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Commit 9328021c authored by Tom Cherry's avatar Tom Cherry
Browse files

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
parent 2a62d427

init/README.md

+6 −0
Original line number Original line Diff line number Diff line
@@ -784,6 +784,12 @@ affected. 




Debugging init

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

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.

environment (user, groups, security label, capabilities, etc) that is hard to replicate manually.

init/service.cpp

+2 −1
Original line number Original line Diff line number Diff line
@@ -490,7 +490,8 @@ Result<void> Service::Start() { 
        SetProcessAttributesAndCaps();

        SetProcessAttributesAndCaps();





        if (!ExpandArgsAndExecv(args_, sigstop_)) {

        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);

        _exit(127);