1 files changed, 462 insertions, 0 deletions
diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
new file mode 100644
index 000000000..faaf33e20
--- /dev/null
+++ b/arch/powerpc/mm/pgtable.c
@@ -0,0 +1,462 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * This file contains common routines for dealing with free of page tables
+ * Along with common page table handling code
+ *
+ *  Derived from arch/powerpc/mm/tlb_64.c:
+ *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
+ *
+ *  Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
+ *  and Cort Dougan (PReP) (cort@cs.nmt.edu)
+ *    Copyright (C) 1996 Paul Mackerras
+ *
+ *  Derived from "arch/i386/mm/init.c"
+ *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
+ *
+ *  Dave Engebretsen <engebret@us.ibm.com>
+ *      Rework for PPC64 port.
+ */
+
+#include <linux/kernel.h>
+#include <linux/gfp.h>
+#include <linux/mm.h>
+#include <linux/percpu.h>
+#include <linux/hardirq.h>
+#include <linux/hugetlb.h>
+#include <asm/tlbflush.h>
+#include <asm/tlb.h>
+#include <asm/hugetlb.h>
+
+static inline int is_exec_fault(void)
+{
+	return current->thread.regs && TRAP(current->thread.regs) == 0x400;
+}
+
+/* We only try to do i/d cache coherency on stuff that looks like
+ * reasonably "normal" PTEs. We currently require a PTE to be present
+ * and we avoid _PAGE_SPECIAL and cache inhibited pte. We also only do that
+ * on userspace PTEs
+ */
+static inline int pte_looks_normal(pte_t pte)
+{
+
+	if (pte_present(pte) && !pte_special(pte)) {
+		if (pte_ci(pte))
+			return 0;
+		if (pte_user(pte))
+			return 1;
+	}
+	return 0;
+}
+
+static struct page *maybe_pte_to_page(pte_t pte)
+{
+	unsigned long pfn = pte_pfn(pte);
+	struct page *page;
+
+	if (unlikely(!pfn_valid(pfn)))
+		return NULL;
+	page = pfn_to_page(pfn);
+	if (PageReserved(page))
+		return NULL;
+	return page;
+}
+
+#ifdef CONFIG_PPC_BOOK3S
+
+/* Server-style MMU handles coherency when hashing if HW exec permission
+ * is supposed per page (currently 64-bit only). If not, then, we always
+ * flush the cache for valid PTEs in set_pte. Embedded CPU without HW exec
+ * support falls into the same category.
+ */
+
+static pte_t set_pte_filter_hash(pte_t pte)
+{
+	if (radix_enabled())
+		return pte;
+
+	pte = __pte(pte_val(pte) & ~_PAGE_HPTEFLAGS);
+	if (pte_looks_normal(pte) && !(cpu_has_feature(CPU_FTR_COHERENT_ICACHE) ||
+				       cpu_has_feature(CPU_FTR_NOEXECUTE))) {
+		struct page *pg = maybe_pte_to_page(pte);
+		if (!pg)
+			return pte;
+		if (!test_bit(PG_arch_1, &pg->flags)) {
+			flush_dcache_icache_page(pg);
+			set_bit(PG_arch_1, &pg->flags);
+		}
+	}
+	return pte;
+}
+
+#else /* CONFIG_PPC_BOOK3S */
+
+static pte_t set_pte_filter_hash(pte_t pte) { return pte; }
+
+#endif /* CONFIG_PPC_BOOK3S */
+
+/* Embedded type MMU with HW exec support. This is a bit more complicated
+ * as we don't have two bits to spare for _PAGE_EXEC and _PAGE_HWEXEC so
+ * instead we "filter out" the exec permission for non clean pages.
