1 files changed, 85 insertions, 0 deletions
diff --git a/fs/romfs/mmap-nommu.c b/fs/romfs/mmap-nommu.c
new file mode 100644
index 000000000..2c4a23113
--- /dev/null
+++ b/fs/romfs/mmap-nommu.c
@@ -0,0 +1,85 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* NOMMU mmap support for RomFS on MTD devices
+ *
+ * Copyright © 2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/mm.h>
+#include <linux/mtd/super.h>
+#include "internal.h"
+
+/*
+ * try to determine where a shared mapping can be made
+ * - only supported for NOMMU at the moment (MMU can't doesn't copy private
+ *   mappings)
+ * - attempts to map through to the underlying MTD device
+ */
+static unsigned long romfs_get_unmapped_area(struct file *file,
+					     unsigned long addr,
+					     unsigned long len,
+					     unsigned long pgoff,
+					     unsigned long flags)
+{
+	struct inode *inode = file->f_mapping->host;
+	struct mtd_info *mtd = inode->i_sb->s_mtd;
+	unsigned long isize, offset, maxpages, lpages;
+	int ret;
+
+	if (!mtd)
+		return (unsigned long) -ENOSYS;
+
+	/* the mapping mustn't extend beyond the EOF */
+	lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	isize = i_size_read(inode);
+	offset = pgoff << PAGE_SHIFT;
+
+	maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	if ((pgoff >= maxpages) || (maxpages - pgoff < lpages))
+		return (unsigned long) -EINVAL;
+
+	if (addr != 0)
+		return (unsigned long) -EINVAL;
+
+	if (len > mtd->size || pgoff >= (mtd->size >> PAGE_SHIFT))
+		return (unsigned long) -EINVAL;
+
+	offset += ROMFS_I(inode)->i_dataoffset;
+	if (offset >= mtd->size)
+		return (unsigned long) -EINVAL;
+	/* the mapping mustn't extend beyond the EOF */
+	if ((offset + len) > mtd->size)
+		len = mtd->size - offset;
+
+	ret = mtd_get_unmapped_area(mtd, len, offset, flags);
+	if (ret == -EOPNOTSUPP)
+		ret = -ENOSYS;
+	return (unsigned long) ret;
+}
+
+/*
+ * permit a R/O mapping to be made directly through onto an MTD device if
+ * possible
+ */
+static int romfs_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -ENOSYS;
+}
+
+static unsigned romfs_mmap_capabilities(struct file *file)
+{
+	struct mtd_info *mtd = file_inode(file)->i_sb->s_mtd;
+
+	if (!mtd)
+		return NOMMU_MAP_COPY;
+	return mtd_mmap_capabilities(mtd);
+}
+
+const struct file_operations romfs_ro_fops = {
+	.llseek			= generic_file_llseek,
+	.read_iter		= generic_file_read_iter,
+	.splice_read		= generic_file_splice_read,
+	.mmap			= romfs_mmap,
+	.get_unmapped_area	= romfs_get_unmapped_area,
+	.mmap_capabilities	= romfs_mmap_capabilities,
+};