From: Junaid Shahid <junaids@xxxxxxxxxx> This adds custom allocation and free functions for ASI page tables. The alloc functions support allocating memory using different GFP reclaim flags, in order to be able to support non-sensitive allocations from both standard and atomic contexts. They also install the page tables locklessly, which makes it slightly simpler to handle non-sensitive allocations from interrupts/exceptions. Signed-off-by: Junaid Shahid <junaids@xxxxxxxxxx> Signed-off-by: Brendan Jackman <jackmanb@xxxxxxxxxx> --- arch/x86/mm/asi.c | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 59 insertions(+) diff --git a/arch/x86/mm/asi.c b/arch/x86/mm/asi.c index 0ba156f879d3..8798aab66748 100644 --- a/arch/x86/mm/asi.c +++ b/arch/x86/mm/asi.c @@ -71,6 +71,65 @@ void asi_unregister_class(int index) } EXPORT_SYMBOL_GPL(asi_unregister_class); +#ifndef mm_inc_nr_p4ds +#define mm_inc_nr_p4ds(mm) do {} while (false) +#endif + +#ifndef mm_dec_nr_p4ds +#define mm_dec_nr_p4ds(mm) do {} while (false) +#endif + +#define pte_offset pte_offset_kernel + +/* + * asi_p4d_alloc, asi_pud_alloc, asi_pmd_alloc, asi_pte_alloc. + * + * These are like the normal xxx_alloc functions, but: + * + * - They use atomic operations instead of taking a spinlock; this allows them + * to be used from interrupts. This is necessary because we use the page + * allocator from interrupts and the page allocator ultimately calls this + * code. + * - They support customizing the allocation flags. + * + * On the other hand, they do not use the normal page allocation infrastructure, + * that means that PTE pages do not have the PageTable type nor the PagePgtable + * flag and we don't increment the meminfo stat (NR_PAGETABLE) as they do. + */ +static_assert(!IS_ENABLED(CONFIG_PARAVIRT)); +#define DEFINE_ASI_PGTBL_ALLOC(base, level) \ +__maybe_unused \ +static level##_t * asi_##level##_alloc(struct asi *asi, \ + base##_t *base, ulong addr, \ + gfp_t flags) \ +{ \ + if (unlikely(base##_none(*base))) { \ + ulong pgtbl = get_zeroed_page(flags); \ + phys_addr_t pgtbl_pa; \ + \ + if (!pgtbl) \ + return NULL; \ + \ + pgtbl_pa = __pa(pgtbl); \ + \ + if (cmpxchg((ulong *)base, 0, \ + pgtbl_pa | _PAGE_TABLE) != 0) { \ + free_page(pgtbl); \ + goto out; \ + } \ + \ + mm_inc_nr_##level##s(asi->mm); \ + } \ +out: \ + VM_BUG_ON(base##_leaf(*base)); \ + return level##_offset(base, addr); \ +} + +DEFINE_ASI_PGTBL_ALLOC(pgd, p4d) +DEFINE_ASI_PGTBL_ALLOC(p4d, pud) +DEFINE_ASI_PGTBL_ALLOC(pud, pmd) +DEFINE_ASI_PGTBL_ALLOC(pmd, pte) + void __init asi_check_boottime_disable(void) { bool enabled = IS_ENABLED(CONFIG_MITIGATION_ADDRESS_SPACE_ISOLATION_DEFAULT_ON); -- 2.45.2.993.g49e7a77208-goog