Isolate the tricky bits..
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pk
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gnu/usr.bin/ld/rtld/sbrk.c
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205
gnu/usr.bin/ld/rtld/sbrk.c
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/*
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* Copyright (c) 1993 Paul Kranenburg
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by Paul Kranenburg.
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* 4. The name of the author may not be used to endorse or promote products
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* derived from this software withough specific prior written permission
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* $Id: sbrk.c,v 1.1 1993/12/08 10:33:45 pk Exp $
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*/
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#include <sys/param.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <sys/file.h>
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#include <sys/time.h>
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#include <sys/resource.h>
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#include <sys/mman.h>
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#ifndef BSD
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#define MAP_COPY MAP_PRIVATE
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#define MAP_FILE 0
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#define MAP_ANON 0
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#endif
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#include <fcntl.h>
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#include <a.out.h>
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#include <stab.h>
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#include <string.h>
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#if __STDC__
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#include <stdarg.h>
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#else
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#include <varargs.h>
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#endif
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#include "ld.h"
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#ifndef BSD /* Need do better than this */
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#define NEED_DEV_ZERO 1
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#endif
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/*
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* Private heap functions.
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*/
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extern char **environ;
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static caddr_t curbrk;
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static void
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init_brk()
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{
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struct rlimit rlim;
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char *cp, **cpp = environ;
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if (getrlimit(RLIMIT_STACK, &rlim) < 0) {
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xprintf("ld.so: brk: getrlimit failure\n");
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_exit(1);
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}
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/*
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* Walk to the top of stack
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*/
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if (*cpp) {
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while (*cpp) cpp++;
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cp = *--cpp;
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while (*cp) cp++;
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} else
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cp = (char *)&cp;
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#define TRY_THIS_FOR_A_CHANGE 0
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#if TRY_THIS_FOR_A_CHANGE
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curbrk = (caddr_t)
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(((long)(cp - 1 - rlim.rlim_max) + PAGSIZ) & ~(PAGSIZ - 1));
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curbrk -= PAGSIZ;
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#else
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curbrk = (caddr_t)
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(((long)(cp - 1 - rlim.rlim_cur) + PAGSIZ) & ~(PAGSIZ - 1));
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#endif
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}
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#if 1
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caddr_t
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sbrk(incr)
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int incr;
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{
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int fd = -1;
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caddr_t oldbrk;
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if (curbrk == 0)
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init_brk();
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#if DEBUG
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xprintf("sbrk: incr = %#x, curbrk = %#x\n", incr, curbrk);
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#endif
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if (incr == 0)
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return curbrk;
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#if TRY_THIS_FOR_A_CHANGE
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if (incr > PAGSIZ)
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return (caddr_t)-1;
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#endif
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incr = (incr + PAGSIZ - 1) & ~(PAGSIZ - 1);
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#ifdef NEED_DEV_ZERO
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fd = open("/dev/zero", O_RDWR, 0);
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if (fd == -1)
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perror("/dev/zero");
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#endif
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if (mmap(curbrk, incr,
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PROT_READ|PROT_WRITE,
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MAP_ANON|MAP_FIXED|MAP_COPY, fd, 0) == (caddr_t)-1) {
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xprintf("Cannot map anonymous memory");
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_exit(1);
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}
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#ifdef NEED_DEV_ZERO
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close(fd);
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#endif
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oldbrk = curbrk;
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#if TRY_THIS_FOR_A_CHANGE
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curbrk -= incr;
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#else
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curbrk += incr;
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#endif
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return oldbrk;
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}
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#else
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caddr_t
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sbrk(incr)
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int incr;
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{
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int fd = -1;
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caddr_t oldbrk;
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xprintf("sbrk: incr = %#x, curbrk = %#x\n", incr, curbrk);
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#if DEBUG
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xprintf("sbrk: incr = %#x, curbrk = %#x\n", incr, curbrk);
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#endif
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if (curbrk == 0 && (curbrk = mmap(0, PAGSIZ,
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PROT_READ|PROT_WRITE,
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MAP_ANON|MAP_COPY, fd, 0)) == (caddr_t)-1) {
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xprintf("Cannot map anonymous memory");
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_exit(1);
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}
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/* There's valid memory from `curbrk' to next page boundary */
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if ((long)curbrk + incr <= (((long)curbrk + PAGSIZ) & ~(PAGSIZ - 1))) {
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oldbrk = curbrk;
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curbrk += incr;
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return oldbrk;
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}
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/*
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* If asking for than currently left in this chunk,
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* go somewhere completely different.
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*/
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#ifdef NEED_DEV_ZERO
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fd = open("/dev/zero", O_RDWR, 0);
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if (fd == -1)
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perror("/dev/zero");
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#endif
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if ((curbrk = mmap(0, incr,
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PROT_READ|PROT_WRITE,
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MAP_ANON|MAP_COPY, fd, 0)) == (caddr_t)-1) {
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perror("Cannot map anonymous memory");
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}
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#ifdef NEED_DEV_ZERO
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close(fd);
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#endif
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oldbrk = curbrk;
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curbrk += incr;
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return oldbrk;
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}
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#endif
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