The Design and Implementation of the FreeBSD Operating System, Second Edition
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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 267992 2014-06-28 03:56:17Z hselasky $");
   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 SYSCTL_INT(_vm_redzone, OID_AUTO, panic, CTLFLAG_RWTUN, &redzone_panic, 0,
   45     "Panic when buffer corruption is detected");     
   46 
   47 #define REDZONE_CHSIZE  (16)
   48 #define REDZONE_CFSIZE  (16)
   49 #define REDZONE_HSIZE   (sizeof(struct stack) + sizeof(u_long) + REDZONE_CHSIZE)
   50 #define REDZONE_FSIZE   (REDZONE_CFSIZE)
   51 
   52 static u_long
   53 redzone_roundup(u_long n)
   54 {
   55 
   56         if (n < REDZONE_HSIZE)
   57                 n = REDZONE_HSIZE;
   58         if (n <= 128)
   59                 return (128);
   60         else if (n <= 256)
   61                 return (256);
   62         else if (n <= 512)
   63                 return (512);
   64         else if (n <= 1024)
   65                 return (1024);
   66         else if (n <= 2048)
   67                 return (2048);
   68         return (PAGE_SIZE);
   69 }
   70 
   71 u_long
   72 redzone_get_size(caddr_t naddr)
   73 {
   74         u_long nsize;
   75 
   76         bcopy(naddr - REDZONE_CHSIZE - sizeof(u_long), &nsize, sizeof(nsize));
   77         return (nsize);
   78 }
   79 
   80 u_long
   81 redzone_size_ntor(u_long nsize)
   82 {
   83 
   84         return (nsize + redzone_roundup(nsize) + REDZONE_FSIZE);
   85 }
   86 
   87 void *
   88 redzone_addr_ntor(caddr_t naddr)
   89 {
   90 
   91         return (naddr - redzone_roundup(redzone_get_size(naddr)));
   92 }
   93 
   94 /*
   95  * Set redzones and remember allocation backtrace.
   96  */
   97 void *
   98 redzone_setup(caddr_t raddr, u_long nsize)
   99 {
  100         struct stack st;
  101         caddr_t haddr, faddr;
  102 
  103         atomic_add_long(&redzone_extra_mem, redzone_size_ntor(nsize) - nsize);
  104 
  105         haddr = raddr + redzone_roundup(nsize) - REDZONE_HSIZE;
  106         faddr = haddr + REDZONE_HSIZE + nsize;
  107 
  108         /* Redzone header. */
  109         stack_save(&st);
  110         bcopy(&st, haddr, sizeof(st));
  111         haddr += sizeof(st);
  112         bcopy(&nsize, haddr, sizeof(nsize));
  113         haddr += sizeof(nsize);
  114         memset(haddr, 0x42, REDZONE_CHSIZE);
  115         haddr += REDZONE_CHSIZE;
  116 
  117         /* Redzone footer. */
  118         memset(faddr, 0x42, REDZONE_CFSIZE);
  119 
  120         return (haddr);
  121 }
  122 
  123 /*
  124  * Verify redzones.
  125  * This function is called on free() and realloc().
  126  */
  127 void
  128 redzone_check(caddr_t naddr)
  129 {
  130         struct stack ast, fst;
  131         caddr_t haddr, faddr;
  132         u_int ncorruptions;
  133         u_long nsize;
  134         int i;
  135 
  136         haddr = naddr - REDZONE_HSIZE;
  137         bcopy(haddr, &ast, sizeof(ast));
  138         haddr += sizeof(ast);
  139         bcopy(haddr, &nsize, sizeof(nsize));
  140         haddr += sizeof(nsize);
  141 
  142         atomic_subtract_long(&redzone_extra_mem,
  143             redzone_size_ntor(nsize) - nsize);
  144 
  145         /* Look for buffer underflow. */
  146         ncorruptions = 0;
  147         for (i = 0; i < REDZONE_CHSIZE; i++, haddr++) {
  148                 if (*(u_char *)haddr != 0x42)
  149                         ncorruptions++;
  150         }
  151         if (ncorruptions > 0) {
  152                 printf("REDZONE: Buffer underflow detected. %u byte%s "
  153                     "corrupted before %p (%lu bytes allocated).\n",
  154                     ncorruptions, ncorruptions == 1 ? "" : "s", naddr, nsize);
  155                 printf("Allocation backtrace:\n");
  156                 stack_print_ddb(&ast);
  157                 printf("Free backtrace:\n");
  158                 stack_save(&fst);
  159                 stack_print_ddb(&fst);
  160                 if (redzone_panic)
  161                         panic("Stopping here.");
  162         }
  163         faddr = naddr + nsize;
  164         /* Look for buffer overflow. */
  165         ncorruptions = 0;
  166         for (i = 0; i < REDZONE_CFSIZE; i++, faddr++) {
  167                 if (*(u_char *)faddr != 0x42)
  168                         ncorruptions++;
  169         }
  170         if (ncorruptions > 0) {
  171                 printf("REDZONE: Buffer overflow detected. %u byte%s corrupted "
  172                     "after %p (%lu bytes allocated).\n", ncorruptions,
  173                     ncorruptions == 1 ? "" : "s", naddr + nsize, nsize);
  174                 printf("Allocation backtrace:\n");
  175                 stack_print_ddb(&ast);
  176                 printf("Free backtrace:\n");
  177                 stack_save(&fst);
  178                 stack_print_ddb(&fst);
  179                 if (redzone_panic)
  180                         panic("Stopping here.");
  181         }
  182 }

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