add --enable-debug-trace-errcodes=backtrace.

* uses libbacktrace to enhance existing "ERR TRACE" messages with backtraces, rendered in same format as the sanitizers.
* adds wc_backtrace_render() and some related callbacks to wolfcrypt/src/logging.c.
* adds an overrideable WOLFSSL_DEBUG_BACKTRACE_RENDER_CLAUSE to the WC_ERR_TRACE() mechanism in wolfssl/wolfcrypt/error-crypt.h.

configure.ac

@@ -217,11 +217,17 @@ AC_ARG_ENABLE([debug-trace-errcodes],
     [ ENABLED_DEBUG_TRACE_ERRCODES=no ]
     )
 
-if test "$ENABLED_DEBUG_TRACE_ERRCODES" = "yes"
+if test "$ENABLED_DEBUG_TRACE_ERRCODES" != "no"
 then
     AM_CFLAGS="$AM_CFLAGS -DWOLFSSL_DEBUG_TRACE_ERROR_CODES"
 fi
 
+if test "$ENABLED_DEBUG_TRACE_ERRCODES" = "backtrace"
+then
+    AM_CFLAGS="$AM_CFLAGS -g -funwind-tables -DWOLFSSL_DEBUG_BACKTRACE_ERROR_CODES"
+    AM_LDFLAGS="$AM_LDFLAGS -lbacktrace"
+fi
+
 # Start without certificates enabled and enable if a certificate algorithm is
 # enabled
 ENABLED_CERTS="no"
@@ -9981,7 +9987,7 @@ echo "" >> $OPTION_FILE
 echo "#endif /* WOLFSSL_OPTIONS_H */" >> $OPTION_FILE
 echo "" >> $OPTION_FILE
 
-if test "$ENABLED_DEBUG_TRACE_ERRCODES" = "yes"
+if test "$ENABLED_DEBUG_TRACE_ERRCODES" != "no"
 then
     support/gen-debug-trace-error-codes.sh || AC_MSG_ERROR([Header generation for debug-trace-errcodes failed.])
 fi

