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202 volume VI os16 Script e sorgenti del kernel 203 « 480008 |{ 480009 | proc_t *ps; 480010 | int status; 480011 | // 480012 | // Get process. 480013 | // 480014 | ps = proc_reference (pid); 480015 | // 480016 | // Verify if ‘fdn_old’ is a valid value. 480017 | // 480018 | if (fdn_old < 0 || 480019 | fdn_old >= OPEN_MAX || 480020 | ps->fd[fdn_old].file == NULL) 480021 | { 480022 | errset (EBADF); // Bad file descriptor. 480023 | return (-1); 480024 | } 480025 | // 480026 | // Check if ‘fd_old’ and ‘fd_new’ are the same. 480027 | // 480028 | if (fdn_old == fdn_new) 480029 | { 480030 | return (fdn_new); 480031 | } 480032 | // 480033 | // Close ‘fdn_new’ if it is open and copy ‘fdn_old’ into it. 480034 | // 480035 | if (ps->fd[fdn_new].file != NULL) 480036 | { 480037 | status = fd_close (pid, fdn_new); 480038 | if (status != 0) 480039 | { 480040 | return (-1); 480041 | } 480042 | } 480043 | ps->fd[fdn_new].fl_flags = ps->fd[fdn_old].fl_flags; 480044 | ps->fd[fdn_new].fd_flags = ps->fd[fdn_old].fd_flags & ~FD_CLOEXEC; 480045 | ps->fd[fdn_new].file = ps->fd[fdn_old].file; 480046 | ps->fd[fdn_new].file->references++; 480047 | return (fdn_new); 480048 |} 104.4.6 kernel/fs/fd_fcntl.c Si veda la sezione 103.3.6. 490001 |#include 490002 |#include 490003 |#include 490004 |#include 490005 |//---------------------------------------------------------------------- 490006 |int 490007 |fd_fcntl (pid_t pid, int fdn, int cmd, int arg) 490008 |{ 490009 | proc_t *ps; 490010 | inode_t *inode; 490011 | int mask; 490012 | // 490013 | // Get process. 490014 | // 490015 | ps = proc_reference (pid); 490016 | // 490017 | // Verify if the file descriptor is valid. 490018 | // 490019 | if (ps->fd[fdn].file == NULL) 490020 | { 490021 | errset (EBADF); // Bad file descriptor. 490022 | return (-1); 490023 | } 490024 | // 490025 | // Reach the inode. 490026 | // 490027 | inode = ps->fd[fdn].file->inode; 490028 | // 490029 | // 490030 | // 490031 | switch (cmd) 490032 | { 490033 | case F_DUPFD: 490034 | return (fd_dup (pid, fdn, arg)); 490035 | break; 490036 | case F_GETFD: 490037 | return (ps->fd[fdn].fd_flags); 490038 | break; 490039 | case F_SETFD: 490040 | ps->fd[fdn].fd_flags = arg; 490041 | return (0); 490042 | case F_GETFL: 490043 | return (ps->fd[fdn].fl_flags); 490044 | case F_SETFL: 490045 | // 490046 | // Calculate a mask with bits that are not to be set. 490047 | // 490048 | mask = (O_ACCMODE 490049 | | O_CREAT 490050 | | O_EXCL 490051 | | O_NOCTTY 490052 | | O_TRUNC); 490053 | // 490054 | // Set to zero the bits that are not to be set from 490055 | // the argument. 490056 | // 490057 | arg = (arg & ~mask); 490058 | // 490059 | // Set to zero the bit that *are* to be set. 490060 | // 490061 | ps->fd[fdn].fl_flags &= mask; 490062 | // 490063 | // Set the bits, already filtered inside the argument. 490064 | // 490065 | ps->fd[fdn].fl_flags |= arg; 490066 | // 490067 | return (0); 490068 | default: 490069 | errset (EINVAL); // Not implemented. 490070 | return (-1); 490071 | } 490072 |} 104.4.7 kernel/fs/fd_lseek.c Si veda la sezione 103.3.7. 500001 |#include 500002 |#include 500003 |#include 500004 |//---------------------------------------------------------------------- 500005 |off_t 500006 |fd_lseek (pid_t pid, int fdn, off_t offset, int whence) 500007 |{ 500008 | inode_t *inode; 500009 | file_t *file; 500010 | fd_t *fd; 500011 | off_t test_offset; 500012 | // 500013 | // Get file descriptor. 500014 | // 500015 | fd = fd_reference (pid, &fdn); 500016 | if (fd == NULL || 500017 | fd->file == NULL || 500018 | fd->file->inode == NULL ) 500019 | { 500020 | errset (EBADF); // Bad file descriptor. 500021 | return (-1); 500022 | } 500023 | // 500024 | // Get file table item. 500025 | // 500026 | file = fd->file; 500027 | // 500028 | // Get inode. 500029 | // 500030 | inode = file->inode; 500031 | // 500032 | // Change position depending on the ‘whence’ parameter. 500033 | // 500034 | if (whence == SEEK_SET) 500035 | { 500036 | if (offset < 0) 500037 | { 500038 | errset (EINVAL); // Invalid argument. 