brk.c

它通过提供glibc兼容使得应用程序移植到较小的c 库时相当得容易. 它能够应用到带虚拟存储的Linux和uClinux上.在大多数带MMU部件的平台上为使它更加紧凑,它也能够编译成共享库.uClib

/* brk system call for Linux/i386.
   Copyright (C) 1995, 1996, 2000 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 Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <errno.h>
#include <unistd.h>
#include <sys/syscall.h>


/* This must be initialized data because commons can't have aliases.  */
void *___brk_addr = 0;


int brk (void *addr)
{
    void *__unbounded newbrk, *__unbounded 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" (__NR_brk), "g" (__ptrvalue (addr)));

    ___brk_addr = newbrk;

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

    return 0;
}