linux-kernel - Re: [PATCH v2] xen x86: fix early boot crash with gcc-10

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Message-ID: <20200413174130.GE3772@zn.tnic>
Date:   Mon, 13 Apr 2020 19:41:30 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     boris.ostrovsky@...cle.com, jgross@...e.com
Cc:     Frédéric Pierret (fepitre) 
        <frederic.pierret@...es-os.org>, sstabellini@...nel.org,
        tglx@...utronix.de, mingo@...hat.com, x86@...nel.org,
        hpa@...or.com, xen-devel@...ts.xenproject.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] xen x86: fix early boot crash with gcc-10

On Mon, Apr 13, 2020 at 05:03:14PM +0200, Frédéric Pierret (fepitre) wrote:
> The change fixes boot failure on VM where kernel (at least v5.4 and v5.6)
> is built with gcc-10 and STACKPROTECTOR_STRONG enabled:
> 
> ```
> Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: cpu_bringup_and_idle+0x93/0xa0
> CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.4.31-1.qubes.x86_64 #1
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.12.0-1 04/01/2014
> Call Trace:
>   dump_stack+0x64/0x88
>    panic+0x10b/0x2ed
>    ? cpu_bringup_and_idle+0x93/0xa0
>    __stack_chk_fail+0x15/0x20
>    cpu_bringup_and_idle+0x93/0xa
> ```
> The change makes successfully booting the VM. The VM is hosted by
> KVM hypervisor and is running Xen into.
> 
> Based on work done by Sergei Trofimovich: https://lkml.org/lkml/2020/3/26/1133
> 
> Signed-off-by: Frédéric Pierret (fepitre) <frederic.pierret@...es-os.org>
> ---
>  arch/x86/xen/smp_pv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c
> index 8fb8a50a28b4..5c8ee4a5bb0c 100644
> --- a/arch/x86/xen/smp_pv.c
> +++ b/arch/x86/xen/smp_pv.c
> @@ -88,7 +88,7 @@ static void cpu_bringup(void)
>  	local_irq_enable();
>  }
>  
> -asmlinkage __visible void cpu_bringup_and_idle(void)
> +asmlinkage __visible void __no_stack_protector cpu_bringup_and_idle(void)
>  {
>  	cpu_bringup();
>  	boot_init_stack_canary();
> -- 

Boris O, Jürgen,

you guys might wanna wait a bit with this one:

https://lkml.kernel.org/r/20200413163540.GD3772@zn.tnic

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette