am 774f9299: libcutils: add support for app tracing

* commit '774f9299912cdf9f2a6b3805bb557e30bafbad05':
  libcutils: add support for app tracing

include/cutils/trace.h

@@ -20,6 +20,7 @@
 #include <sys/cdefs.h>
 #include <sys/types.h>
 #include <stdint.h>
+#include <stdbool.h>
 #include <unistd.h>
 #include <cutils/compiler.h>
 
@@ -62,7 +63,8 @@ __BEGIN_DECLS
 #define ATRACE_TAG_VIDEO            (1<<9)
 #define ATRACE_TAG_CAMERA           (1<<10)
 #define ATRACE_TAG_HAL              (1<<11)
-#define ATRACE_TAG_LAST             ATRACE_TAG_HAL
+#define ATRACE_TAG_APP              (1<<12)
+#define ATRACE_TAG_LAST             ATRACE_TAG_APP
 
 // Reserved for initialization.
 #define ATRACE_TAG_NOT_READY        (1LL<<63)
@@ -96,6 +98,14 @@ void atrace_setup();
  */
 void atrace_update_tags();
 
+/**
+ * Set whether the process is debuggable.  By default the process is not
+ * considered debuggable.  If the process is not debuggable then application-
+ * level tracing is not allowed unless the ro.debuggable system property is
+ * set to '1'.
+ */
+void atrace_set_debuggable(bool debuggable);
+
 /**
  * Flag indicating whether setup has been completed, initialized to 0.
  * Nonzero indicates setup has completed.

libcutils/trace.c

@@ -18,6 +18,7 @@
 #include <fcntl.h>
 #include <limits.h>
 #include <pthread.h>
+#include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>
@@ -29,11 +30,81 @@
 #define LOG_TAG "cutils-trace"
 #include <cutils/log.h>
 
-int32_t               atrace_is_ready     = 0;
+int32_t                atrace_is_ready      = 0;
-int                   atrace_marker_fd    = -1;
+int                    atrace_marker_fd     = -1;
-uint64_t              atrace_enabled_tags = ATRACE_TAG_NOT_READY;
+uint64_t               atrace_enabled_tags  = ATRACE_TAG_NOT_READY;
-static pthread_once_t atrace_once_control = PTHREAD_ONCE_INIT;
+static bool            atrace_is_debuggable = false;
-static pthread_mutex_t atrace_tags_mutex = PTHREAD_MUTEX_INITIALIZER;
+static pthread_once_t  atrace_once_control  = PTHREAD_ONCE_INIT;
+static pthread_mutex_t atrace_tags_mutex    = PTHREAD_MUTEX_INITIALIZER;
+
+// Set whether this process is debuggable, which determines whether
+// application-level tracing is allowed when the ro.debuggable system property
+// is not set to '1'.
+void atrace_set_debuggable(bool debuggable)
+{
+    atrace_is_debuggable = debuggable;
+    atrace_update_tags();
+}
+
+// Check whether the given command line matches one of the comma-separated
+// values listed in the app_cmdlines property.
+static bool atrace_is_cmdline_match(const char* cmdline) {
+    char value[PROPERTY_VALUE_MAX];
+    char* start = value;
+
+    property_get("debug.atrace.app_cmdlines", value, "");
+
+    while (start != NULL) {
+        char* end = strchr(start, ',');
+
+        if (end != NULL) {
+            *end = '\0';
+            end++;
+        }
+
+        if (strcmp(cmdline, start) == 0) {
+            return true;
+        }
+
+        start = end;
+    }
+
+    return false;
+}
+
+// Determine whether application-level tracing is enabled for this process.
+static bool atrace_is_app_tracing_enabled()
+{
+    bool sys_debuggable = false;
+    bool proc_debuggable = false;
+    char value[PROPERTY_VALUE_MAX];
+    bool result = false;
+
+    // Check whether the system is debuggable.
+    property_get("ro.debuggable", value, "0");
+    if (value[0] == '1') {
+        sys_debuggable = true;
+    }
+
+    if (sys_debuggable || atrace_is_debuggable) {
+        // Check whether tracing is enabled for this process.
+        FILE * file = fopen("/proc/self/cmdline", "r");
+        if (file) {
+            char cmdline[4096];
+            if (fgets(cmdline, sizeof(cmdline), file)) {
+                result = atrace_is_cmdline_match(cmdline);
+            } else {
+                ALOGE("Error reading cmdline: %s (%d)", strerror(errno), errno);
+            }
+            fclose(file);
+        } else {
+            ALOGE("Error opening /proc/self/cmdline: %s (%d)", strerror(errno),
+                    errno);
+        }
+    }
+
+    return result;
+}
 
 // Read the sysprop and return the value tags should be set to
 static uint64_t atrace_get_property()
@@ -52,6 +123,15 @@ static uint64_t atrace_get_property()
         ALOGE("Error parsing trace property: Number too large: %s", value);
         return 0;
     }
+
+    // Only set the "app" tag if this process was selected for app-level debug
+    // tracing.
+    if (atrace_is_app_tracing_enabled()) {
+        tags |= ATRACE_TAG_APP;
+    } else {
+        tags &= ~ATRACE_TAG_APP;
+    }
+
     return (tags | ATRACE_TAG_ALWAYS) & ATRACE_TAG_VALID_MASK;
 }