1 files changed, 213 insertions, 0 deletions

diff --git a/arch/powerpc/mm/subpage-prot.c b/arch/powerpc/mm/subpage-prot.c
new file mode 100644
index 000000000000..4cafc0c33d0a
--- /dev/null
+++ b/arch/powerpc/mm/subpage-prot.c
@@ -0,0 +1,213 @@
+/*
+ * Copyright 2007-2008 Paul Mackerras, IBM Corp.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/gfp.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/mm.h>
+#include <linux/hugetlb.h>
+
+#include <asm/pgtable.h>
+#include <asm/uaccess.h>
+#include <asm/tlbflush.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(pgd_t *pgd)
+{
+        struct subpage_prot_table *spt = pgd_subpage_prot(pgd);
+        unsigned long i, j, addr;
+        u32 **p;
+
+        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 < 2; ++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;
+}
+
+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);
+                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 = pgd_subpage_prot(mm->pgd);
+        u32 **spm, *spp;
+        int i, nw;
+        unsigned long next, limit;
+
+        down_write(&mm->mmap_sem);
+        limit = addr + len;
+        if (limit > spt->maxaddr)
+                limit = spt->maxaddr;
+        for (; addr < limit; addr = next) {
+                next = pmd_addr_end(addr, limit);
+                if (addr < 0x100000000) {
+                        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);
+        }
+        up_write(&mm->mmap_sem);
+}
+
+/*
+ * 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.
+ */
+long sys_subpage_prot(unsigned long addr, unsigned long len, u32 __user *map)
+{
+        struct mm_struct *mm = current->mm;
+        struct subpage_prot_table *spt = pgd_subpage_prot(mm->pgd);
+        u32 **spm, *spp;
+        int i, nw;
+        unsigned long next, limit;
+        int err;
+
+        /* Check parameters */
+        if ((addr & ~PAGE_MASK) || (len & ~PAGE_MASK) ||
+            addr >= TASK_SIZE || len >= TASK_SIZE || addr + len > 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(VERIFY_READ, map, (len >> PAGE_SHIFT) * sizeof(u32)))
+                return -EFAULT;
+
+        down_write(&mm->mmap_sem);
+        for (limit = addr + len; addr < limit; addr = next) {
+                next = pmd_addr_end(addr, limit);
+                err = -ENOMEM;
+                if (addr < 0x100000000) {
+                        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);
+                err = -EFAULT;
+                if (__copy_from_user(spp, map, nw * sizeof(u32)))
+                        goto out2;
+                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);
+ out2:
+        return err;
+}