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

[Kees Cook]

On Thu, Feb 24, 2022 at 03:51:45PM +0100, Peter Zijlstra wrote:
> 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.

Stupid question: does CET consider exception and syscall entry points to
be indirect calls? (I would expect so, but they're ever so slightly
differently executed...)

> [...]
>  0 :
> +	ENDBR
>  	.byte	0x6a, vector
>  	jmp	asm_common_interrupt
> -	nop
> -	/* Ensure that the above is 8 bytes max */
> -	. = 0b + 8
> +	/* Ensure that the above is IDT_ALIGN bytes max */
> +	.fill 0b + IDT_ALIGN - ., 1, 0x90

IIUC, these are just padding -- let's use 0xcc instead of 0x90 as we do
in other places (e.g. vmlinux.lds.S).

-- 
Kees Cook