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layout: page

title: DebugApps

permalink: /debugApps/

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This page includes useful information about how to use Open-TEE. This presents a few methods on how to use Open-TEE for debugging TAs/CAs.

if you come upon any problems, please do not hesitate to contact us.

GDB

Using GDB could be divided into two use cases. If you are debugging TA that is already running at Open-TEE, you need only to attach to TA process. For example, to find out if your TA is running:

$ ps waux | grep [our TA bin name]

The TA process name is the same that has been given to your binary. Depending on which building tool you are using, it may add some prefix to the binary name. For example, if you are using QBS then the prefix is “lib”. When you have determined the name, just take the process PID and run the following command:

$ gdb attach [our TA PID]

If you get the following error:

Could not attach to process. If your uid matches the uid of the target
process, check the setting of /proc/sys/kernel/yama/ptrace_scope, or try
again as the root user. For more details, see /etc/sysctl.d/10-ptrace.conf
ptrace: Operation not permitted.

Run the following command and invoke gdb again as above:

$ echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope 

TA is not running

The second case is if your TA is not running. In this case you need to attach to TEE launcher process. This is done because the launcher process becomes new TA by using clone command. Due to that, you should not launch multiple TAs at the same time. This technique is useful if you want to debug TAs createEntryPoint and openSessionEntryPoint functions. We will use the same technique to find out launcher process PID:

$ ps waux | grep tee_launcher

Attach to launcher process:

$ gdb attach [tee_launcher PID]

Now we have to set the GDB to follow the child:

set follow-fork-mode child

Continue GDB (hit “c” and enter) and now it is waiting for your TA.

About the GDB usage, you can use it as you have learned to use it.

Using logs

Open-TEE is using system log for logging useful information about Open-TEE and your TA/CA process. By default it is printing some information but you can add more logging print outs to log by yourself. Open-TEE is providing you:

OT_LOG(priority, format, ...) //Prints also call location
OT_LOG_1(priority, format, ...) //No extra prints

This function is basically a wrapper around syslog-function. For viewing the logs, you can use for example (ubuntu-example):

$ tail -f /var/log/syslog