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RE: Query regarding assembly level debugging support
- From: "Tarun" <tarun at acmet dot com>
- To: "'Peter Barada'" <peter at the-baradas dot com>
- Cc: <gdb at sources dot redhat dot com>, <acmet at vsnl dot net>, <ranjeeta at acmet dot com>, <rm_nair at acmet dot com>
- Date: Wed, 8 Dec 2004 12:32:12 +0530
- Subject: RE: Query regarding assembly level debugging support
> -----Original Message-----
> From: Peter Barada [mailto:peter@the-baradas.com]
> Sent: Thursday, December 02, 2004 7:40 PM
> To: tarun@acmet.com
> Cc: gdb@sources.redhat.com; acmet@vsnl.net; ranjeeta@acmet.com;
> rm_nair@acmet.com
> Subject: Re: Query regarding assembly level debugging support
>
>
> > The linked out file is loaded without errors on GDB. When we run
> >the respective out file on GDB, the control of debugger moves to
label
> >main in the assembly code ( Breakpoint 1, 0xa00200ec in main ()).
When I
> >try to move to next instruction using "nexti", the control moves to
next
> >address (Displaying: 0xa00200f0 in main ()). This continues till the
> >last address is reached. Only the address increments within the
assembly
> >file are displayed and not the actual assembly source.
> >
> > When I try to single step using "step", the message prompted is
> >"Single stepping until exit from function main, which has no line
number
> >information". Whereas if I disassemble one of the addresses give
above,
> >entire assembly code which I am trying to debug is displayed.
> >
> > Does this mean that GDB does not support debugging of the
assembly
> >code?
>
> Peope have been using GDB to debug assembler code for years. A
> couple of tricks:
>
> 1) Use stepi/nexti commands to step or next one *instruction* as
> opposed to source line
> 2) Use the 'disp/i $pc' to have GDB display the assembler instruction
> that will be executed next.
> 3) Use 'i reg' to dump the registers, or 'p $reg' where 'reg' is the
> register name.
>
Thanks for the information. But my query still remains "Can we step
through assembly code?"
I know GDB supports assembly-level debugging but that refers to inline
assembly. To make the point clear, please look at snip below. For the
sample code segment:
<snip>
/* Print the top of the stack if no index is specified. */
if (which < 0)
{
which = stack->top - 1;
if (which < 0)
<snip>
The inline assembly is (assume) represented as:
<snip>
/* Print the top of the stack if no index is specified. */
if (which < 0)
.frame $fp,16,$31 <-
.mask 0x40000000,-8 <-
.fmask 0x00000000,0 <-
subu $sp,$sp,16 <-
{
which = stack->top - 1;
li $2,20 <-
sw $2,0($fp) <-
if (which < 0)
<snip>
Does GDB refer to stepping through the above code as assembly-level
debugging?
If yes, then my requirement is little different. I want to debug the
assembly code itself keeping it as the source code (and not the C
source). To be more specific I want to debug hand written assembly code
(and not the one generated by compiler)
Regards,
Tarun