Messages in this thread | | | Date | Sat, 19 Feb 2022 10:39:00 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 17/29] x86/ibt: Annotate text references |
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On Fri, Feb 18, 2022 at 09:22:16PM -0800, Josh Poimboeuf wrote: > On Fri, Feb 18, 2022 at 05:49:19PM +0100, Peter Zijlstra wrote: > > Annotate away some of the generic code references. This is things > > where we take the address of a symbol for exception handling or return > > addresses (eg. context switch). > > > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > > The vast majority of these annotations can go away if objtool only > requires ENDBR for referenced *STT_FUNC* symbols. > > Anything still needing ANNOTATE_NOENDBR after that, might arguably not > belong as STT_FUNC anyway and it might make sense to convert it to > non-function code (e.g. SYM_CODE{START,END}.
I really rather prefer objtool to err to the side of caution for now. Missing ENDBR typically bricks a box hard, normal consoles don't get around to showing anything. My force_early_printk patches saved the day a number of times.
Given that the only hardware I have with this on is a NUC without serial, this is a massive pain in the arse to debug. That box has been >< close to total destruction a number of times. I never want to do that ever again, life's too short to have to work with a NUC.
> > @@ -564,12 +565,16 @@ SYM_CODE_END(\asmsym) > > .align 16 > > .globl __irqentry_text_start > > __irqentry_text_start: > > + ANNOTATE_NOENDBR // unwinders > > + ud2; > > > > #include <asm/idtentry.h> > > > > .align 16 > > .globl __irqentry_text_end > > __irqentry_text_end: > > + ANNOTATE_NOENDBR > > + ud2; > > Why ud2? If no ud2 then the annotation shouldn't be needed since the > first idt entry has ENDBR.
paranoia :-) just to make absolutely sure nobody ever tries to call __irqentry_text_end, but yes, removed it.
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