1 files changed, 292 insertions, 0 deletions
diff --git a/arch/x86/include/asm/pgtable-3level.h b/arch/x86/include/asm/pgtable-3level.h
new file mode 100644
index 000000000..28421a887
--- /dev/null
+++ b/arch/x86/include/asm/pgtable-3level.h
@@ -0,0 +1,292 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_PGTABLE_3LEVEL_H
+#define _ASM_X86_PGTABLE_3LEVEL_H
+
+#include <asm/atomic64_32.h>
+
+/*
+ * Intel Physical Address Extension (PAE) Mode - three-level page
+ * tables on PPro+ CPUs.
+ *
+ * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
+ */
+
+#define pte_ERROR(e)							\
+	pr_err("%s:%d: bad pte %p(%08lx%08lx)\n",			\
+	       __FILE__, __LINE__, &(e), (e).pte_high, (e).pte_low)
+#define pmd_ERROR(e)							\
+	pr_err("%s:%d: bad pmd %p(%016Lx)\n",				\
+	       __FILE__, __LINE__, &(e), pmd_val(e))
+#define pgd_ERROR(e)							\
+	pr_err("%s:%d: bad pgd %p(%016Lx)\n",				\
+	       __FILE__, __LINE__, &(e), pgd_val(e))
+
+/* Rules for using set_pte: the pte being assigned *must* be
+ * either not present or in a state where the hardware will
+ * not attempt to update the pte.  In places where this is
+ * not possible, use pte_get_and_clear to obtain the old pte
+ * value and then use set_pte to update it.  -ben
+ */
+static inline void native_set_pte(pte_t *ptep, pte_t pte)
+{
+	ptep->pte_high = pte.pte_high;
+	smp_wmb();
+	ptep->pte_low = pte.pte_low;
+}
+
+#define pmd_read_atomic pmd_read_atomic
+/*
+ * pte_offset_map_lock() on 32-bit PAE kernels was reading the pmd_t with
+ * a "*pmdp" dereference done by GCC. Problem is, in certain places
+ * where pte_offset_map_lock() is called, concurrent page faults are
+ * allowed, if the mmap_lock is hold for reading. An example is mincore
+ * vs page faults vs MADV_DONTNEED. On the page fault side
+ * pmd_populate() rightfully does a set_64bit(), but if we're reading the
+ * pmd_t with a "*pmdp" on the mincore side, a SMP race can happen
+ * because GCC will not read the 64-bit value of the pmd atomically.
+ *
+ * To fix this all places running pte_offset_map_lock() while holding the
+ * mmap_lock in read mode, shall read the pmdp pointer using this
+ * function to know if the pmd is null or not, and in turn to know if
+ * they can run pte_offset_map_lock() or pmd_trans_huge() or other pmd
+ * operations.
+ *
+ * Without THP if the mmap_lock is held for reading, the pmd can only
+ * transition from null to not null while pmd_read_atomic() runs. So
+ * we can always return atomic pmd values with this function.
+ *
+ * With THP if the mmap_lock is held for reading, the pmd can become
+ * trans_huge or none or point to a pte (and in turn become "stable")
+ * at any time under pmd_read_atomic(). We could read it truly
+ * atomically here with an atomic64_read() for the THP enabled case (and
+ * it would be a whole lot simpler), but to avoid using cmpxchg8b we
+ * only return an atomic pmdval if the low part of the pmdval is later
+ * found to be stable (i.e. pointing to a pte). We are also returning a
+ * 'none' (zero) pmdval if the low part of the pmd is zero.
+ *
+ * In some cases the high and low part of the pmdval returned may not be
+ * consistent if THP is enabled (the low part may point to previously
+ * mapped hugepage, while the high part may point to a more recently
+ * mapped hugepage), but pmd_none_or_trans_huge_or_clear_bad() only
+ * needs the low part of the pmd to be read atomically to decide if the
+ * pmd is unstable or not, with the only exception when the low part
+ * of the pmd is zero, in which case we return a 'none' pmd.
