Hi,
On Fri, Feb 10, 2017 at 04:56:19PM +0300, Andrey Ryabinin wrote:
> On 02/10/2017 04:02 PM, Dmitry Vyukov wrote:
> > On Fri, Feb 10, 2017 at 1:15 PM, Andrey Ryabinin
> > <aryabinin@xxxxxxxxxxxxx> wrote:
> >> On 02/10/2017 02:18 PM, Thomas Gleixner wrote:
> >>> On Fri, 10 Feb 2017, Dmitry Vyukov wrote:
> diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
> index 8aa6bea..1599a5c 100644
> --- a/arch/x86/mm/dump_pagetables.c
> +++ b/arch/x86/mm/dump_pagetables.c
> @@ -373,6 +373,11 @@ static inline bool is_hypervisor_range(int idx)
> #endif
> }
>
> +static bool pgd_already_checked(pgd_t *prev_pgd, pgd_t *pgd, bool checkwx)
> +{
> + return checkwx && prev_pgd && (pgd_val(*prev_pgd) == pgd_val(*pgd));
> +}
> +
> static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
> bool checkwx)
> {
> @@ -381,6 +386,7 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
> #else
> pgd_t *start = swapper_pg_dir;
> #endif
> + pgd_t *prev_pgd = NULL;
> pgprotval_t prot;
> int i;
> struct pg_state st = {};
> @@ -396,7 +402,8 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
>
> for (i = 0; i < PTRS_PER_PGD; i++) {
> st.current_address = normalize_addr(i * PGD_LEVEL_MULT);
> - if (!pgd_none(*start) && !is_hypervisor_range(i)) {
> + if (!pgd_none(*start) && !is_hypervisor_range(i) &&
> + !pgd_already_checked(prev_pgd, start, checkwx)) {
This means we'll fall into the else case...
> if (pgd_large(*start) || !pgd_present(*start)) {
> prot = pgd_flags(*start);
> note_page(m, &st, __pgprot(prot), 1);
> @@ -408,6 +415,7 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
> note_page(m, &st, __pgprot(0), 1);
... i.e. the note_page() here, where we'll claim that the's nothing
present due to the empty prot.
That'll give erroneous output for the userspace pagetable dumps, so I do
not think this is quite right, even though it gives a boot-time speedup.
Thanks,
Mark.
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