├── Makefile ├── device.h ├── device.c ├── gnutar.h ├── README.md ├── tar.h ├── tar.c ├── sample.tar ├── driver.c └── LICENSE /Makefile: -------------------------------------------------------------------------------- 1 | obj-m+=tarfs.o 2 | 3 | tarfs-y := driver.o tar.o device.o 4 | 5 | all: 6 | make -C /lib/modules/$(shell uname -r)/build/ M=$(PWD) modules 7 | clean: 8 | make -C /lib/modules/$(shell uname -r)/build/ M=$(PWD) clean 9 | -------------------------------------------------------------------------------- /device.h: -------------------------------------------------------------------------------- 1 | #ifndef DEVICE_H 2 | #define DEVICE_H 3 | 4 | #include 5 | #include 6 | 7 | /** 8 | * @brief reads part of the block device into \a baffer 9 | * @param buffer the destination buffer 10 | * @param size the buffer size 11 | * @param offset byte offset in the block device relative to its start 12 | * @param sb the super block descriptor 13 | * @return count of bytes read 14 | */ 15 | size_t tarfs_read(void *buffer, size_t size, off_t offset, 16 | struct super_block *sb); 17 | 18 | #endif 19 | -------------------------------------------------------------------------------- /device.c: -------------------------------------------------------------------------------- 1 | #include 2 | #include 3 | 4 | #include "device.h" 5 | 6 | size_t tarfs_read(void *buffer, size_t size, off_t offset, 7 | struct super_block *sb) 8 | { 9 | struct buffer_head *bh; 10 | size_t pos = 0; 11 | 12 | while (size > 0) { 13 | unsigned int block = (offset + pos) / sb->s_blocksize; 14 | off_t inner_off = (offset + pos) % sb->s_blocksize; 15 | size_t inner_size = min_t(size_t, sb->s_blocksize - inner_off, size); 16 | 17 | bh = sb_bread(sb, block); 18 | 19 | if (!bh) 20 | pr_err("tarfs: Failed to read block %u", block); 21 | 22 | if (bh->b_size != sb->s_blocksize) 23 | pr_err("tarfs: Wanted %lu byte block, but got %lu", sb->s_blocksize, bh->b_size); 24 | 25 | memcpy(buffer, bh->b_data + inner_off, inner_size); 26 | brelse(bh); 27 | 28 | pos += inner_size; 29 | size -= inner_size; 30 | buffer += inner_size; 31 | } 32 | 33 | return pos; 34 | } 35 | -------------------------------------------------------------------------------- /gnutar.h: -------------------------------------------------------------------------------- 1 | #ifndef GNUTAR_H 2 | #define GNUTAR_H 3 | 4 | /* Following is based on 5 | * https://www.gnu.org/software/tar/manual/html_node/Standard.html 6 | * which in turn references `src/tar.h` from the GNU tar project. 7 | */ 8 | 9 | /* Values used in typeflag field. */ 10 | #define REGTYPE '0' /* regular file */ 11 | #define AREGTYPE '\0' /* regular file */ 12 | #define LNKTYPE '1' /* link */ 13 | #define SYMTYPE '2' /* reserved */ 14 | #define CHRTYPE '3' /* character special */ 15 | #define BLKTYPE '4' /* block special */ 16 | #define DIRTYPE '5' /* directory */ 17 | #define FIFOTYPE '6' /* FIFO special */ 18 | #define CONTTYPE '7' /* reserved */ 19 | 20 | /* OLDGNU_MAGIC uses both magic and version fields, which are contiguous. 21 | Found in an archive, it indicates an old GNU header format, which will be 22 | hopefully become obsolescent. With OLDGNU_MAGIC, uname and gname are 23 | valid, though the header is not truly POSIX conforming. */ 24 | #define OLDGNU_MAGIC "ustar " /* 7 chars and a null */ 25 | 26 | /* Jörg Schilling star header */ 27 | 28 | struct star_header 29 | { /* byte offset */ 30 | char name[100]; /* 0 */ 31 | char mode[8]; /* 100 */ 32 | char uid[8]; /* 108 */ 33 | char gid[8]; /* 116 */ 34 | char size[12]; /* 124 */ 35 | char mtime[12]; /* 136 */ 36 | char chksum[8]; /* 148 */ 37 | char typeflag; /* 156 */ 38 | char linkname[100]; /* 157 */ 39 | char magic[6]; /* 257 */ 40 | char version[2]; /* 263 */ 41 | char uname[32]; /* 265 */ 42 | char gname[32]; /* 297 */ 43 | char devmajor[8]; /* 329 */ 44 | char devminor[8]; /* 337 */ 45 | char prefix[131]; /* 345 */ 46 | char atime[12]; /* 476 */ 47 | char ctime[12]; /* 488 */ 48 | /* 500 */ 49 | }; 50 | 51 | #endif 52 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # tarfs 2 | 3 | tarfs is implemented as Linux kernel module filesystem driver. It's more of a 4 | research thing. If you're interested in actually using something like this, 5 | consider writing it using libFuse :) 6 | 7 | ## Features 8 | 9 | * Supports GNU tar files 10 | * Regular files, directories and symlinks 11 | * UID, GID, access/modification/creation time 12 | * Read-only access to files and directories 13 | 14 | ## Compiling 15 | 16 | You'll require the linux development files. For ArchLinux, you need the 17 | `linux-headers` packet. 