1 files changed, 272 insertions, 0 deletions
diff --git a/arch/arm/mm/fault-armv.c b/arch/arm/mm/fault-armv.c
new file mode 100644
index 0000000000..2286c2ea60
--- /dev/null
+++ b/arch/arm/mm/fault-armv.c
@@ -0,0 +1,272 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  linux/arch/arm/mm/fault-armv.c
+ *
+ *  Copyright (C) 1995  Linus Torvalds
+ *  Modifications for ARM processor (c) 1995-2002 Russell King
+ */
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/bitops.h>
+#include <linux/vmalloc.h>
+#include <linux/init.h>
+#include <linux/pagemap.h>
+#include <linux/gfp.h>
+
+#include <asm/bugs.h>
+#include <asm/cacheflush.h>
+#include <asm/cachetype.h>
+#include <asm/tlbflush.h>
+
+#include "mm.h"
+
+static pteval_t shared_pte_mask = L_PTE_MT_BUFFERABLE;
+
+#if __LINUX_ARM_ARCH__ < 6
+/*
+ * We take the easy way out of this problem - we make the
+ * PTE uncacheable.  However, we leave the write buffer on.
+ *
+ * Note that the pte lock held when calling update_mmu_cache must also
+ * guard the pte (somewhere else in the same mm) that we modify here.
+ * Therefore those configurations which might call adjust_pte (those
+ * without CONFIG_CPU_CACHE_VIPT) cannot support split page_table_lock.
+ */
+static int do_adjust_pte(struct vm_area_struct *vma, unsigned long address,
+	unsigned long pfn, pte_t *ptep)
+{
+	pte_t entry = *ptep;
+	int ret;
+
+	/*
+	 * If this page is present, it's actually being shared.
+	 */
+	ret = pte_present(entry);
+
+	/*
+	 * If this page isn't present, or is already setup to
+	 * fault (ie, is old), we can safely ignore any issues.
+	 */
+	if (ret && (pte_val(entry) & L_PTE_MT_MASK) != shared_pte_mask) {
+		flush_cache_page(vma, address, pfn);
+		outer_flush_range((pfn << PAGE_SHIFT),
+				  (pfn << PAGE_SHIFT) + PAGE_SIZE);
+		pte_val(entry) &= ~L_PTE_MT_MASK;
+		pte_val(entry) |= shared_pte_mask;
+		set_pte_at(vma->vm_mm, address, ptep, entry);
+		flush_tlb_page(vma, address);
+	}
+
+	return ret;
+}
+
+#if USE_SPLIT_PTE_PTLOCKS
+/*
+ * If we are using split PTE locks, then we need to take the page
+ * lock here.  Otherwise we are using shared mm->page_table_lock
+ * which is already locked, thus cannot take it.
+ */
+static inline void do_pte_lock(spinlock_t *ptl)
+{
+	/*
+	 * Use nested version here to indicate that we are already
+	 * holding one similar spinlock.
+	 */
+	spin_lock_nested(ptl, SINGLE_DEPTH_NESTING);
+}
+
+static inline void do_pte_unlock(spinlock_t *ptl)
+{
+	spin_unlock(ptl);
+}
+#else /* !USE_SPLIT_PTE_PTLOCKS */
+static inline void do_pte_lock(spinlock_t *ptl) {}
+static inline void do_pte_unlock(spinlock_t *ptl) {}
+#endif /* USE_SPLIT_PTE_PTLOCKS */
+
+static int adjust_pte(struct vm_area_struct *vma, unsigned long address,
+	unsigned long pfn)
+{
+	spinlock_t *ptl;
+	pgd_t *pgd;
+	p4d_t *p4d;
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *pte;
+	int ret;
+
+	pgd = pgd_offset(vma->vm_mm, address);
+	if (pgd_none_or_clear_bad(pgd))
+		return 0;
+
+	p4d = p4d_offset(pgd, address);
+	if (p4d_none_or_clear_bad(p4d))
+		return 0;
+
+	pud = pud_offset(p4d, address);
+	if (pud_none_or_clear_bad(pud))
+		return 0;
+
+	pmd = pmd_offset(pud, address);
+	if (pmd_none_or_clear_bad(pmd))
+		return 0;
+
+	/*
+	 * This is called while another page table is mapped, so we
+	 * must use the nested version.  This also means we need to
+	 * open-code the spin-locking.