+ */
+static inline pte_t set_pte_filter(pte_t pte)
+{
+	struct page *pg;
+
+	if (mmu_has_feature(MMU_FTR_HPTE_TABLE))
+		return set_pte_filter_hash(pte);
+
+	/* No exec permission in the first place, move on */
+	if (!pte_exec(pte) || !pte_looks_normal(pte))
+		return pte;
+
+	/* If you set _PAGE_EXEC on weird pages you're on your own */
+	pg = maybe_pte_to_page(pte);
+	if (unlikely(!pg))
+		return pte;
+
+	/* If the page clean, we move on */
+	if (test_bit(PG_arch_1, &pg->flags))
+		return pte;
+
+	/* If it's an exec fault, we flush the cache and make it clean */
+	if (is_exec_fault()) {
+		flush_dcache_icache_page(pg);
+		set_bit(PG_arch_1, &pg->flags);
+		return pte;
+	}
+
+	/* Else, we filter out _PAGE_EXEC */
+	return pte_exprotect(pte);
+}
+
+static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma,
+				     int dirty)
+{
+	struct page *pg;
+
+	if (mmu_has_feature(MMU_FTR_HPTE_TABLE))
+		return pte;
+
+	/* So here, we only care about exec faults, as we use them
+	 * to recover lost _PAGE_EXEC and perform I$/D$ coherency
+	 * if necessary. Also if _PAGE_EXEC is already set, same deal,
+	 * we just bail out
+	 */
+	if (dirty || pte_exec(pte) || !is_exec_fault())
+		return pte;
+
+#ifdef CONFIG_DEBUG_VM
+	/* So this is an exec fault, _PAGE_EXEC is not set. If it was
+	 * an error we would have bailed out earlier in do_page_fault()
+	 * but let's make sure of it
+	 */
+	if (WARN_ON(!(vma->vm_flags & VM_EXEC)))
+		return pte;
+#endif /* CONFIG_DEBUG_VM */
+
+	/* If you set _PAGE_EXEC on weird pages you're on your own */
+	pg = maybe_pte_to_page(pte);
+	if (unlikely(!pg))
+		goto bail;
+
+	/* If the page is already clean, we move on */
+	if (test_bit(PG_arch_1, &pg->flags))
+		goto bail;
+
+	/* Clean the page and set PG_arch_1 */
+	flush_dcache_icache_page(pg);
+	set_bit(PG_arch_1, &pg->flags);
+
+ bail:
+	return pte_mkexec(pte);
+}
+
+/*
+ * set_pte stores a linux PTE into the linux page table.
+ */
+void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep,
+		pte_t pte)
+{
+	/*
+	 * Make sure hardware valid bit is not set. We don't do
+	 * tlb flush for this update.
+	 */
+	VM_WARN_ON(pte_hw_valid(*ptep) && !pte_protnone(*ptep));
+
+	/* Note: mm->context.id might not yet have been assigned as
+	 * this context might not have been activated yet when this
+	 * is called.
+	 */
+	pte = set_pte_filter(pte);
+
+	/* Perform the setting of the PTE */
+	__set_pte_at(mm, addr, ptep, pte, 0);
+}
+
+void unmap_kernel_page(unsigned long va)
+{
+	pmd_t *pmdp = pmd_off_k(va);
+	pte_t *ptep = pte_offset_kernel(pmdp, va);
+
+	pte_clear(&init_mm, va, ptep);
+	flush_tlb_kernel_range(va, va + PAGE_SIZE);
+}
+
+/*
+ * This is called when relaxing access to a PTE. It's also called in the page
+ * fault path when we don't hit any of the major fault cases, ie, a minor
+ * update of _PAGE_ACCESSED, _PAGE_DIRTY, etc... The generic code will have
+ * handled those two for us, we additionally deal with missing execute
+ * permission here on some processors
+ */
+int ptep_set_access_flags(struct vm_area_struct *vma, unsigned long address,
+			  pte_t *ptep, pte_t entry, int dirty)
+{
+	int changed;
+	entry = set_access_flags_filter(entry, vma, dirty);
+	changed = !pte_same(*(ptep), entry);
+	if (changed) {
+		assert_pte_locked(vma->vm_mm, address);
+		__ptep_set_access_flags(vma, ptep, entry,
+					address, mmu_virtual_psize);
+	}
+	return changed;
+}
+
+#ifdef CONFIG_HUGETLB_PAGE
+int huge_ptep_set_access_flags(struct vm_area_struct *vma,
+			       unsigned long addr, pte_t *ptep,
+			       pte_t pte, int dirty)
+{
+#ifdef HUGETLB_NEED_PRELOAD
+	/*
+	 * The "return 1" forces a call of update_mmu_cache, which will write a
+	 * TLB entry.  Without this, platforms that don't do a write of the TLB
+	 * entry in the TLB miss handler asm will fault ad infinitum.