18 | 19 | After that, just run `make` to build the `tarfs.ko`, which is a loadable 20 | kernel module. 21 | 22 | **Note**: The module was tested with Linux `4.9.11`, on a `x64 ArchLinux` 23 | computer. 24 | 25 | ## Usage 26 | 27 | ```sh 28 | # If not already done, build the module 29 | make 30 | 31 | # Now you can load the module: 32 | sudo insmod tarfs.ko 33 | 34 | # You need a mount directory 35 | mkdir mnt 36 | 37 | # Mount some tar archive. A sample one is included: 38 | sudo mount sample.tar -o loop -t tarfs mnt 39 | 40 | # Discover the archives content 41 | ls mnt -R 42 | cat mnt/hello.c 43 | 44 | # Unmount 45 | sudo umount mnt 46 | 47 | # And unload the kernel module 48 | sudo rmmod tarfs.ko 49 | ``` 50 | 51 | ## File overview 52 | 53 | * **driver.c** The driver code interfacing with Linux 54 | * **device.c/h** Code to read from the underlying block device 55 | * **tar.c/h** Code to read the tar file 56 | * **gnutar.h** Header definition for tar files, taken from 57 | https://www.gnu.org/software/tar/manual/html_node/Standard.html 58 | 59 | ## Implementation 60 | 61 | This project focuses on the interaction part with Linux. That's why the 62 | implementation of the Tar reading code is kept really simple: On mount, all 63 | file entries are read from the tar file, and stored as a linked list. Some 64 | data, like the file path, is stored separatly in the structure to ease access. 65 | 66 | When Linux wants the module to list a directory, or find a specific file, the 67 | whole linked list is iterated, making most file system operations `O(n)`. 68 | 69 | ## Attention 70 | 71 | Please note that you're actually loading stuff into your kernel. That means the 72 | module runs with highest permissions possible (Ring 0 on x86 machines). Also, 73 | if something goes really wrong, your entire computer could hang/crash/freeze. 74 | 75 | It's recommended to try this in a virtual machine. You can create one easily 76 | using programs like `QEMU` or `VirtualBox`. 77 | 78 | ## License 79 | 80 | The enclosed source code, and the `sample.tar` file including its contents, are 81 | subject to the **General Public License version 3** (**GPLv3**). Please see the 82 | included `LICENSE` file for the whole license text. If you're interested in a 83 | legally non-binding explanation of this license, have a look at 84 | [its tl;drLegal page](https://tldrlegal.com/license/gnu-general-public-license-v3-(gpl-3)). 85 | 86 | ## Still reading? 87 | 88 | Thanks for your interest - Have a nice day, and happy hacking! 89 | -------------------------------------------------------------------------------- /tar.h: -------------------------------------------------------------------------------- 1 | #ifndef TAR_H 2 | #define TAR_H 3 | 4 | #include 5 | #include 6 | #include 7 | #include "gnutar.h" 8 | 9 | /** Describes access to an entry in a tar file. */ 10 | struct tar_entry { 11 | /** The entry header. */ 12 | struct star_header header; 13 | 14 | /** Path to the entry. */ 15 | char *dirname; 16 | 17 | /** Name of the entry. */ 18 | char *basename; 19 | 20 | /** File offset to the entry header. */ 21 | unsigned int offset; 22 | 23 | /** File offset to the entry data. */ 24 | unsigned int data_offset; 25 | 26 | /** Length of the data. */ 27 | size_t length; 28 | 29 | /** The inode number of the entry. */ 30 | unsigned long inode; 31 | 32 | /** Mode flags. */ 33 | umode_t mode; 34 | 35 | /** User id */ 36 | uid_t uid; 37 | 38 | /** Group id */ 39 | gid_t gid; 40 | 41 | /** UNIX timestamp of last access. */ 42 | struct timespec atime; 43 | 44 | /** UNIX timestamp of last modification. */ 45 | struct timespec mtime; 46 | 47 | /** UNIX timestamp of creation. */ 48 | struct timespec ctime; 49 | 50 | /** Next entry, or \c NULL if none. */ 51 | struct tar_entry *next; 52 | }; 53 | 54 | /** 55 | * @brief Maps a tar file type to a linux file type. 56 | * @param typeflag the type value 57 | * @return the linux file type 58 | */ 59 | mode_t tar_type_to_posix(int typeflag); 60 | 61 | /** 62 | * @brief Reads a TAR entry 63 | * @param sb the super block to read from 64 | * @param offset the read offset 65 | * @return the read entry, or \c NULL if reading failed 66 | */ 67 | struct tar_entry *tar_read_entry(struct super_block *sb, off_t offset); 68 | 69 | /** 70 | * @brief Reads all tar entries from \a handle into a linked list. 71 | * @param sb the super block to read from 72 | * @return the found entries 73 | * @note Does \b not lock 74 | */ 75 | struct tar_entry *tar_open(struct super_block *sb); 76 | 77 | /** 78 | * @brief Frees memory allocated by \a entry and all following entries. 