Debug the Hafnium in TC platform

Overview

Hafnium is a reference Secure Partition Manager (SPM) for systems that implement the Armv8.4-A Secure-EL2 extension. It enables multiple, isolated Secure Partitions (SPs) to run at Secure-EL1.More information about Hafnium can be found here.

Regarding the TotalCompute software stack which also include the BL32(SPM), the BL32(SPM) is implemented as Hafnium software component. You can find the introduction Here

The TC software stack can both support buildroot and Android build, since the hafnium is part of fimrware, we take buildroot as example.

Getting started

Firstly, let's setup the workspace following the user guide here to build out the whole software stack, let's take the buildroot file system as example as below.

Download and setup the workspace code
Then build the software stack, for example, build cmd as "./run_docker.sh ./build-all.sh build", once build successfully done, the output images is as below:
After the related image is built out, then run the related image to boot up successfully
```
./run-scripts/tc2/run_model.sh -m <model binary path> -d buildroot
```

AP firmware Images and boot

The AP firmware bootflow is as below:

BL1 --> BL2 --> BL1 --> BL31 --> BL32(SPM) --> BL31 --> BL33

Modify and build Hafnium seperatly

The build scirpt "build-scripts/build-hafnium.sh" can be used to build the Hafnium seperately, but the "hafnium.bin" image will be added into FIP package, so the modify and build source code, need to re-package again, the steps can be as below:

build-scripts/run_docker.sh build-scripts/build-hafnium.sh build build-scripts/run_docker.sh build-scripts/build-hafnium.sh deploy build-scripts/run_docker.sh build-scripts/build-tfa.sh build build-scripts/run_docker.sh build-scripts/build-tfa.sh deploy build-scripts/run_docker.sh build-scripts/build-flash-image.sh build build-scripts/run_docker.sh build-scripts/build-flash-image.sh deploy

It needs to add the debug build option to make sure the symble file can be used for debugging as below:

diff --git a/build/BUILD.gn b/build/BUILD.gn
index 1baac1ba..80b9f44d 100644
--- a/build/BUILD.gn
+++ b/build/BUILD.gn
@@ -20,6 +20,7 @@ config("compiler_defaults") {
     "-fstack-protector-all",
   ]

+  asmflags = ["-g"]
   cflags_c = [ "-std=c11" ]

   cflags_cc = [ "-std=c++2a" ]

Setup ARM DS to debug Hafnium

Import the TC22 FVP model

From the ARM DS Debug control pannel, navigate to:

Debug Congtrol--> New Debug Connection... -->Choose "Model Connection --> Debug connection name, such as "TC22-Hafnium-debug" -> Next --> Target Selection --> Add a new model ...

Then, "Select Model Interface(Iris)" --> Next--> choose "Launch and connect to specific model" --> Next --> Browse the Model Path to select the downloaded file path of “TC22 model” --> Finish

At last, the model is imported as below:

Connect the model

Step1: Open the debug configration

Step2: Setup the model parameters

For example, copy below model paramters into the label:

-C board.flashloader0.fname=/data/jetzho01/tc22-2023.04.21/build-scripts/output/deploy/tc2/fip_gpt-tc.bin -C css.rss.rom.raw_image=/data/jetzho01/tc22-2023.04.21/build-scripts/output/deploy/tc2/rss_rom.bin -C css.scp.c0_pik.rvbaraddr_lw=0x1000 -C css.scp.c0_pik.rvbaraddr_up=0x0000 -C css.rss.VMADDRWIDTH=23 -C css.rss.CMU0_NUM_DB_CH=16 -C displayController=2 -C board.smsc_91c111.enabled=1 -C board.hostbridge.userNetworking=1 -C board.hostbridge.userNetPorts="5555=5555,8080=80,8022=22" --data board.dram=/data/jetzho01/tc22-2023.04.21/build-scripts/output/deploy/tc2/tc-fitImage.bin@0x20000000

Step3: Loaded the symbol files to apply and debug

On the window that opens, navigate to the "Debugger" tab, tick "Connect only", tick "Execute debugger commands", and copy-paste the following into the text box to automatically load all symbols into the correct virtual address space each time you connect to the model:

add-symbol-file "<workspace>/build-scripts/output/tmp_build/tfa/build/tc/debug/bl1/bl1.elf" EL3:0x0
add-symbol-file "<workspace>/build-scripts/output/tmp_build/tfa/build/tc/debug/bl2/bl2.elf" EL1S:0x0
add-symbol-file "<workspace>/build-scripts/output/tmp_build/tfa/build/tc/debug/bl31/bl31.elf" EL3:0x0
add-symbol-file "<workspace>/build-scripts/output/tmp_build/hafnium/secure_tc_clang/hafnium.elf" EL2S:0x0

Replacing <workspace> with the path to your workspace directory.

The EL and number at the end of each command (e.g. `EL2S:0') ensure the symbols are loaded into the correct virtual address space and at the correct memory offset, for software uses absolute addresses for its symbols so we ensure an offset of 0.

Click "Apply" and then "Debug" to connect to the paused model. You can now step through the Hafnium code or set a breakpoint on the symbol corresponding to the functionality that you are interested.

Debugging entrypoint for Hafnium

Entry point of Hafnium code piece is here

.section .init.entry, "ax"
.global entry
entry:
	/* Linux aarch64 image header. */
	b 0f
	.word 0
	.quad 0x1000      /* text_offset */
	.quad image_size  /* image_size */
	.quad 0           /* flags */
	.quad 0           /* res2 */
	.quad 0           /* res3 */
	.quad 0           /* res4 */
	.word 0x644d5241  /* magic */
	.word 0

	/*
	 * Calculate the difference between the actual load address and the
	 * preferred one. We'll use this to relocate.
	 */
0:	adrp x25, entry
	add x25, x25, :lo12:entry

How to decide the entrypoint(loading address) of Hafnium for TC22 platform?
The Hafnium(BL32) is loaded by AP BL2, the image address is defined as "BL32_BASE" which can be found at here, specifically for the TC22 platform, the address is redefined as:

"#define TC_EL2SPMC_LOAD_ADDR (TC_TZC_DRAM1_BASE + 0x04000000)"

The TC_TZC_DRAM1_BASE is defined as 0xF900_0000, so the loading address for Hafnium(BL32_BASE) is 0xFD00_0000.

More plaform definition about this can be found here.
Stop at the entrypoint

Set the breakpoint of "entry" which is the entrypoint of Hafnium, then Run, it will stop the first instruction.

Debuging other related functions

The initialize flow of Hafnium
For example, set breakpoint of "one_time_init", jump into it