On Fri, Sep 18, 2020 at 3:25 PM Pavel Machek <[email protected]> wrote: > > On Tue 2020-09-15 11:36:13, Roman Kiryanov wrote: > > On Tue, Sep 15, 2020 at 11:27 AM Borislav Petkov <[email protected]> wrote: > > > > I believe the kernel makes a questionable assumption on how clang > > > > uses registers (gs will not be used if stack protection is disabled). > > > > Both kernel and clang behaves unfortunate here. > > > > > > If the kernel is at fault here and this same thing happens with GCC, > > > sure, but this is a clang-specific fix. > > > > This is fair. Unfortunately I am not an x86 asm expert. I expect the proper > > fix should land into arch/x86/kernel/acpi/wakeup_64.S to init %gs > > (maybe some more registers) before "jmp restore_processor_state". > > That would certainly be nicer / more acceptable solution than patch > being proposed here. > > Code was written with assumption compiler random C code would not use > %gs. If that's no longer true, fixing it in wakeup_64.S _with comments > explaining what goes on_ might be solution.
I looked and restore_processor_state is referenced in several places, so changing wakeup_64.S is not enough. Is moving the beginning of restore_processor_state to an .S file ok? I see restore_processor_state initializes CR registers first, do you know if there is a reason to do so (can I init segment registers before CR ones)? Regards, Roman.