wolfcrypt/src/logging.c

@@ -1674,3 +1674,130 @@ void WOLFSSL_ERROR_MSG(const char* msg)
 }
 
 #endif  /* DEBUG_WOLFSSL || WOLFSSL_NGINX || WOLFSSL_HAPROXY */
+
+#ifdef WOLFSSL_DEBUG_BACKTRACE_ERROR_CODES
+
+#include <backtrace-supported.h>
+
+#if BACKTRACE_SUPPORTED != 1
+    #error WOLFSSL_DEBUG_BACKTRACE_ERROR_CODES is defined but BACKTRACE_SUPPORTED is 0.
+#endif
+
+#if !defined(WOLFSSL_MUTEX_INITIALIZER) && defined(WOLFSSL_NO_ATOMICS)
+    #error WOLFSSL_DEBUG_BACKTRACE_ERROR_CODES requires WOLFSSL_MUTEX_INITIALIZER or wolfSSL_Atomic_Ints.
+#endif
+
+#include <backtrace.h>
+
+static int backtrace_callback(void *data, uintptr_t pc, const char *filename,
+                              int lineno, const char *function)
+{
+    if (function == NULL)
+        return 0;
+    /* the first callback is for the call to wc_print_backtrace() -- skip it. */
+    if (*(int *)data == 0) {
+        *(int *)data = 1;
+        return 0;
+    }
+#ifdef NO_STDIO_FILESYSTEM
+    printf("    #%d %p in %s %s:%d\n", (*(int *)data)++, (void *)pc,
+           function, filename, lineno);
+#else
+    fprintf(stderr, "    #%d %p in %s %s:%d\n", (*(int *)data)++, (void *)pc,
+            function, filename, lineno);
+#endif
+    return 0;
+}
+
+static void backtrace_error(void *data, const char *msg, int errnum) {
+    (void)data;
+#ifdef NO_STDIO_FILESYSTEM
+    printf("ERR TRACE: error %d while backtracing: %s", errnum, msg);
+#else
+    fprintf(stderr, "ERR TRACE: error %d while backtracing: %s", errnum, msg);
+#endif
+}
+
+static void backtrace_creation_error(void *data, const char *msg, int errnum) {
+    (void)data;
+#ifdef NO_STDIO_FILESYSTEM
+    printf("ERR TRACE: internal error %d "
+            "while initializing backtrace facility: %s", errnum, msg);
+    printf("ERR TRACE: internal error "
+           "while initializing backtrace facility");
+#else
+    fprintf(stderr, "ERR TRACE: internal error %d "
+            "while initializing backtrace facility: %s", errnum, msg);
+#endif
+}
+
+static int backtrace_init(struct backtrace_state **backtrace_state) {
+#ifdef WOLFSSL_MUTEX_INITIALIZER
+    static wolfSSL_Mutex backtrace_create_state_mutex =
+        WOLFSSL_MUTEX_INITIALIZER(backtrace_create_state_mutex);
+    if (wc_LockMutex(&backtrace_create_state_mutex) != 0)
+        return -1;
+#elif defined(WOLFSSL_ATOMIC_OPS)
+    static wolfSSL_Atomic_Int init_count = 0;
+    if (wolfSSL_Atomic_Int_FetchAdd(&init_count, 1) != 1)
+        return -1;
+#endif
+    if (*backtrace_state == NULL) {
+        /* passing a NULL filename to backtrace_create_state() tells
+         * libbacktrace to use a target-specific strategy to determine the
+         * executable.  "libbacktrace supports ELF, PE/COFF, Mach-O, and XCOFF
+         * executables with DWARF debugging information.  In other words, it
+         * supports GNU/Linux, *BSD, macOS, Windows, and AIX."
+         */
+        *backtrace_state = backtrace_create_state(
+            NULL, 0, backtrace_creation_error, NULL);
+    }
+#ifdef WOLFSSL_MUTEX_INITIALIZER
+    wc_UnLockMutex(&backtrace_create_state_mutex);
+#endif
+    if (*backtrace_state == NULL)
+        return -1;
+    return 0;
+}
+
+void wc_backtrace_render(void) {
+    static wolfSSL_Mutex backtrace_mutex WOLFSSL_MUTEX_INITIALIZER_CLAUSE(backtrace_mutex);
+    static struct backtrace_state *backtrace_state = NULL;
+    int depth = 0;
+
+#ifndef WOLFSSL_MUTEX_INITIALIZER
+    static wolfSSL_Atomic_Int init_count = 0;
+    if (init_count != 1) {
+        if (wolfSSL_Atomic_Int_FetchSub(&init_count, 1) != -1)
+            return;
+        if (wc_InitMutex(&backtrace_mutex) != 0)
+            return;
+        init_count = 1;
+    }
+#endif
+
+    /* backtrace_state can't be shared between threads even when
+     * BACKTRACE_SUPPORTS_THREADS == 1, so we serialize the render op.  this
+     * helpfully mutexes the initialization too.
+     */
+    if (wc_LockMutex(&backtrace_mutex) != 0)
+        return;
+
+    if (backtrace_state == NULL) {
+        if (backtrace_init(&backtrace_state) < 0) {
+            wc_UnLockMutex(&backtrace_mutex);
+            return;
+        }
+    }
+
+    /* note that the optimizer can produce misleading backtraces, even with
+     * -funwind-tables.  in contrast, the macro-generated "ERR TRACE" message
+     * from WC_ERR_TRACE() always accurately identifies the error code point.
+     */
+    backtrace_full(backtrace_state, 0, backtrace_callback, backtrace_error,
+                   (void *)&depth);
+
+    wc_UnLockMutex(&backtrace_mutex);
+}
+
+#endif /* WOLFSSL_DEBUG_BACKTRACE_ERROR_CODES */

wolfssl/wolfcrypt/error-crypt.h

@@ -298,17 +298,31 @@ WOLFSSL_ABI WOLFSSL_API const char* wc_GetErrorString(int error);
     #undef WOLFSSL_DEBUG_TRACE_ERROR_CODES
 #endif
 #ifdef WOLFSSL_DEBUG_TRACE_ERROR_CODES
+    extern void wc_backtrace_render(void);
     #define WC_NO_ERR_TRACE(label) (CONST_NUM_ERR_ ## label)
+    #ifndef WOLFSSL_DEBUG_BACKTRACE_RENDER_CLAUSE
+        #ifdef WOLFSSL_DEBUG_BACKTRACE_ERROR_CODES
+            #define WOLFSSL_DEBUG_BACKTRACE_RENDER_CLAUSE wc_backtrace_render()
+        #else
+            #define WOLFSSL_DEBUG_BACKTRACE_RENDER_CLAUSE (void)0
+        #endif
+    #endif
     #ifndef WC_ERR_TRACE
         #ifdef NO_STDIO_FILESYSTEM
         #define WC_ERR_TRACE(label)                           \
-            ( printf("ERR TRACE: %s L %d " #label " (%d)\n",  \
+            ( printf("ERR TRACE: %s L %d %s (%d)\n",          \
-                      __FILE__, __LINE__, label), label)
+                      __FILE__, __LINE__, #label, label),     \
+              WOLFSSL_DEBUG_BACKTRACE_RENDER_CLAUSE,          \
+              label                                           \
+            )
         #else
         #define WC_ERR_TRACE(label)                           \
             ( fprintf(stderr,                                 \
-                      "ERR TRACE: %s L %d " #label " (%d)\n", \
+                      "ERR TRACE: %s L %d %s (%d)\n",         \
-                      __FILE__, __LINE__, label), label)
+                      __FILE__, __LINE__, #label, label),     \
+              WOLFSSL_DEBUG_BACKTRACE_RENDER_CLAUSE,          \
+              label                                           \
+            )
         #endif
     #endif
     #include <wolfssl/debug-trace-error-codes.h>