linux-kernel - [PATCH 16/26] x86, pkeys: dump PKRU with other kernel registers

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Message-Id: <20150916174908.2B86AE47@viggo.jf.intel.com>
Date:	Wed, 16 Sep 2015 10:49:08 -0700
From:	Dave Hansen <dave@...1.net>
To:	dave@...1.net
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH 16/26] x86, pkeys: dump PKRU with other kernel registers


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.

Should we dump out PKRU like this in our oopses?

---

 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	2015-09-16 10:48:18.424290612 -0700
+++ b/arch/x86/kernel/process_64.c	2015-09-16 10:48:18.427290748 -0700
@@ -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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