Date: Thu, 10 Nov 2016 22:46:30 +0100 From: Peter Zijlstra <peterz@...radead.org> To: Kees Cook <keescook@...omium.org> Cc: Elena Reshetova <elena.reshetova@...el.com>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, Arnd Bergmann <arnd@...db.de>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <h.peter.anvin@...el.com>, Will Deacon <will.deacon@....com>, Hans Liljestrand <ishkamiel@...il.com>, David Windsor <dwindsor@...il.com> Subject: Re: [RFC v4 PATCH 12/13] x86: implementation for HARDENED_ATOMIC On Thu, Nov 10, 2016 at 01:32:50PM -0800, Kees Cook wrote: > > Also, I hate how #ifdef CONFIG_HARDENED_ATOMIC is sprinkled all over, it > > makes a huge trainwreck of that file. > > I guess the question was "prefer copy/pasting" vs "sprinkled ifdef". I > tend to opt for reducing copy/paste, but this is just a code > organization issue. Likely, then, would be to have two separate > implementations in different .c files and have the Makefile select the > desired version. No, no .c files, this stuff wants to be inline, esp. the unannotated versions, those typically are a single instruction. And you don't need to copy/paste, just: #define atomic_wrap_t atomic_t and use the 'normal' functions. > > Ideally there'd be only a single #ifdef CONFIG_HARNDED_ATOMIC. > > > > I'm also not sure about atomic*_wrap() as an interface, these functions > > already have far too long names. We could simply overload the existing > > functions and select based off the argument type. > > There was a concern over catching type errors when building without > CONFIG_HARDENED_ATOMIC. Again, this is just a code organization issue > -- I think whatever people prefer is fine. In theory, 0-day will > quickly catch the corner cases, but I'd love it if the types couldn't > get mixed up. > > Out of curiosity, how would the arg-type selection look? Are there > other examples of this already in the kernel? See static_branch_likely() / static_branch_unlikely().
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