end a tracing section.
100 Using OSSL_trace_begin() and OSSL_trace_end() to wrap tracing sections
102 The result of trying to produce tracing output outside of such
103 sections is undefined.
107 There are a number of convenience macros defined, to make tracing
110 OSSL_TRACE_BEGIN() and OSSL_TRACE_END() reserve the B<BIO> C<trc_out> and are
111 used as follows to wrap a trace section:
113 OSSL_TRACE_BEGIN(TLS) {
115 BIO_printf(trc_out, ... );
117 } OSSL_TRACE_END(TLS);
119 This will normally expand to:
122 BIO *trc_out = OSSL_trace_begin(OSSL_TRACE_CATEGORY_TLS);
123 if (trc_out != NULL) {
125 BIO_printf(trc_out, ...);
127 OSSL_trace_end(OSSL_TRACE_CATEGORY_TLS, trc_out);
130 OSSL_TRACE_CANCEL() must be used before returning from or jumping out of a
133 OSSL_TRACE_BEGIN(TLS) {
136 OSSL_TRACE_CANCEL(TLS);
139 BIO_printf(trc_out, ... );
141 } OSSL_TRACE_END(TLS);
143 This will normally expand to:
146 BIO *trc_out = OSSL_trace_begin(OSSL_TRACE_CATEGORY_TLS);
147 if (trc_out != NULL) {
149 OSSL_trace_end(OSSL_TRACE_CATEGORY_TLS, trc_out);
152 BIO_printf(trc_out, ... );
154 OSSL_trace_end(OSSL_TRACE_CATEGORY_TLS, trc_out);
158 OSSL_TRACE() and OSSL_TRACE1(), OSSL_TRACE2(), ... OSSL_TRACE9() are
159 so-called one-shot macros:
161 The macro call C<OSSL_TRACE(category, text)>, produces literal text trace output.
163 The macro call C<OSSL_TRACEn(category, format, arg1, ..., argn)> produces
164 printf-style trace output with n format field arguments (n=1,...,9).
167 OSSL_TRACE_BEGIN(category) {
168 BIO_printf(trc_out, format, arg1, ..., argN)
169 } OSSL_TRACE_END(category)
171 Internally, all one-shot macros are implemented using a generic OSSL_TRACEV()
172 macro, since C90 does not support variadic macros. This helper macro has a rather
173 weird synopsis and should not be used directly.
175 The OSSL_TRACE_ENABLED() macro can be used to conditionally execute some code
176 only if a specific trace category is enabled.
177 In some situations this is simpler than entering a trace section using
178 OSSL_TRACE_BEGIN() and OSSL_TRACE_END().
179 For example, the code
181 if (OSSL_TRACE_ENABLED(TLS)) {
187 if (OSSL_trace_enabled(OSSL_TRACE_CATEGORY_TLS) {
193 If producing the trace output requires carrying out auxiliary calculations,
194 this auxiliary code should be placed inside a conditional block which is
195 executed only if the trace category is enabled.
197 The most natural way to do this is to place the code inside the trace section
198 itself because it already introduces such a conditional block.
200 OSSL_TRACE_BEGIN(TLS) {
201 int var = do_some_auxiliary_calculation();
203 BIO_printf(trc_out, "var = %d\n", var);
205 } OSSL_TRACE_END(TLS);
207 In some cases it is more advantageous to use a simple conditional group instead
208 of a trace section. This is the case if calculations and tracing happen in
209 different locations of the code, or if the calculations are so time consuming
210 that placing them inside a (critical) trace section would create too much
213 if (OSSL_TRACE_ENABLED(TLS)) {
214 int var = do_some_auxiliary_calculation();
216 OSSL_TRACE1("var = %d\n", var);
219 Note however that premature optimization of tracing code is in general futile
220 and it's better to keep the tracing code as simple as possible.
221 Because most often the limiting factor for the application's speed is the time
222 it takes to print the trace output, not to calculate it.
224 =head2 Configure Tracing
226 By default, the OpenSSL library is built with tracing disabled. To
227 use the tracing functionality documented here, it is therefore
228 necessary to configure and build OpenSSL with the 'enable-trace' option.
230 When the library is built with tracing disabled:
236 The macro B<OPENSSL_NO_TRACE> is defined in F<< <openssl/opensslconf.h> >>.
240 all functions are still present, but OSSL_trace_enabled() will always
241 report the categories as disabled, and all other functions will do
246 the convenience macros are defined to produce dead code.
247 For example, take this example from L</Macros> section above:
249 OSSL_TRACE_BEGIN(TLS) {
252 OSSL_TRACE_CANCEL(TLS);
255 BIO_printf(trc_out, ... );
257 } OSSL_TRACE_END(TLS);
259 When the tracing API isn't operational, that will expand to:
268 BIO_printf(trc_out, ... );
276 OSSL_trace_enabled() returns 1 if tracing for the given I<type> is
277 operational and enabled, otherwise 0.
279 OSSL_trace_begin() returns a B<BIO> pointer if the given I<type> is enabled,
284 L<OSSL_trace_set_channel(3)>, L<OSSL_trace_set_callback(3)>
288 The OpenSSL Tracing API was added in OpenSSL 3.0.
292 Copyright 2019-2021 The OpenSSL Project Authors. All Rights Reserved.
294 Licensed under the Apache License 2.0 (the "License"). You may not use
295 this file except in compliance with the License. You can obtain a copy
296 in the file LICENSE in the source distribution or at
297 L<https://www.openssl.org/source/license.html>.