From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 28894 invoked by alias); 17 Feb 2004 15:12:34 -0000 Mailing-List: contact gdb-help@sources.redhat.com; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sources.redhat.com Received: (qmail 28886 invoked from network); 17 Feb 2004 15:12:34 -0000 Received: from unknown (HELO baradas.org) (66.166.225.55) by sources.redhat.com with SMTP; 17 Feb 2004 15:12:34 -0000 Received: by baradas.org (Postfix, from userid 500) id 3B86B990D5; Tue, 17 Feb 2004 10:12:33 -0500 (EST) From: Peter Barada To: mohanlaljangir@hotmail.com Cc: cagney@gnu.org, gdb@sources.redhat.com In-reply-to: (mohanlaljangir@hotmail.com) Subject: Re: hardware support for gdb? References: <402CE55C.6070605@gnu.org> <4031535A.7080500@gnu.org> Message-Id: <20040217151233.3B86B990D5@baradas.org> Date: Tue, 17 Feb 2004 15:12:00 -0000 X-SW-Source: 2004-02/txt/msg00193.txt.bz2 >What I understood from this paragraph is that, if a target processor provide >"trace bit" kind of functionality, gdb developer's life is easier otherwise >he has to do some more work(disassembling of instruction). Am I right? Could >you please explain a little about "trace bit" or similar functionality? Is >it the breakpoint instruction, you mentioned about? For more info on a 'trace' bit type architecture, look up any 68000 or ColdFire processor manual. In a nutshell, in an exception, if you patch the status register value to or in the trace bit, then when the return from exception is taken, the processor will execute *one* instruction and then take an exception. This allows you to step the processor one instruction at a time without affecting its execution. If the processor does not have this capability, then gdb inserts an illegal instruction following the instruction it wants to step. The instruction needs to be decoded so if there is a possible branch(or return or jump-to-subroutine), GDB can place another illegal instruction at the target of the branch. This can take quite a while if GDB is comminication with the target via a slow serial line... -- Peter Barada peter@the-baradas.com