+ */
+static inline pmd_t pmd_read_atomic(pmd_t *pmdp)
+{
+	pmdval_t ret;
+	u32 *tmp = (u32 *)pmdp;
+
+	ret = (pmdval_t) (*tmp);
+	if (ret) {
+		/*
+		 * If the low part is null, we must not read the high part
+		 * or we can end up with a partial pmd.
+		 */
+		smp_rmb();
+		ret |= ((pmdval_t)*(tmp + 1)) << 32;
+	}
+
+	return (pmd_t) { ret };
+}
+
+static inline void native_set_pte_atomic(pte_t *ptep, pte_t pte)
+{
+	set_64bit((unsigned long long *)(ptep), native_pte_val(pte));
+}
+
+static inline void native_set_pmd(pmd_t *pmdp, pmd_t pmd)
+{
+	set_64bit((unsigned long long *)(pmdp), native_pmd_val(pmd));
+}
+
+static inline void native_set_pud(pud_t *pudp, pud_t pud)
+{
+#ifdef CONFIG_PAGE_TABLE_ISOLATION
+	pud.p4d.pgd = pti_set_user_pgtbl(&pudp->p4d.pgd, pud.p4d.pgd);
+#endif
+	set_64bit((unsigned long long *)(pudp), native_pud_val(pud));
+}
+
+/*
+ * For PTEs and PDEs, we must clear the P-bit first when clearing a page table
+ * entry, so clear the bottom half first and enforce ordering with a compiler
+ * barrier.
+ */
+static inline void native_pte_clear(struct mm_struct *mm, unsigned long addr,
+				    pte_t *ptep)
+{
+	ptep->pte_low = 0;
+	smp_wmb();
+	ptep->pte_high = 0;
+}
+
+static inline void native_pmd_clear(pmd_t *pmd)
+{
+	u32 *tmp = (u32 *)pmd;
+	*tmp = 0;
+	smp_wmb();
+	*(tmp + 1) = 0;
+}
+
+static inline void native_pud_clear(pud_t *pudp)
+{
+}
+
+static inline void pud_clear(pud_t *pudp)
+{
+	set_pud(pudp, __pud(0));
+
+	/*
+	 * According to Intel App note "TLBs, Paging-Structure Caches,
+	 * and Their Invalidation", April 2007, document 317080-001,
+	 * section 8.1: in PAE mode we explicitly have to flush the
+	 * TLB via cr3 if the top-level pgd is changed...
+	 *
+	 * Currently all places where pud_clear() is called either have
+	 * flush_tlb_mm() followed or don't need TLB flush (x86_64 code or
+	 * pud_clear_bad()), so we don't need TLB flush here.
+	 */
+}
+
+#ifdef CONFIG_SMP
+static inline pte_t native_ptep_get_and_clear(pte_t *ptep)
+{
+	pte_t res;
+
+	res.pte = (pteval_t)arch_atomic64_xchg((atomic64_t *)ptep, 0);
+
+	return res;
+}
+#else
+#define native_ptep_get_and_clear(xp) native_local_ptep_get_and_clear(xp)
+#endif
+
+union split_pmd {
+	struct {
+		u32 pmd_low;
+		u32 pmd_high;
+	};
+	pmd_t pmd;
+};
+
+#ifdef CONFIG_SMP
+static inline pmd_t native_pmdp_get_and_clear(pmd_t *pmdp)
+{
+	union split_pmd res, *orig = (union split_pmd *)pmdp;
+
+	/* xchg acts as a barrier before setting of the high bits */
+	res.pmd_low = xchg(&orig->pmd_low, 0);
+	res.pmd_high = orig->pmd_high;
+	orig->pmd_high = 0;
+
+	return res.pmd;
+}
+#else
+#define native_pmdp_get_and_clear(xp) native_local_pmdp_get_and_clear(xp)
+#endif
+
+#ifndef pmdp_establish
+#define pmdp_establish pmdp_establish
+static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
+		unsigned long address, pmd_t *pmdp, pmd_t pmd)
+{
+	pmd_t old;
+
+	/*
+	 * If pmd has present bit cleared we can get away without expensive
+	 * cmpxchg64: we can update pmdp half-by-half without racing with
+	 * anybody.
