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    SubjectRe: [patch V163 01/51] x86/mm/dump_pagetables: Check PAGE_PRESENT for real
    On Mon, Dec 18, 2017 at 12:42:16PM +0100, Thomas Gleixner wrote:
    > 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)) {

    Just a minor thing: there's a local pr variable a couple of lines up
    which is pgprot_val(prot). So you could do additionally:

    diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
    index dd8820e5da28..1014cfb21c2c 100644
    --- 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) & _PAGE_PRESENT)) {
    + if (!(pr & _PAGE_PRESENT)) {
    /* Not present */
    pt_dump_cont_printf(m, dmsg, " ");
    } else {
    --
    Regardless,

    Reviewed-by: Borislav Petkov <bp@suse.de>

    --
    Regards/Gruss,
    Boris.

    SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
    --

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