// SPDX-License-Identifier: GPL-2.0-or-later /* file-nommu.c: no-MMU version of ramfs * * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) */ #include <linux/module.h> #include <linux/fs.h> #include <linux/mm.h> #include <linux/pagemap.h> #include <linux/highmem.h> #include <linux/init.h> #include <linux/string.h> #include <linux/backing-dev.h> #include <linux/ramfs.h> #include <linux/pagevec.h> #include <linux/mman.h> #include <linux/sched.h> #include <linux/slab.h> #include <linux/uaccess.h> #include "internal.h" static int ramfs_nommu_setattr(struct mnt_idmap *, struct dentry *, struct iattr *); static unsigned long ramfs_nommu_get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags); static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma); static unsigned ramfs_mmap_capabilities(struct file *file) { return NOMMU_MAP_DIRECT | NOMMU_MAP_COPY | NOMMU_MAP_READ | NOMMU_MAP_WRITE | NOMMU_MAP_EXEC; } const struct file_operations ramfs_file_operations = { .mmap_capabilities = ramfs_mmap_capabilities, .mmap = ramfs_nommu_mmap, .get_unmapped_area = ramfs_nommu_get_unmapped_area, .read_iter = generic_file_read_iter, .write_iter = generic_file_write_iter, .fsync = noop_fsync, .splice_read = filemap_splice_read, .splice_write = iter_file_splice_write, .llseek = generic_file_llseek, }; const struct inode_operations ramfs_file_inode_operations = { .setattr = ramfs_nommu_setattr, .getattr = simple_getattr, }; /*****************************************************************************/ /* * add a contiguous set of pages into a ramfs inode when it's truncated from * size 0 on the assumption that it's going to be used for an mmap of shared * memory */ int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize) { unsigned long npages, xpages, loop; struct page *pages; unsigned order; void *data; int ret; gfp_t gfp = mapping_gfp_mask(inode->i_mapping); /* make various checks */ order = get_order(newsize); if (unlikely(order > MAX_PAGE_ORDER)) return -EFBIG; ret = inode_newsize_ok(inode, newsize); if (ret) return ret; i_size_write(inode, newsize); /* allocate enough contiguous pages to be able to satisfy the * request */ pages = alloc_pages(gfp, order); if (!pages) return -ENOMEM; /* split the high-order page into an array of single pages */ xpages = 1UL << order; npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT; split_page(pages, order); /* trim off any pages we don't actually require */ for (loop = npages; loop < xpages; loop++) __free_page(pages + loop); /* clear the memory we allocated */ newsize = PAGE_SIZE * npages; data = page_address(pages); memset(data, 0, newsize); /* attach all the pages to the inode's address space */ for (loop = 0; loop < npages; loop++) { struct page *page = pages + loop; ret = add_to_page_cache_lru(page, inode->i_mapping, loop, gfp); if (ret < 0) goto add_error; /* prevent the page from being discarded on memory pressure */ SetPageDirty(page); SetPageUptodate(page); unlock_page(page); put_page(page); } return 0; add_error: while (loop < npages) __free_page(pages + loop++); return ret; } /*****************************************************************************/ /* * */ static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size) { int ret; /* assume a truncate from zero size is going to be for the purposes of * shared mmap */ if (size == 0) { if (unlikely(newsize >> 32)) return -EFBIG; return ramfs_nommu_expand_for_mapping(inode, newsize); } /* check that a decrease in size doesn't cut off any shared mappings */ if (newsize < size) { ret = nommu_shrink_inode_mappings(inode, size, newsize); if (ret < 0) return ret; } truncate_setsize(inode, newsize); return 0; } /*****************************************************************************/ /* * handle a change of attributes * - we're specifically interested in a change of size */ static int ramfs_nommu_setattr(struct mnt_idmap *idmap, struct dentry *dentry, struct iattr *ia) { struct inode *inode = d_inode(dentry); unsigned int old_ia_valid = ia->ia_valid; int ret = 0; /* POSIX UID/GID verification for setting inode attributes */ ret = setattr_prepare(&nop_mnt_idmap, dentry, ia); if (ret) return ret; /* pick out size-changing events */ if (ia->ia_valid & ATTR_SIZE) { loff_t size = inode->i_size; if (ia->ia_size != size) { ret = ramfs_nommu_resize(inode, ia->ia_size, size); if (ret < 0 || ia->ia_valid == ATTR_SIZE) goto out; } else { /* we skipped the truncate but must still update * timestamps */ ia->ia_valid |= ATTR_MTIME|ATTR_CTIME; } } setattr_copy(&nop_mnt_idmap, inode, ia); out: ia->ia_valid = old_ia_valid; return ret; } /*****************************************************************************/ /* * try to determine where a shared mapping can be made * - we require that: * - the pages to be mapped must exist * - the pages be physically contiguous in sequence */ static unsigned long ramfs_nommu_get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags) { unsigned long maxpages, lpages, nr_folios, loop, ret, nr_pages, pfn; struct inode *inode = file_inode(file); struct folio_batch fbatch; loff_t isize; /* the mapping mustn't extend beyond the EOF */ lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT; isize = i_size_read(inode); ret = -ENOSYS; maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT; if (pgoff >= maxpages) goto out; if (maxpages - pgoff < lpages) goto out; /* gang-find the pages */ folio_batch_init(&fbatch); nr_pages = 0; repeat: nr_folios = filemap_get_folios_contig(inode->i_mapping, &pgoff, ULONG_MAX, &fbatch); if (!nr_folios) { ret = -ENOSYS; return ret; } if (ret == -ENOSYS) { ret = (unsigned long) folio_address(fbatch.folios[0]); pfn = folio_pfn(fbatch.folios[0]); } /* check the pages for physical adjacency */ for (loop = 0; loop < nr_folios; loop++) { if (pfn + nr_pages != folio_pfn(fbatch.folios[loop])) { ret = -ENOSYS; goto out_free; /* leave if not physical adjacent */ } nr_pages += folio_nr_pages(fbatch.folios[loop]); if (nr_pages >= lpages) goto out_free; /* successfully found desired pages*/ } if (nr_pages < lpages) { folio_batch_release(&fbatch); goto repeat; /* loop if pages are missing */ } /* okay - all conditions fulfilled */ out_free: folio_batch_release(&fbatch); out: return ret; } /*****************************************************************************/ /* * set up a mapping for shared memory segments */ static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma) { if (!is_nommu_shared_mapping(vma->vm_flags)) return -ENOSYS; file_accessed(file); vma->vm_ops = &generic_file_vm_ops; return 0; }