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,
10 OSSL_TRACE_STRING, OSSL_TRACE_STRING_MAX, OSSL_trace_string,
18 #include <openssl/trace.h>
20 int OSSL_trace_enabled(int category);
22 BIO *OSSL_trace_begin(int category);
23 void OSSL_trace_end(int category, BIO *channel);
25 /* trace group macros */
26 OSSL_TRACE_BEGIN(category) {
29 /* Leave trace group prematurely in case of an error */
30 OSSL_TRACE_CANCEL(category);
34 } OSSL_TRACE_END(category);
36 /* one-shot trace macros */
37 OSSL_TRACE(category, text)
38 OSSL_TRACE1(category, format, arg1)
39 OSSL_TRACE2(category, format, arg1, arg2)
41 OSSL_TRACE9(category, format, arg1, ..., arg9)
42 OSSL_TRACE_STRING(category, text, full, data, len)
44 #define OSSL_TRACE_STRING_MAX 80
45 int OSSL_trace_string(BIO *out, int text, int full,
46 const unsigned char *data, size_t size);
48 /* check whether a trace category is enabled */
49 if (OSSL_TRACE_ENABLED(category)) {
55 The functions described here are mainly interesting for those who provide
56 OpenSSL functionality, either in OpenSSL itself or in engine modules
59 If the tracing facility is enabled (see L</Configure Tracing> below),
60 these functions are used to generate free text tracing output.
62 The tracing output is divided into types which are enabled
63 individually by the application.
64 The tracing types are described in detail in
65 L<OSSL_trace_set_callback(3)/Trace types>.
66 The fallback type B<OSSL_TRACE_CATEGORY_ALL> should I<not> be used
67 with the functions described here.
69 Tracing for a specific category is enabled at run-time if a so-called
70 I<trace channel> is attached to it. A trace channel is simply a
71 BIO object to which the application can write its trace output.
73 The application has two different ways of registering a trace channel,
74 either by directly providing a BIO object using L<OSSL_trace_set_channel(3)>,
75 or by providing a callback routine using L<OSSL_trace_set_callback(3)>.
76 The latter is wrapped internally by a dedicated BIO object, so for the
77 tracing code both channel types are effectively indistinguishable.
78 We call them a I<simple trace channel> and a I<callback trace channel>,
81 To produce trace output, it is necessary to obtain a pointer to the
82 trace channel (i.e., the BIO object) using OSSL_trace_begin(), write
83 to it using arbitrary BIO output routines, and finally releases the
84 channel using OSSL_trace_end(). The OSSL_trace_begin()/OSSL_trace_end()
85 calls surrounding the trace output create a group, which acts as a
86 critical section (guarded by a mutex) to ensure that the trace output
87 of different threads does not get mixed up.
89 The tracing code normally does not call OSSL_trace_{begin,end}() directly,
90 but rather uses a set of convenience macros, see the L</Macros> section below.
95 OSSL_trace_enabled() can be used to check if tracing for the given
96 I<category> is enabled, i.e., if the tracing facility has been statically
97 enabled (see L</Configure Tracing> below) and a trace channel has been
98 registered using L<OSSL_trace_set_channel(3)> or L<OSSL_trace_set_callback(3)>.
100 OSSL_trace_begin() is used to starts a tracing section, and get the
101 channel for the given I<category> in form of a BIO.
102 This BIO can only be used for output.
104 OSSL_trace_end() is used to end a tracing section.
106 Using OSSL_trace_begin() and OSSL_trace_end() to wrap tracing sections
108 The result of trying to produce tracing output outside of such
109 sections is undefined.
111 OSSL_trace_string() outputs I<data> of length I<size> as a string on BIO I<out>.
112 If I<text> is 0, the function masks any included control characters apart from
113 newlines and makes sure for nonempty input that the output ends with a newline.
114 Unless I<full> is nonzero, the length is limited (with a suitable warning)
115 to B<OSSL_TRACE_STRING_MAX> characters, which currently is 80.
119 There are a number of convenience macros defined, to make tracing
122 OSSL_TRACE_BEGIN() and OSSL_TRACE_END() reserve the B<BIO> C<trc_out> and are
123 used as follows to wrap a trace section:
125 OSSL_TRACE_BEGIN(TLS) {
127 BIO_printf(trc_out, ... );
129 } OSSL_TRACE_END(TLS);
131 This will normally expand to:
134 BIO *trc_out = OSSL_trace_begin(OSSL_TRACE_CATEGORY_TLS);
135 if (trc_out != NULL) {
137 BIO_printf(trc_out, ...);
139 OSSL_trace_end(OSSL_TRACE_CATEGORY_TLS, trc_out);
142 OSSL_TRACE_CANCEL() must be used before returning from or jumping out of a
145 OSSL_TRACE_BEGIN(TLS) {
148 OSSL_TRACE_CANCEL(TLS);
151 BIO_printf(trc_out, ... );
153 } OSSL_TRACE_END(TLS);
155 This will normally expand to:
158 BIO *trc_out = OSSL_trace_begin(OSSL_TRACE_CATEGORY_TLS);
159 if (trc_out != NULL) {
161 OSSL_trace_end(OSSL_TRACE_CATEGORY_TLS, trc_out);
164 BIO_printf(trc_out, ... );
166 OSSL_trace_end(OSSL_TRACE_CATEGORY_TLS, trc_out);
170 OSSL_TRACE() and OSSL_TRACE1(), OSSL_TRACE2(), ... OSSL_TRACE9() are
171 so-called one-shot macros:
