service_runtime/sel_util.c

   1 /*
   2  * Copyright 2008, Google Inc.
   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 are
   7  * met:
   8  *
   9  *     * Redistributions of source code must retain the above copyright
  10  * notice, this list of conditions and the following disclaimer.
  11  *     * Redistributions in binary form must reproduce the above
  12  * copyright notice, this list of conditions and the following disclaimer
  13  * in the documentation and/or other materials provided with the
  14  * distribution.
  15  *     * Neither the name of Google Inc. nor the names of its
  16  * contributors may be used to endorse or promote products derived from
  17  * this software without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  20  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  21  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  22  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  23  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  25  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  26  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  27  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  28  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  29  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  30  */
  31
  32 /*
  33  * NaCl Simple/secure ELF loader (NaCl SEL).
  34  */
  35 #include "native_client/include/portability.h"
  36 #include "native_client/service_runtime/nacl_check.h"
  37 #include "native_client/service_runtime/sel_ldr.h"
  38 #include "native_client/service_runtime/sel_util.h"
  39
  40 /*
  41  * return the smallest power of 2 that is greater than or equal to max_addr
  42  *
  43  * pre: the result is representable as a size_t.
  44  *
  45  * in concrete terms, max_addr <= ~((~0U)>>1) = (unsigned int) INT_MIN
  46  * (assuming size_t is unsigned int).
  47  */
  48 size_t  NaClAppPow2Ceil(size_t  max_addr)
  49 {
  50 #if 0
  51   size_t  addr, t;
  52
  53   /* check precondition */
  54   if ((max_addr & ~((~0U)>>1)) != 0 && (max_addr & ((~0U)>>1)) != 0) {
  55     return 0;
  56   }
  57
  58   /* O( number of one bits in max_addr ) */
  59   for (addr = max_addr; (t = (addr & (addr-1))) != 0; addr = t)
  60     ;
  61   if (addr < max_addr) addr = addr << 1;
  62 #else
  63   size_t  addr;
  64
  65   /* check precondition */
  66   if ((max_addr & ~((~0U)>>1)) != 0 && (max_addr & ((~0U)>>1)) != 0) {
  67     return 0;
  68   }
  69
  70   /* O( number of bits in max_addr ) */
  71   for (addr = 1; addr < max_addr; addr = addr << 1)
  72     ;
  73 #endif
  74
  75   CHECK(addr >= max_addr);
  76   CHECK(addr != 0);
  77   CHECK((addr & (addr-1)) == 0);
  78   return addr;
  79 }