On Fri, Sep 21, 2018 at 08:05:46AM -0700, Yu-cheng Yu wrote:
> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
> index bffa9ef47832..230f65ee881e 100644
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c
> @@ -434,6 +435,23 @@ static __init int setup_disable_shstk(char *s)
> __setup("no_cet_shstk", setup_disable_shstk);
> #endif
>
> +#ifdef CONFIG_X86_INTEL_BRANCH_TRACKING_USER
> +static __init int setup_disable_ibt(char *s)
> +{
> + /* require an exact match without trailing characters */
> + if (strlen(s))
> + return 0;
"s[0] (!= '\0')" will do the same check in constant time.