+	 */
+	ptep_set_access_flags(vma, addr, ptep, pte, dirty);
+	return 1;
+#else
+	int changed, psize;
+
+	pte = set_access_flags_filter(pte, vma, dirty);
+	changed = !pte_same(*(ptep), pte);
+	if (changed) {
+
+#ifdef CONFIG_PPC_BOOK3S_64
+		struct hstate *h = hstate_vma(vma);
+
+		psize = hstate_get_psize(h);
+#ifdef CONFIG_DEBUG_VM
+		assert_spin_locked(huge_pte_lockptr(h, vma->vm_mm, ptep));
+#endif
+
+#else
+		/*
+		 * Not used on non book3s64 platforms.
+		 * 8xx compares it with mmu_virtual_psize to
+		 * know if it is a huge page or not.
+		 */
+		psize = MMU_PAGE_COUNT;
+#endif
+		__ptep_set_access_flags(vma, ptep, pte, addr, psize);
+	}
+	return changed;
+#endif
+}
+
+#if defined(CONFIG_PPC_8xx)
+void set_huge_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pte)
+{
+	pmd_t *pmd = pmd_off(mm, addr);
+	pte_basic_t val;
+	pte_basic_t *entry = &ptep->pte;
+	int num, i;
+
+	/*
+	 * Make sure hardware valid bit is not set. We don't do
+	 * tlb flush for this update.
+	 */
+	VM_WARN_ON(pte_hw_valid(*ptep) && !pte_protnone(*ptep));
+
+	pte = set_pte_filter(pte);
+
+	val = pte_val(pte);
+
+	num = number_of_cells_per_pte(pmd, val, 1);
+
+	for (i = 0; i < num; i++, entry++, val += SZ_4K)
+		*entry = val;
+}
+#endif
+#endif /* CONFIG_HUGETLB_PAGE */
+
+#ifdef CONFIG_DEBUG_VM
+void assert_pte_locked(struct mm_struct *mm, unsigned long addr)
+{
+	pgd_t *pgd;
+	p4d_t *p4d;
+	pud_t *pud;
+	pmd_t *pmd;
+
+	if (mm == &init_mm)
+		return;
+	pgd = mm->pgd + pgd_index(addr);
+	BUG_ON(pgd_none(*pgd));
+	p4d = p4d_offset(pgd, addr);
+	BUG_ON(p4d_none(*p4d));
+	pud = pud_offset(p4d, addr);
+	BUG_ON(pud_none(*pud));
+	pmd = pmd_offset(pud, addr);
+	/*
+	 * khugepaged to collapse normal pages to hugepage, first set
+	 * pmd to none to force page fault/gup to take mmap_lock. After
+	 * pmd is set to none, we do a pte_clear which does this assertion
+	 * so if we find pmd none, return.
+	 */
+	if (pmd_none(*pmd))
+		return;
+	BUG_ON(!pmd_present(*pmd));
+	assert_spin_locked(pte_lockptr(mm, pmd));
+}
+#endif /* CONFIG_DEBUG_VM */
+
+unsigned long vmalloc_to_phys(void *va)
+{
+	unsigned long pfn = vmalloc_to_pfn(va);
+
+	BUG_ON(!pfn);
+	return __pa(pfn_to_kaddr(pfn)) + offset_in_page(va);
+}
+EXPORT_SYMBOL_GPL(vmalloc_to_phys);
+
+/*
+ * We have 4 cases for pgds and pmds:
+ * (1) invalid (all zeroes)
+ * (2) pointer to next table, as normal; bottom 6 bits == 0
+ * (3) leaf pte for huge page _PAGE_PTE set
+ * (4) hugepd pointer, _PAGE_PTE = 0 and bits [2..6] indicate size of table
+ *
+ * So long as we atomically load page table pointers we are safe against teardown,
+ * we can follow the address down to the the page and take a ref on it.
