On Mon, Aug 04, 2025 at 10:59:01PM +0000, Eric Biggers wrote: > On Mon, Aug 04, 2025 at 09:02:27PM +0200, Christophe Leroy wrote: > > > > > > Le 04/08/2025 à 20:09, Eric Biggers a écrit : > > > On Mon, Aug 04, 2025 at 07:42:15PM +0200, Christophe Leroy wrote: > > > > > > > > > > > > Le 03/08/2025 à 22:44, Eric Biggers a écrit : > > > > > MD5 is insecure, is no longer commonly used, and has never been > > > > > optimized for the most common architectures in the kernel. Only mips, > > > > > powerpc, and sparc have optimized MD5 code in the kernel. Of these, > > > > > only the powerpc one is actually testable in QEMU. The mips one works > > > > > only on Cavium Octeon SoCs. > > > > > > > > > > Taken together, it's clear that it's time to retire these additional > > > > > MD5 > > > > > implementations, and focus maintenance on the MD5 generic C code. > > > > > > > > Sorry, for me it is not that clear. Even if MD5 is depracated we still > > > > have > > > > several applications that use MD5 for various reasons on our boards. > > > > > > > > I ran the test on kernel v6.16 with following file: > > > > > > > > # ls -l avion.au > > > > -rw------- 1 root root 12130159 Jan 1 1970 avion.au > > > > > > > > With CONFIG_CRYPTO_MD5_PPC: > > > > > > > > # time md5sum avion.au > > > > 6513851d6109d42477b20cd56bf57f28 avion.au > > > > real 0m 1.02s > > > > user 0m 0.01s > > > > sys 0m 1.01s > > > > > > > > Without CONFIG_CRYPTO_MD5_PPC: > > > > > > > > # time md5sum avion.au > > > > 6513851d6109d42477b20cd56bf57f28 avion.au > > > > real 0m 1.35s > > > > user 0m 0.01s > > > > sys 0m 1.34s > > > > > > > > I think the difference is big enough to consider keeping optimised MD5 > > > > code. > > > > > > But md5sum doesn't use the kernel's MD5 code. So it's implausible that > > > it has any effect on md5sum. The difference you saw must be due to an > > > unrelated reason like I/O caching, CPU frequency, etc. Try running your > > > test multiple times to eliminate other sources of variation. > > > > md5sum uses the kernel's MD5 code: > > > > libkcapi.so.1 => /usr/lib/libkcapi.so.1 (0x6ffa0000) <==
Oh, I think you used the obscure implementation of md5sum from libkcapi-tools, instead of the normal md5sum. Why? Did you check how the normal md5sum performs too? Just doing the calculation in userspace is much more efficient. - Eric
