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

H. Peter Anvin
2018-11-20T18:11:32Z

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@kernel.org>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Dave Hansen <dave.hansen@intel.com>
> Cc: Masami Hiramatsu <mhiramat@kernel.org>
> Co-Developed-by: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Nadav Amit <namit@vmware.com>
> ---
> 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