+	 */
+	pte = pte_offset_map_nolock(vma->vm_mm, pmd, address, &ptl);
+	if (!pte)
+		return 0;
+
+	do_pte_lock(ptl);
+
+	ret = do_adjust_pte(vma, address, pfn, pte);
+
+	do_pte_unlock(ptl);
+	pte_unmap(pte);
+
+	return ret;
+}
+
+static void
+make_coherent(struct address_space *mapping, struct vm_area_struct *vma,
+	unsigned long addr, pte_t *ptep, unsigned long pfn)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	struct vm_area_struct *mpnt;
+	unsigned long offset;
+	pgoff_t pgoff;
+	int aliases = 0;
+
+	pgoff = vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT);
+
+	/*
+	 * If we have any shared mappings that are in the same mm
+	 * space, then we need to handle them specially to maintain
+	 * cache coherency.
+	 */
+	flush_dcache_mmap_lock(mapping);
+	vma_interval_tree_foreach(mpnt, &mapping->i_mmap, pgoff, pgoff) {
+		/*
+		 * If this VMA is not in our MM, we can ignore it.
+		 * Note that we intentionally mask out the VMA
+		 * that we are fixing up.
+		 */
+		if (mpnt->vm_mm != mm || mpnt == vma)
+			continue;
+		if (!(mpnt->vm_flags & VM_MAYSHARE))
+			continue;
+		offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT;
+		aliases += adjust_pte(mpnt, mpnt->vm_start + offset, pfn);
+	}
+	flush_dcache_mmap_unlock(mapping);
+	if (aliases)
+		do_adjust_pte(vma, addr, pfn, ptep);
+}
+
+/*
+ * Take care of architecture specific things when placing a new PTE into
+ * a page table, or changing an existing PTE.  Basically, there are two
+ * things that we need to take care of:
+ *
+ *  1. If PG_dcache_clean is not set for the page, we need to ensure
+ *     that any cache entries for the kernels virtual memory
+ *     range are written back to the page.
+ *  2. If we have multiple shared mappings of the same space in
+ *     an object, we need to deal with the cache aliasing issues.
+ *
+ * Note that the pte lock will be held.
+ */
+void update_mmu_cache_range(struct vm_fault *vmf, struct vm_area_struct *vma,
+		unsigned long addr, pte_t *ptep, unsigned int nr)
+{
+	unsigned long pfn = pte_pfn(*ptep);
+	struct address_space *mapping;
+	struct folio *folio;
+
+	if (!pfn_valid(pfn))
+		return;
+
+	/*
+	 * The zero page is never written to, so never has any dirty
+	 * cache lines, and therefore never needs to be flushed.
+	 */
+	if (is_zero_pfn(pfn))
+		return;
+
+	folio = page_folio(pfn_to_page(pfn));
+	mapping = folio_flush_mapping(folio);
+	if (!test_and_set_bit(PG_dcache_clean, &folio->flags))
+		__flush_dcache_folio(mapping, folio);
+	if (mapping) {
+		if (cache_is_vivt())
+			make_coherent(mapping, vma, addr, ptep, pfn);
+		else if (vma->vm_flags & VM_EXEC)
+			__flush_icache_all();
+	}
+}
+#endif	/* __LINUX_ARM_ARCH__ < 6 */
+
+/*
+ * Check whether the write buffer has physical address aliasing
+ * issues.  If it has, we need to avoid them for the case where
+ * we have several shared mappings of the same object in user
+ * space.
+ */
+static int __init check_writebuffer(unsigned long *p1, unsigned long *p2)
+{
+	register unsigned long zero = 0, one = 1, val;
+
+	local_irq_disable();
+	mb();
+	*p1 = one;
+	mb();
+	*p2 = zero;
+	mb();
+	val = *p1;
+	mb();
+	local_irq_enable();
+	return val != zero;
+}
+
+void __init check_writebuffer_bugs(void)
+{
+	struct page *page;
+	const char *reason;
+	unsigned long v = 1;
+
+	pr_info("CPU: Testing write buffer coherency: ");
+
+	page = alloc_page(GFP_KERNEL);
+	if (page) {
+		unsigned long *p1, *p2;
+		pgprot_t prot = __pgprot_modify(PAGE_KERNEL,
+					L_PTE_MT_MASK, L_PTE_MT_BUFFERABLE);
+
+		p1 = vmap(&page, 1, VM_IOREMAP, prot);
+		p2 = vmap(&page, 1, VM_IOREMAP, prot);
+
+		if (p1 && p2) {
+			v = check_writebuffer(p1, p2);
+			reason = "enabling work-around";
+		} else {
+			reason = "unable to map memory\n";
+		}
+
+		vunmap(p1);
+		vunmap(p2);
+		put_page(page);
+	} else {
+		reason = "unable to grab page\n";
+	}
+
+	if (v) {
+		pr_cont("failed, %s\n", reason);
+		shared_pte_mask = L_PTE_MT_UNCACHED;
+	} else {
+		pr_cont("ok\n");
+	}
+}