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Re: Single stepping in mips

To: Ralf Baechle <ralf@linux-mips.org>
Subject: Re: Single stepping in mips
From: "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>
Date: Wed, 4 Jun 2003 16:16:48 +0200 (MET DST)
Cc: "Krishnakumar. R" <krishnakumar@naturesoft.net>, linux-mips@linux-mips.org
In-reply-to: <20030604055319.GB8778@linux-mips.org>
Organization: Technical University of Gdansk
Original-recipient: rfc822;linux-mips@linux-mips.org
Sender: linux-mips-bounce@linux-mips.org
On Wed, 4 Jun 2003, Ralf Baechle wrote:

> > But the need is to raise an exception after instr1 (at addr1) is executed.
> > One solution is using a break at instr2 (at addr2).
> > But suppose instr1 is a jmp then there is no point
> > in keeping a break at addr2.
> > (inorder to raise an exception after instr1 is executed).
> 
> You understood correctly.  Now jumps and even more so the conditional
> branches are sort of the ugly part of the whole thing.  The easiest
> method is probably inserting a branch at the jump's destination address
> or in case of a branch at the branch target and the instruction following
> it's delay slot.  So that's a lot of inserting and removing of
> breakpoints ...

 In a more finegrained but also more complicated example, you probably
want to insert a breakpoint in the delay slot first and at the second step
evaluate the branch's condition and put a breakpoint at the next
instruction to be executed.  I'm not sure if the current version of gdb
does the first step, but it inserts a single breakpoint in the second one
only.  For branch likely instructions adjust the two steps as necessary. 

-- 
+  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
+--------------------------------------------------------------+
+        e-mail: macro@ds2.pg.gda.pl, PGP key available        +


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