linux-kernel - Re: [PATCH] arm64: Initialize jump labels before setup_machine

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Date:   Thu, 2 Jun 2022 08:50:17 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, linux-kernel@...r.kernel.org,
        patches@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Dominik Brodowski <linux@...inikbrodowski.net>
Subject: Re: [PATCH] arm64: Initialize jump labels before setup_machine_fdt()

Hi Stephen,

On 6/2/22, Stephen Boyd <swboyd@...omium.org> wrote:
> A static key warning splat appears during early boot on arm64 systems
> that credit randomness from devicetrees that contain an "rng-seed"
> property. This is because setup_machine_fdt() is called before
> jump_label_init() during setup_arch(). Let's swap the order of these two
> calls so that jump labels are initialized before the devicetree is
> unflattened and the rng seed is credited.
>
>  static_key_enable_cpuslocked(): static key '0xffffffe51c6fcfc0' used before
> call to jump_label_init()
>  WARNING: CPU: 0 PID: 0 at kernel/jump_label.c:166
> static_key_enable_cpuslocked+0xb0/0xb8
>  Modules linked in:
>  CPU: 0 PID: 0 Comm: swapper Not tainted 5.18.0+ #224
> 44b43e377bfc84bc99bb5ab885ff694984ee09ff
>  pstate: 600001c9 (nZCv dAIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>  pc : static_key_enable_cpuslocked+0xb0/0xb8
>  lr : static_key_enable_cpuslocked+0xb0/0xb8
>  sp : ffffffe51c393cf0
>  x29: ffffffe51c393cf0 x28: 000000008185054c x27: 00000000f1042f10
>  x26: 0000000000000000 x25: 00000000f10302b2 x24: 0000002513200000
>  x23: 0000002513200000 x22: ffffffe51c1c9000 x21: fffffffdfdc00000
>  x20: ffffffe51c2f0831 x19: ffffffe51c6fcfc0 x18: 00000000ffff1020
>  x17: 00000000e1e2ac90 x16: 00000000000000e0 x15: ffffffe51b710708
>  x14: 0000000000000066 x13: 0000000000000018 x12: 0000000000000000
>  x11: 0000000000000000 x10: 00000000ffffffff x9 : 0000000000000000
>  x8 : 0000000000000000 x7 : 61632065726f6665 x6 : 6220646573752027
>  x5 : ffffffe51c641d25 x4 : ffffffe51c13142c x3 : ffff0a00ffffff05
>  x2 : 40000000ffffe003 x1 : 00000000000001c0 x0 : 0000000000000065
>  Call trace:
>   static_key_enable_cpuslocked+0xb0/0xb8
>   static_key_enable+0x2c/0x40
>   crng_set_ready+0x24/0x30
>   execute_in_process_context+0x80/0x90
>   _credit_init_bits+0x100/0x154
>   add_bootloader_randomness+0x64/0x78
>   early_init_dt_scan_chosen+0x140/0x184
>   early_init_dt_scan_nodes+0x28/0x4c
>   early_init_dt_scan+0x40/0x44
>   setup_machine_fdt+0x7c/0x120
>   setup_arch+0x74/0x1d8
>   start_kernel+0x84/0x44c
>   __primary_switched+0xc0/0xc8
>  ---[ end trace 0000000000000000 ]---
>  random: crng init done
>  Machine model: Google Lazor (rev1 - 2) with LTE
>
> Cc: Hsin-Yi Wang <hsinyi@...omium.org>
> Cc: Douglas Anderson <dianders@...omium.org>
> Cc: Ard Biesheuvel <ardb@...nel.org>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Jason A. Donenfeld <Jason@...c4.com>
> Cc: Dominik Brodowski <linux@...inikbrodowski.net>
> Fixes: f5bda35fba61 ("random: use static branch for crng_ready()")
> Signed-off-by: Stephen Boyd <swboyd@...omium.org>

Thanks for fixing this.

    Reviewed-by: Jason A. Donenfeld <Jason@...c4.com>

In looking at the matter more in depth, it looks like riscv does
things in the right order, but arm32 still does not. AFAICT, it uses
the logic in init/main.c, in which jump_label_init() is called before
setup_arch()->setup_machine_fdt(). Want to submit a patch for arm32?

Jason