liblog: Add android_set_log_frontend am: 850d06e1c9 am: 9d68551f47

am: b6c6c7e3d3

Change-Id: I942aff87d5a45b5e18bb03c2ea2ebf7bfebd976d

liblog/README

@@ -108,6 +108,11 @@ SYNOPSIS
 
        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 @@ DESCRIPTION
        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 @@ SEE ALSO
 
 
 
-                                  17 Oct 2016                        LIBLOG(3)
+                                  08 Feb 2017                        LIBLOG(3)

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 */

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 @@ LIBLOG_ABI_PUBLIC int __android_log_security_bswrite(int32_t tag,
 
     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;
+}

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 @@ TEST(liblog, __android_log_btwrite__android_logger_list_read) {
 #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)
 {