u-boot does not supports updating the metadata chacksums

Signed-off-by: Jean-Jacques Hiblot jjhiblot@ti.com Reviewed-by: Tom Rini trini@konsulko.com

---

Changes in v4: None Changes in v3: None Changes in v2: - Prevent write access if metadata checksum is enabled

fs/ext4/ext4_write.c | 12 ++++++++++-- include/ext4fs.h | 1 + 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/ext4_write.c b/fs/ext4/ext4_write.c index a7f543f7df..1de29236f0 100644 --- a/fs/ext4/ext4_write.c +++ b/fs/ext4/ext4_write.c @@ -858,12 +858,19 @@ int ext4fs_write(const char *fname, unsigned char *buffer,

g_parent_inode = zalloc(fs->inodesz); if (!g_parent_inode) - goto fail; + goto fail_ext4fs_init;

if (ext4fs_init() != 0) { printf("error in File System init\n"); - return -1; + goto fail_ext4fs_init; + } + + if (le32_to_cpu(fs->sb->feature_ro_compat) & + EXT4_FEATURE_RO_COMPAT_METADATA_CSUM) { + printf("u-boot doesn't support updating the metadata checksums yet\n"); + goto fail; } + inodes_per_block = fs->blksz / fs->inodesz; parent_inodeno = ext4fs_get_parent_inode_num(fname, filename, F_FILE); if (parent_inodeno == -1) @@ -990,6 +997,7 @@ int ext4fs_write(const char *fname, unsigned char *buffer, return 0; fail: ext4fs_deinit(); +fail_ext4fs_init: free(inode_buffer); free(g_parent_inode); free(temp_ptr); diff --git a/include/ext4fs.h b/include/ext4fs.h index bb55639107..bcf440364e 100644 --- a/include/ext4fs.h +++ b/include/ext4fs.h @@ -32,6 +32,7 @@ #define EXT4_EXTENTS_FL 0x00080000 /* Inode uses extents */ #define EXT4_EXT_MAGIC 0xf30a #define EXT4_FEATURE_RO_COMPAT_GDT_CSUM 0x0010 +#define EXT4_FEATURE_RO_COMPAT_METADATA_CSUM 0x0400 #define EXT4_FEATURE_INCOMPAT_EXTENTS 0x0040 #define EXT4_FEATURE_INCOMPAT_64BIT 0x0080 #define EXT4_INDIRECT_BLOCKS 12

There is no need to modify the buffer passed to ext4fs_write_file(). The memset() call is not required here and was likely copied from the equivalent part of the ext4fs_read_file() function where we do need it.

Signed-off-by: Jean-Jacques Hiblot jjhiblot@ti.com

---

Changes in v4: - replaced u64 and u32 with uint64_t and uint32_t

Changes in v3: - reworded commit log

Changes in v2: None

fs/ext4/ext4_common.c | 2 +- fs/ext4/ext4_common.h | 2 +- fs/ext4/ext4_write.c | 11 +++++------ include/ext4fs.h | 2 +- 4 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c index 67e2471bd3..1ff2cd28a6 100644 --- a/fs/ext4/ext4_common.c +++ b/fs/ext4/ext4_common.c @@ -190,7 +190,7 @@ uint32_t ext4fs_div_roundup(uint32_t size, uint32_t n) return res; }

-void put_ext4(uint64_t off, void *buf, uint32_t size) +void put_ext4(uint64_t off, const void *buf, uint32_t size) { uint64_t startblock; uint64_t remainder; diff --git a/fs/ext4/ext4_common.h b/fs/ext4/ext4_common.h index 1ee81ab7ce..4dff1914d9 100644 --- a/fs/ext4/ext4_common.h +++ b/fs/ext4/ext4_common.h @@ -72,7 +72,7 @@ int ext4fs_iget(int inode_no, struct ext2_inode *inode); void ext4fs_allocate_blocks(struct ext2_inode *file_inode, unsigned int total_remaining_blocks, unsigned int *total_no_of_block); -void put_ext4(uint64_t off, void *buf, uint32_t size); +void put_ext4(uint64_t off, const void *buf, uint32_t size); struct ext2_block_group *ext4fs_get_group_descriptor (const struct ext_filesystem *fs, uint32_t bg_idx); uint64_t ext4fs_bg_get_block_id(const struct ext2_block_group *bg, diff --git a/fs/ext4/ext4_write.c b/fs/ext4/ext4_write.c index 1de29236f0..51ca1c0916 100644 --- a/fs/ext4/ext4_write.c +++ b/fs/ext4/ext4_write.c @@ -752,7 +752,7 @@ void ext4fs_deinit(void) * contigous sectors as ext4fs_read_file */ static int ext4fs_write_file(struct ext2_inode *file_inode, - int pos, unsigned int len, char *buf) + int pos, unsigned int len, const char *buf) { int i; int blockcnt; @@ -764,7 +764,7 @@ static int ext4fs_write_file(struct ext2_inode *file_inode, int delayed_start = 0; int delayed_extent = 0; int delayed_next = 0; - char *delayed_buf = NULL; + const char *delayed_buf = NULL;

