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Fri, 13 Feb 2026 18:44:30 +0000 (UTC) Received: from f42-zbm-amd (unknown [10.22.88.16]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id EFB7230001B9; Fri, 13 Feb 2026 18:44:29 +0000 (UTC) Date: Fri, 13 Feb 2026 11:44:27 -0700 From: Kevin Buettner To: Abhay Kandpal Cc: gdb-patches@sourceware.org Subject: Re: [PATCH] gcore: Handle unreadable pages within readable memory regions Message-ID: <20260213114427.7da9d1dc@f42-zbm-amd> In-Reply-To: References: <20260130082212.2002944-2-kevinb@redhat.com> Organization: Red Hat MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: FaEwvMQ38jpVzBS2UgSQ0W2aGDcPrOZDVSQdYaD4eHQ_1771008271 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: gdb-patches-bounces~public-inbox=simark.ca@sourceware.org On Tue, 10 Feb 2026 23:28:27 +0530 Abhay Kandpal wrote: > Hi Kevin, >=20 > Thanks for sharing this patch and for the detailed end-to-end explanation= =E2=80=94 it matches exactly what I=E2=80=99ve been seeing. >=20 > I=E2=80=99ve independently hit the same issue with glibc 2.42 on kernels = > 6.3, due to the MADV_GUARD_INSTALL change. > The behavior is reproducible with both upstream and custom GDB. >=20 > I tested your patch on ppc64le and x86_64, and it fixes the problem on bo= th. > This looks like a generic GDB issue triggered by the new glibc stack layo= ut rather than an architecture-specific problem. >=20 > The approach of falling back to page-by-page reads on failure looks corre= ct to me. > Thanks again for the clear analysis and fix. Hi Abhay, Thanks for your review! I ended up posting a v2 patch which does not use the constant SPARSE_BLOCK_SIZE. It is used for other purposes in the file. The number associated with this constant makes sense, but it seemed better to instead define a new constant for the size of the fallback memory reads= . The v2 patch is here: https://sourceware.org/pipermail/gdb-patches/2026-February/224948.html Kevin