79 | * @param entry the entry to free 80 | */ 81 | void tar_free(struct tar_entry *entry); 82 | 83 | /** 84 | * @brief Reads data of \a entry from \a handle starting at \a off into 85 | * \a buffer. 86 | * @param sb the super block to read from 87 | * @param entry the entry to read 88 | * @param off offset in the data 89 | * @param buffer the target buffer 90 | * @param len maximum count of bytes to read 91 | * @return the count of bytes read 92 | * @note Does \b not lock 93 | */ 94 | size_t tar_read(struct super_block *sb, struct tar_entry *entry, 95 | unsigned int off, void *buffer, size_t len); 96 | 97 | /** 98 | * @brief Finds an entry starting at \a entry by its \a dirname and \a basename. 99 | * @param entry the start entry 100 | * @param dirname the directory path name of the entry 101 | * @param basename the base name of the entry 102 | * @return the found entry or \c NULL 103 | */ 104 | struct tar_entry *tar_find(struct tar_entry *entry, const char *dirname, 105 | const char *basename); 106 | 107 | #endif 108 | -------------------------------------------------------------------------------- /tar.c: -------------------------------------------------------------------------------- 1 | #include 2 | #include 3 | #include 4 | 5 | #include "tar.h" 6 | #include "device.h" 7 | 8 | /** Aligns \a x on a 512 boundary. */ 9 | #define ALIGN_SECTOR(x) (((x) % 512 > 0) ? 512 - ((x) % 512) : 0) 10 | 11 | #define OCTAL (8) 12 | 13 | mode_t tar_type_to_posix(int typeflag) 14 | { 15 | switch(typeflag) { 16 | case REGTYPE: 17 | case AREGTYPE: 18 | return S_IFREG; 19 | case DIRTYPE: 20 | return S_IFDIR; 21 | case SYMTYPE: 22 | return S_IFLNK; 23 | case CHRTYPE: 24 | return S_IFCHR; 25 | case BLKTYPE: 26 | return S_IFBLK; 27 | case FIFOTYPE: 28 | return S_IFIFO; 29 | default: 30 | return 0; 31 | } 32 | } 33 | 34 | /** 35 | * @brief Allocates a string by combining prefix and name from \a header. 36 | * @return the string, must be free'd later by the caller. 37 | */ 38 | static char *build_name(struct star_header *header) 39 | { 40 | char *prefix_end = memchr(header->prefix, 0, sizeof(header->prefix)); 41 | char *name_end = memchr(header->name, 0, sizeof(header->name)); 42 | 43 | size_t prefix_len = prefix_end - header->prefix; 44 | size_t name_len = name_end - header->name; 45 | 46 | char *name = kmalloc(prefix_len + name_len + 1, GFP_KERNEL); 47 | 48 | if (!name) 49 | return NULL; 50 | 51 | memcpy(name, header->prefix, prefix_len); 52 | memcpy(name + prefix_len, header->name, name_len); 53 | name[prefix_len + name_len] = 0x0; 54 | 55 | // The path name ends with a slash if the entry is a directory 56 | if (name[prefix_len + name_len - 1] == '/') 57 | name[prefix_len + name_len - 1] = 0x0; 58 | 59 | return name; 60 | } 61 | 62 | /** 63 | * @brief Reads a tar header at the \a offset. 64 | * @param sb the superblock to read from 65 | * @param offset the 512-byte aligned offset 66 | * @return the entry on success, else \c NULL 67 | */ 68 | struct tar_entry *tar_read_entry(struct super_block *sb, off_t offset) 69 | { 70 | struct star_header header; 71 | char *full_name = NULL; 72 | char *basename = NULL; 73 | struct tar_entry *entry = NULL; 74 | unsigned int length = 0; 75 | unsigned int mode = 0; 76 | uid_t uid = 0; 77 | gid_t gid = 0; 78 | struct timespec atime, mtime, ctime; 79 | 80 | // Read the header, and return NULL if there can't be a header. 81 | if (tarfs_read(&header, sizeof(header), offset, sb) != sizeof(header)) { 82 | pr_err("tarfs: read failure"); 83 | return NULL; 84 | } 85 | 86 | // Check for the header magic value 87 | if (memcmp(header.magic, OLDGNU_MAGIC, sizeof(header.magic)) != 0) { 88 | return NULL; 89 | } 90 | 91 | // Parse the data length from the header 92 | if (kstrtouint(header.size, OCTAL, &length) != 0) { 93 | pr_info("tarfs: failed to read size"); 94 | return NULL; 95 | } 96 | 97 | // Parse mode 98 | if (kstrtouint(header.mode, OCTAL, &mode) != 0) { 99 | pr_info("tarfs: failed to read mode"); 100 | return NULL; 101 | } 102 | 103 | if (kstrtouint(header.uid, OCTAL, &uid) != 0) { 104 | pr_info("tarfs: failed to read uid"); 105 | return NULL; 106 | } 107 | 108 | if (kstrtouint(header.gid, OCTAL, &gid) != 0) { 109 | pr_info("tarfs: failed to read gid"); 110 | return NULL; 111 | } 112 | 113 | // Modification time is the most likely to be present 114 | if (kstrtoul(header.mtime, OCTAL, &mtime.tv_sec) != 0) { 115 | mtime.tv_sec = 0; 116 | mtime.tv_nsec = 0; 117 | } 118 | 119 | if (kstrtoul(header.atime, OCTAL, &atime.tv_sec) != 0) { 120 | atime = mtime; // Copy mtime if not set 121 | } 122 | 123 | if (kstrtoul(header.ctime, OCTAL, &ctime.tv_sec) != 0) { 124 | ctime = mtime; // Copy mtime if not set 125 | } 126 | 127 | // Build the full name of the entry 128 | full_name = build_name(&header); 129 | if (!full_name) { 130 | pr_info("tarfs: name allocation error"); 131 | return NULL; 132 | } 133 | 134 | // Split path name into dirname and basename. If the file resides in the 135 | // root, take the full name as basename and point dirname to the trailing 136 | // NUL byte. Else, NUL the last slash ("/") and set the pointers accordingly. 