/* Adjust len so it we can't read past the end of the file. */ if (len > filesize) @@ -816,7 +816,6 @@ static int ext4fs_write_file(struct ext2_inode *file_inode, (uint32_t) delayed_extent); previous_block_number = -1; } - memset(buf, 0, fs->blksz - skipfirst); } buf += fs->blksz - skipfirst; } @@ -830,8 +829,8 @@ static int ext4fs_write_file(struct ext2_inode *file_inode, return len; }

-int ext4fs_write(const char *fname, unsigned char *buffer, - unsigned long sizebytes) +int ext4fs_write(const char *fname, const char *buffer, + unsigned long sizebytes) { int ret = 0; struct ext2_inode *file_inode = NULL; @@ -950,7 +949,7 @@ int ext4fs_write(const char *fname, unsigned char *buffer, if (ext4fs_put_metadata(temp_ptr, itable_blkno)) goto fail; /* copy the file content into data blocks */ - if (ext4fs_write_file(file_inode, 0, sizebytes, (char *)buffer) == -1) { + if (ext4fs_write_file(file_inode, 0, sizebytes, buffer) == -1) { printf("Error in copying content\n"); /* FIXME: Deallocate data blocks */ goto fail; diff --git a/include/ext4fs.h b/include/ext4fs.h index bcf440364e..d4dcefaa96 100644 --- a/include/ext4fs.h +++ b/include/ext4fs.h @@ -128,7 +128,7 @@ extern int gindex; int ext4fs_init(void); void ext4fs_deinit(void); int ext4fs_filename_unlink(char *filename); -int ext4fs_write(const char *fname, unsigned char *buffer, +int ext4fs_write(const char *fname, const char *buffer, unsigned long sizebytes); int ext4_write_file(const char *filename, void *buf, loff_t offset, loff_t len, loff_t *actwrite);

Re-use the functions used to write/create a file, to support creation of a symbolic link. The difference with a regular file are small: - The inode mode is flagged with S_IFLNK instead of S_IFREG - The ext2_dirent's filetype is FILETYPE_SYMLINK instead of FILETYPE_REG - Instead of storing the content of a file in allocated blocks, the path to the target is stored. And if the target's path is short enough, no block is allocated and the target's path is stored in ext2_inode.b.symlink

As with regulars files, if a file/symlink with the same name exits, it is unlinked first and then re-created.

Signed-off-by: Jean-Jacques Hiblot jjhiblot@ti.com Reviewed-by: Tom Rini trini@konsulko.com

---

Changes in v4: None Changes in v3: None Changes in v2: - Fix issue in ext4fs_delete_file() when target in not stored in an allocated block

fs/ext4/ext4_common.c | 2 +- fs/ext4/ext4_write.c | 55 +++++++++++++++++++++++++++++++++++-------- include/ext4fs.h | 3 ++- 3 files changed, 48 insertions(+), 12 deletions(-)

diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c index 1ff2cd28a6..4bc23ab92e 100644 --- a/fs/ext4/ext4_common.c +++ b/fs/ext4/ext4_common.c @@ -607,7 +607,7 @@ restart_read: dir->direntlen = cpu_to_le16(fs->blksz - totalbytes);

dir->namelen = strlen(filename); - dir->filetype = FILETYPE_REG; /* regular file */ + dir->filetype = file_type; temp_dir = (char *)dir; temp_dir = temp_dir + sizeof(struct ext2_dirent); memcpy(temp_dir, filename, strlen(filename)); diff --git a/fs/ext4/ext4_write.c b/fs/ext4/ext4_write.c index 51ca1c0916..52720a80f0 100644 --- a/fs/ext4/ext4_write.c +++ b/fs/ext4/ext4_write.c @@ -431,7 +431,7 @@ fail: free(journal_buffer); }

