Messages in this thread | | | Date | Tue, 17 Oct 2023 09:34:41 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH RFC 1/7] x86/head/64: Mark star tup gdt and startup gdt descr as initdata |
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On October 17, 2023 6:02:27 AM PDT, Ingo Molnar <mingo@kernel.org> wrote: > >* Hou Wenlong <houwenlong.hwl@antgroup.com> wrote: > >> Hi Ingo, >> >> I have sent patch #6 separately for x86. Do you have any ideas about >> building the head code as PIE? Should I resend the patchset for the PIE >> feature? > >So I had a brief look, and despite reading 0/43 it was unclear to me what >the precise advantages of building as PIE are. > >Ie. could you please outline: > > - *Exactly* how much PIE based KASLR randomization would gain us in terms > of randomization granularity and effective number of randomization bits, > compared to the current status quo? > > - How is code generation changed at the instruction level - how does > kernel size change and what are the micro-advantages/disadvantages? > > - Are there any other advantages/motivation than improving KASLR? > >Ie. before asking us to apply ~50 patches and add a whole new build mode >and the maintainance overhead to support it into infinity and beyond, could >you please offer a better list of pros and cons? > >Thanks, > > Ingo
If the goal is better KASLR, then what we really should spend time on was Kristen Accardi's fgKASLR patches, which not only exponentially(!) increases the randomization entrophy but also *actually* avoids the "one leak and it's over" problem.
However, she gave up on it because she got no interest, despite working code.
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