src/core/posix_io.c

   1 /*
   2  * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2 of the
   7  * License, or any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17  */
  18
  19 #include <stdlib.h>
  20 #include <string.h>
  21 #include <errno.h>
  22 #include <gpxe/list.h>
  23 #include <gpxe/xfer.h>
  24 #include <gpxe/open.h>
  25 #include <gpxe/process.h>
  26 #include <gpxe/posix_io.h>
  27
  28 /** @file
  29  *
  30  * POSIX-like I/O
  31  *
  32  * These functions provide traditional blocking I/O semantics.  They
  33  * are designed to be used by the PXE TFTP API.  Because they block,
  34  * they may not be used by most other portions of the gPXE codebase.
  35  */
  36
  37 /** An open file */
  38 struct posix_file {
  39         /** Reference count for this object */
  40         struct refcnt refcnt;
  41         /** List of open files */
  42         struct list_head list;
  43         /** File descriptor */
  44         int fd;
  45         /** Overall status
  46          *
  47          * Set to -EINPROGRESS while data transfer is in progress.
  48          */
  49         int rc;
  50         /** Data transfer interface */
  51         struct xfer_interface xfer;
  52         /** Current seek position */
  53         size_t pos;
  54         /** File size */
  55         size_t filesize;
  56         /** Received data queue */
  57         struct list_head data;
  58 };
  59
  60 /** List of open files */
  61 static LIST_HEAD ( posix_files );
  62
  63 /** Minimum file descriptor that will ever be allocated */
  64 #define POSIX_FD_MIN ( 1 )
  65
  66 /** Maximum file descriptor that will ever be allocated */
  67 #define POSIX_FD_MAX ( 255 )
  68
  69 /**
  70  * Free open file
  71  *
  72  * @v refcnt            Reference counter
  73  */
  74 static void posix_file_free ( struct refcnt *refcnt ) {
  75         struct posix_file *file =
  76                 container_of ( refcnt, struct posix_file, refcnt );
  77         struct io_buffer *iobuf;
  78         struct io_buffer *tmp;
  79
  80         list_for_each_entry_safe ( iobuf, tmp, &file->data, list ) {
  81                 list_del ( &iobuf->list );
  82                 free_iob ( iobuf );
  83         }
  84         free ( file );
  85 }
  86
  87 /**
  88  * Terminate file data transfer
  89  *
  90  * @v file              POSIX file
  91  * @v rc                Reason for termination
  92  */
  93 static void posix_file_finished ( struct posix_file *file, int rc ) {
  94         xfer_nullify ( &file->xfer );
  95         xfer_close ( &file->xfer, rc );
  96         file->rc = rc;
  97 }
  98
  99 /**
 100  * Handle close() event
 101  *
 102  * @v xfer              POSIX file data transfer interface
 103  * @v rc                Reason for close
 104  */
 105 static void posix_file_xfer_close ( struct xfer_interface *xfer, int rc ) {
 106         struct posix_file *file =
 107                 container_of ( xfer, struct posix_file, xfer );
 108
 109         posix_file_finished ( file, rc );
 110 }
 111
 112 /**
 113  * Handle seek() event
 114  *
 115  * @v xfer              POSIX file data transfer interface
 116  * @v pos               New position
 117  * @ret rc              Return status code
 118  */
 119 static int posix_file_xfer_seek ( struct xfer_interface *xfer, off_t offset,
 120                                   int whence ) {
 121         struct posix_file *file =
 122                 container_of ( xfer, struct posix_file, xfer );
 123
 124         switch ( whence ) {
 125         case SEEK_SET:
 126                 file->pos = offset;
 127                 break;
 128         case SEEK_CUR:
 129                 file->pos += offset;
 130                 break;
 131         }
 132
 133         if ( file->filesize < file->pos )
 134                 file->filesize = file->pos;
 135
 136         return 0;
 137 }
 138
 139 /**
 140  * Handle deliver_iob() event
 141  *
 142  * @v xfer              POSIX file data transfer interface
 143  * @v iobuf             I/O buffer
 144  * @ret rc              Return status code
 145  */
 146 static int posix_file_xfer_deliver_iob ( struct xfer_interface *xfer,
 147                                          struct io_buffer *iobuf ) {
 148         struct posix_file *file =
 149                 container_of ( xfer, struct posix_file, xfer );
 150
 151         list_add_tail ( &iobuf->list, &file->data );
 152         return 0;
 153 }
 154
 155 /** POSIX file data transfer interface operations */
 156 static struct xfer_interface_operations posix_file_xfer_operations = {
 157         .close          = posix_file_xfer_close,
 158         .vredirect      = xfer_vopen,
 159         .request        = ignore_xfer_request,
 160         .seek           = posix_file_xfer_seek,
 161         .alloc_iob      = default_xfer_alloc_iob,
 162         .deliver_iob    = posix_file_xfer_deliver_iob,
 163         .deliver_raw    = xfer_deliver_as_iob,
 164 };
 165
 166 /**
 167  * Identify file by file descriptor
 168  *
 169  * @v fd                File descriptor
 170  * @ret file            Corresponding file, or NULL
 171  */
 172 static struct posix_file * posix_fd_to_file ( int fd ) {
 173         struct posix_file *file;
 174
 175         list_for_each_entry ( file, &posix_files, list ) {
 176                 if ( file->fd == fd )
 177                         return file;
 178         }
 179         return NULL;
 180 }
 181
 182 /**
 183  * Find an available file descriptor
 184  *
