Re: [PATCH v5 02/10] x86/jump_label: Use text_poke_early() during early init

[H. Peter Anvin]

On 11/13/18 5:07 AM, Nadav Amit wrote:
> There is no apparent reason not to use text_poke_early() while we are
> during early-init and we do not patch code that might be on the stack
> (i.e., we'll return to the middle of the patched code). This appears to
> be the case of jump-labels, so do so.
> 
> This is required for the next patches that would set a temporary mm for
> patching, which is initialized after some static-keys are
> enabled/disabled.
> 
> Cc: Andy Lutomirski <luto@xxxxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
> Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> Co-Developed-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Signed-off-by: Nadav Amit <namit@xxxxxxxxxx>
> ---
>  arch/x86/kernel/jump_label.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
> index aac0c1f7e354..ed5fe274a7d8 100644
> --- a/arch/x86/kernel/jump_label.c
> +++ b/arch/x86/kernel/jump_label.c
> @@ -52,7 +52,12 @@ static void __ref __jump_label_transform(struct jump_entry *entry,
>  	jmp.offset = jump_entry_target(entry) -
>  		     (jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE);
>  
> -	if (early_boot_irqs_disabled)
> +	/*
> +	 * As long as we're UP and not yet marked RO, we can use
> +	 * text_poke_early; SYSTEM_BOOTING guarantees both, as we switch to
> +	 * SYSTEM_SCHEDULING before going either.
> +	 */
> +	if (system_state == SYSTEM_BOOTING)
>  		poker = text_poke_early;
>  
>  	if (type == JUMP_LABEL_JMP) {
> 

Can't we make this test in text_poke() directly, please?

	-hpa