From 1279013dee790c84758e5fc5bed33b5c9df2af9b Mon Sep 17 00:00:00 2001
From: Jamie Gennis <jgennis@google.com>
Date: Wed, 6 Jun 2012 18:12:48 -0700
Subject: [PATCH] Enable tracing on user builds

This change adds init.rc steps to:
 * allow kernel tracing to be enabled via adb
 * allow a limited set of kernel trace events to be enabled via adb
 * allow the kernel trace to be read via adb
 * allow all users to write to the kernel trace from userland

Bug: 6513400
Change-Id: Ic3c189b5697aa5edf88d2f507c932971bed6caff
---
 rootdir/init.rc       |  6 +-----
 rootdir/init.trace.rc | 31 +++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 5 deletions(-)
 create mode 100644 rootdir/init.trace.rc

diff --git a/rootdir/init.rc b/rootdir/init.rc
index aa1bb92ad..ef1dc3d66 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -6,6 +6,7 @@
 
 import /init.${ro.hardware}.rc
 import /init.usb.rc
+import /init.trace.rc
 
 on early-init
     # Set init and its forked children's oom_adj.
@@ -367,10 +368,6 @@ service console /system/bin/sh
 on property:ro.debuggable=1
     start console
 
-# Allow writing to the kernel trace log.  Enabling tracing still requires root.
-on property:ro.debuggable=1
-    chmod 0222 /sys/kernel/debug/tracing/trace_marker
-
 # adbd is controlled via property triggers in init.<platform>.usb.rc
 service adbd /sbin/adbd
     class core
@@ -505,4 +502,3 @@ service mdnsd /system/bin/mdnsd
     socket mdnsd stream 0660 mdnsr inet
     disabled
     oneshot
-
diff --git a/rootdir/init.trace.rc b/rootdir/init.trace.rc
new file mode 100644
index 000000000..1d114f538
--- /dev/null
+++ b/rootdir/init.trace.rc
@@ -0,0 +1,31 @@
+## Permissions to allow system-wide tracing to the kernel trace buffer.
+##
+on boot
+
+# Allow writing to the kernel trace log.
+    chmod 0222 /sys/kernel/debug/tracing/trace_marker
+
+# Allow the shell group to enable (some) kernel tracing.
+    chown root shell /sys/kernel/debug/tracing/trace_clock
+    chown root shell /sys/kernel/debug/tracing/buffer_size_kb
+    chown root shell /sys/kernel/debug/tracing/options/overwrite
+    chown root shell /sys/kernel/debug/tracing/events/sched/sched_switch/enable
+    chown root shell /sys/kernel/debug/tracing/events/sched/sched_wakeup/enable
+    chown root shell /sys/kernel/debug/tracing/events/power/cpu_frequency/enable
+    chown root shell /sys/kernel/debug/tracing/events/power/cpu_idle/enable
+    chown root shell /sys/kernel/debug/tracing/events/cpufreq_interactive/enable
+    chown root shell /sys/kernel/debug/tracing/tracing_on
+
+    chmod 0664 /sys/kernel/debug/tracing/trace_clock
+    chmod 0664 /sys/kernel/debug/tracing/buffer_size_kb
+    chmod 0664 /sys/kernel/debug/tracing/options/overwrite
+    chmod 0664 /sys/kernel/debug/tracing/events/sched/sched_switch/enable
+    chmod 0664 /sys/kernel/debug/tracing/events/sched/sched_wakeup/enable
+    chmod 0664 /sys/kernel/debug/tracing/events/power/cpu_frequency/enable
+    chmod 0664 /sys/kernel/debug/tracing/events/power/cpu_idle/enable
+    chmod 0664 /sys/kernel/debug/tracing/events/cpufreq_interactive/enable
+    chmod 0664 /sys/kernel/debug/tracing/tracing_on
+
+# Allow only the shell group to read and truncate the kernel trace.
+    chown root shell /sys/kernel/debug/tracing/trace
+    chmod 0660 /sys/kernel/debug/tracing/trace