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FreeBSD/Linux Kernel Cross Reference
sys/vm/redzone.c

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    1 /*-
    2  * Copyright (c) 2006 Pawel Jakub Dawidek <pjd@FreeBSD.org>
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
   15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
   18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   24  * SUCH DAMAGE.
   25  */
   26 
   27 #include <sys/cdefs.h>
   28 __FBSDID("$FreeBSD: head/sys/vm/redzone.c 227309 2011-11-07 15:43:11Z ed $");
   29 
   30 #include <sys/param.h>
   31 #include <sys/systm.h>
   32 #include <sys/kernel.h>
   33 #include <sys/stack.h>
   34 #include <sys/sysctl.h>
   35 
   36 #include <vm/redzone.h>
   37 
   38 
   39 static SYSCTL_NODE(_vm, OID_AUTO, redzone, CTLFLAG_RW, NULL, "RedZone data");
   40 static u_long redzone_extra_mem = 0;
   41 SYSCTL_ULONG(_vm_redzone, OID_AUTO, extra_mem, CTLFLAG_RD, &redzone_extra_mem,
   42     0, "Extra memory allocated by redzone");     
   43 static int redzone_panic = 0;
   44 TUNABLE_INT("vm.redzone.panic", &redzone_panic);
   45 SYSCTL_INT(_vm_redzone, OID_AUTO, panic, CTLFLAG_RW, &redzone_panic, 0,
   46     "Panic when buffer corruption is detected");     
   47 
   48 #define REDZONE_CHSIZE  (16)
   49 #define REDZONE_CFSIZE  (16)
   50 #define REDZONE_HSIZE   (sizeof(struct stack) + sizeof(u_long) + REDZONE_CHSIZE)
   51 #define REDZONE_FSIZE   (REDZONE_CFSIZE)
   52 
   53 static u_long
   54 redzone_roundup(u_long n)
   55 {
   56 
   57         if (n < REDZONE_HSIZE)
   58                 n = REDZONE_HSIZE;
   59         if (n <= 128)
   60                 return (128);
   61         else if (n <= 256)
   62                 return (256);
   63         else if (n <= 512)
   64                 return (512);
   65         else if (n <= 1024)
   66                 return (1024);
   67         else if (n <= 2048)
   68                 return (2048);
   69         return (PAGE_SIZE);
   70 }
   71 
   72 u_long
   73 redzone_get_size(caddr_t naddr)
   74 {
   75         u_long nsize;
   76 
   77         bcopy(naddr - REDZONE_CHSIZE - sizeof(u_long), &nsize, sizeof(nsize));
   78         return (nsize);
   79 }
   80 
   81 u_long
   82 redzone_size_ntor(u_long nsize)
   83 {
   84 
   85         return (nsize + redzone_roundup(nsize) + REDZONE_FSIZE);
   86 }
   87 
   88 void *
   89 redzone_addr_ntor(caddr_t naddr)
   90 {
   91 
   92         return (naddr - redzone_roundup(redzone_get_size(naddr)));
   93 }
   94 
   95 /*
   96  * Set redzones and remember allocation backtrace.
   97  */
   98 void *
   99 redzone_setup(caddr_t raddr, u_long nsize)
  100 {
  101         struct stack st;
  102         caddr_t haddr, faddr;
  103 
  104         atomic_add_long(&redzone_extra_mem, redzone_size_ntor(nsize) - nsize);
  105 
  106         haddr = raddr + redzone_roundup(nsize) - REDZONE_HSIZE;
  107         faddr = haddr + REDZONE_HSIZE + nsize;
  108 
  109         /* Redzone header. */
  110         stack_save(&st);
  111         bcopy(&st, haddr, sizeof(st));
  112         haddr += sizeof(st);
  113         bcopy(&nsize, haddr, sizeof(nsize));
  114         haddr += sizeof(nsize);
  115         memset(haddr, 0x42, REDZONE_CHSIZE);
  116         haddr += REDZONE_CHSIZE;
  117 
  118         /* Redzone footer. */
  119         memset(faddr, 0x42, REDZONE_CFSIZE);
  120 
  121         return (haddr);
  122 }
  123 
  124 /*
  125  * Verify redzones.
  126  * This function is called on free() and realloc().
  127  */
  128 void
  129 redzone_check(caddr_t naddr)
  130 {
  131         struct stack ast, fst;
  132         caddr_t haddr, faddr;
  133         u_int ncorruptions;
  134         u_long nsize;
  135         int i;
  136 
  137         haddr = naddr - REDZONE_HSIZE;
  138         bcopy(haddr, &ast, sizeof(ast));
  139         haddr += sizeof(ast);
  140         bcopy(haddr, &nsize, sizeof(nsize));
  141         haddr += sizeof(nsize);
  142 
  143         atomic_subtract_long(&redzone_extra_mem,
  144             redzone_size_ntor(nsize) - nsize);
  145 
  146         /* Look for buffer underflow. */
  147         ncorruptions = 0;
  148         for (i = 0; i < REDZONE_CHSIZE; i++, haddr++) {
  149                 if (*(u_char *)haddr != 0x42)
  150                         ncorruptions++;
  151         }
  152         if (ncorruptions > 0) {
  153                 printf("REDZONE: Buffer underflow detected. %u byte%s "
  154                     "corrupted before %p (%lu bytes allocated).\n",
  155                     ncorruptions, ncorruptions == 1 ? "" : "s", naddr, nsize);
  156                 printf("Allocation backtrace:\n");
  157                 stack_print_ddb(&ast);
  158                 printf("Free backtrace:\n");
  159                 stack_save(&fst);
  160                 stack_print_ddb(&fst);
  161                 if (redzone_panic)
  162                         panic("Stopping here.");
  163         }
  164         faddr = naddr + nsize;
  165         /* Look for buffer overflow. */
  166         ncorruptions = 0;
  167         for (i = 0; i < REDZONE_CFSIZE; i++, faddr++) {
  168                 if (*(u_char *)faddr != 0x42)
  169                         ncorruptions++;
  170         }
  171         if (ncorruptions > 0) {
  172                 printf("REDZONE: Buffer overflow detected. %u byte%s corrupted "
  173                     "after %p (%lu bytes allocated).\n", ncorruptions,
  174                     ncorruptions == 1 ? "" : "s", naddr + nsize, nsize);
  175                 printf("Allocation backtrace:\n");
  176                 stack_print_ddb(&ast);
  177                 printf("Free backtrace:\n");
  178                 stack_save(&fst);
  179                 stack_print_ddb(&fst);
  180                 if (redzone_panic)
  181                         panic("Stopping here.");
  182         }
  183 }

Cache object: 3ebced5991c9b2733e7d13b7fe82d46e


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