Allow tracing service to access kallsyms on userdebug
This CL allows the traced_probes service to temporarily
lower kptr_restrict and read /proc/kallsyms.
This is allowed only on userdebug/eng builds.
The lowering of kptr_restrict is done via an init
property because the kernel checks that the kptr_restrict
writer is CAP_SYS_ADMIN, regardless of the /proc file ACLs [1].
[1] https://github.com/torvalds/linux/blob/4cbffc461ec91287c4cb1d0e27b01b988d0b8fba/kernel/sysctl.c#L2254
Bug: 136133013
Design doc: go/perfetto-kallsyms
Test: perfetto_integrationtests --gtest_filter=PerfettoTest.KernelAddressSymbolization in r.android.com/1454882
Change-Id: Ic06e7a9a74c0f3e42fa63f7f41decc385c9fea2c
diff --git a/private/traced_probes.te b/private/traced_probes.te
index 36f9c51..f010a77 100644
--- a/private/traced_probes.te
+++ b/private/traced_probes.te
@@ -29,6 +29,11 @@
# Allow procfs access
r_dir_file(traced_probes, domain)
+# Allow to temporarily lift the kptr_restrict setting and build a symbolization
+# map reading /proc/kallsyms.
+userdebug_or_eng(`set_prop(traced_probes, lower_kptr_restrict_prop)')
+allow traced_probes proc_kallsyms:file r_file_perms;
+
# Allow to read packages.list file.
allow traced_probes packages_list_file:file r_file_perms;