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

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