Debugging TORO with BOCHS and GDB

In the following lines I'll tray to explain how debug Toro using bochs+gdb. I often used qemu instance of bochs but the latest days I figured out some rare behaviors so I replaced qemu for bochs with good results. 

Before to start we have to compile bochs for such purpose, after download the source run the next command in order to compile it:

> ./configure --enable-cpu-level=6 --enable-all-optimizations --enable-x86-64 --enable-pci --enable-vmx --enable-disasm --enable-debugger-gui --enable-logging --enable-fpu --enable-3dnow --enable-sb16=dummy --enable-cdrom --enable-x86-debugger --enable-iodebug --disable-plugins --disable-docbook --enable-gdb-stub     

> make install

It is not possible to enable the smp support and gdb stub at the same time. If the compilation was right we'll be able to run bochs with gdb support.

Now It is needed to compile the toro application within the debug symbols, if there're any old .o or .ppu file they must be deleted because they don't have symbols information. We should execute in the toro source directory the next commands:

> fpc ToroHello.pas -g -oToroHello -Fu../rtl/ -Fu../rtl/drivers

> ./build 4 ToroHello boot.o ToroHello.img

This procedure is for ToroHello.pas but it's the same for other toro's app.

So far, we've the bochs and the Toro's image, now we have to build the .bochsrc file and launch bochs.  The following lines may be useful:

megs: 32

ata0-master: type=disk, path="ToroHello.img"

boot: c

log: bochsout.txt

gdbstub: enabled=1

Check that we've indeed to enable the gdbstub in the bochs' source file.

The next step is to run bochs and then GDB:

> bochs

> gdb ToroHello

If we run gdb in the toro/test directory .gdbinit will be used, otherwise we have to connect to bochs manually as follow:

> (gdb) target remote localhost:1234 

If everything goes well we are able to set breakpoints and uses all the tools of gdb. For instance we could do:

> (gdb) b KERNELSTART

> (gdb) c

In the first line a breakpoint is set at KERNELSTART and then the virtual machine continues until comes back when the breakpoint is reached.

Many commands could be usefull in this point like n, for running line by line, step for stepping into, info registers and soon on.

There're a lot of information that we can get at this point but that's for another tutorial ;)

Matias E. Vara

www.torokernel.org

Old TORO

Since 2006, the year in which TORO objectives were modified, the TORO OS project corresponding to the version 1.xx was discontinued. These versions achieved a great success in terms of functionality. The most stable version was 1.1.3, sometimes I see the source of those versions and I feel very sorry of have abandoned it, however it was impossible to me to continue with both projects simultaneously. So I decided to make a small tribute to those versions. For that i will show next how to test TORO 1.1.3 through BOCHS. I've put some screenshots for you to observe the beauty of a shell in PASCAL. Enjoy it!

For these simulations is necessary x86 Bochs, remember that the 1.1.3 version is only for 32 bits. Here I include the torobch.bxrc file contents.

megs: 256

romimage: file=BIOS-bochs-latest, address=0xf0000

floppya: 1_44=toro-1.1.3.img, status=inserted

boot: floppy

It is necessary to download the toro-1.1.3 image from the link:

http://sourceforge.net/projects/toro/files/images/toro-1.1.3/toro-1.1.3.img/download

If everything is allright, the first window you will see when execute BOCHS will be:

Corresponds the GRUB bootloader, there you select TORO-1.1.3 and press enter.

It will start to load the OS and then the Shell:

We are ready to enter commands on TORO. The first command we will see is the ls that, as you already know, lists the actual directory.

Now we go to the directory where finds TORO's source using cd.

And we are going to run echo printk.pas, this will display the file content on screen.

You can see all Shell commands at /BIN directory, these are:

Running reboot the system is closed and we can turn off the virtual machine.

I hope you enjoyed it, make your own experiences running commands. You can also burn the image in a 3 ½ floppy and try it in a real machine.

Attention: Versions 1.x.x have no relation with version 0.xx, they are different things.

Matias E. Vara

www.torokernel.org