-static int ext4fs_delete_file(int inodeno) +static int ext4fs_delete_file(int inodeno, int type) { struct ext2_inode inode; short status; @@ -465,6 +465,15 @@ static int ext4fs_delete_file(int inodeno) if (le32_to_cpu(inode.size) % fs->blksz) no_blocks++;

+ /* + * special case for symlinks whose target are small enough that + *it fits in struct ext2_inode.b.symlink: no block had been allocated + */ + if (type == FILETYPE_SYMLINK && + le32_to_cpu(inode.size) <= sizeof(inode.b.symlink)) { + no_blocks = 0; + } + if (le32_to_cpu(inode.flags) & EXT4_EXTENTS_FL) { /* FIXME delete extent index blocks, i.e. eh_depth >= 1 */ struct ext4_extent_header *eh = @@ -830,7 +839,7 @@ static int ext4fs_write_file(struct ext2_inode *file_inode, }

int ext4fs_write(const char *fname, const char *buffer, - unsigned long sizebytes) + unsigned long sizebytes, int type) { int ret = 0; struct ext2_inode *file_inode = NULL; @@ -853,8 +862,12 @@ int ext4fs_write(const char *fname, const char *buffer, struct ext2_block_group *bgd = NULL; struct ext_filesystem *fs = get_fs(); ALLOC_CACHE_ALIGN_BUFFER(char, filename, 256); + bool store_link_in_inode = false; memset(filename, 0x00, 256);

+ if (type != FILETYPE_REG && type != FILETYPE_SYMLINK) + return -1; + g_parent_inode = zalloc(fs->inodesz); if (!g_parent_inode) goto fail_ext4fs_init; @@ -884,7 +897,7 @@ int ext4fs_write(const char *fname, const char *buffer, /* check if the filename is already present in root */ existing_file_inodeno = ext4fs_filename_unlink(filename); if (existing_file_inodeno != -1) { - ret = ext4fs_delete_file(existing_file_inodeno); + ret = ext4fs_delete_file(existing_file_inodeno, type); fs->first_pass_bbmap = 0; fs->curr_blkno = 0;

@@ -893,8 +906,16 @@ int ext4fs_write(const char *fname, const char *buffer, if (ret) goto fail; } - /* calucalate how many blocks required */ - bytes_reqd_for_file = sizebytes; + + /* calculate how many blocks required */ + if (type == FILETYPE_SYMLINK && + sizebytes <= sizeof(file_inode->b.symlink)) { + store_link_in_inode = true; + bytes_reqd_for_file = 0; + } else { + bytes_reqd_for_file = sizebytes; + } + blks_reqd_for_file = lldiv(bytes_reqd_for_file, fs->blksz); if (do_div(bytes_reqd_for_file, fs->blksz) != 0) { blks_reqd_for_file++; @@ -907,7 +928,7 @@ int ext4fs_write(const char *fname, const char *buffer, goto fail; }

- inodeno = ext4fs_update_parent_dentry(filename, FILETYPE_REG); + inodeno = ext4fs_update_parent_dentry(filename, type); if (inodeno == -1) goto fail; /* prepare file inode */ @@ -915,14 +936,23 @@ int ext4fs_write(const char *fname, const char *buffer, if (!inode_buffer) goto fail; file_inode = (struct ext2_inode *)inode_buffer; - file_inode->mode = cpu_to_le16(S_IFREG | S_IRWXU | - S_IRGRP | S_IROTH | S_IXGRP | S_IXOTH); + file_inode->size = cpu_to_le32(sizebytes); + if (type == FILETYPE_SYMLINK) { + file_inode->mode = cpu_to_le16(S_IFLNK | S_IRWXU | S_IRWXG | + S_IRWXO); + if (store_link_in_inode) { + strncpy(file_inode->b.symlink, buffer, sizebytes); + sizebytes = 0; + } + } else { + file_inode->mode = cpu_to_le16(S_IFREG | S_IRWXU | S_IRGRP | + S_IROTH | S_IXGRP | S_IXOTH); + } /* ToDo: Update correct time */ file_inode->mtime = cpu_to_le32(timestamp); file_inode->atime = cpu_to_le32(timestamp); file_inode->ctime = cpu_to_le32(timestamp); file_inode->nlinks = cpu_to_le16(1); - file_inode->size = cpu_to_le32(sizebytes);

