On May 4, 2016 6:35:44 PM PDT, Jeffrey Walton <noloader@xxxxxxxxx> wrote: >On Wed, May 4, 2016 at 5:52 PM, John Denker <jsd@xxxxxxxx> wrote: >> On 05/04/2016 02:42 PM, I wrote: >> >>> I find it very odd that the other seven functions were not >>> upgraded. I suggest the attached fix-others.diff would make >>> things more consistent. >> >> Here's a replacement patch. >> ... > >+1, commit it. > >Its good for three additional reasons. First, this change means the >kernel is teaching the next generation the correct way to do things. >Many developers aspire to be kernel hackers, and they sometimes use >the code from bitops.h. I've actually run across the code in >production during an audit where the developers cited bitops.h. > >Second, it preserves a "silent and dark" cockpit during analysis. That >is, when analysis is run, no findings are generated. Auditors and >security folks like quiet tools, much like the way pilots like their >cockpits (flashing lights and sounding buzzers usually means something >is wrong). > >Third, the pattern is recognized by the major compilers, so the kernel >should not have any trouble when porting any of the compilers. I often >use multiple compiler to tease out implementation defined behavior in >a effort to achieve greater portability. Here are the citations to >ensure the kernel is safe with the pattern: > > * GCC: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57157 > * ICC: http://software.intel.com/en-us/forums/topic/580884 > >However, Clang may cause trouble because they don't want the >responsibility of recognizing the pattern: > > * https://llvm.org/bugs/show_bug.cgi?id=24226#c8 > >Instead, they provide a defective rotate. The "defect" here is its >non-constant time due to the branch, so it may not be suitable for >high-integrity or high-assurance code like linux-crypto: > > * https://llvm.org/bugs/show_bug.cgi?id=24226#c5 > >Jeff So you are actually saying outright that we should sacrifice *actual* portability in favor of *theoretical* portability? What kind of twilight zone did we just step into?! -- Sent from my Android device with K-9 Mail. Please excuse brevity and formatting. -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