137 | basename = strrchr(full_name, '/'); 138 | if (basename) { 139 | *basename = 0x0; 140 | basename++; 141 | } else { 142 | basename = full_name; 143 | full_name = basename + strlen(basename); 144 | } 145 | 146 | // Fill in structure 147 | entry = kzalloc(sizeof(struct tar_entry), GFP_KERNEL); 148 | entry->header = header; 149 | entry->dirname = full_name; 150 | entry->basename = basename; 151 | entry->offset = offset; 152 | entry->data_offset = offset + sizeof(header) + ALIGN_SECTOR(sizeof(header)); 153 | entry->length = length; 154 | entry->mode = mode; 155 | entry->uid = uid; 156 | entry->gid = gid; 157 | entry->atime = atime; 158 | entry->mtime = mtime; 159 | entry->ctime = ctime; 160 | return entry; 161 | } 162 | 163 | /** 164 | * @brief Reads all file headers from the \a sb 165 | * @param sb the underlying super block 166 | * @return the first entry, pointing at all other entries 167 | */ 168 | struct tar_entry *tar_open(struct super_block *sb) 169 | { 170 | struct tar_entry *first = tar_read_entry(sb, 0); 171 | struct tar_entry *parent = first; 172 | struct tar_entry *next; 173 | unsigned long count = 2; 174 | off_t offset = 0; 175 | off_t length; 176 | 177 | while (parent) { 178 | parent->inode = count; // Assign inode number 179 | count++; 180 | 181 | length = parent->data_offset + parent->length; 182 | 183 | // Skip leading data of the previously read entry 184 | offset = length + ALIGN_SECTOR(length); 185 | 186 | // Read next entry 187 | next = tar_read_entry(sb, offset); 188 | parent->next = next; 189 | parent = next; 190 | } 191 | 192 | return first; 193 | } 194 | 195 | /** 196 | * @brief Frees the \a entry, and all connected entries 197 | * @param entry the entry to deallocate 198 | */ 199 | void tar_free(struct tar_entry *entry) 200 | { 201 | while (entry) { 202 | struct tar_entry *next = entry->next; 203 | 204 | if (entry->dirname < entry->basename) 205 | kfree(entry->dirname); 206 | else 207 | kfree(entry->basename); 208 | 209 | kfree(entry); 210 | entry = next; 211 | } 212 | } 213 | 214 | /** 215 | * @brief Reads the payload of \a entry into \a buffer. 216 | * @param sb the underlying super block 217 | * @param entry the entry to read from 218 | * @param off the offset inside the file data 219 | * @param buffer the target buffer 220 | * @param len byte count to read 221 | * @return count of read bytes 222 | */ 223 | size_t tar_read(struct super_block *sb, struct tar_entry *entry, 224 | unsigned int off, void *buffer, size_t len) 225 | { 226 | size_t to_read = min_t(size_t, len, entry->length - off); 227 | return tarfs_read(buffer, to_read, entry->data_offset + off, sb); 228 | } 229 | 230 | /** 231 | * @brief Finds an entry by its path. 232 | * @param entry the start entry 233 | * @param dirname the path to the directory containing the target entry 234 | * @param basename the name of the target entry in its parent directory 235 | * @return the found entry, or \c NULL 236 | */ 237 | struct tar_entry *tar_find(struct tar_entry *entry, const char *dirname, 238 | const char *basename) 239 | { 240 | while (entry) { 241 | if (!strcmp(entry->basename, basename) && 242 | !strcmp(entry->dirname, dirname)) { 243 | return entry; 244 | } 245 | 246 | entry = entry->next; 247 | } 248 | 249 | return NULL; 250 | } 251 | -------------------------------------------------------------------------------- /sample.tar: -------------------------------------------------------------------------------- 1 | greet.c0000644000175000017500000000025213060557663013420 0ustar papierkorbpapierkorb#include 2 | 3 | int main(int argc, char **argv) { 4 | if (argc > 1) { 5 | printf("Hello, %s!\n", argv[1]); 6 | } else { 7 | printf("Hello, World!\n"); 8 | } 9 | 10 | return 0; 11 | } 12 | Example tape archive by Stefan Merettig: https://github.com/papierkorb/tarfhello.c0000644000175000017500000000011413060557566013414 0ustar papierkorbpapierkorb#include 13 | 14 | int main() { 15 | printf("Hello, World!