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 /**
  64  * Free open file
  65  *
  66  * @v refcnt            Reference counter
  67  */
  68 static void posix_file_free ( struct refcnt *refcnt ) {
  69         struct posix_file *file =
  70                 container_of ( refcnt, struct posix_file, refcnt );
  71         struct io_buffer *iobuf;
  72         struct io_buffer *tmp;
  73
  74         list_for_each_entry_safe ( iobuf, tmp, &file->data, list ) {
  75                 list_del ( &iobuf->list );
  76                 free_iob ( iobuf );
  77         }
  78         free ( file );
  79 }
  80
  81 /**
  82  * Terminate file data transfer
  83  *
  84  * @v file              POSIX file
  85  * @v rc                Reason for termination
  86  */
  87 static void posix_file_finished ( struct posix_file *file, int rc ) {
  88         xfer_nullify ( &file->xfer );
  89         xfer_close ( &file->xfer, rc );
  90         file->rc = rc;
  91 }
  92
  93 /**
  94  * Handle close() event
  95  *
  96  * @v xfer              POSIX file data transfer interface
  97  * @v rc                Reason for close
  98  */
  99 static void posix_file_xfer_close ( struct xfer_interface *xfer, int rc ) {
 100         struct posix_file *file =
 101                 container_of ( xfer, struct posix_file, xfer );
 102
 103         posix_file_finished ( file, rc );
 104 }
 105
 106 /**
 107  * Handle seek() event
 108  *
 109  * @v xfer              POSIX file data transfer interface
 110  * @v pos               New position
 111  * @ret rc              Return status code
 112  */
 113 static int posix_file_xfer_seek ( struct xfer_interface *xfer, off_t offset,
 114                                   int whence ) {
 115         struct posix_file *file =
 116                 container_of ( xfer, struct posix_file, xfer );
 117
 118         switch ( whence ) {
 119         case SEEK_SET:
 120                 file->pos = offset;
 121                 break;
 122         case SEEK_CUR:
 123                 file->pos += offset;
 124                 break;
 125         }
 126
 127         if ( file->filesize < file->pos )
 128                 file->filesize = file->pos;
 129
 130         return 0;
 131 }
 132
 133 /**
 134  * Handle deliver_iob() event
 135  *
 136  * @v xfer              POSIX file data transfer interface
 137  * @v iobuf             I/O buffer
 138  * @v meta              Data transfer metadata, or NULL
 139  * @ret rc              Return status code
 140  */
 141 static int
 142 posix_file_xfer_deliver_iob ( struct xfer_interface *xfer,
 143                               struct io_buffer *iobuf,
 144                               struct xfer_metadata *meta __unused ) {
 145         struct posix_file *file =
 146                 container_of ( xfer, struct posix_file, xfer );
 147
 148         list_add_tail ( &iobuf->list, &file->data );
 149         return 0;
 150 }
 151
 152 /** POSIX file data transfer interface operations */
 153 static struct xfer_interface_operations posix_file_xfer_operations = {
 154         .close          = posix_file_xfer_close,
 155         .vredirect      = xfer_vopen,
 156         .seek           = posix_file_xfer_seek,
 157         .window         = unlimited_xfer_window,
 158         .alloc_iob      = default_xfer_alloc_iob,
 159         .deliver_iob    = posix_file_xfer_deliver_iob,
 160         .deliver_raw    = xfer_deliver_as_iob,
 161 };
 162
 163 /**
 164  * Identify file by file descriptor
 165  *
 166  * @v fd                File descriptor
 167  * @ret file            Corresponding file, or NULL
 168  */
 169 static struct posix_file * posix_fd_to_file ( int fd ) {
 170         struct posix_file *file;
 171
 172         list_for_each_entry ( file, &posix_files, list ) {
 173                 if ( file->fd == fd )
 174                         return file;
 175         }
 176         return NULL;
 177 }
 178
 179 /**
 180  * Find an available file descriptor
 181  *
 182  * @ret fd              File descriptor, or negative error number
 183  */
 184 static int posix_find_free_fd ( void ) {
 185         int fd;
 186
 187         for ( fd = POSIX_FD_MIN ; fd <= POSIX_FD_MAX ; fd++ ) {
 188                 if ( ! posix_fd_to_file ( fd ) )
 189                         return fd;
 190         }
 191         DBG ( "POSIX could not find free file descriptor\n" );
 192         return -ENFILE;
 193 }
 194
 195 /**
 196  * Open file
 197  *
 198  * @v uri_string        URI string
 199  * @ret fd              File descriptor, or negative error number
 200  */
 201 int open ( const char *uri_string ) {
 202         struct posix_file *file;
 203         int fd;
 204         int rc;
 205
 206         /* Find a free file descriptor to use */
 207         fd = posix_find_free_fd();
 208         if ( fd < 0 )
 209                 return fd;
 210
 211         /* Allocate and initialise structure */
 212         file = zalloc ( sizeof ( *file ) );
 213         if ( ! file )
 214                 return -ENOMEM;
 215         file->refcnt.free = posix_file_free;
 216         file->fd = fd;
 217         file->rc = -EINPROGRESS;
 218         xfer_init ( &file->xfer, &posix_file_xfer_operations,
