liblog: Add android_set_log_frontend
android_set_log_frontend allows one to select LOGGER_DEFAULT,
LOGGER_LOGD or LOGGER_NULL, the latter allows a runtime mechanism to
turn logging on or off. LOGGER_DEFAULT is LOGGER_LOGD.
Test: gTest liblog-unit-tests notably liblog.android_set_log_frontend
and liblog-benchmarks before and after.
Bug: 27405083
Change-Id: I365dbee9f7d83112da0ef8d1cace748d247773c8
diff --git a/liblog/README b/liblog/README
index 610338c..922b5e3 100644
--- a/liblog/README
+++ b/liblog/README
@@ -108,6 +108,11 @@
int android_log_destroy(android_log_context *ctx)
+ #include <log/log_frontend.h>
+
+ int android_set_log_frontend(int frontend_flag)
+ int android_get_log_frontend()
+
Link with -llog
DESCRIPTION
@@ -162,6 +167,12 @@
when opening the sub-log. It is recommended to open the log
ANDROID_LOG_RDONLY in these cases.
+ android_set_log_frontend() selects frontend filters. Argument is either
+ LOGGER_DEFAULT, LOGGER_LOGD or LOGGER_NULL. The latter drops all
+ content on the floor. Both android_set_log_frontend() and
+ android_get_log_frontend() return the current frontend mask, or a
+ negative errno for any problems.
+
ERRORS
If messages fail, a negative error code will be returned to the caller.
@@ -194,4 +205,4 @@
- 17 Oct 2016 LIBLOG(3)
+ 08 Feb 2017 LIBLOG(3)
diff --git a/liblog/include/log/log_frontend.h b/liblog/include/log/log_frontend.h
new file mode 100644
index 0000000..c2f8b7b
--- /dev/null
+++ b/liblog/include/log/log_frontend.h
@@ -0,0 +1,33 @@
+/*
+**
+** Copyright 2017, The Android Open Source Project
+**
+** This file is dual licensed. It may be redistributed and/or modified
+** under the terms of the Apache 2.0 License OR version 2 of the GNU
+** General Public License.
+*/
+
+#ifndef _LIBS_LOG_FRONTEND_H
+#define _LIBS_LOG_FRONTEND_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * Logging frontends, bit mask to select features. Function returns selection.
+ */
+#define LOGGER_DEFAULT 0x0
+#define LOGGER_LOGD 0x1
+#define LOGGER_KERNEL 0x2 /* Reserved/Deprecated */
+#define LOGGER_NULL 0x4 /* Does not release resources of other selections */
+
+/* Both return the selected frontend flag mask, or negative errno */
+int android_set_log_frontend(int frontend_flag);
+int android_get_log_frontend();
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _LIBS_LOG_FRONTEND_H */
diff --git a/liblog/logger_write.c b/liblog/logger_write.c
index 2599a53..bff77f8 100644
--- a/liblog/logger_write.c
+++ b/liblog/logger_write.c
@@ -25,6 +25,7 @@
#endif
#include <log/event_tag_map.h>
+#include <log/log_frontend.h>
#include <private/android_filesystem_config.h>
#include <private/android_logger.h>
@@ -618,3 +619,67 @@
return write_to_log(LOG_ID_SECURITY, vec, 4);
}
+
+static int __write_to_log_null(log_id_t log_id, struct iovec* vec, size_t nr)
+{
+ size_t len, i;
+
+ if ((log_id < LOG_ID_MIN) || (log_id >= LOG_ID_MAX)) {
+ return -EINVAL;
+ }
+
+ for (len = i = 0; i < nr; ++i) {
+ len += vec[i].iov_len;
+ }
+ if (!len) {
+ return -EINVAL;
+ }
+ return len;
+}
+
+/* Following functions need access to our internal write_to_log status */
+
+LIBLOG_ABI_PUBLIC int android_set_log_frontend(int frontend_flag)
+{
+ if (frontend_flag < 0) {
+ return -EINVAL;
+ }
+
+ __android_log_lock();
+
+ if (frontend_flag & LOGGER_NULL) {
+ write_to_log = __write_to_log_null;
+