\n"); 16 | return 0; 17 | } 18 | a_dir/0000755000175000017500000000000013060573314013214 5ustar papierkorbpapierkorba_dir/hello.c0000777000175000017500000000000013060560055016140 2../hello.custar papierkorbpapierkorba_dir/fac.rb0000644000175000017500000000013113060573301014261 0ustar papierkorbpapierkorb#!/usr/bin/env ruby 19 | 20 | def fac(n) 21 | return 1 if n < 1 22 | 1.upto(n).reduce(:*) 23 | end 24 | 25 | p fac 10 26 | -------------------------------------------------------------------------------- /driver.c: -------------------------------------------------------------------------------- 1 | #include 2 | #include 3 | #include 4 | #include 5 | #include 6 | #include 7 | 8 | #include 9 | #include 10 | #include 11 | #include 12 | 13 | #include "tar.h" 14 | 15 | MODULE_LICENSE("GPL"); 16 | MODULE_AUTHOR("Stefan Merettig"); 17 | MODULE_DESCRIPTION("A tar filesystem driver"); 18 | MODULE_VERSION("0.1"); 19 | 20 | #define WRITE_MASK (0222) 21 | #define ROOT_INO_MODE (S_IFDIR | 0555) 22 | #define ROOT_INO (0) 23 | 24 | static struct super_operations tarfs_super_ops; 25 | static const struct inode_operations tarfs_dir_inode_operations; 26 | static const struct inode_operations tarfs_file_inode_operations; 27 | static const struct inode_operations tarfs_symlink_inode_operations; 28 | static const struct file_operations tarfs_dir_operations; 29 | static const struct file_operations tarfs_file_operations; 30 | 31 | /** 32 | * @brief Finds an tar entry by its inode number. 33 | * @param entry the start entry 34 | * @param inode the inode number 35 | * @return the found entry or \c NULL 36 | */ 37 | static struct tar_entry *tarfs_find_by_inode(struct tar_entry *entry, 38 | unsigned long inode) 39 | { 40 | while (entry) { 41 | if (entry->inode == inode) 42 | return entry; 43 | entry = entry->next; 44 | } 45 | 46 | return NULL; 47 | } 48 | 49 | /** 50 | * @brief Reads from a file. 51 | * @param file the accessed file 52 | * @param userbuf the target buffer in \b user-space 53 | * @param count byte count to read 54 | * @param pos the position to read from, updated afterwards 55 | * @return count of bytes read 56 | */ 57 | static ssize_t tarfs_file_read(struct file *file, char __user *userbuf, 58 | size_t count, loff_t *pos) 59 | { 60 | struct inode *inode = file_inode(file); 61 | struct super_block *sb = inode->i_sb; 62 | struct tar_entry *root = (struct tar_entry *) sb->s_fs_info; 63 | struct tar_entry *entry; 64 | size_t advanced; 65 | unsigned long not_copied; 66 | void *buffer = NULL; 67 | 68 | if (!root) 69 | return -ENOENT; 70 | 71 | entry = tarfs_find_by_inode(root, inode->i_ino); 72 | if (!entry) 73 | return -ENOENT; 74 | 75 | buffer = kzalloc(count, GFP_KERNEL); 76 | advanced = tar_read(sb, entry, *pos, buffer, count); 77 | not_copied = copy_to_user(userbuf, buffer, advanced); 78 | kfree(buffer); 79 | 80 | if (not_copied > advanced) 81 | return -EBADF; // Is this a good error code? 82 | 83 | advanced -= not_copied; 84 | *pos += advanced; 85 | 86 | return advanced; 87 | } 88 | 89 | /** 90 | * @brief Releases a file handle. 91 | * @param inode the affected inode 92 | * @param file the file to close 93 | * @return \c 0 94 | */ 95 | static int tarfs_file_release(struct inode *inode, struct file *file) 96 | { 97 | return 0; 98 | } 99 | 100 | /** 101 | * @brief Returns the POSIX ACL of a inode. Not supported, thus always \c NULL 102 | * @param inode the inode 103 | * @param flags lookup flags 104 | * @return \c NULL 105 | */ 106 | static struct posix_acl *tarfs_get_acl(struct inode *inode, int flags) 107 | { 108 | return NULL; 109 | } 110 | 111 | /** 112 | * @brief Returns the POSIX file mode of \a entry. 113 | * @param entry the entry to get the file mode from 114 | * @return the file mode 115 | */ 116 | static mode_t tarfs_entry_mode(struct tar_entry *entry) 117 | { 118 | mode_t mode = entry->mode & ~WRITE_MASK; 119 | mode |= tar_type_to_posix(entry->header.typeflag); 120 | return mode; 121 | } 122 | 123 | /** 124 | * @brief Returns the full path to an \a entry. 125 | * @param entry the entry to get the path from 126 | * @return Allocated string of the path, must be freed later 127 | */ 128 | static char *tarfs_full_name(struct tar_entry *entry) 129 | { 130 | size_t dirlen = strlen(entry->dirname); 131 | size_t baselen = strlen(entry->basename); 132 | size_t len = dirlen + baselen + 2; 133 | char *result = kzalloc(len, GFP_KERNEL); 134 | 135 | if (!result) 136 | return NULL; 137 | 138 | // Don't prepend a "/" in for top-level entries. 