[syslinux] Can't get COM32 + GDB to work

[Don Hiatt]

On Thu, May 20, 2010 at 2:40 PM, Sebastian Herbszt <herbszt at gmx.de> wrote:
> Sebastian Herbszt wrote:
>>
>> Don Hiatt wrote:
>>>
>>> [Sorry, I sent this reply to hpa (sorry) instead of the list]
>>
>> <snip>
>>
>>> Breakpoints still don't work. Here is the gdb session. From syslinux's
>>> "boot:" I type "/boot/hello" and it runs but doesn't trigger the
>>> breakpoint in main().
>>>
>>>
>>> Reading symbols from /export/devel/syslinux/core/extlinux.elf...done.
>>> (gdb) target remote localhost:1234
>>> Remote debugging using localhost:1234
>>> 0x000f1996 in ?? ()
>>> (gdb) add-symbol-file com32/samples/hello.elf free_high_memory
>>> add symbol table from file "com32/samples/hello.elf" at
>>>       .text_addr = 0x0
>>> (y or n) y
>>> Reading symbols from
>>> /export/devel/syslinux/com32/samples/hello.elf...done.
>>> (gdb) b hello.c:main
>>> Breakpoint 1 at 0xa4: file hello.c, line 24.
>>
>> Does 0xa4 look correct? Shouldn't it be somewhere above free_high_memory?
>
> $ objdump -x core/pxelinux.elf | grep free_high_memory
> 00160000 g       *ABS*  00000000 free_high_memory
>
> (gdb) file core/pxelinux.elf
> (gdb) target remote ...
> (gdb) add-symbol-file com32/samples/hello.elf 0x00160000
> add symbol table from file "com32/samples/hello.elf" at
>       .text_addr = 0x160000
> (y or n) y
> (gdb) break hello.c:main
> Breakpoint 1 at 0x160000: file hello.c, line 24.
> (gdb) c
> Continuing.
>
> Breakpoint 1, main (argc=28628, argv=0x0) at hello.c:24
> 24      {
> Current language:  auto
> The current source language is "auto; currently c".
> (gdb)
>
> This seems to work with Bochs. If i use "free_high_memory" instead of
> 0x00160000 it doesn't.
>

Thanks! I totally ignored the output. I now see the break point
triggered in QEMU but it just continues on. I'm going to try Bochs but
this is great, thanks again!