500039 | return ((off_t) -1); 500040 | } 500041 | else 500042 | { 500043 | fd->file->offset = offset; 500044 | } 500045 | } 500046 | else if (whence == SEEK_CUR) 500047 | { 500048 | test_offset = fd->file->offset; 500049 | test_offset += offset; 500050 | if (test_offset < 0) 500051 | { 500052 | errset (EINVAL); // Invalid argument. 500053 | return ((off_t) -1); 500054 | } 500055 | else 500056 | { 500057 | fd->file->offset = test_offset; 500058 | } 500059 | } 500060 | else if (whence == SEEK_END) 500061 | { 500062 | test_offset = inode->size; 500063 | test_offset += offset; 500064 | if (test_offset < 0) 500065 | { 500066 | errset (EINVAL); // Invalid argument. 500067 | return ((off_t) -1); 500068 | } 500069 | else 500070 | { 500071 | fd->file->offset = test_offset; 500072 | } 500073 | } 500074 | else 500075 | { 500076 | errset (EINVAL); // Invalid argument. 500077 | return ((off_t) -1); 500078 | } 500079 | // 500080 | // Return the new file position. 500081 | // 500082 | return (fd->file->offset); 500083 |} 104.4.8 kernel/fs/fd_open.c Si veda la sezione 103.3.8. 510001 |#include 510002 |#include 510003 |#include 510004 |#include 510005 |//---------------------------------------------------------------------- 510006 |int 510007 |fd_open (pid_t pid, const char *path, int oflags, mode_t mode) 510008 |{ 510009 | proc_t *ps; 510010 | inode_t *inode; 510011 | int status; 510012 | file_t *file; 510013 | fd_t *fd; 510014 | int fdn; 510015 | char full_path[PATH_MAX]; 510016 | int perm; 510017 | tty_t *tty; 510018 | mode_t umask; 510019 | int errno_save; « «
204 volume VI os16 Script e sorgenti del kernel 205 510020 | // 510021 | // Get process. 510022 | // 510023 | ps = proc_reference (pid); 510024 | // 510025 | // Correct the mode with the umask. As it is not a directory, to the 510026 | // mode are removed execution and sticky permissions. 510027 | // 510028 | umask = ps->umask | 01111; 510029 | mode &= ~umask; 510030 | // 510031 | // Check open options. 510032 | // 510033 | if (oflags & O_WRONLY) 510034 | { 510035 | // 510036 | // The file is to be opened for write, or for read/write. 510037 | // Try to get inode. 510038 | // 510039 | inode = path_inode (pid, path); 510040 | if (inode == NULL) 510041 | { 510042 | // 510043 | // Cannot get the inode. See if there is the creation 510044 | // option. 510045 | // 510046 | if (oflags & O_CREAT) 510047 | { 510048 | // 510049 | // Try to create the missing inode: the file must be a 510050 | // regular one, so add the mode. 510051 | // 510052 | path_full (path, ps->path_cwd, full_path); 510053 | inode = path_inode_link (pid, full_path, NULL, 510054 | (mode | S_IFREG)); 510055 | if (inode == NULL) 510056 | { 510057 | // 510058 | // Sorry: cannot create the inode! Variable ‘errno’ 510059 | // is already set by ‘path_inode_link()’. 510060 | // 510061 | errset (errno); 510062 | return (-1); 510063 | } 510064 | } 510065 | else 510066 | { 510067 | // 510068 | // Cannot open the inode. Variable ‘errno’ 510069 | // should be already set by ‘path_inode()’. 510070 | // 510071 | errset (errno); 510072 | return (-1); 510073 | } 510074 | } 510075 | // 510076 | // The inode was read or created: check if it must be 510077 | // truncated. It can be truncated only if it is a regular 510078 | // file. 510079 | // 510080 | if (oflags & O_TRUNC && inode->mode & S_IFREG) 510081 | { 510082 | // 510083 | // Truncate inode. 510084 | // 510085 | status = inode_truncate (inode); 510086 | if (status != 0) 510087 | { 510088 | // 510089 | // Cannot truncate the inode: release it and return. 510090 | // But this error should never happen, because the 510091 | // function ‘inode_truncate()’ will not return any 510092 | // other value than zero. 510093 | // 510094 | errno_save = errno; 510095 | inode_put (inode); 510096 | errset (errno_save); 510097 | return (-1); 510098 | } 510099 | } 510100 | } 510101 | else 510102 | { 510103 | // 510104 | // The file is to be opened for read, but not for write. 510105 | // Try to get inode. 