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