/* Allocate data blocks */ ext4fs_allocate_blocks(file_inode, blocks_remaining, @@ -1015,7 +1045,7 @@ int ext4_write_file(const char *filename, void *buf, loff_t offset, return -1; }

- ret = ext4fs_write(filename, buf, len); + ret = ext4fs_write(filename, buf, len, FILETYPE_REG); if (ret) { printf("** Error ext4fs_write() **\n"); goto fail; @@ -1030,3 +1060,8 @@ fail:

return -1; } + +int ext4fs_create_link(const char *target, const char *fname) +{ + return ext4fs_write(fname, target, strlen(target), FILETYPE_SYMLINK); +} diff --git a/include/ext4fs.h b/include/ext4fs.h index d4dcefaa96..946dc6a302 100644 --- a/include/ext4fs.h +++ b/include/ext4fs.h @@ -129,9 +129,10 @@ int ext4fs_init(void); void ext4fs_deinit(void); int ext4fs_filename_unlink(char *filename); int ext4fs_write(const char *fname, const char *buffer, - unsigned long sizebytes); + unsigned long sizebytes, int type); int ext4_write_file(const char *filename, void *buf, loff_t offset, loff_t len, loff_t *actwrite); +int ext4fs_create_link(const char *target, const char *fname); #endif

struct ext_filesystem *get_fs(void);

Test cases are: 1) basic link creation, verify it can be followed 2) chained links, verify it can be followed 3) replace exiting file a with a link, and a link with a link. verify it can be followed 4) create a broken link, verify it can't be followed

Signed-off-by: Jean-Jacques Hiblot jjhiblot@ti.com Reviewed-by: Tom Rini trini@konsulko.com

---

Changes in v4: None Changes in v3: - removed FS integrity test (fsck) in python tests

Changes in v2: - Added python tests for symlinks under sandbox

test/py/tests/test_fs/conftest.py | 75 ++++++++++++++++ test/py/tests/test_fs/fstest_defs.py | 3 + test/py/tests/test_fs/test_symlink.py | 125 ++++++++++++++++++++++++++ 3 files changed, 203 insertions(+) create mode 100644 test/py/tests/test_fs/test_symlink.py

diff --git a/test/py/tests/test_fs/conftest.py b/test/py/tests/test_fs/conftest.py index 745ed0ed38..9324657d21 100644 --- a/test/py/tests/test_fs/conftest.py +++ b/test/py/tests/test_fs/conftest.py @@ -13,6 +13,7 @@ supported_fs_basic = ['fat16', 'fat32', 'ext4'] supported_fs_ext = ['fat16', 'fat32'] supported_fs_mkdir = ['fat16', 'fat32'] supported_fs_unlink = ['fat16', 'fat32'] +supported_fs_symlink = ['ext4']

# # Filesystem test specific setup @@ -48,6 +49,7 @@ def pytest_configure(config): global supported_fs_ext global supported_fs_mkdir global supported_fs_unlink + global supported_fs_symlink

def intersect(listA, listB): return [x for x in listA if x in listB] @@ -59,6 +61,7 @@ def pytest_configure(config): supported_fs_ext = intersect(supported_fs, supported_fs_ext) supported_fs_mkdir = intersect(supported_fs, supported_fs_mkdir) supported_fs_unlink = intersect(supported_fs, supported_fs_unlink) + supported_fs_symlink = intersect(supported_fs, supported_fs_symlink)

def pytest_generate_tests(metafunc): """Parametrize fixtures, fs_obj_xxx @@ -84,6 +87,9 @@ def pytest_generate_tests(metafunc): if 'fs_obj_unlink' in metafunc.fixturenames: metafunc.parametrize('fs_obj_unlink', supported_fs_unlink, indirect=True, scope='module') + if 'fs_obj_symlink' in metafunc.fixturenames: + metafunc.parametrize('fs_obj_symlink', supported_fs_symlink, + indirect=True, scope='module')

