libc/stdio/read.c

   1 /*
   2  *  ZeX/OS
   3  *  Copyright (C) 2007  Tomas 'ZeXx86' Jedrzejek (zexx86@gmail.com)
   4  *  Copyright (C) 2009  Tomas 'ZeXx86' Jedrzejek (zexx86@gmail.com)
   5  *
   6  *  This program is free software: you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation, either version 3 of the License, or
   9  *  (at your option) any later version.
  10  *
  11  *  This program is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU General Public License
  17  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20
  21 #include <errno.h>
  22
  23 int read (unsigned fd, void *buf, unsigned len)
  24 {
  25         asm volatile (
  26                 "movl $21, %%eax;"
  27                 "movl %0, %%ecx;"
  28                 "movl %1, %%ebx;"
  29                 "movl %2, %%edx;"
  30                 "int $0x80;" :: "g" (fd), "b" (buf), "g" (len) : "%eax", "%ecx", "%edx", "memory");
  31
  32         /* get return value */
  33         int *memptr = (int *) 0x9000;
  34         int *ret = memptr;
  35
  36         errno_update ();
  37
  38         return (int) *ret;
  39 }
  40