----- On May 14, 2020, at 12:31 AM, Andy Lutomirski [email protected] wrote: > On Wed, May 13, 2020 at 6:44 PM Mathieu Desnoyers > <[email protected]> wrote: >> >> ----- On May 5, 2020, at 9:44 AM, Thomas Gleixner [email protected] 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.
Indeed, on x86-32 the macro SAVE_ALL contains cld. That architecture appears to be OK. What I am concerned about is the idtentry, idtentry_mce_db, and idtentry_df macros introduced in entry_64.S by this series. Those are supposed to be technically equivalent to the prior code, which indeed has the ASM_CLAC but no "cld". So maybe the cld happens to be hidden elsewhere, but I'm clearly missing it ? Or is it not needed for some reason ? Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
