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Date: Mon, 18 Dec 2017 12:42:16 +0100
From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: x86@kernel.org, Linus Torvalds <torvalds@linux-foundation.org>,
        Andy Lutomirsky <luto@kernel.org>,
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Subject: [patch V163 01/51] x86/mm/dump_pagetables: Check PAGE_PRESENT for real
References: <20171218114215.239543034@linutronix.de>
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From: Thomas Gleixner <tglx@linutronix.de>

The check for a present page in printk_prot():

       if (!pgprot_val(prot)) {
                /* Not present */

is bogus. If a PTE is set to PAGE_NONE then the pgprot_val is not zero and
the entry is decoded in bogus ways, e.g. as RX GLB. That is confusing when
analyzing mapping correctness. Check for the present bit to make an
informed decision.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/mm/dump_pagetables.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -140,7 +140,7 @@ static void printk_prot(struct seq_file
 	static const char * const level_name[] =
 		{ "cr3", "pgd", "p4d", "pud", "pmd", "pte" };
 
-	if (!pgprot_val(prot)) {
+	if (!(pgprot_val(prot) & _PAGE_PRESENT)) {
 		/* Not present */
 		pt_dump_cont_printf(m, dmsg, "                              ");
 	} else {