139 | if (dirlen < 1) 140 | strncpy(result, entry->basename, baselen); 141 | else 142 | snprintf(result, len, "%s/%s", entry->dirname, entry->basename); 143 | 144 | return result; 145 | } 146 | 147 | /** 148 | * @brief Builds an inode structure out of an \a entry. 149 | * @param sb the super block 150 | * @param entry the entry 151 | * @return a filled inode structure 152 | */ 153 | static struct inode *tarfs_build_inode(struct super_block *sb, 154 | struct tar_entry *entry) 155 | { 156 | struct inode *inode = new_inode(sb); 157 | mode_t mode = tarfs_entry_mode(entry); 158 | 159 | if (!inode) 160 | return NULL; 161 | 162 | inode->i_ino = entry->inode; 163 | inode->i_mode = mode; 164 | inode->i_uid.val = entry->uid; 165 | inode->i_gid.val = entry->gid; 166 | inode->i_size = entry->length; 167 | inode->i_atime = entry->atime; 168 | inode->i_mtime = entry->mtime; 169 | inode->i_ctime = entry->ctime; 170 | 171 | switch (entry->header.typeflag) { 172 | case DIRTYPE: 173 | inode->i_op = &tarfs_dir_inode_operations; 174 | inode->i_fop = &tarfs_dir_operations; 175 | break; 176 | case SYMTYPE: 177 | inode->i_link = entry->header.linkname; 178 | inode->i_op = &tarfs_symlink_inode_operations; 179 | break; 180 | default: 181 | inode->i_op = &tarfs_file_inode_operations; 182 | inode->i_fop = &tarfs_file_operations; 183 | break; 184 | } 185 | 186 | return inode; 187 | } 188 | 189 | /** 190 | * @brief Builds the lookup path for the \a dir. 191 | * @param dir the directory to get a path to 192 | * @param entry the root entry 193 | * @return the path, must be freed later on 194 | */ 195 | static char *build_lookup_path(struct inode *dir, struct tar_entry *entry) 196 | { 197 | if (dir->i_ino == ROOT_INO) 198 | return kzalloc(1, GFP_KERNEL); 199 | 200 | entry = tarfs_find_by_inode(entry, dir->i_ino); 201 | if (!entry) // Unknown directory? 202 | return NULL; 203 | 204 | return tarfs_full_name(entry); 205 | } 206 | 207 | /** 208 | * @brief Looks up an entry by an inode for user access 209 | * @param dir the containing directory 210 | * @param dentry the entry to look up 211 | * @param flags lookup flags 212 | * @return the found directory entry 213 | */ 214 | static struct dentry *tarfs_lookup(struct inode *dir, struct dentry *dentry, 215 | unsigned int flags) 216 | { 217 | struct tar_entry *entry; 218 | struct tar_entry *found_entry; 219 | char *dir_path = NULL; 220 | struct inode *inode = NULL; 221 | 222 | if (!dir->i_sb) 223 | pr_err("Missing superblock in inode %lu", dir->i_ino); 224 | 225 | entry = (struct tar_entry *) dir->i_sb->s_fs_info; 226 | dir_path = build_lookup_path(dir, entry); 227 | 228 | // Search for entry in the directory 229 | found_entry = tar_find(entry, dir_path, dentry->d_name.name); 230 | if (found_entry) 231 | inode = tarfs_build_inode(dir->i_sb, found_entry); 232 | 233 | kfree(dir_path); 234 | return d_splice_alias(inode, dentry); 235 | } 236 | 237 | /** 238 | * @brief Iterates over the directory in \a file, emitting found entries. 239 | * @param file the directory to iterate on 240 | * @param ctx the iteration context to emit to 241 | * @return an error code 242 | */ 243 | static int tarfs_readdir(struct file *file, struct dir_context *ctx) 244 | { 245 | struct inode *inode = file_inode(file); 246 | struct super_block *sb = inode->i_sb; 247 | struct tar_entry *entry = (struct tar_entry *) sb->s_fs_info; 248 | char *dir_path = build_lookup_path(inode, entry); 249 | int namelen; 250 | 251 | if (ctx->pos > 0) 252 | goto out; 253 | 254 | // Tell the reader the total count of elements. 255 | if (!dir_emit_dots(file, ctx)) 256 | goto out; 257 | 258 | while (entry) { 259 | if (!strcmp(dir_path, entry->dirname)) { 260 | ctx->pos++; 261 | 262 | namelen = strlen(entry->basename); 263 | if (!dir_emit(ctx, entry->basename, namelen, entry->inode, entry->mode >> 12)) 264 | break; 265 | } 266 | 267 | entry = entry->next; 268 | } 269 | 270 | out: 271 | kfree(dir_path); 272 | return 0; 273 | } 274 | 275 | /** 276 | * @brief Sets up the \a sb. 277 | * @param sb the super block 278 | * @param data 279 | * @param silent if messages shall be suppressed 280 | * @return an error code 281 | */ 282 | static int tarfs_fill_sb(struct super_block *sb, void *data, int silent) 283 | { 284 | struct inode *root = NULL; 285 | struct tar_entry *entry = NULL; 286 | 287 | sb->s_flags |= MS_RDONLY | MS_NOATIME; /* This fs is read-only */ 288 | sb->s_op = &tarfs_super_ops; 289 | 290 | if (!(entry = tar_open(sb))) { 291 | pr_err("failed to read tar index"); 292 | return -ENOMEM; 293 | } 294 | 295 | sb->s_fs_info = entry; 296 | 297 | if (!