+ __android_log_unlock();
+
+ return LOGGER_NULL;
+ }
+
+ /* Anything else, act as if LOGGER_DEFAULT */
+
+ /* generically we only expect these two values for write_to_log */
+ if ((write_to_log != __write_to_log_init) &&
+ (write_to_log != __write_to_log_daemon)) {
+ write_to_log = __write_to_log_init;
+ }
+
+ __android_log_unlock();
+
+ return LOGGER_DEFAULT;
+}
+
+LIBLOG_ABI_PUBLIC int android_get_log_frontend()
+{
+ int ret = LOGGER_DEFAULT;
+
+ __android_log_lock();
+ if (write_to_log == __write_to_log_null) {
+ ret = LOGGER_NULL;
+ } else if ((write_to_log != __write_to_log_init) &&
+ (write_to_log != __write_to_log_daemon)) {
+ ret = -EINVAL;
+ }
+ __android_log_unlock();
+
+ return ret;
+}
diff --git a/liblog/tests/liblog_test.cpp b/liblog/tests/liblog_test.cpp
index 5faf8e1..379fe47 100644
--- a/liblog/tests/liblog_test.cpp
+++ b/liblog/tests/liblog_test.cpp
@@ -37,6 +37,7 @@
#include <gtest/gtest.h>
#include <log/logprint.h>
#include <log/log_event_list.h>
+#include <log/log_frontend.h>
#include <private/android_filesystem_config.h>
#include <private/android_logger.h>
@@ -225,6 +226,75 @@
#endif
}
+// This test makes little sense standalone, and requires the tests ahead
+// and behind us, to make us whole. We could incorporate a prefix and
+// suffix test to make this standalone, but opted to not complicate this.
+TEST(liblog, android_set_log_frontend) {
+#ifdef __ANDROID__
+ int logger = android_get_log_frontend();
+ EXPECT_NE(LOGGER_NULL, logger);
+
+ EXPECT_EQ(LOGGER_NULL, android_set_log_frontend(LOGGER_NULL));
+ EXPECT_EQ(LOGGER_NULL, android_get_log_frontend());
+
+ pid_t pid = getpid();
+
+ struct logger_list *logger_list;
+ ASSERT_TRUE(NULL != (logger_list = android_logger_list_open(
+ LOG_ID_EVENTS, ANDROID_LOG_RDONLY | ANDROID_LOG_NONBLOCK, 1000, pid)));
+
+ log_time ts(CLOCK_MONOTONIC);
+ ASSERT_LT(0, __android_log_btwrite(0, EVENT_TYPE_LONG, &ts, sizeof(ts)));
+
+ usleep(1000000);
+
+ int count = 0;
+
+ for (;;) {
+ log_msg log_msg;
+ if (android_logger_list_read(logger_list, &log_msg) <= 0) {
+ break;
+ }
+
+ ASSERT_EQ(log_msg.entry.pid, pid);
+
+ if ((log_msg.entry.len != sizeof(android_log_event_long_t))
+ || (log_msg.id() != LOG_ID_EVENTS)) {
+ continue;
+ }
+
+ android_log_event_long_t* eventData;
+ eventData = reinterpret_cast<android_log_event_long_t*>(log_msg.msg());
+
+ if (!eventData || (eventData->payload.type != EVENT_TYPE_LONG)) {
+ continue;
+ }
+
+ log_time tx(reinterpret_cast<char*>(&eventData->payload.data));
+ if (ts == tx) {
+ ++count;
+ }
+ }
+
+ android_logger_list_close(logger_list);
+
+ EXPECT_EQ(logger, android_set_log_frontend(logger));
+ EXPECT_EQ(logger, android_get_log_frontend());
+
+ // False negative if liblog.__android_log_btwrite__android_logger_list_read
+ // fails above, so we will likely succeed. But we will have so many
+ // failures elsewhere that it is probably not worthwhile for us to
+ // highlight yet another disappointment.
+ EXPECT_EQ(0, count);
+ // We also expect failures in the following tests if the set does not
+ // react in an appropriate manner internally, yet passes, so we depend
+ // on this test being in the middle of a series of tests performed in
+ // the same process.
+#else
+ GTEST_LOG_(INFO) << "This test does nothing.\n";
+#endif
+}
+
#ifdef __ANDROID__
static inline int32_t get4LE(const char* src)
{