+ * This function need to be called with interrupts disabled. We use this variant
+ * when we have MSR[EE] = 0 but the paca->irq_soft_mask = IRQS_ENABLED
+ */
+pte_t *__find_linux_pte(pgd_t *pgdir, unsigned long ea,
+			bool *is_thp, unsigned *hpage_shift)
+{
+	pgd_t *pgdp;
+	p4d_t p4d, *p4dp;
+	pud_t pud, *pudp;
+	pmd_t pmd, *pmdp;
+	pte_t *ret_pte;
+	hugepd_t *hpdp = NULL;
+	unsigned pdshift;
+
+	if (hpage_shift)
+		*hpage_shift = 0;
+
+	if (is_thp)
+		*is_thp = false;
+
+	/*
+	 * Always operate on the local stack value. This make sure the
+	 * value don't get updated by a parallel THP split/collapse,
+	 * page fault or a page unmap. The return pte_t * is still not
+	 * stable. So should be checked there for above conditions.
+	 * Top level is an exception because it is folded into p4d.
+	 */
+	pgdp = pgdir + pgd_index(ea);
+	p4dp = p4d_offset(pgdp, ea);
+	p4d  = READ_ONCE(*p4dp);
+	pdshift = P4D_SHIFT;
+
+	if (p4d_none(p4d))
+		return NULL;
+
+	if (p4d_is_leaf(p4d)) {
+		ret_pte = (pte_t *)p4dp;
+		goto out;
+	}
+
+	if (is_hugepd(__hugepd(p4d_val(p4d)))) {
+		hpdp = (hugepd_t *)&p4d;
+		goto out_huge;
+	}
+
+	/*
+	 * Even if we end up with an unmap, the pgtable will not
+	 * be freed, because we do an rcu free and here we are
+	 * irq disabled
+	 */
+	pdshift = PUD_SHIFT;
+	pudp = pud_offset(&p4d, ea);
+	pud  = READ_ONCE(*pudp);
+
+	if (pud_none(pud))
+		return NULL;
+
+	if (pud_is_leaf(pud)) {
+		ret_pte = (pte_t *)pudp;
+		goto out;
+	}
+
+	if (is_hugepd(__hugepd(pud_val(pud)))) {
+		hpdp = (hugepd_t *)&pud;
+		goto out_huge;
+	}
+
+	pdshift = PMD_SHIFT;
+	pmdp = pmd_offset(&pud, ea);
+	pmd  = READ_ONCE(*pmdp);
+
+	/*
+	 * A hugepage collapse is captured by this condition, see
+	 * pmdp_collapse_flush.
+	 */
+	if (pmd_none(pmd))
+		return NULL;
+
+#ifdef CONFIG_PPC_BOOK3S_64
+	/*
+	 * A hugepage split is captured by this condition, see
+	 * pmdp_invalidate.
+	 *
+	 * Huge page modification can be caught here too.
+	 */
+	if (pmd_is_serializing(pmd))
+		return NULL;
+#endif
+
+	if (pmd_trans_huge(pmd) || pmd_devmap(pmd)) {
+		if (is_thp)
+			*is_thp = true;
+		ret_pte = (pte_t *)pmdp;
+		goto out;
+	}
+
+	if (pmd_is_leaf(pmd)) {
+		ret_pte = (pte_t *)pmdp;
+		goto out;
+	}
+
+	if (is_hugepd(__hugepd(pmd_val(pmd)))) {
+		hpdp = (hugepd_t *)&pmd;
+		goto out_huge;
+	}
+
+	return pte_offset_kernel(&pmd, ea);
+
+out_huge:
+	if (!hpdp)
+		return NULL;
+
+	ret_pte = hugepte_offset(*hpdp, ea, pdshift);
+	pdshift = hugepd_shift(*hpdp);
+out:
+	if (hpage_shift)
+		*hpage_shift = pdshift;
+	return ret_pte;
+}
+EXPORT_SYMBOL_GPL(__find_linux_pte);