From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 17590 invoked by alias); 8 Mar 2004 14:09:51 -0000 Mailing-List: contact gdb-patches-help@sources.redhat.com; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sources.redhat.com Received: (qmail 17582 invoked from network); 8 Mar 2004 14:09:49 -0000 Received: from unknown (HELO nevyn.them.org) (66.93.172.17) by sources.redhat.com with SMTP; 8 Mar 2004 14:09:49 -0000 Received: from drow by nevyn.them.org with local (Exim 4.30 #1 (Debian)) id 1B0LS1-0003qX-2S; Mon, 08 Mar 2004 09:09:49 -0500 Date: Fri, 19 Mar 2004 00:09:00 -0000 From: Daniel Jacobowitz To: Richard Earnshaw Cc: gdb-patches@sources.redhat.com Subject: Re: [rfa/arm] Handle bx and blx Message-ID: <20040308140948.GA14686@nevyn.them.org> Mail-Followup-To: Richard Earnshaw , gdb-patches@sources.redhat.com References: <20040307201539.GA22007@nevyn.them.org> <200403081017.i28AHrE08741@pc960.cambridge.arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200403081017.i28AHrE08741@pc960.cambridge.arm.com> User-Agent: Mutt/1.5.1i X-SW-Source: 2004-03/txt/msg00151.txt.bz2 On Mon, Mar 08, 2004 at 10:17:53AM +0000, Richard Earnshaw wrote: > > On Wed, Mar 03, 2004 at 04:01:55PM +0000, Richard Earnshaw wrote: > > > > The software single-step implementation in GDB doesn't know either BX or > > > > BLX. This results in losing control of the inferior when we single-step > > > > over them. I based this on the ARM ARM, so I'm pretty sure I've got the > > > > numbers correct. > > > > > > > > OK to check in? > > > > > > > > -- > > > > Daniel Jacobowitz > > > > MontaVista Software Debian GNU/Linux Developer > > > > > > > > 2004-02-28 Daniel Jacobowitz > > > > > > > > * arm-tdep.c (thumb_get_next_pc): Handle BX. > > > > (arm_get_next_pc): Handle BX and BLX. > > > > > > Yikes! Yes, this is OK. However, Thumb has BLX (2 variants) as well. > > > > Right you are. I've checked in the above; if I'm reading > > thumb_get_next_pc and the ARM correctly, then the below is all I need > > for BLX. The first form is already handled since we don't check H. > > The second form can be handled identically to BX by relaxing a test. > > > > OK? > > > > -- > > Daniel Jacobowitz > > MontaVista Software Debian GNU/Linux Developer > > > > 2004-03-07 Daniel Jacobowitz > > > > * arm-tdep.c (thumb_get_next_pc): Handle Thumb BLX. > > Very close, and possibly good enough for most purposes. But the ARM ARM > says that in the blx(1) case, the resulting address should be masked with > 0xfffffffc. That means that there are two theoretical encodings for each > target ARM-state instruction. I think you need to add a test for H=01 and > if so, to apply the mask to nextpc. Except it also says: Bit[0] for BLX If H == 01, then bit[0] of the instruction must be zero, or the instruction is UNDEFINED. The offset calculation method described in Usage above ensures that the offset calculated for a BLX instruction is a multiple of four, and that this restriction is obeyed. So I think the mask really isn't needed, or am I reading that wrong? -- Daniel Jacobowitz MontaVista Software Debian GNU/Linux Developer From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 17590 invoked by alias); 8 Mar 2004 14:09:51 -0000 Mailing-List: contact gdb-patches-help@sources.redhat.com; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sources.redhat.com Received: (qmail 17582 invoked from network); 8 Mar 2004 14:09:49 -0000 Received: from unknown (HELO nevyn.them.org) (66.93.172.17) by sources.redhat.com with SMTP; 8 Mar 2004 14:09:49 -0000 Received: from drow by nevyn.them.org with local (Exim 4.30 #1 (Debian)) id 1B0LS1-0003qX-2S; Mon, 08 Mar 2004 09:09:49 -0500 Date: Mon, 08 Mar 2004 14:09:00 -0000 From: Daniel Jacobowitz To: Richard Earnshaw Cc: gdb-patches@sources.redhat.com Subject: Re: [rfa/arm] Handle bx and blx Message-ID: <20040308140948.GA14686@nevyn.them.org> Mail-Followup-To: Richard Earnshaw , gdb-patches@sources.redhat.com References: <20040307201539.GA22007@nevyn.them.org> <200403081017.i28AHrE08741@pc960.cambridge.arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200403081017.i28AHrE08741@pc960.cambridge.arm.com> User-Agent: Mutt/1.5.1i X-SW-Source: 2004-03.o/txt/msg00151.txt Message-ID: <20040308140900.vm1IGwLUG6sA86bj9WCrqB3M8-0HOlU6iXVBn_bSFXA@z> On Mon, Mar 08, 2004 at 10:17:53AM +0000, Richard Earnshaw wrote: > > On Wed, Mar 03, 2004 at 04:01:55PM +0000, Richard Earnshaw wrote: > > > > The software single-step implementation in GDB doesn't know either BX or > > > > BLX. This results in losing control of the inferior when we single-step > > > > over them. I based this on the ARM ARM, so I'm pretty sure I've got the > > > > numbers correct. > > > > > > > > OK to check in? > > > > > > > > -- > > > > Daniel Jacobowitz > > > > MontaVista Software Debian GNU/Linux Developer > > > > > > > > 2004-02-28 Daniel Jacobowitz > > > > > > > > * arm-tdep.c (thumb_get_next_pc): Handle BX. > > > > (arm_get_next_pc): Handle BX and BLX. > > > > > > Yikes! Yes, this is OK. However, Thumb has BLX (2 variants) as well. > > > > Right you are. I've checked in the above; if I'm reading > > thumb_get_next_pc and the ARM correctly, then the below is all I need > > for BLX. The first form is already handled since we don't check H. > > The second form can be handled identically to BX by relaxing a test. > > > > OK? > > > > -- > > Daniel Jacobowitz > > MontaVista Software Debian GNU/Linux Developer > > > > 2004-03-07 Daniel Jacobowitz > > > > * arm-tdep.c (thumb_get_next_pc): Handle Thumb BLX. > > Very close, and possibly good enough for most purposes. But the ARM ARM > says that in the blx(1) case, the resulting address should be masked with > 0xfffffffc. That means that there are two theoretical encodings for each > target ARM-state instruction. I think you need to add a test for H=01 and > if so, to apply the mask to nextpc. Except it also says: Bit[0] for BLX If H == 01, then bit[0] of the instruction must be zero, or the instruction is UNDEFINED. The offset calculation method described in Usage above ensures that the offset calculated for a BLX instruction is a multiple of four, and that this restriction is obeyed. So I think the mask really isn't needed, or am I reading that wrong? -- Daniel Jacobowitz MontaVista Software Debian GNU/Linux Developer