 185  * @ret fd              File descriptor, or negative error number
 186  */
 187 static int posix_find_free_fd ( void ) {
 188         int fd;
 189
 190         for ( fd = POSIX_FD_MIN ; fd <= POSIX_FD_MAX ; fd++ ) {
 191                 if ( ! posix_fd_to_file ( fd ) )
 192                         return fd;
 193         }
 194         DBG ( "POSIX could not find free file descriptor\n" );
 195         return -ENFILE;
 196 }
 197
 198 /**
 199  * Open file
 200  *
 201  * @v uri_string        URI string
 202  * @ret fd              File descriptor, or negative error number
 203  */
 204 int open ( const char *uri_string ) {
 205         struct posix_file *file;
 206         int fd;
 207         int rc;
 208
 209         /* Find a free file descriptor to use */
 210         fd = posix_find_free_fd();
 211         if ( fd < 0 )
 212                 return fd;
 213
 214         /* Allocate and initialise structure */
 215         file = malloc ( sizeof ( *file ) );
 216         if ( ! file )
 217                 return -ENOMEM;
 218         memset ( file, 0, sizeof ( *file ) );
 219         file->refcnt.free = posix_file_free;
 220         file->fd = fd;
 221         file->rc = -EINPROGRESS;
 222         xfer_init ( &file->xfer, &posix_file_xfer_operations,
 223                     &file->refcnt );
 224         INIT_LIST_HEAD ( &file->data );
 225
 226         /* Open URI on data transfer interface */
 227         if ( ( rc = xfer_open_uri ( &file->xfer, uri_string ) ) != 0 )
 228                 goto err;
 229
 230         /* Wait for open to succeed or fail */
 231         while ( list_empty ( &file->data ) ) {
 232                 step();
 233                 if ( file->rc == 0 )
 234                         break;
 235                 if ( file->rc != -EINPROGRESS ) {
 236                         rc = file->rc;
 237                         goto err;
 238                 }
 239         }
 240
 241         /* Add to list of open files.  List takes reference ownership. */
 242         list_add ( &file->list, &posix_files );
 243         DBG ( "POSIX opened %s as file %d\n", uri_string, fd );
 244         return fd;
 245
 246  err:
 247         posix_file_finished ( file, rc );
 248         ref_put ( &file->refcnt );
 249         return rc;
 250 }
 251
 252 /**
 253  * Read data from file
 254  *
 255  * @v buffer            Data buffer
 256  * @v offset            Starting offset within data buffer
 257  * @v len               Maximum length to read
 258  * @ret len             Actual length read, or negative error number
 259  */
 260 ssize_t read_user ( int fd, userptr_t buffer, off_t offset, size_t max_len ) {
 261         struct posix_file *file;
 262         struct io_buffer *iobuf;
 263         size_t frag_len;
 264         ssize_t len = 0;
 265
 266         /* Identify file */
 267         file = posix_fd_to_file ( fd );
 268         if ( ! file )
 269                 return -EBADF;
 270
 271         while ( 1 ) {
 272                 /* Try to fetch more data if none available */
 273                 if ( list_empty ( &file->data ) )
 274                         step();
 275                 /* Dequeue at most one received I/O buffer into user buffer */
 276                 list_for_each_entry ( iobuf, &file->data, list ) {
 277                         frag_len = iob_len ( iobuf );
 278                         if ( frag_len > max_len )
 279                                 frag_len = max_len;
 280                         copy_to_user ( buffer, offset, iobuf->data,
 281                                        frag_len );
 282                         iob_pull ( iobuf, frag_len );
 283                         if ( ! iob_len ( iobuf ) ) {
 284                                 list_del ( &iobuf-> list );
 285                                 free_iob ( iobuf );
 286                         }
 287                         file->pos += frag_len;
 288                         len += frag_len;
 289                         offset += frag_len;
 290                         max_len -= frag_len;
 291                         break;
 292                 }
 293                 /* If buffer is full, return */
 294                 if ( ! max_len )
 295                         return len;
 296                 /* If file has completed, return */
 297                 if ( file->rc != -EINPROGRESS )
 298                         return ( file->rc ? file->rc : len );
 299         }
 300 }
 301
 302 /**
 303  * Determine file size
 304  *
 305  * @v fd                File descriptor
 306  * @ret size            File size, or negative error number
 307  */
 308 ssize_t fsize ( int fd ) {
 309         struct posix_file *file;
 310
 311         /* Identify file */
 312         file = posix_fd_to_file ( fd );
 313         if ( ! file )
 314                 return -EBADF;
 315
 316         return file->filesize;
 317 }
 318
 319 /**
 320  * Close file
 321  *
 322  * @v fd                File descriptor
 323  * @ret rc              Return status code
 324  */
 325 int close ( int fd ) {
 326         struct posix_file *file;
 327
 328         /* Identify file */
 329         file = posix_fd_to_file ( fd );
 330         if ( ! file )
 331                 return -EBADF;
 332
 333         /* Terminate data transfer */
 334         posix_file_finished ( file, 0 );
 335
 336         /* Remove from list of open files and drop reference */
 337         list_del ( &file->list );
 338         ref_put ( &file->refcnt );
 339         return 0;
 340 }