x86/mm/dump_pagetables: Check PAGE_PRESENT for real

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>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index 5e3ac6fe6c9e32ed1906f4f9bf736310a7193c7d..1014cfb21c2c79204694dd87c16b381d7825c6c0 100644 (file)
--- 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 *m, pgprot_t prot, int level, bool dmsg)
        static const char * const level_name[] =
                { "cr3", "pgd", "p4d", "pud", "pmd", "pte" };
 
-       if (!pgprot_val(prot)) {
+       if (!(pr & _PAGE_PRESENT)) {
                /* Not present */
                pt_dump_cont_printf(m, dmsg, "                              ");
        } else {