4. How to Debug¶
4.1. How to debug the security monitor (bbl) and the linux kernel?¶
We use QEMU+GDB to debug the security monitor or the kernel. QEMU is an effective way to debug them.
All cores will immediately hang at the first instruction (i.e., bootrom), waiting for
gdb to be attached.
Now, run a riscv
gdb in another terminal. You can feed it with the
bbl binary or the kernel image to add debug information. (You may
want to compile them with the debugging flag
For example, if you want to debug with the
If you want to debug with the kernel’s debug information
Then, attach to QEMU:
(gdb) target remote localhost:1234
Now, you can start debugging the SM (bbl) or the kernel. Try to set breakpoints and run.
Before setting breakpoints, you should run following command:
(gdb) set riscv use_compressed_breakpoints no
To see why we need that command, see this issue
4.2. Logging QEMU debug messages¶
QEMU provides a great option to collect the logs.
If you add
-D [filename] flag to the QEMU command, it will print out the logs into
You can also choose which kind of logs you want to print out, using
-d [options] flag.
./riscv-qemu/riscv64-softmmu/qemu-system-riscv64 -d in_asm -D debug.log #...etc...