From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gdb-return-46680-listarch-gdb=sources.redhat.com@sourceware.org>
Received: (qmail 41011 invoked by alias); 28 Oct 2018 16:47:14 -0000
Mailing-List: contact gdb-help@sourceware.org; run by ezmlm
Precedence: bulk
List-Id: <gdb.sourceware.org>
List-Subscribe: <mailto:gdb-subscribe@sourceware.org>
List-Archive: <http://sourceware.org/ml/gdb/>
List-Post: <mailto:gdb@sourceware.org>
List-Help: <mailto:gdb-help@sourceware.org>, <http://sourceware.org/ml/#faqs>
Sender: gdb-owner@sourceware.org
Received: (qmail 40999 invoked by uid 89); 28 Oct 2018 16:47:13 -0000
Authentication-Results: sourceware.org; auth=none
X-Spam-SWARE-Status: No, score=-0.6 required=5.0 tests=AWL,BAYES_00,SPF_HELO_PASS,SPF_PASS,UNSUBSCRIBE_BODY autolearn=no version=3.3.2 spammy=adjusted, morgan, force, Morgan
X-HELO: smtp.polymtl.ca
Received: from smtp.polymtl.ca (HELO smtp.polymtl.ca) (132.207.4.11) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Sun, 28 Oct 2018 16:47:12 +0000
Received: from simark.ca (simark.ca [158.69.221.121])	(authenticated bits=0)	by smtp.polymtl.ca (8.14.7/8.14.7) with ESMTP id w9SGl5tF007713	(version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT)	for <gdb@sourceware.org>; Sun, 28 Oct 2018 12:47:10 -0400
Received: by simark.ca (Postfix, from userid 112)	id 85D4D1EA6F; Sun, 28 Oct 2018 12:47:05 -0400 (EDT)
Received: from simark.ca (localhost [127.0.0.1])	by simark.ca (Postfix) with ESMTP id 291A01E4C2;	Sun, 28 Oct 2018 12:47:01 -0400 (EDT)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII; format=flowed
Content-Transfer-Encoding: 7bit
Date: Sun, 28 Oct 2018 16:47:00 -0000
From: Simon Marchi <simon.marchi@polymtl.ca>
To: Bill Morgan <arthurwilliammorgan@gmail.com>
Cc: gdb@sourceware.org
Subject: Re: win32-arm-low.c regptr 96 bits stored in 32 bit variable
In-Reply-To: <CAM4wpo8KAB4ff0F9+XwWkRyT_3uT6NPUQThbuM9z0fSxW8CyWw@mail.gmail.com>
References: <CAM4wpo8KAB4ff0F9+XwWkRyT_3uT6NPUQThbuM9z0fSxW8CyWw@mail.gmail.com>
Message-ID: <c7affefd2ba4e71ec0a69a3fc352461a@polymtl.ca>
X-Sender: simon.marchi@polymtl.ca
User-Agent: Roundcube Webmail/1.3.6
X-IsSubscribed: yes
X-SW-Source: 2018-10/txt/msg00055.txt.bz2

On 2018-10-26 18:40, Bill Morgan wrote:
> Should this static variable ULONG zero be at least 96 bits?
> 
> static char *
> regptr (CONTEXT* c, int r)
> {
>   if (mappings[r] < 0)
>   {
>     static ULONG zero;
>     /* Always force value to zero, in case the user tried to write
>        to this register before.  */
>     zero = 0;
>     return (char *) &zero;
>   }
>   else
>     return (char *) c + mappings[r];
> }
> 
> reg-arm.dat shows 96 bits for the ones that have mappings[r] == -1
> 
> name:arm
> xmlarch:arm
> expedite:r11,sp,pc
> 32:r0
> 32:r1
> 32:r2
> 32:r3
> 32:r4
> 32:r5
> 32:r6
> 32:r7
> 32:r8
> 32:r9
> 32:r10
> 32:r11
> 32:r12
> 32:sp
> 32:lr
> 32:pc
> 96:f0
> 96:f1
> 96:f2
> 96:f3
> 96:f4
> 96:f5
> 96:f6
> 96:f7
> 32:fps
> 32:cpsr

Hi Bill,

By inspection, it does seem like a mistake, and that we would need to 
return a pointer to a buffer at least as big as register r.  But I have 
no idea how to build/run/test gdbserver on win32/arm.  If you are able 
to confirm that there is a problem and test a fix, could you please 
provide a patch?

To avoid this kind of problem again, we could return a pointer to a 
dynamically-sized buffer adjusted to the size of the register.  
Something like this:

static char *
regptr (CONTEXT* c, struct regcache *regcache, int r)
{
   if (mappings[r] < 0)
   {
     static gdb::byte_vector zero;
     /* Always force value to zero, in case the user tried to write
        to this register before.  */
     zero.assign (regcache_register_size (regcache, r), 0);
     return (char *) zero.data ();
   }
   else
     return (char *) c + mappings[r];
}

Simon