llkd: Add stack symbol checking
Feature outlined here is only available on userdebug or eng builds.
Blocked for security reasons because requires ptrace capabilities.
Add ro.llk.stack to list a set of symbols that should rarely happen
but if persistent in multiple checks, indicates a live lock condition.
At ro.llk.stack.timeout_ms the process is sent a kill, if it remains,
then panic the kernel.
There is no ABA detection in the paths, the condition for the
stack symbol being present instantaneously must be its rarity of
being caught. If a livelock occurs in the path of the symbol, then
it is possible more than one path could be stuck in the state, but
the best candidate symbols are found underneath a lock resulting in
only one process being the culprit, and the best aim. There may be
processes that induce a look of persistence, if so the symbol is not
a candidate for checking.
Add ro.llk.blacklist.process.stack to list process names we want
to skip checking. This configuration parameter is also used to
prevent sepolicy noise when trying to acquire stacks from non
ptrace'able services.
Test: gTest llkd_unit_tests
Bug: 33808187
Bug: 111910505
Bug: 80502612
Change-Id: Ie71221e371b189bbdda2a1155d47826997842dcc
diff --git a/llkd/llkd.rc b/llkd/llkd.rc
index e538cdb..b1f96a8 100644
--- a/llkd/llkd.rc
+++ b/llkd/llkd.rc
@@ -3,15 +3,8 @@
setprop llk.enable ${ro.llk.enable:-0}
setprop khungtask.enable ${ro.khungtask.enable:-0}
-on property:ro.debuggable=1
- setprop llk.enable ${ro.llk.enable:-1}
- setprop khungtask.enable ${ro.khungtask.enable:-1}
-
-on property:ro.llk.enable=eng
- setprop llk.enable ${ro.debuggable:-0}
-
-on property:ro.khungtask.enable=eng
- setprop khungtask.enable ${ro.debuggable:-0}
+on property:ro.llk.enable=true
+ setprop llk.enable true
on property:llk.enable=1
setprop llk.enable true
@@ -19,6 +12,9 @@
on property:llk.enable=0
setprop llk.enable false
+on property:ro.khungtask.enable=true
+ setprop khungtask.enable true
+
on property:khungtask.enable=1
setprop khungtask.enable true
@@ -36,9 +32,9 @@
write /proc/sys/kernel/hung_task_panic 0
on property:llk.enable=true
- start llkd
+ start llkd-${ro.debuggable:-0}
-service llkd /system/bin/llkd
+service llkd-0 /system/bin/llkd
class late_start
disabled
user llkd