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Mon, 31 Jul 2023 14:58:10 -0700 (PDT) Date: Mon, 31 Jul 2023 22:58:09 +0100 From: Lorenzo Stoakes To: Jiri Olsa Cc: David Hildenbrand , Baoquan He , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton , Uladzislau Rezki , Matthew Wilcox , Liu Shixin , Jens Axboe , Alexander Viro Subject: Re: [PATCH v8 1/4] fs/proc/kcore: avoid bounce buffer for ktext data Message-ID: <27ad89fe-1b69-4d62-916f-d494b32c8ddf@lucifer.local> References: <86fd0ccb-f460-651f-8048-1026d905a2d6@redhat.com> <32b8c5e4-c8e3-0244-1b1a-ca33bd44f38a@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: C547C40010 X-Rspam-User: X-Stat-Signature: 3obaiwhr9b1xztdk8bjcafpts6jk6w47 X-Rspamd-Server: rspam01 X-HE-Tag: 1690840692-36078 X-HE-Meta: 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 8Tj3Du3i jOLLKaBObAi8pwRTktqDdFpj2WQiF0tYlu85pBup9CdmJrEx+WfFAxIvGQWUa2NhvVOArqXNQApkghZ9p5FBHvUSugfdyZsa62AP0Ap7AN4YwBKBXWqReEGQysYoPeN5fa/V6gDThSKWLR5XNWRth4sBdla3YRdLAle1aHwjsHVaIQrxYwpmEnWULi0ROFtGs8BLTcJXECjemRIOtL8wzskr9Pn/gN28Vu1r72aAKz2uIqmzdoMvpM0DLvT+14sEIy/yizsSBUh5zY28TYKV1SHPqmafALtGE5+c8nrbQKRfee6vaNoKS/K+kPpbpO/2q5UIh5zjbUDqm6y9ZxjBoqmifpLRaOJvt5WhogXXfcXnrUr3n67JRhDZ+v3EWreMpSCvrNaIjdYli2NVe48MxPx/wUAHMJ33aoP9BKXn9aeMA4UfRYPjqt+thSe404zjlJHQeg1Ak+2sLBSZJX1PK62qEx0SRypOqDZXD X-Bogosity: Ham, tests=bogofilter, spamicity=0.000662, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jul 31, 2023 at 11:50:22PM +0200, Jiri Olsa wrote: > > Ummmm what? I can't! What repro are you seeing on x86, exactly? > > # cat /proc/kallsyms | grep ksys_read > ffffffff8151e450 T ksys_read > > # objdump -d --start-address=0xffffffff8151e450 --stop-address=0xffffffff8151e460 /proc/kcore > > /proc/kcore: file format elf64-x86-64 > > objdump: Reading section load1 failed because: Bad address > > > jirka Locally I don't see this issue. How odd. The bug doesn't manifest as a 'bad address' in the arm64 repros either. I wonder if this is something unrelated... In any case I have a candidate fix for the bug at https://lore.kernel.org/all/20230731215021.70911-1-lstoakes@gmail.com/ which should hopefully address the underlying issue with minimum change.