(root = new_inode(sb))) { 298 | pr_err("failed to allocate root inode"); 299 | return -ENOMEM; 300 | } 301 | 302 | root->i_ino = ROOT_INO; 303 | root->i_sb = sb; 304 | root->i_op = &tarfs_dir_inode_operations; 305 | root->i_fop = &tarfs_dir_operations; 306 | root->i_atime = CURRENT_TIME; 307 | root->i_mtime = CURRENT_TIME; 308 | root->i_ctime = CURRENT_TIME; 309 | inode_init_owner(root, NULL, ROOT_INO_MODE); 310 | 311 | if (!(sb->s_root = d_make_root(root))) { 312 | pr_err("failed to create root inode"); 313 | return -ENOMEM; 314 | } 315 | 316 | return 0; 317 | } 318 | 319 | /** 320 | * @brief Called by linux to mount \a dev. 321 | * @param type our file system type 322 | * @param flags mount flags 323 | * @param dev the device path to mount 324 | * @param data 325 | * @return the root directory entry 326 | */ 327 | static struct dentry *tarfs_mount(struct file_system_type *type, int flags, 328 | char const *dev, void *data) 329 | { 330 | return mount_bdev(type, flags, dev, data, tarfs_fill_sb); 331 | } 332 | 333 | /** 334 | * @brief Called by linux to unmount \a sb. 335 | * @param sb the super block of the instance to unmount 336 | */ 337 | static void tarfs_kill_sb(struct super_block *sb) 338 | { 339 | struct tar_entry *entry = (struct tar_entry *) sb->s_fs_info; 340 | 341 | tar_free(entry); 342 | kill_litter_super(sb); 343 | } 344 | 345 | static struct super_operations tarfs_super_ops = { 346 | }; 347 | 348 | static const struct file_operations tarfs_file_operations = { 349 | .llseek = generic_file_llseek, 350 | .read = tarfs_file_read, 351 | .open = generic_file_open, 352 | .release = tarfs_file_release, 353 | }; 354 | 355 | static const struct inode_operations tarfs_file_inode_operations = { 356 | .get_acl = tarfs_get_acl, 357 | }; 358 | 359 | static const struct file_operations tarfs_dir_operations = { 360 | .llseek = generic_file_llseek, 361 | .read = generic_read_dir, 362 | .iterate_shared = tarfs_readdir, 363 | }; 364 | 365 | static const struct inode_operations tarfs_dir_inode_operations = { 366 | .lookup = tarfs_lookup, 367 | .get_acl = tarfs_get_acl, 368 | }; 369 | 370 | static const struct inode_operations tarfs_symlink_inode_operations = { 371 | .get_link = simple_get_link, 372 | .readlink = generic_readlink, 373 | .get_acl = tarfs_get_acl, 374 | }; 375 | 376 | static struct file_system_type tarfs_type = { 377 | .owner = THIS_MODULE, 378 | .name = "tarfs", 379 | .mount = tarfs_mount, 380 | .kill_sb = tarfs_kill_sb, 381 | .fs_flags = FS_REQUIRES_DEV, 382 | }; 383 | 384 | /** @brief Called by linux to initialize the module. */ 385 | static int __init tarfs_init(void) 386 | { 387 | pr_info("tarfs: Initializing"); 388 | return register_filesystem(&tarfs_type); 389 | } 390 | 391 | /** @brief Called by linux to unload the module. */ 392 | static void __exit tarfs_exit(void) 393 | { 394 | pr_info("tarfs: Exiting"); 395 | unregister_filesystem(&tarfs_type); 396 | } 397 | 398 | module_init(tarfs_init); 399 | module_exit(tarfs_exit); 400 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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You may not convey a covered 525 | work if you are a party to an arrangement with a third party that is 526 | in the business of distributing software, under which you make payment 527 | to the third party based on the extent of your activity of conveying 528 | the work, and under which the third party grants, to any of the 529 | parties who would receive the covered work from you, a discriminatory 530 | patent license (a) in connection with copies of the covered work 531 | conveyed by you (or copies made from those copies), or (b) primarily 532 | for and in connection with specific products or compilations that 533 | contain the covered work, unless you entered into that arrangement, 534 | or that patent license was granted, prior to 28 March 2007. 535 | 536 | Nothing in this License shall be construed as excluding or limiting 537 | any implied license or other defenses to infringement that may 538 | otherwise be available to you under applicable patent law. 539 | 540 | 12. No Surrender of Others' Freedom. 541 | 542 | If conditions are imposed on you (whether by court order, agreement or 543 | otherwise) that contradict the conditions of this License, they do not 544 | excuse you from the conditions of this License. If you cannot convey a 545 | covered work so as to satisfy simultaneously your obligations under this 546 | License and any other pertinent obligations, then as a consequence you may 547 | not convey it at all. For example, if you agree to terms that obligate you 548 | to collect a royalty for further conveying from those to whom you convey 549 | the Program, the only way you could satisfy both those terms and this 550 | License would be to refrain entirely from conveying the Program. 