From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 92230 invoked by alias); 23 May 2018 10:32:51 -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 92139 invoked by uid 89); 23 May 2018 10:32:50 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-24.9 required=5.0 tests=AWL,BAYES_00,GIT_PATCH_0,GIT_PATCH_1,GIT_PATCH_2,GIT_PATCH_3,RCVD_IN_DNSWL_NONE,SPF_PASS autolearn=ham version=3.3.2 spammy=gdbarch.sh, gdbarchsh, UD:gdbarch.sh X-HELO: rock.gnat.com Received: from rock.gnat.com (HELO rock.gnat.com) (205.232.38.15) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 23 May 2018 10:32:47 +0000 Received: from localhost (localhost.localdomain [127.0.0.1]) by filtered-rock.gnat.com (Postfix) with ESMTP id 8A2D3117D02; Wed, 23 May 2018 06:32:45 -0400 (EDT) Received: from rock.gnat.com ([127.0.0.1]) by localhost (rock.gnat.com [127.0.0.1]) (amavisd-new, port 10024) with LMTP id pJtDmuMOYEZv; Wed, 23 May 2018 06:32:45 -0400 (EDT) Received: from joel.gnat.com (localhost.localdomain [127.0.0.1]) by rock.gnat.com (Postfix) with ESMTP id 6F760117CC7; Wed, 23 May 2018 06:32:45 -0400 (EDT) Received: by joel.gnat.com (Postfix, from userid 1000) id D97918330C; Wed, 23 May 2018 06:32:44 -0400 (EDT) Date: Wed, 23 May 2018 11:36:00 -0000 From: Joel Brobecker To: Omair Javaid Cc: gdb-patches@sourceware.org Subject: Re: [PATCH] [PR gdb/23210] Unset gdbarch significant_addr_bit by default Message-ID: <20180523103244.2e6tseom5tsll3kf@adacore.com> References: <1527023088-10837-1-git-send-email-omair.javaid@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1527023088-10837-1-git-send-email-omair.javaid@linaro.org> User-Agent: NeoMutt/20170113 (1.7.2) X-SW-Source: 2018-05/txt/msg00620.txt.bz2 Hi Omair, > This patch fixes a bug introduced by fix to AArch64 pointer tagging. > > In our fix for tagged pointer support our agreed approach was to sign > extend user-space address after clearing tag bits. This is not same > for all architectures and this patch allows sign extension for > addresses on targets which specifically set significant_addr_bit. > > More information about patch that caused the issues and discussion > around tagged pointer support can be found in links below: > > https://sourceware.org/ml/gdb-patches/2018-05/msg00000.html > https://sourceware.org/ml/gdb-patches/2017-12/msg00159.html > > gdb/ChangeLog: > > 2018-05-23 Omair Javaid > > * gdbarch.c (verify_gdbarch): Update. > * utils.c (address_significant): Update. I haven't delved into the actual patch and whether the approach used is correct, but skimming it, I did notice a couple of things. The first one is that gdbarch.c is a generated file, so you should adjust gdbarch.sh instead so that executing gdbarch.sh gives you the gdbarch.c file with the behavior you want. In particular, I think you probably need to remove the default value for significant_addr_bit. > --- > gdb/gdbarch.c | 3 +-- > gdb/utils.c | 5 +++-- > 2 files changed, 4 insertions(+), 4 deletions(-) > > diff --git a/gdb/gdbarch.c b/gdb/gdbarch.c > index c430ebe..5593911 100644 > --- a/gdb/gdbarch.c > +++ b/gdb/gdbarch.c > @@ -615,8 +615,7 @@ verify_gdbarch (struct gdbarch *gdbarch) > /* Skip verify of stabs_argument_has_addr, invalid_p == 0 */ > /* Skip verify of convert_from_func_ptr_addr, invalid_p == 0 */ > /* Skip verify of addr_bits_remove, invalid_p == 0 */ > - if (gdbarch->significant_addr_bit == 0) > - gdbarch->significant_addr_bit = gdbarch_addr_bit (gdbarch); > + /* Skip verify of significant_addr_bit, invalid_p == 0 */ > /* Skip verify of software_single_step, has predicate. */ > /* Skip verify of single_step_through_delay, has predicate. */ > /* Skip verify of print_insn, invalid_p == 0 */ > diff --git a/gdb/utils.c b/gdb/utils.c > index 9c5bf68..91c0f2b 100644 > --- a/gdb/utils.c > +++ b/gdb/utils.c > @@ -2708,10 +2708,11 @@ address_significant (gdbarch *gdbarch, CORE_ADDR addr) > /* Clear insignificant bits of a target address and sign extend resulting > address, avoiding shifts larger or equal than the width of a CORE_ADDR. > The local variable ADDR_BIT stops the compiler reporting a shift overflow > - when it won't occur. */ > + when it won't occur. Skip updating of target address if current target has > + not set gdbarch significant_addr_bit. */ Small nit (GNU Coding Style): Two spaces after the period. > int addr_bit = gdbarch_significant_addr_bit (gdbarch); > > - if (addr_bit < (sizeof (CORE_ADDR) * HOST_CHAR_BIT)) > + if (addr_bit && (addr_bit < (sizeof (CORE_ADDR) * HOST_CHAR_BIT))) > { > CORE_ADDR sign = (CORE_ADDR) 1 << (addr_bit - 1); > addr &= ((CORE_ADDR) 1 << addr_bit) - 1; > -- > 2.7.4 -- Joel