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From:   Pavel Tatashin <pasha.tatashin@oracle.com>
Date:   Mon, 25 Jun 2018 10:06:10 -0400
Message-ID: <CAGM2reaOZiCsJbLonrZH0-uPQFLG4Xek0mJ4gNZe7K6iJFU=Xw@mail.gmail.com>
Subject: Re: [PATCH v12 01/11] x86: text_poke() may access uninitialized
 struct pages
To:     peterz@infradead.org
Cc:     tglx@linutronix.de, Steven Sistare <steven.sistare@oracle.com>,
        Daniel Jordan <daniel.m.jordan@oracle.com>,
        linux@armlinux.org.uk, schwidefsky@de.ibm.com,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        John Stultz <john.stultz@linaro.org>, sboyd@codeaurora.org,
        x86@kernel.org, LKML <linux-kernel@vger.kernel.org>,
        mingo@redhat.com, hpa@zytor.com, douly.fnst@cn.fujitsu.com,
        prarit@redhat.com, feng.tang@intel.com,
        Petr Mladek <pmladek@suse.com>, gnomes@lxorguk.ukuu.org.uk,
        linux-s390@vger.kernel.org, Steven Rostedt <rostedt@goodmis.org>
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> Also, I think the better condition is @early_boot_irqs_disabled, until
> we enable IRQs for the first time, text_poke_early() should be fine. And
> once we enable interrupts, all that other crud should really be working.

Sure, I will use early_boot_irqs_disabled flag. I think, we still want
to have BUG_ON(!after_bootmem); in text_poke(). I could do
BUG_ON(early_boot_irqs_disabled), but I am worried that there are call
sites that might be using text_poke() between mem_init() and
local_irq_enable() in start_kernel().

>
> This gives:
>
> diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
> index e56c95be2808..425ba6102828 100644
> --- a/arch/x86/kernel/jump_label.c
> +++ b/arch/x86/kernel/jump_label.c
> @@ -46,6 +46,9 @@ static void __jump_label_transform(struct jump_entry *entry,
>         const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
>         const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
>
> +       if (early_boot_irqs_disabled)
> +               poker = text_poke_early;
> +
>         if (type == JUMP_LABEL_JMP) {
>                 if (init) {
>                         /*
>
> > Also, modify text_poke_early to call sync_core().

Also, we still need to add __ref to __jump_label_transform as
text_poke_early() is __init