linux-kernel - Re: [PATCH v6 2/2] arm64: enable context tracking

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Date:	Fri, 30 May 2014 19:23:49 +0100
From:	Will Deacon <will.deacon@....com>
To:	Larry Bassel <larry.bassel@...aro.org>
Cc:	Catalin Marinas <Catalin.Marinas@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	"khilman@...aro.org" <khilman@...aro.org>
Subject: Re: [PATCH v6 2/2] arm64: enable context tracking

On Thu, May 29, 2014 at 10:45:04PM +0100, Larry Bassel wrote:
> Make calls to ct_user_enter when the kernel is exited
> and ct_user_exit when the kernel is entered (in el0_da,
> el0_ia, el0_svc, el0_irq and all of the "error" paths).
> 
> These macros expand to function calls which will only work
> properly if el0_sync and related code has been rearranged
> (in a previous patch of this series).
> 
> The calls to ct_user_exit are made after hw debugging has been
> enabled (enable_dbg_and_irq).
> 
> The call to ct_user_enter is made at the beginning of the
> kernel_exit macro.
> 
> This patch is based on earlier work by Kevin Hilman.
> Save/restore optimizations were also done by Kevin.

Apparently I'm feeling pedantic today, one minor comment below...

> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> index b0101b9..3c484e2 100644
> --- a/arch/arm64/kernel/entry.S
> +++ b/arch/arm64/kernel/entry.S
> @@ -30,6 +30,32 @@
>  #include <asm/unistd32.h>
>  
>  /*
> + * Context tracking subsystem.  Used to instrument transitions
> + * between user and kernel mode.
> + */
> +	.macro ct_user_exit, restore = 0
> +#ifdef CONFIG_CONTEXT_TRACKING
> +	bl	context_tracking_user_exit
> +	.if \restore == 1

... I know we already changed this argument from \save, but maybe just
naming it \syscall makes most sense now?

If you make that change:

  Acked-by: Will Deacon <will.deacon@....com>

I'd like to give these some stress testing before it gets merged, so I'm
not sure if it'll make it for 3.16 given where we are at the moment.

Will
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