On Tue, Jun 06, 2017 at 03:51:26PM +0200, Hans Petter Selasky wrote: > On 03/31/17 02:04, Allan Jude wrote: > > Author: allanjude > > Date: Fri Mar 31 00:04:32 2017 > > New Revision: 316311 > > URL: https://svnweb.freebsd.org/changeset/base/316311 > > > > > > > > Modified: head/sys/boot/i386/zfsboot/zfsboot.c > > ============================================================================== > > --- head/sys/boot/i386/zfsboot/zfsboot.c Thu Mar 30 23:49:57 2017 > > (r316310) > > +++ head/sys/boot/i386/zfsboot/zfsboot.c Fri Mar 31 00:04:32 2017 > > (r316311) > > @@ -926,7 +926,7 @@ load(void) > > zfsargs.primary_pool = primary_spa->spa_guid; > > #ifdef LOADER_GELI_SUPPORT > > bcopy(gelipw, zfsargs.gelipw, sizeof(zfsargs.gelipw)); > > - bzero(gelipw, sizeof(gelipw)); > > + explicit_bzero(gelipw, sizeof(gelipw)); > > #else > > zfsargs.gelipw[0] = '\0'; > > #endif > > > > Hi Allan, > > For ARM platforms you'll need to do a write memory barrier before the > explicit_bzero() returns, else the memory can be recovered by > invalidating the memory area by the next thread which is allocating this > memory ??? Note that loader execution is single threaded / single core. As is, it is not possible for the cache invalidation targeting the generic memory in loader to occur.
That said, if we consider usage of the explicit_bzero() in more complete environment, then a memory barrier is definitely useless for the stated purpose. After the writing thread issued a barrier, cache is not flushed to RAM. In other words, cache flush is probably worth doing there, as you noted. But this raises a question, shouldn't the explicit_bzero() implementation handle the cache flush ? _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
