perf_event: rules for system and simpleperf domain
This patch adds the necessary rules to support the existing usage of
perf_event_open by the system partition, which almost exclusively
concerns the simpleperf profiler. A new domain is introduced for some
(but not all) executions of the system image simpleperf. The following
configurations are supported:
* shell -> shell process (no domain transition)
* shell -> debuggable app (through shell -> runas -> runas_app)
* shell -> profileable app (through shell -> simpleperf_app_runner ->
untrusted_app -> simpleperf)
* debuggable/profile app -> self (through untrusted_app -> simpleperf)
simpleperf_app_runner still enters the untrusted_app domain immediately
before exec to properly inherit the categories related to MLS. My
understanding is that a direct transition would require modifying
external/selinux and seapp_contexts as with "fromRunAs", which seems
unnecessarily complex for this case.
runas_app can still run side-loaded binaries and use perf_event_open,
but it checks that the target app is exactly "debuggable"
(profileability is insufficient).
system-wide profiling is effectively constrained to "su" on debug
builds.
See go/perf-event-open-security for a more detailed explanation of the
scenarios covered here.
Tested: "atest CtsSimpleperfTestCases" on crosshatch-user/userdebug
Tested: manual simpleperf invocations on crosshatch-userdebug
Bug: 137092007
Change-Id: I2100929bae6d81f336f72eff4235fd5a78b94066
diff --git a/private/file_contexts b/private/file_contexts
index 2ab86fd..560d190 100644
--- a/private/file_contexts
+++ b/private/file_contexts
@@ -338,6 +338,7 @@
/system/bin/watchdogd u:object_r:watchdogd_exec:s0
/system/bin/apexd u:object_r:apexd_exec:s0
/system/bin/gsid u:object_r:gsid_exec:s0
+/system/bin/simpleperf u:object_r:simpleperf_exec:s0
/system/bin/simpleperf_app_runner u:object_r:simpleperf_app_runner_exec:s0
/system/bin/notify_traceur\.sh u:object_r:notify_traceur_exec:s0
/system/bin/migrate_legacy_obb_data\.sh u:object_r:migrate_legacy_obb_data_exec:s0