logcatd: trampoline persist.logd.logpersistd to logd.logpersistd

Best practices so that device can set logd.logpersistd properties.
Values can be overriden with trampolines for persist.logd.logpersistd
values except as designed for empty content to keep out of the way.

This allows us to set logd.logpersistd* for a non-persistent collection
that does not survive a reboot, and to use persist.logd.logpersistd*
for persistent collection that does survive a reboot.

Added logd.logpersistd.enable to gate when logpersist service can be
run allowing the properties to be adjusted safely prior to this state
as is the case for device property.

NB: /init will complain when trying to trampoline an empty property,
    this is acceptable for functionality, but may be considered
    annoying from the logging perspective.

Bug: 28936216
Bug: 29831823
Change-Id: I97317e8eedfae4daa8e3ef39e64e7c5c23d8b573

logcat/logcatd.rc

@@ -1,21 +1,62 @@
+#
+# init scriptures for logcatd persistent logging.
+#
+# Make sure any property changes are only performed with /data mounted, after
+# post-fs-data state because otherwise behavior is undefined. The exceptions
+# are device adjustments for logcatd service properties (persist.* overrides
+# notwithstanding) for logd.logpersistd.size and logd.logpersistd.buffer.
+
+# persist to non-persistent trampolines to permit device properties can be
+# overridden when /data mounts, or during runtime.
+on property:persist.logd.logpersistd.size=256
+    setprop persist.logd.logpersistd.size ""
+    setprop logd.logpersistd.size ""
+
+on property:persist.logd.logpersistd.size=*
+    # expect /init to report failure if property empty (default)
+    setprop logd.logpersistd.size ${persist.logd.logpersistd.size}
+
+on property:persist.logd.logpersistd.buffer=all
+    setprop persist.logd.logpersistd.buffer ""
+    setprop logd.logpersistd.buffer ""
+
+on property:persist.logd.logpersistd.buffer=*
+    # expect /init to report failure if property empty (default)
+    setprop logd.logpersistd.buffer ${persist.logd.logpersistd.buffer}
+
 on property:persist.logd.logpersistd=logcatd
+    setprop logd.logpersistd logcatd
+
+# enable, prep and start logcatd service
+on load_persist_props_action
+    setprop logd.logpersistd.enable true
+
+on property:logd.logpersistd.enable=true && property:logd.logpersistd=logcatd
     # all exec/services are called with umask(077), so no gain beyond 0700
     mkdir /data/misc/logd 0700 logd log
     # logd for write to /data/misc/logd, log group for read from pstore (-L)
-    exec - logd log -- /system/bin/logcat -L -b ${persist.logd.logpersistd.buffer:-all} -v threadtime -v usec -v printable -D -f /data/misc/logd/logcat -r 1024 -n ${persist.logd.logpersistd.size:-256}
+    exec - logd log -- /system/bin/logcat -L -b ${logd.logpersistd.buffer:-all} -v threadtime -v usec -v printable -D -f /data/misc/logd/logcat -r 1024 -n ${logd.logpersistd.size:-256}
     start logcatd
 
-on property:persist.logd.logpersistd=clear
+# stop logcatd service and clear data
+on property:logd.logpersistd.enable=true && property:logd.logpersistd=clear
+    setprop persist.logd.logpersistd ""
     stop logcatd
     # logd for clear of only our files in /data/misc/logd
-    exec - logd log -- /system/bin/logcat -c -f /data/misc/logd/logcat -n ${persist.logd.logpersistd.size:-256}
-    setprop persist.logd.logpersistd ""
+    exec - logd log -- /system/bin/logcat -c -f /data/misc/logd/logcat -n ${logd.logpersistd.size:-256}
+    setprop logd.logpersistd ""
 
-on property:persist.logd.logpersistd=stop
+# stop logcatd service
+on property:logd.logpersistd=stop
+    setprop persist.logd.logpersistd ""
     stop logcatd
-    setprop persist.logd.logpersistd ""
+    setprop logd.logpersistd ""
 
-service logcatd /system/bin/logcat -b ${persist.logd.logpersistd.buffer:-all} -v threadtime -v usec -v printable -D -f /data/misc/logd/logcat -r 1024 -n ${persist.logd.logpersistd.size:-256}
+on property:logd.logpersistd.enable=false
+    stop logcatd
+
+# logcatd service
+service logcatd /system/bin/logcat -b ${logd.logpersistd.buffer:-all} -v threadtime -v usec -v printable -D -f /data/misc/logd/logcat -r 1024 -n ${logd.logpersistd.size:-256}
     class late_start
     disabled
     # logd for write to /data/misc/logd, log group for read from log daemon

