linux-kernel - Re: [PATCH] static_key: Improve uninizialized key warning

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Message-ID: <20171018071514.191d0506@gandalf.local.home>
Date:   Wed, 18 Oct 2017 07:15:14 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        Ingo Molnar <mingo@...nel.org>,
        Juergen Gross <jgross@...e.com>,
        Jason Baron <jbaron@...mai.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] static_key: Improve uninizialized key warning

On Wed, 18 Oct 2017 12:39:13 +0200
Borislav Petkov <bp@...en8.de> wrote:

> From: Borislav Petkov <bp@...e.de>
> 
> Right now it says:
> 
>   static_key_disable_cpuslocked used before call to jump_label_init
>   ------------[ cut here ]------------
>   WARNING: CPU: 0 PID: 0 at kernel/jump_label.c:161 static_key_disable_cpuslocked+0x68/0x70
>   Modules linked in:
>   CPU: 0 PID: 0 Comm: swapper Not tainted 4.14.0-rc5+ #1
>   Hardware name: SGI.COM C2112-4GP3/X10DRT-P-Series, BIOS 2.0a 05/09/2016
>   task: ffffffff81c0e480 task.stack: ffffffff81c00000
>   RIP: 0010:static_key_disable_cpuslocked+0x68/0x70
>   RSP: 0000:ffffffff81c03ef0 EFLAGS: 00010096 ORIG_RAX: 0000000000000000
>   RAX: 0000000000000041 RBX: ffffffff81c32680 RCX: ffffffff81c5cbf8
>   RDX: 0000000000000001 RSI: 0000000000000092 RDI: 0000000000000002
>   RBP: ffff88807fffd240 R08: 726f666562206465 R09: 0000000000000136
>   R10: 0000000000000000 R11: 696e695f6c656261 R12: ffffffff82158900
>   R13: ffffffff8215f760 R14: 0000000000000001 R15: 0000000000000008
>   FS:  0000000000000000(0000) GS:ffff883f7f400000(0000) knlGS:0000000000000000
>   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   CR2: ffff88807ffff000 CR3: 0000000001c09000 CR4: 00000000000606b0
>   Call Trace:
>    static_key_disable+0x16/0x20
>    start_kernel+0x15a/0x45d
>    ? load_ucode_intel_bsp+0x11/0x2d
>    secondary_startup_64+0xa5/0xb0
>   Code: 48 c7 c7 a0 15 cf 81 e9 47 53 4b 00 48 89 df e8 5f fc ff ff eb e8 48 c7 c6 \
> 	c0 97 83 81 48 c7 c7 d0 ff a2 81 31 c0 e8 c5 9d f5 ff <0f> ff eb a7 0f ff eb \
> 	b0 e8 eb a2 4b 00 53 48 89 fb e8 42 0e f0
> 
> but it doesn't tell me which key it is. So dump its address too:
> 
>   static_key_disable_cpuslocked, key ffffffff81c32680 used before call to jump_label_init
> 
> so that it can be found:
> 
>   $ objdump -D vmlinux | grep ffffffff81c32680
>   ffffffff81c32680 <virt_spin_lock_key>:
>   ffffffff81c32680:       01 00                   add    %eax,(%rax)
> 
> The problem is then obvious:
> 
>   smp_prepare_boot_cpu() ->
>   native_smp_prepare_boot_cpu()->
>   native_pv_lock_init()
> 
> which disables that key gets called before jump_label_init().
> 
> Signed-off-by: Borislav Petkov <bp@...e.de>
>


Acked-by: Steven Rostedt <rostedt@...dmis.org>

-- Steve