510106 | // 510107 | inode = path_inode (pid, path); 510108 | if (inode == NULL) 510109 | { 510110 | // 510111 | // Cannot open the file. 510112 | // 510113 | errset (errno); 510114 | return (-1); 510115 | } 510116 | } 510117 | // 510118 | // An inode was opened: check type and access permissions. 510119 | // All file types are good, even directories, as the type 510120 | // DIR is implemented through file descriptors. 510121 | // 510122 | perm = 0; 510123 | if (oflags & O_RDONLY) perm |= 4; 510124 | if (oflags & O_WRONLY) perm |= 2; 510125 | status = inode_check (inode, S_IFMT, perm, ps->uid); 510126 | if (status != 0) 510127 | { 510128 | // 510129 | // The file type is not correct or the user does not have 510130 | // permissions. 510131 | // 510132 | return (-1); 510133 | } 510134 | // 510135 | // Allocate the file, inside the file table. 510136 | // 510137 | file = file_reference (-1); 510138 | if (file == NULL) 510139 | { 510140 | // 510141 | // Cannot allocate the file inside the file table: release the 510142 | // inode, update ‘errno’ and return. 510143 | // 510144 | inode_put (inode); 510145 | errset (ENFILE); // Too many files open in system. 510146 | return (-1); 510147 | } 510148 | // 510149 | // Put some data inside the file item. Only options 510150 | // O_RDONLY and O_WRONLY are kept here, because the O_APPEND 510151 | // is saved inside the file descriptor table. 510152 | // 510153 | file->references = 1; 510154 | file->oflags = (oflags & (O_RDONLY | O_WRONLY)); 510155 | file->inode = inode; 510156 | // 510157 | // Allocate the file descriptor: variable ‘fdn’ will be modified 510158 | // by the call to ‘fd_reference()’. 510159 | // 510160 | fdn = -1; 510161 | fd = fd_reference (pid, &fdn); 510162 | if (fd == NULL) 510163 | { 510164 | // 510165 | // Cannot allocate the file descriptor: remove the item from 510166 | // file table. 510167 | // 510168 | file->references = 0; 510169 | file->oflags = 0; 510170 | file->inode = NULL; 510171 | // 510172 | // Release the inode. 510173 | // 510174 | inode_put (inode); 510175 | // 510176 | // Return an error. 510177 | // 510178 | errset (EMFILE); // Too many open files. 510179 | return (-1); 510180 | } 510181 | // 510182 | // File descriptor allocated: put some data inside the 510183 | // file descriptor item. 510184 | // 510185 | fd->fl_flags = (oflags & (O_RDONLY | O_WRONLY | O_APPEND)); 510186 | fd->fd_flags = 0; 510187 | fd->file = file; 510188 | fd->file->offset = 0; 510189 | // 510190 | // Check if it is a terminal (currently only consoles), if it is 510191 | // opened for read and write, and if it have to be set as the 510192 | // controlling terminal. This thing is done here because there is 510193 | // not a real device driver. 510194 | // 510195 | if ((S_ISCHR (inode->mode)) && 510196 | (oflags & O_RDONLY) && 510197 | (oflags & O_WRONLY)) 510198 | { 510199 | // 510200 | // The inode is a character special file (related to a character 510201 | // device), opened for read and write! 510202 | // 510203 | if ((inode->direct[0] & 0xFF00) == (DEV_CONSOLE_MAJOR direct[0]); 510210 | // 510211 | // Verify that the terminal is not already the controlling 510212 | // terminal of some process group. 510213 | // 510214 | if (tty->pgrp == 0) 510215 | { 510216 | // 510217 | // The terminal is free: verify if the current process 510218 | // needs a controlling terminal. 510219 | // 510220 | if (ps->device_tty == 0 && ps->pgrp == pid) 510221 | { 510222 | // 510223 | // It is a group leader with no controlling 510224 | // terminal: set the controlling terminal. 510225 | // 510226 | ps->device_tty = inode->direct[0]; 510227 | tty->pgrp = ps->pgrp; 510228 | } 510229 | } 510230 | } 510231 | } 510232 | // 510233 | // Return the file descriptor. 510234 | // 510235 | return (fdn); 510236 |} 104.4.9 kernel/fs/fd_read.c Si veda la sezione 103.3.9. 520001 |#include 520002 |#include 520003 |#include 520004 |#include 520005 |//---------------------------------------------------------------------- 520006 |ssize_t 520007 |fd_read (pid_t pid, int fdn, void *buffer, size_t count, int *eof) 520008 |{ 520009 | fd_t *fd; 520010 | ssize_t size_read; «
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