# # Helper functions @@ -525,3 +531,72 @@ def fs_obj_unlink(request, u_boot_config): call('rmdir %s' % mount_dir, shell=True) if fs_img: call('rm -f %s' % fs_img, shell=True) + +# +# Fixture for symlink fs test +# +# NOTE: yield_fixture was deprecated since pytest-3.0 +@pytest.yield_fixture() +def fs_obj_symlink(request, u_boot_config): + """Set up a file system to be used in symlink fs test. + + Args: + request: Pytest request object. + u_boot_config: U-boot configuration. + + Return: + A fixture for basic fs test, i.e. a triplet of file system type, + volume file name and a list of MD5 hashes. + """ + fs_type = request.param + fs_img = '' + + fs_ubtype = fstype_to_ubname(fs_type) + check_ubconfig(u_boot_config, fs_ubtype) + + mount_dir = u_boot_config.persistent_data_dir + '/mnt' + + small_file = mount_dir + '/' + SMALL_FILE + medium_file = mount_dir + '/' + MEDIUM_FILE + + try: + + # 3GiB volume + fs_img = mk_fs(u_boot_config, fs_type, 0x40000000, '1GB') + + # Mount the image so we can populate it. + check_call('mkdir -p %s' % mount_dir, shell=True) + mount_fs(fs_type, fs_img, mount_dir) + + # Create a subdirectory. + check_call('mkdir %s/SUBDIR' % mount_dir, shell=True) + + # Create a small file in this image. + check_call('dd if=/dev/urandom of=%s bs=1M count=1' + % small_file, shell=True) + + # Create a medium file in this image. + check_call('dd if=/dev/urandom of=%s bs=10M count=1' + % medium_file, shell=True) + + # Generate the md5sums of reads that we will test against small file + out = check_output( + 'dd if=%s bs=1M skip=0 count=1 2> /dev/null | md5sum' + % small_file, shell=True) + md5val = [out.split()[0]] + out = check_output( + 'dd if=%s bs=10M skip=0 count=1 2> /dev/null | md5sum' + % medium_file, shell=True) + md5val.extend([out.split()[0]]) + + umount_fs(mount_dir) + except CalledProcessError: + pytest.skip('Setup failed for filesystem: ' + fs_type) + return + else: + yield [fs_ubtype, fs_img, md5val] + finally: + umount_fs(mount_dir) + call('rmdir %s' % mount_dir, shell=True) + if fs_img: + call('rm -f %s' % fs_img, shell=True) diff --git a/test/py/tests/test_fs/fstest_defs.py b/test/py/tests/test_fs/fstest_defs.py index 5f107562d9..35b2bb6518 100644 --- a/test/py/tests/test_fs/fstest_defs.py +++ b/test/py/tests/test_fs/fstest_defs.py @@ -6,6 +6,9 @@ MIN_FILE='testfile' # $SMALL_FILE is the name of the 1MB file in the file system image SMALL_FILE='1MB.file'

+# $MEDIUM_FILE is the name of the 10MB file in the file system image +MEDIUM_FILE='10MB.file' + # $BIG_FILE is the name of the 2.5GB file in the file system image BIG_FILE='2.5GB.file'

