On 07/15/2015 07:37 PM, Catalin Marinas wrote:
> Ok, so simply taking the call out of the loop won't work unless we
> conditionally define these functions (wouldn't be too bad since we have
> some #if CONFIG_PGTABLE_LEVELS already introduced by this patch but it
> would be nicer without).
>
> Anyway, I think we can keep the current iterations but exit early if
> !pud_none() because it means we already populated it (reworked to match
> other such patterns throughout the kernel with pgd_populate called from
> the pud function; and untested):
>
> void kasan_early_pmd_populate(pud_t *pud, unsigned long addr, unsigned long end)
> {
> pmd_t *pmd;
> unsigned long next;
>
> if (pud_none(*pud))
> pud_populate(&init_mm, pud, kasan_zero_pmd);
>
> pmd = pmd_offset(pud, addr);
> do {
> next = pmd_addr_end(addr, end);
> kasan_early_pte_populate(pmd, addr, next);
> } while (pmd++, addr = next, addr != end && pmd_none(*pmd));
> }
>
> void kasan_early_pud_populate(pgd_t *pgd, unsigned long addr, unsigned long end)
> {
> pud_t *pud;
> unsigned long next;
>
> if (pgd_none(*pgd))
> pgd_populate(&init_mm, pgd, kasan_zero_pud);
>
> pud = pud_offset(pgd, addr);
> do {
> next = pud_addr_end(addr, end);
> kasan_early_pmd_populate(pud, addr, next);
> } while (pud++, addr = next, addr != end && pud_none(*pud));
> }
>
> Given that we check pud_none() after the first iterations, it covers the
> lower levels if needed.
>
I think this may work, if pud_none(*pud) will be replaced with !pud_val(*pud).
We can't use pud_none() because with 2-level page tables it's always false, so
we will never go down to pmd level where swapper_pg_dir populated.
But you gave me another idea how we could use p?d_none() and avoid rewriting table entries:
void kasan_early_pmd_populate(unsigned long start, unsigned long end, pte_t *pte)
{
unsigned long addr = start;
long next;
do {
pgd_t *pgd = pgd_offset_k(addr);
pud_t *pud = pud_offset(pgd, addr);
pmd_t *pmd = pmd_offset(pud, addr);
if (!pmd_none(*pmd))
break;
pmd_populate_kernel(&init_mm, pmd, pte);
next = pgd_addr_end(addr, end);
next = pud_addr_end(addr, next)
next = pmd_addr_end(addr, next);
} while(addr = next, addr != end);
}
void kasan_early_pud_populate(unsigned long start, unsigned long end, pmd_t *pmd)
{
unsigned long addr = start;
long next;
do {
pgd_t *pgd = pgd_offset_k(addr);
pud_t *pud = pud_offset(pgd, addr);
if (!pud_none(*pud))
break;
pud_populate(&init_mm, pud, pmd);
next = pud_addr_end(addr, pgd_addr_end(addr, end));
} while(addr = next, addr != end);
}
void kasan_early_pgd_populate(...)
{
//something similar to above
....
}
static void __init kasan_map_early_shadow(void)
{
kasan_early_pgd_populate(KASAN_SHADOW_START, KASAN_SHADOW_END, kasan_zero_pud);
kasan_early_pud_populate(KASAN_SHADOW_START, KASAN_SHADOW_END, kasan_zero_pmd);
kasan_early_pmd_populate(KASAN_SHADOW_START, KASAN_SHADOW_END, kasan_zero_pte);
kasan_early_pte_populate();
}
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