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[46.139.12.213]) by smtp.gmail.com with ESMTPSA id f192sm5021347wmd.12.2018.11.22.12.56.47 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 22 Nov 2018 12:56:47 -0800 (PST) Date: Thu, 22 Nov 2018 21:56:45 +0100 From: Ingo Molnar To: Andy Lutomirski Cc: "Bae, Chang Seok" , Thomas Gleixner , "H. Peter Anvin" , Andi Kleen , Dave Hansen , "Ravi V. Shankar" , LKML Subject: Re: [PATCH v5] x86/fsgsbase/64: Fix the base write helper functions Message-ID: <20181122205645.GA36550@gmail.com> References: <20181116232728.23538-1-chang.seok.bae@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Andy Lutomirski wrote: > On Fri, Nov 16, 2018 at 3:27 PM Chang S. Bae wrote: > > > > The helper functions that purport to write the base should just write it > > only. It shouldn't have magic optimizations to change the index. > > > > Make the index explicitly changed from the caller, instead of including > > the code in the helpers. > > > > Subsequently, the task write helpers do not handle for the current task > > anymore. The range check for a base value is also factored out, to > > minimize code redundancy from the caller. > > > > v2: Fix further on the task write functions. Revert the changes on the > > task read helpers. > > > > v3: Fix putreg(). Edit the changelog. > > > > v4: Update the task write helper functions and do_arch_prctl_64(). Fix > > the comment in putreg(). > > > > v5: Fix preempt_disable() calls in do_arch_prctl_64() > > Reviewed-by: Andy Lutomirski > > Ingo, Thomas: can we get this in x86/urgent, please? Sadly this commit introduced a boot failure on both an Intel and an AMD 64-bit testbox. Symptoms range from silent bootup hang in early userspace to segfaults like this: [ 21.885741] random: systemd: uninitialized urandom read (16 bytes read) [ 21.964778] systemd[1]: segfault at 28 ip 00005584d8d8247d sp 00007ffc7a05aed0 error 4 in systemd[5584d8d0d000+137000] [ 21.977664] Code: c3 4c 89 ff e8 94 78 fa ff eb bb 48 89 c3 eb f1 00 00 00 00 00 00 00 00 00 00 00 00 00 41 55 41 54 55 53 48 89 fd 48 83 ec 28 <64> 48 8b 04 25 28 00 00 00 48 89 44 24 18 31 c0 48 85 ff 74 6e 48 [ 22.000004] systemd[1]: segfault at 28 ip 00005584d8db0a3d sp 00007ffc7a05a7e0 error 4 in systemd[5584d8d0d000+137000] [ 22.012869] Code: 49 89 e9 ba 67 01 00 00 bf 04 00 00 00 31 c0 e8 c9 1c 03 00 59 31 c0 5e e9 ff fa ff ff 41 54 55 53 89 fb 48 81 ec 40 01 00 00 <64> 48 8b 04 25 28 00 00 00 48 89 84 24 38 01 00 00 31 c0 e8 fb 92 I've zapped the commit from x86/urgent because it's clearly not ready yet. I used a fairly regular distro .config and a fairly regular distro - nothing fancy. Thanks, Ingo