Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH v3 28/46] kmsan: entry: handle register passing from uninstrumented code | Date | Wed, 27 Apr 2022 15:32:23 +0200 |
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On Tue, Apr 26 2022 at 18:42, Alexander Potapenko wrote:
Can you please use 'entry:' as prefix. Slapping kmsan in front of everything does not really make sense.
> Replace instrumentation_begin() with instrumentation_begin_with_regs() > to let KMSAN handle the non-instrumented code and unpoison pt_regs > passed from the instrumented part.
That should be:
from the non-instrumented part or passed to the instrumented part
right?
> --- a/kernel/entry/common.c > +++ b/kernel/entry/common.c > @@ -23,7 +23,7 @@ static __always_inline void __enter_from_user_mode(struct pt_regs *regs) > CT_WARN_ON(ct_state() != CONTEXT_USER); > user_exit_irqoff(); > > - instrumentation_begin(); > + instrumentation_begin_with_regs(regs);
I can see what you are trying to do, but this will end up doing the same thing over and over. Let's just look at a syscall.
__visible noinstr void do_syscall_64(struct pt_regs *regs, int nr) { ... nr = syscall_enter_from_user_mode(regs, nr)
__enter_from_user_mode(regs) ..... instrumentation_begin_with_regs(regs); ....
instrumentation_begin_with_regs(regs); ....
instrumentation_begin_with_regs(regs);
if (!do_syscall_x64(regs, nr) && !do_syscall_x32(regs, nr) && nr != -1) { /* Invalid system call, but still a system call. */ regs->ax = __x64_sys_ni_syscall(regs); }
instrumentation_end();
syscall_exit_to_user_mode(regs); instrumentation_begin_with_regs(regs); __syscall_exit_to_user_mode_work(regs); instrumentation_end(); __exit_to_user_mode();
That means you memset state four times and unpoison regs four times. I'm not sure whether that's desired.
instrumentation_begin()/end() are not really suitable IMO. They were added to allow objtool to validate that nothing escapes into instrumentable code unless annotated accordingly.
Thanks,
tglx
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