Re: [PATCH v2 07/39] x86/entry: Sprinkle ENDBR dust

[Josh Poimboeuf]

On Thu, Feb 24, 2022 at 03:51:45PM +0100, Peter Zijlstra wrote:
> Kernel entry points should be having ENDBR on for IBT configs.
> 
> The SYSCALL entry points are found through taking their respective
> address in order to program them in the MSRs, while the exception
> entry points are found through UNWIND_HINT_IRET_REGS.
> 
> The rule is that any UNWIND_HINT_IRET_REGS at sym+0 should have an
> ENDBR, see the later objtool ibt validation patch.

Could the "rule" be changed to only check global syms?  It seems
unlikely a local symbol would need ENDBR.

Then you wouldn't need this annotation:

>  SYM_CODE_START_LOCAL(early_idt_handler_common)
> +	UNWIND_HINT_IRET_REGS offset=16
> +	ANNOTATE_NOENDBR
>  	/*
>  	 * The stack is the hardware frame, an error code or zero, and the
>  	 * vector number.

-- 
Josh