linker: Enable debug logging via properties
This patch lets developers tune logging of dlopen/dlerror with
setting system property.
Note that for security purposes this option is disabled on user build
for non-debuggable apps.
For starters there are 3 debug options:
dlerror - enables logging of all dlerrors
dlopen - traces dlopen calls
To enable system-wide logging (works only for userdebug/eng builds)
use debug.ld.all property.
To enable logging for particular app use debug.ld.app.<appname> property.
Example: Running "adb shell setprop debug.ld.all dlerror,dlopen" will log all
dlerror message as well as trace all calls to dlopen.
Bug: http://b/29458203
Change-Id: I2392c80a795509e16fe5689d0500d18b99772a64
diff --git a/linker/linker_logger.cpp b/linker/linker_logger.cpp
new file mode 100644
index 0000000..7499a83
--- /dev/null
+++ b/linker/linker_logger.cpp
@@ -0,0 +1,119 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <string.h>
+#include <sys/prctl.h>
+#include <sys/system_properties.h>
+#include <unistd.h>
+
+#include <string>
+#include <vector>
+
+#include "android-base/strings.h"
+#include "linker_logger.h"
+#include "private/libc_logging.h"
+
+LinkerLogger g_linker_logger;
+
+static const char* kSystemLdDebugProperty = "debug.ld.all";
+static const std::string kLdDebugPropertyPrefix = "debug.ld.app.";
+
+static const char* kOptionErrors = "dlerror";
+static const char* kOptionDlopen = "dlopen";
+
+static std::string property_get(const char* name) {
+ char value[PROP_VALUE_MAX] = {};
+ __system_property_get(name, value);
+ return value;
+}
+
+static uint32_t ParseProperty(const std::string& value) {
+ if (value.empty()) {
+ return 0;
+ }
+
+ std::vector<std::string> options = android::base::Split(value, ",");
+
+ uint32_t flags = 0;
+
+ for (const auto& o : options) {
+ if (o == kOptionErrors) {
+ flags |= kLogErrors;
+ } else if (o == kOptionDlopen){
+ flags |= kLogDlopen;
+ } else {
+ __libc_format_log(ANDROID_LOG_WARN, "linker", "Unknown debug.ld option \"%s\", will ignore.", o.c_str());
+ }
+ }
+
+ return flags;
+}
+
+void LinkerLogger::ResetState() {
+ // the most likely scenario app is not debuggable and
+ // is running on user build - the logging is disabled.
+ if (prctl(PR_GET_DUMPABLE, 0, 0, 0, 0) == 0) {
+ return;
+ }
+
+ flags_ = 0;
+ // check flag applied to all processes first
+ std::string value = property_get(kSystemLdDebugProperty);
+ flags_ |= ParseProperty(value);
+
+ // get process basename
+ std::string process_name = basename(g_argv0);
+
+ std::string property_name = std::string(kLdDebugPropertyPrefix) + process_name;
+
+ // Property names are limited to PROP_NAME_MAX.
+
+ if (property_name.size() >= PROP_NAME_MAX) {
+ size_t count = PROP_NAME_MAX - 1;
+ // remove trailing dots...
+ while (property_name[count-1] == '.') {
+ --count;
+ }
+
+ property_name = property_name.substr(0, count);
+ }
+ value = property_get(property_name.c_str());
+ flags_ |= ParseProperty(value);
+}
+
+void LinkerLogger::Log(uint32_t type, const char* format, ...) {
+ if ((flags_ & type) == 0) {
+ return;
+ }
+
+ va_list ap;
+ va_start(ap, format);
+ __libc_format_log_va_list(ANDROID_LOG_DEBUG, "linker", format, ap);
+ va_end(ap);
+}
+