173 The macro call C<OSSL_TRACE(category, text)>, produces literal text trace output.
175 The macro call C<OSSL_TRACEn(category, format, arg1, ..., argn)> produces
176 printf-style trace output with n format field arguments (n=1,...,9).
179 OSSL_TRACE_BEGIN(category) {
180 BIO_printf(trc_out, format, arg1, ..., argN);
181 } OSSL_TRACE_END(category)
183 Internally, all one-shot macros are implemented using a generic OSSL_TRACEV()
184 macro, since C90 does not support variadic macros. This helper macro has a rather
185 weird synopsis and should not be used directly.
187 The macro call C<OSSL_TRACE_STRING(category, text, full, data, len)>
188 outputs I<data> of length I<size> as a string
189 if tracing for the given I<category> is enabled.
192 OSSL_TRACE_BEGIN(category) {
193 OSSL_trace_string(trc_out, text, full, data, len);
194 } OSSL_TRACE_END(category)
196 The OSSL_TRACE_ENABLED() macro can be used to conditionally execute some code
197 only if a specific trace category is enabled.
198 In some situations this is simpler than entering a trace section using
199 OSSL_TRACE_BEGIN() and OSSL_TRACE_END().
200 For example, the code
202 if (OSSL_TRACE_ENABLED(TLS)) {
208 if (OSSL_trace_enabled(OSSL_TRACE_CATEGORY_TLS) {
214 If producing the trace output requires carrying out auxiliary calculations,
215 this auxiliary code should be placed inside a conditional block which is
216 executed only if the trace category is enabled.
218 The most natural way to do this is to place the code inside the trace section
219 itself because it already introduces such a conditional block.
221 OSSL_TRACE_BEGIN(TLS) {
222 int var = do_some_auxiliary_calculation();
224 BIO_printf(trc_out, "var = %d\n", var);
226 } OSSL_TRACE_END(TLS);
228 In some cases it is more advantageous to use a simple conditional group instead
229 of a trace section. This is the case if calculations and tracing happen in
230 different locations of the code, or if the calculations are so time consuming
231 that placing them inside a (critical) trace section would create too much
234 if (OSSL_TRACE_ENABLED(TLS)) {
235 int var = do_some_auxiliary_calculation();
237 OSSL_TRACE1("var = %d\n", var);
240 Note however that premature optimization of tracing code is in general futile
241 and it's better to keep the tracing code as simple as possible.
242 Because most often the limiting factor for the application's speed is the time
243 it takes to print the trace output, not to calculate it.
245 =head2 Configure Tracing
247 By default, the OpenSSL library is built with tracing disabled. To
248 use the tracing functionality documented here, it is therefore
249 necessary to configure and build OpenSSL with the 'enable-trace' option.
251 When the library is built with tracing disabled:
257 The macro B<OPENSSL_NO_TRACE> is defined in F<< <openssl/opensslconf.h> >>.
261 all functions are still present, but OSSL_trace_enabled() will always
262 report the categories as disabled, and all other functions will do
267 the convenience macros are defined to produce dead code.
268 For example, take this example from L</Macros> section above:
270 OSSL_TRACE_BEGIN(TLS) {
273 OSSL_TRACE_CANCEL(TLS);
276 BIO_printf(trc_out, ... );
278 } OSSL_TRACE_END(TLS);
280 When the tracing API isn't operational, that will expand to:
289 BIO_printf(trc_out, ... );
297 OSSL_trace_enabled() returns 1 if tracing for the given I<type> is
298 operational and enabled, otherwise 0.
300 OSSL_trace_begin() returns a B<BIO> pointer if the given I<type> is enabled,
303 OSSL_trace_string() returns the number of characters emitted, or -1 on error.
307 L<OSSL_trace_set_channel(3)>, L<OSSL_trace_set_callback(3)>
311 The OpenSSL Tracing API was added in OpenSSL 3.0.
313 OSSL_TRACE_STRING(), OSSL_TRACE_STRING_MAX, and OSSL_trace_string
314 were added in OpenSSL 3.2.
318 Copyright 2019-2023 The OpenSSL Project Authors. All Rights Reserved.
320 Licensed under the Apache License 2.0 (the "License"). You may not use
321 this file except in compliance with the License. You can obtain a copy
322 in the file LICENSE in the source distribution or at
323 L<https://www.openssl.org/source/license.html>.