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Documentation/rv-virt: Add section on how to debugging with GDB

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Add a section on how to debug RISC-V emulator using QEMU and GDB.
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Tiago Medicci Serrano 2024-01-31 15:06:38 -03:00 committed by Xiang Xiao
parent 28470f7aed
commit c86cb9e7ef
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Documentation/platforms/risc-v/qemu-rv/boards/rv-virt/index.rst
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@ -277,3 +277,50 @@ smp64
Similar to the `nsh`_ configuration, but with SMP support
This configuration is used for 64-bit RISC-V
RISC-V GDB Debugging
====================
First of all, make sure to select ``CONFIG_DEBUG_SYMBOLS=y`` in `menuconfig`.
After building the kernel (and the applications, in kernel mode), use the toolchain's GDB
to debug RISC-V applications. For instance, if you are using the xPack's prebuilt toolchain,
you can use the following command to start GDB::
$ riscv-none-elf-gdb-py3 -ix tools/gdb/__init__.py --tui nuttx
To use QEMU for debugging, one should add the parameters ``-s -S`` to the QEMU command line.
For instance::
$ qemu-system-riscv32 -semihosting -M virt,aclint=on -cpu rv32 -smp 8 -bios none -kernel nuttx -nographic -s -S
Then, in GDB, use the following command to connect to QEMU::
$ target extended-remote localhost:1234
Debugging Applications in Kernel Mode
-------------------------------------
In kernel mode, only the kernel symbols are loaded by default.
If needed, one should also load the application symbols using the following command::
$ add-symbol-file <file> <address>
``address`` refers to the ``.text`` section of the application and can be retrieved from the ELF file using the following command::
$ readelf -WS <file> | grep .text
For instance, to check the ``.text`` section address of the ``hello`` application, use the following command::
$ readelf -WS ../apps/bin/hello | grep .text
[ 1] .text PROGBITS c0000000 001000 0009e0 00 AX 0 0 2
Then, look for the ``.text`` section address and use the ``c0000000`` as the address to load the symbols.
For instance, if you want to load the ``hello`` application, you can use the following command in GDB::
$ add-symbol-file ../apps/bin/hello 0xc0000000
Then, you can set breakpoints, step through the code, and inspect the memory and registers of the applications too.