linux-kernel - [PATCH 21/31] x86, pkeys: dump PKRU with other kernel registers

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Message-Id: <20160129181712.EEDD7B1F@viggo.jf.intel.com>
Date:	Fri, 29 Jan 2016 10:17:12 -0800
From:	Dave Hansen <dave@...1.net>
To:	linux-kernel@...r.kernel.org
Cc:	linux-mm@...ck.org, x86@...nel.org, torvalds@...ux-foundation.org,
	Dave Hansen <dave@...1.net>, dave.hansen@...ux.intel.com
Subject: [PATCH 21/31] x86, pkeys: dump PKRU with other kernel registers


From: Dave Hansen <dave.hansen@...ux.intel.com>

Protection Keys never affect kernel mappings.  But, they can
affect whether the kernel will fault when it touches a user
mapping.  The kernel doesn't touch user mappings without some
careful choreography and these accesses don't generally result in
oopses.  But, if one does, we definitely want to have PKRU
available so we can figure out if protection keys played a role.

Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
---

 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	2016-01-28 15:52:25.978661494 -0800
+++ b/arch/x86/kernel/process_64.c	2016-01-28 15:52:25.981661632 -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)
_