init: add tips for debugging linker errors when launching init services
Test: we can see linker errors in dmesg when following these tips
Change-Id: I86b65e01d06ed7c0b908c4512d55872cd5595eca
diff --git a/init/README.md b/init/README.md
index 29b972d..cdf3487 100644
--- a/init/README.md
+++ b/init/README.md
@@ -784,6 +784,12 @@
Debugging init
--------------
+When a service starts from init, it may fail to `execv()` the service. This is not typical, and may
+point to an error happening in the linker as the new service is started. The linker in Android
+prints its logs to `logd` and `stderr`, so they are visible in `logcat`. If the error is encountered
+before it is possible to access `logcat`, the `stdio_to_kmsg` service option may be used to direct
+the logs that the linker prints to `stderr` to `kmsg`, where they can be read via a serial port.
+
Launching init services without init is not recommended as init sets up a significant amount of
environment (user, groups, security label, capabilities, etc) that is hard to replicate manually.
diff --git a/init/service.cpp b/init/service.cpp
index e8b75d4..0b73dc5 100644
--- a/init/service.cpp
+++ b/init/service.cpp
@@ -490,7 +490,8 @@
SetProcessAttributesAndCaps();
if (!ExpandArgsAndExecv(args_, sigstop_)) {
- PLOG(ERROR) << "cannot execve('" << args_[0] << "')";
+ PLOG(ERROR) << "cannot execv('" << args_[0]
+ << "'). See the 'Debugging init' section of init's README.md for tips";
}
_exit(127);