crash_dump: during early boot, output to kmsg on userdebug.
Crashes that happen before tombstoned is running are extremely hard to
diagnose, because tombstones aren't written to disk, and the window of
opportunity to get logs via `adb logcat` is small (potentially
nonexistent).
Solve this by adding a world-writable /dev/kmsg_debug on userdebug
builds, and writing to it in addition to logcat when tombstoned hasn't
started yet.
Bug: http://b/36574794
Test: stop tombstoned; crasher; dmesg
Change-Id: I46ba2dd67c188be74bd931f8a5536b6342d537f2
diff --git a/init/init.cpp b/init/init.cpp
index dafaf21..5e98707 100644
--- a/init/init.cpp
+++ b/init/init.cpp
@@ -933,6 +933,9 @@
LOG(INFO) << "Running restorecon...";
selinux_android_restorecon("/dev", 0);
selinux_android_restorecon("/dev/kmsg", 0);
+ if constexpr (WORLD_WRITABLE_KMSG) {
+ selinux_android_restorecon("/dev/kmsg_debug", 0);
+ }
selinux_android_restorecon("/dev/socket", 0);
selinux_android_restorecon("/dev/random", 0);
selinux_android_restorecon("/dev/urandom", 0);
@@ -1037,7 +1040,13 @@
setgroups(arraysize(groups), groups);
mount("sysfs", "/sys", "sysfs", 0, NULL);
mount("selinuxfs", "/sys/fs/selinux", "selinuxfs", 0, NULL);
+
mknod("/dev/kmsg", S_IFCHR | 0600, makedev(1, 11));
+
+ if constexpr (WORLD_WRITABLE_KMSG) {
+ mknod("/dev/kmsg_debug", S_IFCHR | 0622, makedev(1, 11));
+ }
+
mknod("/dev/random", S_IFCHR | 0666, makedev(1, 8));
mknod("/dev/urandom", S_IFCHR | 0666, makedev(1, 9));