From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 35746 invoked by alias); 15 Dec 2015 12:11:06 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 35718 invoked by uid 89); 15 Dec 2015 12:11:05 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.9 required=5.0 tests=AWL,BAYES_00,SPF_HELO_PASS,T_RP_MATCHES_RCVD autolearn=ham version=3.3.2 X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Tue, 15 Dec 2015 12:11:04 +0000 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (Postfix) with ESMTPS id A136149DD9; Tue, 15 Dec 2015 12:11:03 +0000 (UTC) Received: from [127.0.0.1] (ovpn01.gateway.prod.ext.phx2.redhat.com [10.5.9.1]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id tBFCB2cZ005664; Tue, 15 Dec 2015 07:11:02 -0500 Message-ID: <56700356.8070706@redhat.com> Date: Tue, 15 Dec 2015 12:11:00 -0000 From: Pedro Alves User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Tristan Gingold , Christopher Friedt CC: gdb-patches@sourceware.org Subject: Re: cortex-m xml register descriptions for m-system References: <566F108D.1000401@redhat.com> In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-SW-Source: 2015-12/txt/msg00284.txt.bz2 On 12/15/2015 11:44 AM, Tristan Gingold wrote: > >> On 15 Dec 2015, at 00:11, Christopher Friedt wrote: >> >> On Dec 14, 2015 1:55 PM, "Pedro Alves" wrote: >>> >>> On 12/14/2015 05:04 PM, Christopher Friedt wrote: >>>> Hi list, >>>> >>>> I've been using GDB and OpenOCD to debug ARM Cortex-M devices for >>>> quite a while. One thing that I always noticed when using OpenOCD is >>>> that the m-system registers are listed, which is *incredibly* useful >>>> for writing code on just about any Cortex-M microcontroller. >>>> >>>> Somewhat recently, Qemu has also begun to support Cortex-M based >>>> virtual devices, and it seems to be fairly usable. >>>> >>>> The down side, is that they do not expose the m-system registers, >>>> simply because binutils-gdb does not (at this time) have an XML file >>>> for them. >>>> >>>> Just to catch anyone up to speed who might be reading this, the >>>> m-system registers are >>>> >>>> MSP (main stack pointer) >>>> PSP (process stack pointer) >>>> PRIMASK (1-bit register that says if interrupts are enabled) >>>> BASEPRI (8-bit register that sets the NVIC base priority) >>>> FAULTMASK (1-bit register that says if fault interrupts are enabled) >>>> CONTROL (3-bit register that indicates presence of FP, whether PSP is >>>> selected, and whether running in unprivileged mode) >>>> >>>> Now, these are "system" registers, and on a full blown microprocessor, >>>> it might be unusual to expose them, but on a microcontroller, it's >>>> quite important. The other debuggers that I have seen (IAR, >>>> specifically) also list the m-system registers along with the general >>>> purpose ones for Cortex-M. >>>> >>>> The following XML is sufficient to describe the m-system registers so >>>> that they appear to the GDB client. >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>> >>> Does GDB need to be aware of these registers at all? That is, does gdb >>> need to be aware of org.gnu.gdb.arm.m-system? Usually GDB needs to >>> be aware of specific registers if for instance Dwarf can refer to them. >>> Otherwise, the design of xml descriptions is such that you're free >>> to send any additional registers you want without a specific feature. >>> GDB will show them. >> >> Hmm... It's hard for me to say. The MSP and PSP are banked stack >> pointers, control instructs the core which stack pointer to use, and >> they are also tightly coupled to exception entry, so I would lean >> towards yes? > > I do think so too. > > I have just written a patch so that gdb unwinds correctly on cortex-m > exceptions, and this of course requires that gdb knows about at least > psp. > > I plan to submit it early January. > > Tristan. > Thanks, Pedro Alves