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Fri, 29 May 2020 14:53:28 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id B934030047A; Fri, 29 May 2020 16:53:25 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 30B8820185BD9; Fri, 29 May 2020 16:53:25 +0200 (CEST) Date: Fri, 29 May 2020 16:53:25 +0200 From: Peter Zijlstra To: Christoph Hellwig Cc: Randy Dunlap , Andrew Morton , broonie@kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-next@vger.kernel.org, mhocko@suse.cz, mm-commits@vger.kernel.org, sfr@canb.auug.org.au, Josh Poimboeuf , Linus Torvalds , viro@ZenIV.linux.org.uk, x86@kernel.org, Steven Rostedt Subject: Re: mmotm 2020-05-13-20-30 uploaded (objtool warnings) Message-ID: <20200529145325.GB706518@hirez.programming.kicks-ass.net> References: <20200514033104.kRFL_ctMQ%akpm@linux-foundation.org> <611fa14d-8d31-796f-b909-686d9ebf84a9@infradead.org> <20200528172005.GP2483@worktop.programming.kicks-ass.net> <20200529135750.GA1580@lst.de> <20200529143556.GE706478@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200529143556.GE706478@hirez.programming.kicks-ass.net> X-Rspamd-Queue-Id: AB863180AD80F X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, May 29, 2020 at 04:35:56PM +0200, Peter Zijlstra wrote: > On Fri, May 29, 2020 at 03:57:51PM +0200, Christoph Hellwig wrote: > > On Thu, May 28, 2020 at 07:20:05PM +0200, Peter Zijlstra wrote: > > > > on x86_64: > > > > > > > > arch/x86/lib/csum-wrappers_64.o: warning: objtool: csum_and_copy_from_user()+0x2a4: call to memset() with UACCESS enabled > > > > arch/x86/lib/csum-wrappers_64.o: warning: objtool: csum_and_copy_to_user()+0x243: return with UACCESS enabled > > > > > > Urgh, that's horrible code. That's got plain stac()/clac() calls on > > > instead of the regular uaccess APIs. > > > > Does it? If this is from the code in linux-next, then the code does a > > user_access_begin/end in csum_and_copy_{from,to}_user, then uses > > unsafe_{get,put}_user inside those function itself. But then they call > > csum_partial_copy_generic with the __user casted away, but without any > > comment on why this is safe. > > Bah, clearly I was looking at the wrong tree. You're right, Al cleaned > it all up. > > Let me try and figure out why objtool is unhappy with it. *groan*, this is one of those CONFIG_PROFILE_ALL_BRANCHES builds. If I disable that it goes away. Still trying to untangle the mess it generated, but on first go it looks like objtool is right, but I'm not sure what went wrong.