libc/sysdeps/linux/i386/brk.c

   1 /* brk system call for Linux/i386.
   2    Copyright (C) 1995, 1996, 2000 Free Software Foundation, Inc.
   3    Copyright (c) 2015 mirabilos <tg@mirbsd.org>
   4    This file is part of uclibc-ng, derived from the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library 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 GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <errno.h>
  21 #include <unistd.h>
  22 #include <sys/syscall.h>
  23
  24 /* This must be initialized data because commons can't have aliases.  */
  25 void *__curbrk attribute_hidden = 0;
  26
  27 int brk(void *addr)
  28 {
  29         void *newbrk;
  30
  31         /*
  32          * EBC is used in PIC code, we need to save/restore it manually.
  33          * Unfortunately, GCC won't do that for us even if we use con-
  34          * straints, and we cannot push it either as ESP clobbers are
  35          * silently ignored, but EDX is preserved, so it's scratch space.
  36          */
  37         __asm__("xchgl  %%edx,%%ebx"
  38             "\n int     $0x80"
  39             "\n xchgl   %%edx,%%ebx"
  40                 : "=a" (newbrk)
  41                 : "0" (__NR_brk), "d" (addr)
  42                 : "cc"
  43         );
  44
  45         __curbrk = newbrk;
  46
  47         if (newbrk < addr) {
  48                 __set_errno(ENOMEM);
  49                 return -1;
  50         }
  51
  52         return 0;
  53 }
  54 libc_hidden_def(brk)