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

Peter Zijlstra
2018-11-20T18:21:04Z

On Tue, Nov 20, 2018 at 10:10:14AM -0800, H. Peter Anvin wrote:
> 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?

He does that in 9/10 iirc.