1 files changed, 285 insertions, 0 deletions
diff --git a/arch/powerpc/mm/book3s64/subpage_prot.c b/arch/powerpc/mm/book3s64/subpage_prot.c
new file mode 100644
index 000000000000..9ba07e55c489
--- /dev/null
+++ b/arch/powerpc/mm/book3s64/subpage_prot.c
@@ -0,0 +1,285 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright 2007-2008 Paul Mackerras, IBM Corp.
+ */
+
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/gfp.h>
+#include <linux/types.h>
+#include <linux/mm.h>
+#include <linux/hugetlb.h>
+#include <linux/syscalls.h>
+
+#include <asm/pgtable.h>
+#include <linux/uaccess.h>
+
+/*
+ * Free all pages allocated for subpage protection maps and pointers.
+ * Also makes sure that the subpage_prot_table structure is
+ * reinitialized for the next user.
+ */
+void subpage_prot_free(struct mm_struct *mm)
+{
+	struct subpage_prot_table *spt = mm_ctx_subpage_prot(&mm->context);
+	unsigned long i, j, addr;
+	u32 **p;
+
+	if (!spt)
+		return;
+
+	for (i = 0; i < 4; ++i) {
+		if (spt->low_prot[i]) {
+			free_page((unsigned long)spt->low_prot[i]);
+			spt->low_prot[i] = NULL;
+		}
+	}
+	addr = 0;
+	for (i = 0; i < (TASK_SIZE_USER64 >> 43); ++i) {
+		p = spt->protptrs[i];
+		if (!p)
+			continue;
+		spt->protptrs[i] = NULL;
+		for (j = 0; j < SBP_L2_COUNT && addr < spt->maxaddr;
+		     ++j, addr += PAGE_SIZE)
+			if (p[j])
+				free_page((unsigned long)p[j]);
+		free_page((unsigned long)p);
+	}
+	spt->maxaddr = 0;
+	kfree(spt);
+}
+
+static void hpte_flush_range(struct mm_struct *mm, unsigned long addr,
+			     int npages)
+{
+	pgd_t *pgd;
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *pte;
+	spinlock_t *ptl;
+
+	pgd = pgd_offset(mm, addr);
+	if (pgd_none(*pgd))
+		return;
+	pud = pud_offset(pgd, addr);
+	if (pud_none(*pud))
+		return;
+	pmd = pmd_offset(pud, addr);
+	if (pmd_none(*pmd))
+		return;
+	pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
+	arch_enter_lazy_mmu_mode();
+	for (; npages > 0; --npages) {
+		pte_update(mm, addr, pte, 0, 0, 0);
+		addr += PAGE_SIZE;
+		++pte;
+	}
+	arch_leave_lazy_mmu_mode();
+	pte_unmap_unlock(pte - 1, ptl);
+}
+
+/*
+ * Clear the subpage protection map for an address range, allowing
+ * all accesses that are allowed by the pte permissions.
+ */
+static void subpage_prot_clear(unsigned long addr, unsigned long len)
+{
+	struct mm_struct *mm = current->mm;
+	struct subpage_prot_table *spt;
+	u32 **spm, *spp;
+	unsigned long i;
+	size_t nw;
+	unsigned long next, limit;
+
+	down_write(&mm->mmap_sem);
+
+	spt = mm_ctx_subpage_prot(&mm->context);
+	if (!spt)
+		goto err_out;
+
+	limit = addr + len;
+	if (limit > spt->maxaddr)
+		limit = spt->maxaddr;
+	for (; addr < limit; addr = next) {
+		next = pmd_addr_end(addr, limit);
+		if (addr < 0x100000000UL) {
+			spm = spt->low_prot;
+		} else {
+			spm = spt->protptrs[addr >> SBP_L3_SHIFT];
+			if (!spm)
+				continue;
+		}
+		spp = spm[(addr >> SBP_L2_SHIFT) & (SBP_L2_COUNT - 1)];
+		if (!spp)
+			continue;
+		spp += (addr >> PAGE_SHIFT) & (SBP_L1_COUNT - 1);
+
+		i = (addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
+		nw = PTRS_PER_PTE - i;
+		if (addr + (nw << PAGE_SHIFT) > next)
+			nw = (next - addr) >> PAGE_SHIFT;
+
+		memset(spp, 0, nw * sizeof(u32));
+
+		/* now flush any existing HPTEs for the range */
+		hpte_flush_range(mm, addr, nw);
+	}
+
+err_out:
+	up_write(&mm->mmap_sem);
+}
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static int subpage_walk_pmd_entry(pmd_t *pmd, unsigned long addr,
+				  unsigned long end, struct mm_walk *walk)
+{
+	struct vm_area_struct *vma = walk->vma;
+	split_huge_pmd(vma, pmd, addr);
+	return 0;
+}
+
+static void subpage_mark_vma_nohuge(struct mm_struct *mm, unsigned long addr,
+				    unsigned long len)
+{
+	struct vm_area_struct *vma;
+	struct mm_walk subpage_proto_walk = {
+		.mm = mm,
+		.pmd_entry = subpage_walk_pmd_entry,
+	};
+
+	/*
+	 * We don't try too hard, we just mark all the vma in that range
+	 * VM_NOHUGEPAGE and split them.
