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 58 EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS); 59 60 /* 61 * The Linux kernel doesn't allow for links longer than a block 62 * (counting the NUL terminator) 63 */ 64 target_len = strnlen(target, fs->blocksize + 1); 65 if (target_len >= fs->blocksize) { 66 retval = EXT2_ET_INVALID_ARGUMENT; 67 goto cleanup; 68 } 69 70 /* 71 * Allocate a data block for slow links 72 */ 73 retval = ext2fs_get_mem(fs->blocksize, &block_buf); 74 if (retval) 75 goto cleanup; 76 memset(block_buf, 0, fs->blocksize); 77 strncpy(block_buf, target, fs->blocksize); 78 79 memset(&inode, 0, sizeof(struct ext2_inode)); 80 fastlink = (target_len < sizeof(inode.i_block)); 81 if (!fastlink) { 82 retval = ext2fs_new_block2(fs, ext2fs_find_inode_goal(fs, ino, 83 &inode, 84 0), 85 NULL, &blk); 86 if (retval) 87 goto cleanup; 88 } 89 90 /* 91 * Allocate an inode, if necessary 92 */ 93 if (!ino) { 94 retval = ext2fs_new_inode(fs, parent, LINUX_S_IFLNK | 0755, 95 0, &ino); 96 if (retval) 97 goto cleanup; 98 } 99 100 /* 101 * Create the inode structure.... 102 */ 103 inode.i_mode = LINUX_S_IFLNK | 0777; 104 inode.i_uid = inode.i_gid = 0; 105 inode.i_links_count = 1; 106 ext2fs_inode_size_set(fs, &inode, target_len); 107 /* The time fields are set by ext2fs_write_new_inode() */ 108 109 inlinelink = !fastlink && ext2fs_has_feature_inline_data(fs->super); 110 if (fastlink) { 111 /* Fast symlinks, target stored in inode */ 112 strcpy((char *)&inode.i_block, target); 113 } else if (inlinelink) { 114 /* Try inserting an inline data symlink */ 115 inode.i_flags |= EXT4_INLINE_DATA_FL; 116 retval = ext2fs_write_new_inode(fs, ino, &inode); 117 if (retval) 118 goto cleanup; 119 retval = ext2fs_inline_data_set(fs, ino, &inode, block_buf, 120 target_len); 121 if (retval) { 122 inode.i_flags &= ~EXT4_INLINE_DATA_FL; 123 inlinelink = 0; 124 goto need_block; 125 } 126 retval = ext2fs_read_inode(fs, ino, &inode); 127 if (retval) 128 goto cleanup; 129 } else { 130 need_block: 131 /* Slow symlinks, target stored in the first block */ 132 ext2fs_iblk_set(fs, &inode, 1); 133 if (ext2fs_has_feature_extents(fs->super)) { 134 /* 135 * The extent bmap is setup after the inode and block 136 * have been written out below. 137 */ 138 inode.i_flags |= EXT4_EXTENTS_FL; 139 } 140 } 141 142 /* 143 * Write out the inode and inode data block. The inode generation 144 * number is assigned by write_new_inode, which means that the 145 * operations using ino must come after it. 146 */ 147 if (inlinelink) 148 retval = ext2fs_write_inode(fs, ino, &inode); 149 else 150 retval = ext2fs_write_new_inode(fs, ino, &inode); 151 if (retval) 152 goto cleanup; 153 154 if (!fastlink && !inlinelink) { 155 retval = ext2fs_bmap2(fs, ino, &inode, NULL, BMAP_SET, 0, NULL, 156 &blk); 157 if (retval) 158 goto cleanup; 159 160 retval = io_channel_write_blk64(fs->io, blk, 1, block_buf); 161 if (retval) 162 goto cleanup; 163 } 164 165 /* 166 * Link the symlink into the filesystem hierarchy 167 */ 168 if (name) { 169 retval = ext2fs_lookup(fs, parent, name, strlen(name), 0, 170 &scratch_ino); 171 if (!retval) { 172 retval = EXT2_ET_FILE_EXISTS; 173 goto cleanup; 174 } 175 if (retval != EXT2_ET_FILE_NOT_FOUND) 176 goto cleanup; 177 retval = ext2fs_link(fs, parent, name, ino, EXT2_FT_SYMLINK); 178 if (retval) 179 goto cleanup; 180 } 181 182 /* 183 * Update accounting.... 184 */ 185 if (!fastlink && !inlinelink) 186 ext2fs_block_alloc_stats2(fs, blk, +1); 187 ext2fs_inode_alloc_stats2(fs, ino, +1, 0); 188 189 cleanup: 190 if (block_buf) 191 ext2fs_free_mem(&block_buf); 192 return retval; 193 } 194 195 /* 196 * Test whether an inode is a fast symlink. 197 * 198 * A fast symlink has its symlink data stored in inode->i_block. 199 */ 200 int ext2fs_is_fast_symlink(struct ext2_inode *inode) 201 { 202 return LINUX_S_ISLNK(inode->i_mode) && EXT2_I_SIZE(inode) && 203 EXT2_I_SIZE(inode) < sizeof(inode->i_block); 204 } 205
