liblog: suppress pmsg on user builds

- add optimized & cached LIBLOG_HIDDEN __android_log_is_debuggable()
- check when writing, either LOG_ID_SECURITY, SafetyNet or
  debuggable when pushing content to the pmsg buffer.

Bug: 27566046
Change-Id: I85f1b55ec329b38e00f4183836b6ed53046c323d

1 files changed, 31 insertions, 0 deletions

diff --git a/liblog/log_is_loggable.c b/liblog/log_is_loggable.c
index 551fa7684..79a567051 100644
--- a/liblog/log_is_loggable.c
+++ b/liblog/log_is_loggable.c
@@ -259,6 +259,37 @@ LIBLOG_ABI_PUBLIC int __android_log_is_loggable(int prio, const char *tag,
     return logLevel >= 0 && prio >= logLevel;
 }
 
+LIBLOG_HIDDEN int __android_log_is_debuggable()
+{
+    static uint32_t serial;
+    static struct cache tag_cache;
+    static const char key[] = "ro.debuggable";
+    int ret;
+
+    if (tag_cache.c) { /* ro property does not change after set */
+        ret = tag_cache.c == '1';
+    } else if (lock()) {
+        struct cache temp_cache = { NULL, -1, '\0' };
+        refresh_cache(&temp_cache, key);
+        ret = temp_cache.c == '1';
+    } else {
+        int change_detected = check_cache(&tag_cache);
+        uint32_t current_serial = __system_property_area_serial();
+        if (current_serial != serial) {
+            change_detected = 1;
+        }
+        if (change_detected) {
+            refresh_cache(&tag_cache, key);
+            serial = current_serial;
+        }
+        ret = tag_cache.c == '1';
+
+        unlock();
+    }
+
+    return ret;
+}
+
 /*
  * For properties that are read often, but generally remain constant.
  * Since a change is rare, we will accept a trylock failure gracefully.