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[46.139.12.213]) by smtp.gmail.com with ESMTPSA id z13sm54820935wrw.36.2019.04.10.04.43.01 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 10 Apr 2019 04:43:02 -0700 (PDT) Date: Wed, 10 Apr 2019 13:42:59 +0200 From: Ingo Molnar To: Elena Reshetova , Andy Lutomirski Cc: luto@kernel.org, linux-kernel@vger.kernel.org, luto@amacapital.net, jpoimboe@redhat.com, keescook@chromium.org, jannh@google.com, enrico.perla@intel.com, mingo@redhat.com, bp@alien8.de, tglx@linutronix.de, peterz@infradead.org, gregkh@linuxfoundation.org Subject: Re: [PATCH 1/1] x86/entry/64: randomize kernel stack offset upon syscall Message-ID: <20190410114259.GB9293@gmail.com> References: <20190410112103.15170-1-elena.reshetova@intel.com> <20190410112103.15170-2-elena.reshetova@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190410112103.15170-2-elena.reshetova@intel.com> 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 * Elena Reshetova wrote: > 2) Andy's tests, misc-tests: ./timing_test_64 10M sys_enosys > base: 10000000 loops in 1.62224s = 162.22 nsec / loop > random_offset (prandom_u32() every syscall): 10000000 loops in 1.64660s = 166.26 nsec / loop Stupid question, how did you manage to buil timing_test_64? Here it fails with a bog standard gcc 7.3.0 x86-64 distro toolchain: dagon:~/luto-misc-tests.git> make timing_test_64 g++ -m64 -o timing_test_64 -O2 -g -std=gnu++11 -pthread -Wall timing_test.cc -lrt -ldl /usr/bin/ld: /tmp/cc8VRkuV.o: relocation R_X86_64_32S against `.text.startup' can not be used when making a PIE object; recompile with -fPIC /usr/bin/ld: final link failed: Nonrepresentable section on outputcollect2: error: ld returned 1 exit status Makefile:39: recipe for target 'timing_test_64' failed I'm using cb7f9f0592f8, which is like 1.5 years old - is this still the latest and greatest: git://git.kernel.org/pub/scm/linux/kernel/git/luto/misc-tests.git ? Thanks, Ingo