Re: [patch V4 part 3 09/29] x86/entry/32: Provide macro to emit IDT entry stubs

Andy Lutomirski
2020-05-14T04:31:48Z

On Wed, May 13, 2020 at 6:44 PM Mathieu Desnoyers
<mathieu.desnoyers@efficios.com> wrote:
>
> ----- On May 5, 2020, at 9:44 AM, Thomas Gleixner tglx@linutronix.de wrote:
>
> [...]
>
> > +.macro idtentry vector asmsym cfunc has_error_code:req sane=0
> > +SYM_CODE_START(\asmsym)
> > + ASM_CLAC
> > + cld
>
> Looking at the various interrupt and trap entry points for 32 and 64-bit
> x86, I notice a lack of consistency in use of the following instruction
> sequence at the asm entry point:
>
> - ASM_CLAC,
> - cld (clear direction flag).
>
> Are they always needed, or only for interrupt handlers ?

They're needed for all entries except SYSCALL, but they're hidden
inside helpers in many cases.