linux-kernel - Re: [RFC PATCH] irqchip/gic-v3: Make gic_handle

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <237b00d0-8a8d-ede6-91b1-c3e23e61925c@arm.com>
Date:   Fri, 29 Mar 2019 13:58:40 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Zenghui Yu <yuzenghui@...wei.com>, julien.thierry@....com,
        rostedt@...dmis.org
Cc:     mingo@...hat.com, catalin.marinas@....com, will.deacon@....com,
        mark.rutland@....com, linux@...linux.org.uk, james.morse@....com,
        suzuki.poulose@....com, wanghaibin.wang@...wei.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] irqchip/gic-v3: Make gic_handle_irq() notrace

Hi Zenghui,

On 29/03/2019 13:23, Zenghui Yu wrote:
> Enable pseudo NMI together with function_graph tracer, will lead
> the system to a hang. This is easy to reproduce,
> 
>   1) Set "irqchip.gicv3_pseudo_nmi=1" on the kernel command line
>   2) echo function_graph > /sys/kernel/debug/tracing/current_tracer
> 
> This patch (RFC) set gic_handle_irq() as notrace and it seems works
> fine now. But I have no idea about what the issue is exactly, and
> you can regard this patch as a report then :)
> 
> Can someone give a look at it and provide some explanations ?
> 
> Thanks!
> 
> Cc: Julien Thierry <julien.thierry@....com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Signed-off-by: Zenghui Yu <yuzenghui@...wei.com>
> ---
>  drivers/irqchip/irq-gic-v3.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
> index 15e55d3..8d0c25f 100644
> --- a/drivers/irqchip/irq-gic-v3.c
> +++ b/drivers/irqchip/irq-gic-v3.c
> @@ -487,7 +487,7 @@ static inline void gic_handle_nmi(u32 irqnr, struct pt_regs *regs)
>  		gic_deactivate_unhandled(irqnr);
>  }
>  
> -static asmlinkage void __exception_irq_entry gic_handle_irq(struct pt_regs *regs)
> +static asmlinkage notrace void __exception_irq_entry gic_handle_irq(struct pt_regs *regs)
>  {
>  	u32 irqnr;
>  
> 


That's interesting. Do you have any out of tree patch that actually
makes use of the pseudo-NMI feature? Without those patches, the
behaviour should stay unchanged.

On the other hand, if you can generate pseudo-NMIs, you could end-up
tracing gic_handle_irq whilst being inside the tracing code with
interrupts being notionally disabled (and that could be pretty bad).

So, patches or no patches?

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...