Debugging OP-TEE TA

When developing applications, it is inevitable that there will be a need for debugging. This tutorial introduces how to configure the debug environment in OP-TEE enabled QEMU environment. You may also check OP-TEE documentation for more information about running QEMU for Arm v8.

To debug TEE core running QEMU with GDB, it is necessary to disable TEE ASLR with CFG_CORE_ASLR ?= n in OP-TEE/optee_os/mk/config.mk. Note that you need to recompile QEMU with make run again. You can also choose to add the compilation information directly at compile time.

$ make run CFG_CORE_ASLR=n

Since we will debug the TA remotely with a gdb server, please also add the GDBSERVER=y flag when compiling QEMU.

To debug a TA, you need to first start a gdb on the host machine. Then run target remote :1234 to connect to the remote QEMU GDB server.

$ ./path/to/qemu-v8-project/out-br/host/bin/aarch64-buildroot-linux-gnu-gdb
(gdb) target remote :1234
Remote debugging using :1234
warning: No executable has been specified and target does not support
determining executable automatically.  Try using the "file" command.
0xffffb30b00ea12b4 in ?? ()

Next, in the GDB console, load the symbol table of the TEE core library.

(gdb) symbol-file /path/to/qemu-v8-project/optee_os/out/arm/core/tee.elf

Taking hello_world-rs as an example, you can get the start address of the text section from the log in the secure world console, which is 0x40014000.

D/LD:  ldelf:168 ELF (133af0ca-bdab-11eb-9130-43bf7873bf67) at 0x40014000

Then, you can load symbols from TA file (in debug build) to the address.

(gdb) add-symbol-file /path/to/examples/hello_world-rs/ta/target/aarch64-unknown-linux-gnu/debug/ta 0x40014000

Now, you can add breakpoints according to your own needs in the corresponding functions or addresses.

(gdb) b invoke_command
Breakpoint 2 at 0xe11bb08: invoke_command. (6 locations)

Last, initiate the boot. You can execute hello_world-rs in the normal world console, and will see that the breakpoint we set was hit.

(gdb) c
Continuing.
[Switching to Thread 1.2]

Thread 2 hit Breakpoint 2, ta::invoke_command (cmd_id=0, params=0x4010ff00) at src/main.rs:50
50	    trace_println!("[+] TA invoke command");