On Mon, Jun 15, 2020 at 04:53:36PM +0200, Marco Elver wrote: > On Mon, 15 Jun 2020, Peter Zijlstra wrote: > > > On Mon, Jun 15, 2020 at 09:53:06AM +0200, Marco Elver wrote: > > > > > > Disabling KCOV for smp_processor_id now moves the crash elsewhere. In > > > the case of KASAN into its 'memcpy' wrapper, called after > > > __this_cpu_read in fixup_bad_iret. This is making me suspicious, > > > because it shouldn't be called from the noinstr functions. > > > > With your .config, objtool complains about exactly that though: > > > > vmlinux.o: warning: objtool: fixup_bad_iret()+0x8e: call to memcpy() leaves > > .noinstr.text section > > > > The utterly gruesome thing below 'cures' that. > > Is __memcpy() generally available? I think that bypasses KASAN and > whatever else.
Yes, I think so. x86_64 needs lib/memcpy_64.S in .noinstr.text then. For i386 it's an __always_inline inline-asm thing.
