sysdeps/unix/sysv/linux/i386/brk.c

   1 /* brk system call for Linux/i386.
   2    Copyright (C) 1995, 1996, 2000 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <errno.h>
  21 #include <unistd.h>
  22 #include <sysdep.h>
  23
  24 #include <bp-checks.h>
  25
  26 /* This must be initialized data because commons can't have aliases.  */
  27 void *__curbrk = 0;
  28
  29 /* Old braindamage in GCC's crtstuff.c requires this symbol in an attempt
  30    to work around different old braindamage in the old Linux ELF dynamic
  31    linker.  */
  32 weak_alias (__curbrk, ___brk_addr)
  33
  34 int
  35 __brk (void *addr)
  36 {
  37   void *__unbounded newbrk, *__unbounded scratch;
  38
  39   asm ("movl %%ebx, %1\n"       /* Save %ebx in scratch register.  */
  40        "movl %3, %%ebx\n"       /* Put ADDR in %ebx to be syscall arg.  */
  41        "int $0x80 # %2\n"       /* Perform the system call.  */
  42        "movl %1, %%ebx\n"       /* Restore %ebx from scratch register.  */
  43        : "=a" (newbrk), "=r" (scratch)
  44        : "0" (SYS_ify (brk)), "g" (__ptrvalue (addr)));
  45
  46   __curbrk = newbrk;
  47
  48   if (newbrk < addr)
  49     {
  50       __set_errno (ENOMEM);
  51       return -1;
  52     }
  53
  54   return 0;
  55 }
  56 weak_alias (__brk, brk)