diff --git a/test/py/tests/test_fs/test_symlink.py b/test/py/tests/test_fs/test_symlink.py new file mode 100644 index 0000000000..bc4e679437 --- /dev/null +++ b/test/py/tests/test_fs/test_symlink.py @@ -0,0 +1,125 @@ +# SPDX-License-Identifier: GPL-2.0+ +# Copyright (c) 2018, Texas Instrument +# Author: Jean-Jacques Hiblot jjhiblot@ti.com +# +# U-Boot File System:symlink Test + +""" +This test verifies unlink operation (deleting a file or a directory) +on file system. +""" + +import pytest +import re +from fstest_defs import * + + +@pytest.mark.boardspec('sandbox') +@pytest.mark.slow +class TestSymlink(object): + def test_symlink1(self, u_boot_console, fs_obj_symlink): + """ + Test Case 1 - create a link. and follow it when reading + """ + fs_type, fs_img, md5val = fs_obj_symlink + with u_boot_console.log.section('Test Case 1 - create link and read'): + output = u_boot_console.run_command_list([ + 'host bind 0 %s' % fs_img, + 'setenv filesize', + 'ln host 0:0 %s /%s.link ' % (SMALL_FILE, SMALL_FILE), + ]) + assert('' in ''.join(output)) + + output = u_boot_console.run_command_list([ + '%sload host 0:0 %x /%s.link' % (fs_type, ADDR, SMALL_FILE), + 'printenv filesize']) + assert('filesize=100000' in ''.join(output)) + + # Test Case 4b - Read full 1MB of small file + output = u_boot_console.run_command_list([ + 'md5sum %x $filesize' % ADDR, + 'setenv filesize']) + assert(md5val[0] in ''.join(output)) + + def test_symlink2(self, u_boot_console, fs_obj_symlink): + """ + Test Case 2 - create chained links + """ + fs_type, fs_img, md5val = fs_obj_symlink + with u_boot_console.log.section('Test Case 2 - create chained links'): + output = u_boot_console.run_command_list([ + 'host bind 0 %s' % fs_img, + 'setenv filesize', + 'ln host 0:0 %s /%s.link1 ' % (SMALL_FILE, SMALL_FILE), + 'ln host 0:0 /%s.link1 /SUBDIR/%s.link2' % ( + SMALL_FILE, SMALL_FILE), + 'ln host 0:0 SUBDIR/%s.link2 /%s.link3' % ( + SMALL_FILE, SMALL_FILE), + ]) + assert('' in ''.join(output)) + + output = u_boot_console.run_command_list([ + '%sload host 0:0 %x /%s.link3' % (fs_type, ADDR, SMALL_FILE), + 'printenv filesize']) + assert('filesize=100000' in ''.join(output)) + + # Test Case 4b - Read full 1MB of small file + output = u_boot_console.run_command_list([ + 'md5sum %x $filesize' % ADDR, + 'setenv filesize']) + assert(md5val[0] in ''.join(output)) + + def test_symlink3(self, u_boot_console, fs_obj_symlink): + """ + Test Case 3 - replace file/link with link + """ + fs_type, fs_img, md5val = fs_obj_symlink + with u_boot_console.log.section('Test Case 1 - create link and read'): + output = u_boot_console.run_command_list([ + 'host bind 0 %s' % fs_img, + 'setenv filesize', + 'ln host 0:0 %s /%s ' % (MEDIUM_FILE, SMALL_FILE), + 'ln host 0:0 %s /%s.link ' % (MEDIUM_FILE, MEDIUM_FILE), + ]) + assert('' in ''.join(output)) + + output = u_boot_console.run_command_list([ + '%sload host 0:0 %x /%s' % (fs_type, ADDR, SMALL_FILE), + 'printenv filesize']) + assert('filesize=a00000' in ''.join(output)) + + output = u_boot_console.run_command_list([ + 'md5sum %x $filesize' % ADDR, + 'setenv filesize']) + assert(md5val[1] in ''.join(output)) + + output = u_boot_console.run_command_list([ + 'ln host 0:0 %s.link /%s ' % (MEDIUM_FILE, SMALL_FILE), + '%sload host 0:0 %x /%s' % (fs_type, ADDR, SMALL_FILE), + 'printenv filesize']) + assert('filesize=a00000' in ''.join(output)) + + output = u_boot_console.run_command_list([ + 'md5sum %x $filesize' % ADDR, + 'setenv filesize']) + assert(md5val[1] in ''.join(output)) + + def test_symlink4(self, u_boot_console, fs_obj_symlink): + """ + Test Case 4 - create a broken link + """ + fs_type, fs_img, md5val = fs_obj_symlink + with u_boot_console.log.section('Test Case 1 - create link and read'): + + output = u_boot_console.run_command_list([ + 'setenv filesize', + 'ln host 0:0 nowhere /link ', + ]) + assert('' in ''.join(output)) + + output = u_boot_console.run_command( + '%sload host 0:0 %x /link' % + (fs_type, ADDR)) + with u_boot_console.disable_check('error_notification'): + output = u_boot_console.run_command('printenv filesize') + assert('"filesize" not defined' in ''.join(output))