Date: Wed, 23 Jul 2014 17:45:51 -0700 From: Tim Kientzle <tim@kientzle.com> To: Pedro Giffuni <pfg@freebsd.org> Cc: Shawn Webb <lattera@gmail.com>, Oliver Pinter <oliver.pntr@gmail.com>, Robert Watson <rwatson@freebsd.org>, freebsd-arch@freebsd.org, PaX Team <pageexec@freemail.hu>, Bryan Drewery <bdrewery@freebsd.org> Subject: Re: [RFC] ASLR Whitepaper and Candidate Final Patch Message-ID: <796EDB88-3768-48AA-B909-8A7FFBED0C1E@kientzle.com> In-Reply-To: <D7CEDB47-2818-461A-BB70-479BEBDCEEE9@freebsd.org> References: <96C72773-3239-427E-A90B-D05FF0F5B782@freebsd.org> <20140720201858.GB29618@pwnie.vrt.sourcefire.com> <alpine.BSF.2.11.1407230017490.88645@fledge.watson.org> <20140723004543.GH29618@pwnie.vrt.sourcefire.com> <D7CEDB47-2818-461A-BB70-479BEBDCEEE9@freebsd.org>
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On Jul 23, 2014, at 4:37 PM, Pedro Giffuni <pfg@freebsd.org> wrote: > Hi; > > Il giorno 22/lug/2014, alle ore 19:45, Shawn Webb <lattera@gmail.com> ha scritto: > >>>> ... >>> >>> Hi Shawn: >>> >>> Great news that this work is coming to fruition -- ASLR is long overdue. >>> >>> Are you having any luck with performance measurements? Unixbench seems like a >>> good starting point, but I wonder if it would be useful to look, in >>> particular, at memory-mapping intensive workloads that might be affected as a >>> result of changes in kernel VM data-structure use, or greater fragmentation of >>> the address space. I'm not sure I have a specific application here in mind -- >>> in the past I might have pointed out tools such as ElectricFence that tend to >>> increase fragmentation themselves. >> >> The unixbench tests on that laptop have finished. However, I've been >> fighting a pesky migraine these last couple days, so I haven't had the >> opportunity to aggregate the results into a nice little spreadsheet. I'm >> hoping to finish it up by the end of the week. >> >> I'll take a look at ElectricFence this weekend. Additionally, I have a >> netbook somewhere. Once I find it and its power cord, I'll install >> FreeBSD/x86 and re-run the same tests on that. >> > > Somewhat related to ElectricFence… will ASLR have an adverse effect on debuggers? > > I googled around and got to this: > > http://www.outflux.net/blog/archives/2010/07/03/gdb-turns-off-aslr/ > > So I guess we may have to patch gdb (and lldb)? I suspect the issue here is that debugging often requires multiple runs of a program with repeatable behavior between runs. Consider: * I run the program under GDB, it crashes at a certain PC address * I restart the program, set a breakpoint at that PC address I want to be confident that the PC address where I’m setting the breakpoint will have the same meaning between runs. Timhelp
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