+#ifdef CONFIG_MMU
+
+static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
+ int write)
+{
+ struct page *page;
+ int ret;
+
+#ifdef CONFIG_STACK_GROWSUP
+ if (write) {
+ ret = expand_stack_downwards(bprm->vma, pos);
+ if (ret < 0)
+ return NULL;
+ }
+#endif
+ ret = get_user_pages(current, bprm->mm, pos,
+ 1, write, 1, &page, NULL);
+ if (ret <= 0)
+ return NULL;
+
+ if (write) {
+ struct rlimit *rlim = current->signal->rlim;
+ unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
+
+ /*
+ * Limit to 1/4-th the stack size for the argv+env strings.
+ * This ensures that:
+ * - the remaining binfmt code will not run out of stack space,
+ * - the program will have a reasonable amount of stack left
+ * to work from.
+ */
+ if (size > rlim[RLIMIT_STACK].rlim_cur / 4) {
+ put_page(page);
+ return NULL;
+ }
+ }
+
+ return page;
+}
+
+static void put_arg_page(struct page *page)
+{
+ put_page(page);
+}
+
+static void free_arg_page(struct linux_binprm *bprm, int i)
+{
+}
+
+static void free_arg_pages(struct linux_binprm *bprm)
+{
+}
+
+static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
+ struct page *page)
+{
+ flush_cache_page(bprm->vma, pos, page_to_pfn(page));
+}
+
+static int __bprm_mm_init(struct linux_binprm *bprm)
+{
+ int err = -ENOMEM;
+ struct vm_area_struct *vma = NULL;
+ struct mm_struct *mm = bprm->mm;
+
+ bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
+ if (!vma)
+ goto err;
+
+ down_write(&mm->mmap_sem);
+ vma->vm_mm = mm;
+
+ /*
+ * Place the stack at the largest stack address the architecture
+ * supports. Later, we'll move this to an appropriate place. We don't
+ * use STACK_TOP because that can depend on attributes which aren't
+ * configured yet.
+ */
+ vma->vm_end = STACK_TOP_MAX;
+ vma->vm_start = vma->vm_end - PAGE_SIZE;
+
+ vma->vm_flags = VM_STACK_FLAGS;
+ vma->vm_page_prot = protection_map[vma->vm_flags & 0x7];
+ err = insert_vm_struct(mm, vma);
+ if (err) {
+ up_write(&mm->mmap_sem);
+ goto err;
+ }
+
+ mm->stack_vm = mm->total_vm = 1;
+ up_write(&mm->mmap_sem);
+
+ bprm->p = vma->vm_end - sizeof(void *);
+
+ return 0;
+
+err:
+ if (vma) {
+ bprm->vma = NULL;
+ kmem_cache_free(vm_area_cachep, vma);
+ }
+
+ return err;
+}
+
+static bool valid_arg_len(struct linux_binprm *bprm, long len)
+{
+ return len <= MAX_ARG_STRLEN;
+}
+
+#else
+
+static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
+ int write)
+{
+ struct page *page;
+
+ page = bprm->page[pos / PAGE_SIZE];
+ if (!page && write) {
+ page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
+ if (!page)
+ return NULL;
+ bprm->page[pos / PAGE_SIZE] = page;
+ }
+
+ return page;
+}
+
+static void put_arg_page(struct page *page)
+{
+}
+
+static void free_arg_page(struct linux_binprm *bprm, int i)
+{
+ if (bprm->page[i]) {
+ __free_page(bprm->page[i]);
+ bprm->page[i] = NULL;
+ }
+}
+
+static void free_arg_pages(struct linux_binprm *bprm)
+{
+ int i;
+
+ for (i = 0; i < MAX_ARG_PAGES; i++)
+ free_arg_page(bprm, i);
+}
+
+static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
+ struct page *page)
+{
+}
+
+static int __bprm_mm_init(struct linux_binprm *bprm)
+{
+ bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
+ return 0;
+}
+
+static bool valid_arg_len(struct linux_binprm *bprm, long len)
+{
+ return len <= bprm->p;
+}
+
+#endif /* CONFIG_MMU */
+
+/*
+ * Create a new mm_struct and populate it with a temporary stack
+ * vm_area_struct. We don't have enough context at this point to set the stack
+ * flags, permissions, and offset, so we use temporary values. We'll update
+ * them later in setup_arg_pages().
+ */
+int bprm_mm_init(struct linux_binprm *bprm)
+{
+ int err;
+ struct mm_struct *mm = NULL;
+
+ bprm->mm = mm = mm_alloc();
+ err = -ENOMEM;
+ if (!mm)
+ goto err;
+
+ err = init_new_context(current, mm);
+ if (err)
+ goto err;
+
+ err = __bprm_mm_init(bprm);
+ if (err)
+ goto err;
+
+ return 0;
+
+err:
+ if (mm) {
+ bprm->mm = NULL;
+ mmdrop(mm);
+ }
+
+ return err;
+}
+