1 /* 2 * symlink.c --- make a symlink in the filesystem, based on mkdir.c 3 * 4 * Copyright (c) 2012, Intel Corporation. 5 * All Rights Reserved. 6 * 7 * %Begin-Header% 8 * This file may be redistributed under the terms of the GNU Library 9 * General Public License, version 2. 10 * %End-Header% 11 */ 12 13 #include "config.h" 14 #include <stdio.h> 15 #include <string.h> 16 #if HAVE_UNISTD_H 17 #include <unistd.h> 18 #endif 19 #include <fcntl.h> 20 #include <time.h> 21 #if HAVE_SYS_STAT_H 22 #include <sys/stat.h> 23 #endif 24 #if HAVE_SYS_TYPES_H 25 #include <sys/types.h> 26 #endif 27 28 #include "ext2_fs.h" 29 #include "ext2fs.h" 30 31 #ifndef HAVE_STRNLEN 32 /* 33 * Incredibly, libc5 doesn't appear to have strnlen. So we have to 34 * provide our own. 35 */ 36 static int my_strnlen(const char * s, int count) 37 { 38 const char *cp = s; 39 40 while (count-- && *cp) 41 cp++; 42 return cp - s; 43 } 44 #define strnlen(str, x) my_strnlen((str),(x)) 45 #endif 46 47 errcode_t ext2fs_symlink(ext2_filsys fs, ext2_ino_t parent, ext2_ino_t ino, 48 const char *name, const char *target) 49 { 50 errcode_t retval; 51 struct ext2_inode inode; 52 ext2_ino_t scratch_ino; 53 blk64_t blk; 54 int fastlink, inlinelink; 55 unsigned int target_len; 56 char *block_buf = 0; 57 int drop_refcount = 0; 58 59 EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS); 60 61 /* 62 * The Linux kernel doesn't allow for links longer than a block 63 * (counting the NUL terminator) 64 */ 65 target_len = strnlen(target, fs->blocksize + 1); 66 if (target_len >= fs->blocksize) { 67 retval = EXT2_ET_INVALID_ARGUMENT; 68 goto cleanup; 69 } 70 71 /* 72 * Allocate a data block for slow links 73 */ 74 retval = ext2fs_get_mem(fs->blocksize, &block_buf); 75 if (retval) 76 goto cleanup; 77 memset(block_buf, 0, fs->blocksize); 78 strncpy(block_buf, target, fs->blocksize); 79 80 memset(&inode, 0, sizeof(struct ext2_inode)); 81 fastlink = (target_len < sizeof(inode.i_block)); 82 if (!fastlink) { 83 retval = ext2fs_new_block2(fs, ext2fs_find_inode_goal(fs, ino, 84 &inode, 85 0), 86 NULL, &blk); 87 if (retval) 88 goto cleanup; 89 } 90 91 /* 92 * Allocate an inode, if necessary 93 */ 94 if (!ino) { 95 retval = ext2fs_new_inode(fs, parent, LINUX_S_IFLNK | 0755, 96 0, &ino); 97 if (retval) 98 goto cleanup; 99 } 100 101 /* 102 * Create the inode structure.... 103 */ 104 inode.i_mode = LINUX_S_IFLNK | 0777; 105 inode.i_uid = inode.i_gid = 0; 106 inode.i_links_count = 1; 107 ext2fs_inode_size_set(fs, &inode, target_len); 108 /* The time fields are set by ext2fs_write_new_inode() */ 109 110 inlinelink = !fastlink && ext2fs_has_feature_inline_data(fs->super); 111 if (fastlink) { 112 /* Fast symlinks, target stored in inode */ 113 strcpy((char *)&inode.i_block, target); 114 } else if (inlinelink) { 115 /* Try inserting an inline data symlink */ 116 inode.i_flags |= EXT4_INLINE_DATA_FL; 117 retval = ext2fs_write_new_inode(fs, ino, &inode); 118 if (retval) 119 goto cleanup; 120 retval = ext2fs_inline_data_set(fs, ino, &inode, block_buf, 121 target_len); 122 if (retval) { 123 inode.i_flags &= ~EXT4_INLINE_DATA_FL; 124 inlinelink = 0; 125 goto need_block; 126 } 127 retval = ext2fs_read_inode(fs, ino, &inode); 128 if (retval) 129 goto cleanup; 130 } else { 131 need_block: 132 /* Slow symlinks, target stored in the first block */ 133 ext2fs_iblk_set(fs, &inode, 1); 134 if (ext2fs_has_feature_extents(fs->super)) { 135 /* 136 * The extent bmap is setup after the inode and block 137 * have been written out below. 138 */ 139 inode.i_flags |= EXT4_EXTENTS_FL; 140 } 141 } 142 143 /* 144 * Write out the inode and inode data block. The inode generation 145 * number is assigned by write_new_inode, which means that the 146 * operations using ino must come after it. 147 */ 148 if (inlinelink) 149 retval = ext2fs_write_inode(fs, ino, &inode); 150 else 151 retval = ext2fs_write_new_inode(fs, ino, &inode); 152 if (retval) 153 goto cleanup; 154 155 if (!fastlink && !inlinelink) { 156 retval = ext2fs_bmap2(fs, ino, &inode, NULL, BMAP_SET, 0, NULL, 157 &blk); 158 if (retval) 159 goto cleanup; 160 161 retval = io_channel_write_blk64(fs->io, blk, 1, block_buf); 162 if (retval) 163 goto cleanup; 164 } 165 166 /* 167 * Update accounting.... 168 */ 169 if (!fastlink && !inlinelink) 170 ext2fs_block_alloc_stats2(fs, blk, +1); 171 ext2fs_inode_alloc_stats2(fs, ino, +1, 0); 172 drop_refcount = 1; 173 174 /* 175 * Link the symlink into the filesystem hierarchy 176 */ 177 if (name) { 178 retval = ext2fs_lookup(fs, parent, name, strlen(name), 0, 179 &scratch_ino); 180 if (!retval) { 181 retval = EXT2_ET_FILE_EXISTS; 182 goto cleanup; 183 } 184 if (retval != EXT2_ET_FILE_NOT_FOUND) 185 goto cleanup; 186 retval = ext2fs_link(fs, parent, name, ino, EXT2_FT_SYMLINK); 187 if (retval) 188 goto cleanup; 189 } 190 drop_refcount = 0; 191 192 cleanup: 193 if (block_buf) 194 ext2fs_free_mem(&block_buf); 195 if (drop_refcount) { 196 if (!fastlink && !inlinelink) 197 ext2fs_block_alloc_stats2(fs, blk, -1); 198 ext2fs_inode_alloc_stats2(fs, ino, -1, 0); 199 } 200 return retval; 201 } 202 203 /* 204 * Test whether an inode is a fast symlink. 205 * 206 * A fast symlink has its symlink data stored in inode->i_block. 207 */ 208 int ext2fs_is_fast_symlink(struct ext2_inode *inode) 209 { 210 return LINUX_S_ISLNK(inode->i_mode) && EXT2_I_SIZE(inode) && 211 EXT2_I_SIZE(inode) < sizeof(inode->i_block); 212 }