linux-kernel - Re: [PATCH 21/34] x86, pkeys: dump PKRU with other kernel registers

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Date:	Tue, 8 Dec 2015 19:19:08 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Dave Hansen <dave@...1.net>
cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
	dave.hansen@...ux.intel.com
Subject: Re: [PATCH 21/34] x86, pkeys: dump PKRU with other kernel
 registers

On Thu, 3 Dec 2015, Dave Hansen wrote:

> 
> From: Dave Hansen <dave.hansen@...ux.intel.com>
> 
> I'm a bit ambivalent about whether this is needed or not.
>
> Protection Keys never affect kernel mappings.  But, they can
> affect whether the kernel will fault when it touches a user
> mapping.  But, the kernel doesn't touch user mappings without
> some careful choreography and these accesses don't generally
> result in oopses.

Well, if we miss some careful choreography at some place, this
information is going to be helpful.

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
 
> Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
> ---
> 
>  b/arch/x86/kernel/process_64.c |    2 ++
>  1 file changed, 2 insertions(+)
> 
> diff -puN arch/x86/kernel/process_64.c~pkeys-30-kernel-error-dumps arch/x86/kernel/process_64.c
> --- a/arch/x86/kernel/process_64.c~pkeys-30-kernel-error-dumps	2015-12-03 16:21:27.874773264 -0800
> +++ b/arch/x86/kernel/process_64.c	2015-12-03 16:21:27.877773400 -0800
> @@ -116,6 +116,8 @@ void __show_regs(struct pt_regs *regs, i
>  	printk(KERN_DEFAULT "DR0: %016lx DR1: %016lx DR2: %016lx\n", d0, d1, d2);
>  	printk(KERN_DEFAULT "DR3: %016lx DR6: %016lx DR7: %016lx\n", d3, d6, d7);
>  
> +	if (boot_cpu_has(X86_FEATURE_OSPKE))
> +		printk(KERN_DEFAULT "PKRU: %08x\n", read_pkru());
>  }
>  
>  void release_thread(struct task_struct *dead_task)
> _
> 
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