stepping through a flat binary in qemu

stepping through a flat binary in qemu

[fpga]

Hi. 
I'm trying to step through a tiny real-to-pmode os in qemu using gdb.

I'm using 
   nasm -f bin emakeimg.asm -o enth.fbin
to assemble the thing and then pasting the 16bit flat binary to a floppy
image
i.e. no debugging symbols.

I've booted the os in qemu with 
"qemu -s -S -fda boot.img -boot a" 
& also without "-s" (use gstabs)

In another terminal I debug the same image and connect to qemu via
"target remote localhost:1234".
If I type "cont" the OS starts to execute.

If I try to step by typing "break" gdb complains about no symbols.
Is it possible to step through this 16 bit bootloader code and into the OS
proper with no symbols & if not what's the easiest way of putting symbols
in.

I have a problem that if I try to assemble as elf, I have multiple [ORG
statements in the code] which only bin files recognise.

Any help much appreciated.

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Re: stepping through a flat binary in qemu

[fpga]

fpga wrote:
> 
> Hi. 
> I'm trying to step through a tiny real-to-pmode os in qemu using gdb.
> 
> I'm using 
>    nasm -f bin emakeimg.asm -o enth.fbin
> to assemble the thing and then pasting the 16bit flat binary to a floppy
> image
> i.e. no debugging symbols.
> 
> I've booted the os in qemu with 
> "qemu -s -S -fda boot.img -boot a" 
> & also without "-s" (use gstabs)
> 
> In another terminal I debug the same image and connect to qemu via
> "target remote localhost:1234".
> If I type "cont" the OS starts to execute.
> 
> If I try to step by typing "break" gdb complains about no symbols.
> Is it possible to step through this 16 bit bootloader code and into the OS
> proper with no symbols & if not what's the easiest way of putting symbols
> in.
> 
> I have a problem that if I try to assemble as elf, I have multiple [ORG
> statements in the code] which only bin files recognise.
> 
> Any help much appreciated.
> 
> 


Its ok I've sorted it using this thread
http://qemu-forum.ipi.fi/viewtopic.php?f=22&t=4544
Thanks very much dhbaird!
If there's any more useful advice re this I'd appreciate it

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Re: stepping through a flat binary in qemu

[Michael Snyder]

fpga wrote:
> Hi. 
> I'm trying to step through a tiny real-to-pmode os in qemu using gdb.
> 
> I'm using 
>    nasm -f bin emakeimg.asm -o enth.fbin
> to assemble the thing and then pasting the 16bit flat binary to a floppy
> image
> i.e. no debugging symbols.
> 
> I've booted the os in qemu with 
> "qemu -s -S -fda boot.img -boot a" 
> & also without "-s" (use gstabs)
> 
> In another terminal I debug the same image and connect to qemu via
> "target remote localhost:1234".
> If I type "cont" the OS starts to execute.
> 
> If I try to step by typing "break" gdb complains about no symbols.
> Is it possible to step through this 16 bit bootloader code and into the OS
> proper with no symbols & if not what's the easiest way of putting symbols
> in.
> 
> I have a problem that if I try to assemble as elf, I have multiple [ORG
> statements in the code] which only bin files recognise.
> 
> Any help much appreciated.

Probably need to use stepi, since step depends on line symbols.

Re: stepping through a flat binary in qemu

[fpga]

Michael Snyder-6 wrote:
> 
> fpga wrote:
>> Hi. 
>> I'm trying to step through a tiny real-to-pmode os in qemu using gdb.
>> 
>> I'm using 
>>    nasm -f bin emakeimg.asm -o enth.fbin
>> to assemble the thing and then pasting the 16bit flat binary to a floppy
>> image
>> i.e. no debugging symbols.
>> 
>> I've booted the os in qemu with 
>> "qemu -s -S -fda boot.img -boot a" 
>> & also without "-s" (use gstabs)
>> 
>> In another terminal I debug the same image and connect to qemu via
>> "target remote localhost:1234".
>> If I type "cont" the OS starts to execute.
>> 
>> If I try to step by typing "break" gdb complains about no symbols.
>> Is it possible to step through this 16 bit bootloader code and into the
>> OS
>> proper with no symbols & if not what's the easiest way of putting symbols
>> in.
>> 
>> I have a problem that if I try to assemble as elf, I have multiple [ORG
>> statements in the code] which only bin files recognise.
>> 
>> Any help much appreciated.
> 
> Probably need to use stepi, since step depends on line symbols.
> 
> 
Yes that works
Thanks Michael 

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