551 | 552 | 13. Use with the GNU Affero General Public License. 553 | 554 | Notwithstanding any other provision of this License, you have 555 | permission to link or combine any covered work with a work licensed 556 | under version 3 of the GNU Affero General Public License into a single 557 | combined work, and to convey the resulting work. The terms of this 558 | License will continue to apply to the part which is the covered work, 559 | but the special requirements of the GNU Affero General Public License, 560 | section 13, concerning interaction through a network will apply to the 561 | combination as such. 562 | 563 | 14. Revised Versions of this License. 564 | 565 | The Free Software Foundation may publish revised and/or new versions of 566 | the GNU General Public License from time to time. Such new versions will 567 | be similar in spirit to the present version, but may differ in detail to 568 | address new problems or concerns. 569 | 570 | Each version is given a distinguishing version number. If the 571 | Program specifies that a certain numbered version of the GNU General 572 | Public License "or any later version" applies to it, you have the 573 | option of following the terms and conditions either of that numbered 574 | version or of any later version published by the Free Software 575 | Foundation. If the Program does not specify a version number of the 576 | GNU General Public License, you may choose any version ever published 577 | by the Free Software Foundation. 578 | 579 | If the Program specifies that a proxy can decide which future 580 | versions of the GNU General Public License can be used, that proxy's 581 | public statement of acceptance of a version permanently authorizes you 582 | to choose that version for the Program. 583 | 584 | Later license versions may give you additional or different 585 | permissions. However, no additional obligations are imposed on any 586 | author or copyright holder as a result of your choosing to follow a 587 | later version. 588 | 589 | 15. Disclaimer of Warranty. 590 | 591 | THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY 592 | APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT 593 | HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY 594 | OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, 595 | THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 596 | PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM 597 | IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF 598 | ALL NECESSARY SERVICING, REPAIR OR CORRECTION. 599 | 600 | 16. Limitation of Liability. 601 | 602 | IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING 603 | WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS 604 | THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY 605 | GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE 606 | USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF 607 | DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD 608 | PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), 609 | EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF 610 | SUCH DAMAGES. 611 | 612 | 17. Interpretation of Sections 15 and 16. 613 | 614 | If the disclaimer of warranty and limitation of liability provided 615 | above cannot be given local legal effect according to their terms, 616 | reviewing courts shall apply local law that most closely approximates 617 | an absolute waiver of all civil liability in connection with the 618 | Program, unless a warranty or assumption of liability accompanies a 619 | copy of the Program in return for a fee. 620 | 621 | END OF TERMS AND CONDITIONS 622 | 623 | How to Apply These Terms to Your New Programs 624 | 625 | If you develop a new program, and you want it to be of the greatest 626 | possible use to the public, the best way to achieve this is to make it 627 | free software which everyone can redistribute and change under these terms. 628 | 629 | To do so, attach the following notices to the program. It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | 635 | Copyright (C) 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see . 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | Copyright (C) 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . 675 | --------------------------------------------------------------------------------