On Wed, Jun 17, 2020 at 05:55:17PM +0200, Peter Zijlstra wrote: > On Wed, Jun 17, 2020 at 05:19:59PM +0200, Marco Elver wrote: > > > > Does GCC (8, as per the new KASAN thing) have that > > > __builtin_memcpy_inline() ? > > > > No, sadly it doesn't. Only Clang 11. :-/ > > > > But using a call to __memcpy() somehow breaks with Clang+KCSAN. Yet, > > it's not the memcpy that BUGs, but once again check_preemption_disabled > > (which is noinstr!). Just adding calls anywhere here seems to results in > > unpredictable behaviour. Are we running out of stack space? > > Very likely, bad_iret is running on that entry_stack you found, and as > you found, it is puny. > > Andy wanted to make it a full page a while ago, so I suppose the > question is do we do that now?
Andy suggested doing the full page; untested patches here: git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git x86/entry
