linux-kernel - Re: [PATCH] arm64: Move jump_label_init() before parse_early

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Date:   Thu, 27 Jun 2019 09:30:03 +0200
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Alexander Potapenko <glider@...gle.com>, Qian Cai <cai@....pw>
Subject: Re: [PATCH] arm64: Move jump_label_init() before parse_early_param()

On Wed, 26 Jun 2019 at 22:51, Kees Cook <keescook@...omium.org> wrote:
>
> While jump_label_init() was moved earlier in the boot process in commit
> efd9e03facd0 ("arm64: Use static keys for CPU features"), it wasn't
> early enough for early params to use it. The old state of things was as
> described here...
>
> init/main.c calls out to arch-specific things before general jump
> label and early param handling:
>
> asmlinkage __visible void __init start_kernel(void)
> {
>         ...
>         setup_arch(&command_line);
>         ...
>         smp_prepare_boot_cpu();
>         ...
>         /* parameters may set static keys */
>         jump_label_init();
>         parse_early_param();
>         ...
> }
>
> x86 setup_arch() wants those earlier, so it handles jump label and
> early param:
>
> void __init setup_arch(char **cmdline_p)
> {
>         ...
>         jump_label_init();
>         ...
>         parse_early_param();
>         ...
> }
>
> arm64 setup_arch() only had early param:
>
> void __init setup_arch(char **cmdline_p)
> {
>         ...
>         parse_early_param();
>         ...
> }
>
> with jump label later in smp_prepare_boot_cpu():
>
> void __init smp_prepare_boot_cpu(void)
> {
>         ...
>         jump_label_init();
>         ...
> }
>
> This moves arm64 jump_label_init() from smp_prepare_boot_cpu() to
> setup_arch(), as done already on x86, in preparation from early param
> usage in the init_on_alloc/free() series:
> https://lkml.kernel.org/r/1561572949.5154.81.camel@lca.pw
>
> Signed-off-by: Kees Cook <keescook@...omium.org>

Acked-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>

> ---
>  arch/arm64/kernel/setup.c | 5 +++++
>  arch/arm64/kernel/smp.c   | 5 -----
>  2 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index 7e541f947b4c..9c4bad7d7131 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -283,6 +283,11 @@ void __init setup_arch(char **cmdline_p)
>
>         setup_machine_fdt(__fdt_pointer);
>
> +       /*
> +        * Initialise the static keys early as they may be enabled by the
> +        * cpufeature code and early parameters.
> +        */
> +       jump_label_init();
>         parse_early_param();
>
>         /*
> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> index 6dcf9607d770..20c456b3862c 100644
> --- a/arch/arm64/kernel/smp.c
> +++ b/arch/arm64/kernel/smp.c
> @@ -424,11 +424,6 @@ void __init smp_cpus_done(unsigned int max_cpus)
>  void __init smp_prepare_boot_cpu(void)
>  {
>         set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
> -       /*
> -        * Initialise the static keys early as they may be enabled by the
> -        * cpufeature code.
> -        */
> -       jump_label_init();
>         cpuinfo_store_boot_cpu();
>
>         /*
> --
> 2.17.1
>
>
> --
> Kees Cook