Date: Fri, 12 Jun 2020 09:57:20 +0200 From: Mikhail Morfikov <mmorfikov@...il.com> To: lkrg-users@...ts.openwall.com Subject: Re: RE: ISRA optimized functions On 12/06/2020 00:19, Adam Zabrocki wrote: > > I would need to do manual investigation how your build process looks and works. > However, I don't think it makes any sense. Actually it's not just my build process, only the kernel's bindeb-pkg target which I think all people using Debian call when they're building their custom kernels. It produces simple deb packages that can be installed via apt-get/aptitude to make the system clean when you don't need them anymore. So this is quite common technique to build the kernel, at least on Debian/Ubuntu. > However, which function would be affected by such optimization purely > depends on the kernel configuration. I have a question. There's "Compiler optimization level" in the kernel config with the following options to choose: CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE: This is the default optimization level for the kernel, building with the "-O2" compiler flag for best performance and most helpful compile-time warnings. CONFIG_CC_OPTIMIZE_FOR_SIZE: Choosing this option will pass "-Os" to your compiler resulting in a smaller kernel. So either one is used with the default to CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE. Maybe this is the problem with "-O2"? If so, it's default and I don't think this "-O2" flag can be removed without changing kernel distro config, which I don't think is likely to happen. The following is from the Debian default kernel config: $ grep CONFIG_CC_OPTIMIZE /boot/config-5.6.0-2-amd64 CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE=y # CONFIG_CC_OPTIMIZE_FOR_SIZE is not set Download attachment "signature.asc" of type "application/pgp-signature" (229 bytes)
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