+	 */
+	vma = find_vma(mm, addr);
+	/*
+	 * If the range is in unmapped range, just return
+	 */
+	if (vma && ((addr + len) <= vma->vm_start))
+		return;
+
+	while (vma) {
+		if (vma->vm_start >= (addr + len))
+			break;
+		vma->vm_flags |= VM_NOHUGEPAGE;
+		walk_page_vma(vma, &subpage_proto_walk);
+		vma = vma->vm_next;
+	}
+}
+#else
+static void subpage_mark_vma_nohuge(struct mm_struct *mm, unsigned long addr,
+				    unsigned long len)
+{
+	return;
+}
+#endif
+
+/*
+ * Copy in a subpage protection map for an address range.
+ * The map has 2 bits per 4k subpage, so 32 bits per 64k page.
+ * Each 2-bit field is 0 to allow any access, 1 to prevent writes,
+ * 2 or 3 to prevent all accesses.
+ * Note that the normal page protections also apply; the subpage
+ * protection mechanism is an additional constraint, so putting 0
+ * in a 2-bit field won't allow writes to a page that is otherwise
+ * write-protected.
+ */
+SYSCALL_DEFINE3(subpage_prot, unsigned long, addr,
+		unsigned long, len, u32 __user *, map)
+{
+	struct mm_struct *mm = current->mm;
+	struct subpage_prot_table *spt;
+	u32 **spm, *spp;
+	unsigned long i;
+	size_t nw;
+	unsigned long next, limit;
+	int err;
+
+	if (radix_enabled())
+		return -ENOENT;
+
+	/* Check parameters */
+	if ((addr & ~PAGE_MASK) || (len & ~PAGE_MASK) ||
+	    addr >= mm->task_size || len >= mm->task_size ||
+	    addr + len > mm->task_size)
+		return -EINVAL;
+
+	if (is_hugepage_only_range(mm, addr, len))
+		return -EINVAL;
+
+	if (!map) {
+		/* Clear out the protection map for the address range */
+		subpage_prot_clear(addr, len);
+		return 0;
+	}
+
+	if (!access_ok(map, (len >> PAGE_SHIFT) * sizeof(u32)))
+		return -EFAULT;
+
+	down_write(&mm->mmap_sem);
+
+	spt = mm_ctx_subpage_prot(&mm->context);
+	if (!spt) {
+		/*
+		 * Allocate subpage prot table if not already done.
+		 * Do this with mmap_sem held
+		 */
+		spt = kzalloc(sizeof(struct subpage_prot_table), GFP_KERNEL);
+		if (!spt) {
+			err = -ENOMEM;
+			goto out;
+		}
+		mm->context.hash_context->spt = spt;
+	}
+
+	subpage_mark_vma_nohuge(mm, addr, len);
+	for (limit = addr + len; addr < limit; addr = next) {
+		next = pmd_addr_end(addr, limit);
+		err = -ENOMEM;
+		if (addr < 0x100000000UL) {
+			spm = spt->low_prot;
+		} else {
+			spm = spt->protptrs[addr >> SBP_L3_SHIFT];
+			if (!spm) {
+				spm = (u32 **)get_zeroed_page(GFP_KERNEL);
+				if (!spm)
+					goto out;
+				spt->protptrs[addr >> SBP_L3_SHIFT] = spm;
+			}
+		}
+		spm += (addr >> SBP_L2_SHIFT) & (SBP_L2_COUNT - 1);
+		spp = *spm;
+		if (!spp) {
+			spp = (u32 *)get_zeroed_page(GFP_KERNEL);
+			if (!spp)
+				goto out;
+			*spm = spp;
+		}
+		spp += (addr >> PAGE_SHIFT) & (SBP_L1_COUNT - 1);
+
+		local_irq_disable();
+		demote_segment_4k(mm, addr);
+		local_irq_enable();
+
+		i = (addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
+		nw = PTRS_PER_PTE - i;
+		if (addr + (nw << PAGE_SHIFT) > next)
+			nw = (next - addr) >> PAGE_SHIFT;
+
+		up_write(&mm->mmap_sem);
+		if (__copy_from_user(spp, map, nw * sizeof(u32)))
+			return -EFAULT;
+		map += nw;
+		down_write(&mm->mmap_sem);
+
+		/* now flush any existing HPTEs for the range */
+		hpte_flush_range(mm, addr, nw);
+	}
+	if (limit > spt->maxaddr)
+		spt->maxaddr = limit;
+	err = 0;
+ out:
+	up_write(&mm->mmap_sem);
+	return err;
+}