 219                     &file->refcnt );
 220         INIT_LIST_HEAD ( &file->data );
 221
 222         /* Open URI on data transfer interface */
 223         if ( ( rc = xfer_open_uri_string ( &file->xfer, uri_string ) ) != 0 )
 224                 goto err;
 225
 226         /* Wait for open to succeed or fail */
 227         while ( list_empty ( &file->data ) ) {
 228                 step();
 229                 if ( file->rc == 0 )
 230                         break;
 231                 if ( file->rc != -EINPROGRESS ) {
 232                         rc = file->rc;
 233                         goto err;
 234                 }
 235         }
 236
 237         /* Add to list of open files.  List takes reference ownership. */
 238         list_add ( &file->list, &posix_files );
 239         DBG ( "POSIX opened %s as file %d\n", uri_string, fd );
 240         return fd;
 241
 242  err:
 243         posix_file_finished ( file, rc );
 244         ref_put ( &file->refcnt );
 245         return rc;
 246 }
 247
 248 /**
 249  * Check file descriptors for readiness
 250  *
 251  * @v readfds           File descriptors to check
 252  * @v wait              Wait until data is ready
 253  * @ret nready          Number of ready file descriptors
 254  */
 255 int select ( fd_set *readfds, int wait ) {
 256         struct posix_file *file;
 257         int fd;
 258
 259         do {
 260                 for ( fd = POSIX_FD_MIN ; fd <= POSIX_FD_MAX ; fd++ ) {
 261                         if ( ! FD_ISSET ( fd, readfds ) )
 262                                 continue;
 263                         file = posix_fd_to_file ( fd );
 264                         if ( ! file )
 265                                 return -EBADF;
 266                         if ( ( list_empty ( &file->data ) ) &&
 267                              ( file->rc != -EINPROGRESS ) )
 268                                 continue;
 269                         /* Data is available or status has changed */
 270                         FD_ZERO ( readfds );
 271                         FD_SET ( fd, readfds );
 272                         return 1;
 273                 }
 274                 step();
 275         } while ( wait );
 276
 277         return 0;
 278 }
 279
 280 /**
 281  * Read data from file
 282  *
 283  * @v buffer            Data buffer
 284  * @v offset            Starting offset within data buffer
 285  * @v len               Maximum length to read
 286  * @ret len             Actual length read, or negative error number
 287  *
 288  * This call is non-blocking; if no data is available to read then
 289  * -EWOULDBLOCK will be returned.
 290  */
 291 ssize_t read_user ( int fd, userptr_t buffer, off_t offset, size_t max_len ) {
 292         struct posix_file *file;
 293         struct io_buffer *iobuf;
 294         size_t len;
 295
 296         /* Identify file */
 297         file = posix_fd_to_file ( fd );
 298         if ( ! file )
 299                 return -EBADF;
 300
 301         /* Try to fetch more data if none available */
 302         if ( list_empty ( &file->data ) )
 303                 step();
 304
 305         /* Dequeue at most one received I/O buffer into user buffer */
 306         list_for_each_entry ( iobuf, &file->data, list ) {
 307                 len = iob_len ( iobuf );
 308                 if ( len > max_len )
 309                         len = max_len;
 310                 copy_to_user ( buffer, offset, iobuf->data, len );
 311                 iob_pull ( iobuf, len );
 312                 if ( ! iob_len ( iobuf ) ) {
 313                         list_del ( &iobuf->list );
 314                         free_iob ( iobuf );
 315                 }
 316                 file->pos += len;
 317                 return len;
 318         }
 319
 320         /* If file has completed, return (after returning all data) */
 321         if ( file->rc != -EINPROGRESS )
 322                 return file->rc;
 323
 324         /* No data ready and file still in progress; return -WOULDBLOCK */
 325         return -EWOULDBLOCK;
 326 }
 327
 328 /**
 329  * Determine file size
 330  *
 331  * @v fd                File descriptor
 332  * @ret size            File size, or negative error number
 333  */
 334 ssize_t fsize ( int fd ) {
 335         struct posix_file *file;
 336
 337         /* Identify file */
 338         file = posix_fd_to_file ( fd );
 339         if ( ! file )
 340                 return -EBADF;
 341
 342         return file->filesize;
 343 }
 344
 345 /**
 346  * Close file
 347  *
 348  * @v fd                File descriptor
 349  * @ret rc              Return status code
 350  */
 351 int close ( int fd ) {
 352         struct posix_file *file;
 353
 354         /* Identify file */
 355         file = posix_fd_to_file ( fd );
 356         if ( ! file )
 357                 return -EBADF;
 358
 359         /* Terminate data transfer */
 360         posix_file_finished ( file, 0 );
 361
 362         /* Remove from list of open files and drop reference */
 363         list_del ( &file->list );
 364         ref_put ( &file->refcnt );
 365         return 0;
 366 }