logcat/logpersist

@@ -8,8 +8,16 @@ case `getprop ro.debuggable` in
    ;;
 esac
 
-data=/data/misc/logd
 property=persist.logd.logpersistd
+
+case `getprop ${property#persist.}.enable` in
+true) ;;
+*) echo "${progname} - Disabled"
+   exit 1
+   ;;
+esac
+
+data=/data/misc/logd
 service=logcatd
 size_default=256
 buffer_default=all
@@ -69,11 +77,11 @@ case ${progname} in
   su logd xargs cat
   ;;
 *.start)
-  current_buffer="`getprop ${property}.buffer`"
-  current_size="`getprop ${property}.size`"
-  if [ "${service}" = "`getprop ${property}`" ]; then
+  current_buffer="`getprop ${property#persist.}.buffer`"
+  current_size="`getprop ${property#persist.}.size`"
+  if [ "${service}" = "`getprop ${property#persist.}`" ]; then
     if [ "true" = "${clear}" ]; then
-      setprop ${property} "clear"
+      setprop ${property#persist.} "clear"
     elif [ "${buffer}|${size}" != "${current_buffer}|${current_size}" ]; then
       echo   "ERROR: Changing existing collection parameters from" >&2
       if [ "${buffer}" != "${current_buffer}" ]; then
@@ -96,22 +104,30 @@ case ${progname} in
       exit 1
     fi
   elif [ "true" = "${clear}" ]; then
-    setprop ${property} "clear"
+    setprop ${property#persist.} "clear"
   fi
   if [ -n "${buffer}${current_buffer}" ]; then
     setprop ${property}.buffer "${buffer}"
+    if [ -z "${buffer}" ]; then
+      # deal with trampoline for empty properties
+      setprop ${property#persist.}.buffer ""
+    fi
   fi
   if [ -n "${size}${current_size}" ]; then
     setprop ${property}.size "${size}"
+    if [ -z "${size}" ]; then
+      # deal with trampoline for empty properties
+      setprop ${property#persist.}.size ""
+    fi
   fi
-  while [ "clear" = "`getprop ${property}`" ]; do
+  while [ "clear" = "`getprop ${property#persist.}`" ]; do
     continue
   done
   # ${service}.rc does the heavy lifting with the following trigger
   setprop ${property} ${service}
-  getprop ${property}
   # 20ms done, to permit process feedback check
   sleep 1
+  getprop ${property#persist.}
   # also generate an error return code if not found running
   pgrep -u ${data##*/} ${service%d}
   ;;
@@ -124,13 +140,17 @@ case ${progname} in
   else
     setprop ${property} "stop"
   fi
-  if [ -n "`getprop ${property}.buffer`" ]; then
+  if [ -n "`getprop ${property#persist.}.buffer`" ]; then
     setprop ${property}.buffer ""
+    # deal with trampoline for empty properties
+    setprop ${property#persist.}.buffer ""
   fi
-  if [ -n "`getprop ${property}.size`" ]; then
+  if [ -n "`getprop ${property#persist.}.size`" ]; then
     setprop ${property}.size ""
+    # deal with trampoline for empty properties
+    setprop ${property#persist.}.size ""
   fi
-  while [ "clear" = "`getprop ${property}`" ]; do
+  while [ "clear" = "`getprop ${property#persist.}`" ]; do
     continue
   done
   ;;

logd/README.property

@@ -1,4 +1,4 @@
-The properties that logd responds to are:
+The properties that logd and friends react to are:
 
 name                       type default  description
 ro.logd.auditd.dmesg       bool   true   selinux audit messages duplicated and
@@ -9,8 +9,16 @@ ro.logd.kernel             bool+ svelte+ Enable klogd daemon
 ro.logd.statistics         bool+ svelte+ Enable logcat -S statistics.
 ro.debuggable              number        if not "1", logd.statistics &
                                          ro.logd.kernel default false.
+logd.logpersistd.enable    bool   auto   Safe to start logpersist daemon service
+logd.logpersistd          string persist Enable logpersist daemon, "logcatd"
+                                         turns on logcat -f in logd context.
+					 Responds to logcatd, clear and stop.
+logd.logpersistd.buffer          persist logpersistd buffers to collect
+logd.logpersistd.size            persist logpersistd size in MB
 persist.logd.logpersistd   string        Enable logpersist daemon, "logcatd"
-                                         turns on logcat -f in logd context
+                                         turns on logcat -f in logd context.
+persist.logd.logpersistd.buffer    all   logpersistd buffers to collect
+persist.logd.logpersistd.size      256   logpersistd size in MB
 persist.logd.size          number  ro    Global default size of the buffer for
                                          all log ids at initial startup, at
                                          runtime use: logcat -b all -G <value>
@@ -44,6 +52,7 @@ log.tag.<tag>             string persist The <tag> specific logging level.
 persist.log.tag.<tag>      string build  default for log.tag.<tag>
 
 NB:
+- auto - managed by /init
 - bool+ - "true", "false" and comma separated list of "eng" (forced false if
   ro.debuggable is not "1") or "svelte" (forced false if ro.config.low_ram is
   true).