+	 */
+	if (!(pmd_val(pmd) & _PAGE_PRESENT)) {
+		union split_pmd old, new, *ptr;
+
+		ptr = (union split_pmd *)pmdp;
+
+		new.pmd = pmd;
+
+		/* xchg acts as a barrier before setting of the high bits */
+		old.pmd_low = xchg(&ptr->pmd_low, new.pmd_low);
+		old.pmd_high = ptr->pmd_high;
+		ptr->pmd_high = new.pmd_high;
+		return old.pmd;
+	}
+
+	do {
+		old = *pmdp;
+	} while (cmpxchg64(&pmdp->pmd, old.pmd, pmd.pmd) != old.pmd);
+
+	return old;
+}
+#endif
+
+#ifdef CONFIG_SMP
+union split_pud {
+	struct {
+		u32 pud_low;
+		u32 pud_high;
+	};
+	pud_t pud;
+};
+
+static inline pud_t native_pudp_get_and_clear(pud_t *pudp)
+{
+	union split_pud res, *orig = (union split_pud *)pudp;
+
+#ifdef CONFIG_PAGE_TABLE_ISOLATION
+	pti_set_user_pgtbl(&pudp->p4d.pgd, __pgd(0));
+#endif
+
+	/* xchg acts as a barrier before setting of the high bits */
+	res.pud_low = xchg(&orig->pud_low, 0);
+	res.pud_high = orig->pud_high;
+	orig->pud_high = 0;
+
+	return res.pud;
+}
+#else
+#define native_pudp_get_and_clear(xp) native_local_pudp_get_and_clear(xp)
+#endif
+
+/* Encode and de-code a swap entry */
+#define SWP_TYPE_BITS		5
+
+#define SWP_OFFSET_FIRST_BIT	(_PAGE_BIT_PROTNONE + 1)
+
+/* We always extract/encode the offset by shifting it all the way up, and then down again */
+#define SWP_OFFSET_SHIFT	(SWP_OFFSET_FIRST_BIT + SWP_TYPE_BITS)
+
+#define MAX_SWAPFILES_CHECK() BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > SWP_TYPE_BITS)
+#define __swp_type(x)			(((x).val) & ((1UL << SWP_TYPE_BITS) - 1))
+#define __swp_offset(x)			((x).val >> SWP_TYPE_BITS)
+#define __swp_entry(type, offset)	((swp_entry_t){(type) | (offset) << SWP_TYPE_BITS})
+
+/*
+ * Normally, __swp_entry() converts from arch-independent swp_entry_t to
+ * arch-dependent swp_entry_t, and __swp_entry_to_pte() just stores the result
+ * to pte. But here we have 32bit swp_entry_t and 64bit pte, and need to use the
+ * whole 64 bits. Thus, we shift the "real" arch-dependent conversion to
+ * __swp_entry_to_pte() through the following helper macro based on 64bit
+ * __swp_entry().
+ */
+#define __swp_pteval_entry(type, offset) ((pteval_t) { \
+	(~(pteval_t)(offset) << SWP_OFFSET_SHIFT >> SWP_TYPE_BITS) \
+	| ((pteval_t)(type) << (64 - SWP_TYPE_BITS)) })
+
+#define __swp_entry_to_pte(x)	((pte_t){ .pte = \
+		__swp_pteval_entry(__swp_type(x), __swp_offset(x)) })
+/*
+ * Analogically, __pte_to_swp_entry() doesn't just extract the arch-dependent
+ * swp_entry_t, but also has to convert it from 64bit to the 32bit
+ * intermediate representation, using the following macros based on 64bit
+ * __swp_type() and __swp_offset().
+ */
+#define __pteval_swp_type(x) ((unsigned long)((x).pte >> (64 - SWP_TYPE_BITS)))
+#define __pteval_swp_offset(x) ((unsigned long)(~((x).pte) << SWP_TYPE_BITS >> SWP_OFFSET_SHIFT))
+
+#define __pte_to_swp_entry(pte)	(__swp_entry(__pteval_swp_type(pte), \
+					     __pteval_swp_offset(pte)))
+
+#include <asm/pgtable-invert.h>
+
+#endif /* _ASM_X86_PGTABLE_3LEVEL_H */