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

/* brk system call for Linux/i386.
Copyright (C) 1995, 1996 Free Software Foundation, Inc.
This file is part of the GNU C Library.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.  */

#include <errno.h>
#include <unistd.h>
#include <sysdep.h>

void *__curbrk;

/* Old braindamage in GCC's crtstuff.c requires this symbol in an attempt
   to work around different old braindamage in the old Linux ELF dynamic
   linker.  */
weak_alias (__curbrk, ___brk_addr)

int
__brk (void *addr)
{
  void *newbrk, *scratch;

  asm ("movl %%ebx, %1\n"	/* Save %ebx in scratch register.  */
       "movl %3, %%ebx\n"	/* Put ADDR in %ebx to be syscall arg.  */
       "int $0x80 # %2\n"	/* Perform the system call.  */
       "movl %1, %%ebx\n"	/* Restore %ebx from scratch register.  */
       : "=a" (newbrk), "=r" (scratch)
       : "0" (SYS_ify (brk)), "g" (addr));

  __curbrk = newbrk;

  if (newbrk < addr)
    {
      errno = ENOMEM;
      return -1;
    }

  return 0;
}
weak_alias (__brk, brk)