third_party/tcmalloc/chromium/src/linux_shadow_stacks.cc

   1 // Copyright (c) 2006-2010 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "linux_shadow_stacks.h"
   6
   7 #include <stdio.h>
   8 #include <stdlib.h>
   9 #include <string.h>
  10 #include <unistd.h>
  11
  12 static const int kMaxShadowIndex = 2048;
  13 static const char kOverflowMessage[] = "Shadow stack overflow\n";
  14
  15 // Thread-local vars.
  16 __thread
  17 int shadow_index = -1;
  18 __thread
  19 void *shadow_ip_stack[kMaxShadowIndex];
  20 __thread
  21 void *shadow_sp_stack[kMaxShadowIndex];
  22
  23 enum Status {UNINITIALIZED = -1, DISABLED, ENABLED};
  24 Status status = UNINITIALIZED;
  25
  26 void init() {
  27   if (!getenv("KEEP_SHADOW_STACKS")) {
  28     status = DISABLED;
  29     return;
  30   }
  31   status = ENABLED;
  32 }
  33
  34 void __cyg_profile_func_enter(void *this_fn, void *call_site) {
  35   if (status == DISABLED) return;
  36   if (status == UNINITIALIZED) {
  37     init();
  38     if (status == DISABLED) return;
  39   }
  40   shadow_index++;
  41   if (shadow_index > kMaxShadowIndex) {
  42     // Avoid memory allocation when reporting an error.
  43     write(2, kOverflowMessage, sizeof(kOverflowMessage));
  44     int a = 0;
  45     a = a / a;
  46   }
  47   // Update the shadow IP stack
  48   shadow_ip_stack[shadow_index] = this_fn;
  49   // Update the shadow SP stack. The code for obtaining the frame address was
  50   // borrowed from Google Perftools, http://code.google.com/p/google-perftools/
  51   //
  52   // Copyright (c) 2005, Google Inc.
  53   // All rights reserved.
  54   //
  55   // Redistribution and use in source and binary forms, with or without
  56   // modification, are permitted provided that the following conditions are
  57   // met:
  58   //
  59   //     * Redistributions of source code must retain the above copyright
  60   // notice, this list of conditions and the following disclaimer.
  61   //     * Redistributions in binary form must reproduce the above
  62   // copyright notice, this list of conditions and the following disclaimer
  63   // in the documentation and/or other materials provided with the
  64   // distribution.
  65   //     * Neither the name of Google Inc. nor the names of its
  66   // contributors may be used to endorse or promote products derived from
  67   // this software without specific prior written permission.
  68   //
  69   // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  70   // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  71   // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  72   // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  73   // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  74   // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  75   // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  76   // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  77   // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  78   // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  79   // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  80   void **sp;
  81 #if (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 2) || __llvm__
  82   // __builtin_frame_address(0) can return the wrong address on gcc-4.1.0-k8.
  83   // It's always correct on llvm, and the techniques below aren't (in
  84   // particular, llvm-gcc will make a copy of this_fn, so it's not in sp[2]),
  85   // so we also prefer __builtin_frame_address when running under llvm.
  86   sp = reinterpret_cast<void**>(__builtin_frame_address(0));
  87 #elif defined(__i386__)
  88   // Stack frame format:
  89   //    sp[0]   pointer to previous frame
  90   //    sp[1]   caller address
  91   //    sp[2]   first argument
  92   //    ...
  93   // NOTE: This will break under llvm, since result is a copy and not in sp[2]
  94   sp = (void **)&this_fn - 2;
  95 #elif defined(__x86_64__)
  96   unsigned long rbp;
  97   // Move the value of the register %rbp into the local variable rbp.
  98   // We need 'volatile' to prevent this instruction from getting moved
  99   // around during optimization to before function prologue is done.
 100   // An alternative way to achieve this
 101   // would be (before this __asm__ instruction) to call Noop() defined as
 102   //   static void Noop() __attribute__ ((noinline));  // prevent inlining
 103   //   static void Noop() { asm(""); }  // prevent optimizing-away
 104   __asm__ volatile ("mov %%rbp, %0" : "=r" (rbp));
 105   // Arguments are passed in registers on x86-64, so we can't just
 106   // offset from &result
 107   sp = (void **) rbp;
 108 #else
 109 # error Cannot obtain SP (possibly compiling on a non x86 architecture)
 110 #endif
 111   shadow_sp_stack[shadow_index] = (void*)sp;
 112   return;
 113 }
 114
 115 void __cyg_profile_func_exit(void *this_fn, void *call_site) {
 116   if (status == DISABLED) return;
 117   shadow_index--;
 118 }
 119
 120 void *get_shadow_ip_stack(int *index /*OUT*/) {
 121   *index = shadow_index;
 122   return shadow_ip_stack;
 123 }
 124
 125 void *get_shadow_sp_stack(int *index /*OUT*/) {
 126   *index = shadow_index;
 127   return shadow_sp_stack;
 128 }