// SPDX-License-Identifier: GPL-2.0
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/*
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* memfd test file-system
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* This file uses FUSE to create a dummy file-system with only one file /memfd.
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* This file is read-only and takes 1s per read.
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*
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* This file-system is used by the memfd test-cases to force the kernel to pin
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* pages during reads(). Due to the 1s delay of this file-system, this is a
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* nice way to test race-conditions against get_user_pages() in the kernel.
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*
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* We use direct_io==1 to force the kernel to use direct-IO for this
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* file-system.
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*/
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#define FUSE_USE_VERSION 26
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#include <fuse.h>
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#include <stdio.h>
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#include <string.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <unistd.h>
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static const char memfd_content[] = "memfd-example-content";
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static const char memfd_path[] = "/memfd";
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static int memfd_getattr(const char *path, struct stat *st)
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{
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memset(st, 0, sizeof(*st));
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if (!strcmp(path, "/")) {
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st->st_mode = S_IFDIR | 0755;
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st->st_nlink = 2;
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} else if (!strcmp(path, memfd_path)) {
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st->st_mode = S_IFREG | 0444;
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st->st_nlink = 1;
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st->st_size = strlen(memfd_content);
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} else {
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return -ENOENT;
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}
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return 0;
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}
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static int memfd_readdir(const char *path,
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void *buf,
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fuse_fill_dir_t filler,
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off_t offset,
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struct fuse_file_info *fi)
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{
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if (strcmp(path, "/"))
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return -ENOENT;
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filler(buf, ".", NULL, 0);
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filler(buf, "..", NULL, 0);
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filler(buf, memfd_path + 1, NULL, 0);
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return 0;
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}
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static int memfd_open(const char *path, struct fuse_file_info *fi)
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{
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if (strcmp(path, memfd_path))
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return -ENOENT;
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if ((fi->flags & 3) != O_RDONLY)
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return -EACCES;
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/* force direct-IO */
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fi->direct_io = 1;
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return 0;
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}
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static int memfd_read(const char *path,
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char *buf,
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size_t size,
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off_t offset,
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struct fuse_file_info *fi)
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{
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size_t len;
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if (strcmp(path, memfd_path) != 0)
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return -ENOENT;
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sleep(1);
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len = strlen(memfd_content);
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if (offset < len) {
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if (offset + size > len)
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size = len - offset;
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memcpy(buf, memfd_content + offset, size);
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} else {
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size = 0;
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}
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return size;
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}
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static struct fuse_operations memfd_ops = {
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.getattr = memfd_getattr,
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.readdir = memfd_readdir,
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.open = memfd_open,
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.read = memfd_read,
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};
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int main(int argc, char *argv[])
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{
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return fuse_main(argc, argv, &memfd_ops, NULL);
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}
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