OpenCores
URL https://opencores.org/ocsvn/openrisc/openrisc/trunk

Subversion Repositories openrisc

[/] [openrisc/] [trunk/] [gnu-old/] [gcc-4.2.2/] [gcc/] [config/] [host-linux.c] - Blame information for rev 820

Go to most recent revision | Details | Compare with Previous | View Log

Line No. Rev Author Line
1 38 julius
/* Linux host-specific hook definitions.
2
   Copyright (C) 2004, 2005, 2007 Free Software Foundation, Inc.
3
 
4
   This file is part of GCC.
5
 
6
   GCC is free software; you can redistribute it and/or modify it
7
   under the terms of the GNU General Public License as published
8
   by the Free Software Foundation; either version 3, or (at your
9
   option) any later version.
10
 
11
   GCC is distributed in the hope that it will be useful, but WITHOUT
12
   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
13
   or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
14
   License for more details.
15
 
16
   You should have received a copy of the GNU General Public License
17
   along with GCC; see the file COPYING3.  If not see
18
   <http://www.gnu.org/licenses/>.  */
19
 
20
#include "config.h"
21
#include "system.h"
22
#include "coretypes.h"
23
#include <sys/mman.h>
24
#include <limits.h>
25
#include "hosthooks.h"
26
#include "hosthooks-def.h"
27
 
28
 
29
/* Linux has a feature called exec-shield-randomize that perturbs the
30
   address of non-fixed mapped segments by a (relatively) small amount.
31
   The feature is intended to make it harder to attack the system with
32
   buffer overflow attacks, since every invocation of a program will
33
   have its libraries and data segments at slightly different addresses.
34
 
35
   This feature causes us problems with PCH because it makes it that
36
   much harder to acquire a stable location at which to map our PCH
37
   data file.
38
 
39
   [ The feature causes other points of non-determinism within the
40
     compiler as well, so we'd *really* like to be able to have the
41
     driver disable exec-shield-randomize for the process group, but
42
     that isn't possible at present.  ]
43
 
44
   We're going to try several things:
45
 
46
      * Select an architecture specific address as "likely" and see
47
        if that's free.  For our 64-bit hosts, we can easily choose
48
        an address in Never Never Land.
49
 
50
      * If exec-shield-randomize is disabled, then just use the
51
        address chosen by mmap in step one.
52
 
53
      * If exec-shield-randomize is enabled, then temporarily allocate
54
        32M of memory as a buffer, then allocate PCH memory, then
55
        free the buffer.  The theory here is that the perturbation is
56
        no more than 16M, and so by allocating our buffer larger than
57
        that we make it considerably more likely that the address will
58
        be free when we want to load the data back.
59
*/
60
 
61
#undef HOST_HOOKS_GT_PCH_GET_ADDRESS
62
#define HOST_HOOKS_GT_PCH_GET_ADDRESS linux_gt_pch_get_address
63
 
64
#undef HOST_HOOKS_GT_PCH_USE_ADDRESS
65
#define HOST_HOOKS_GT_PCH_USE_ADDRESS linux_gt_pch_use_address
66
 
67
/* For various ports, try to guess a fixed spot in the vm space
68
   that's probably free.  */
69
#if defined(__alpha)
70
# define TRY_EMPTY_VM_SPACE     0x10000000000
71
#elif defined(__ia64)
72
# define TRY_EMPTY_VM_SPACE     0x2000000100000000
73
#elif defined(__x86_64)
74
# define TRY_EMPTY_VM_SPACE     0x1000000000
75
#elif defined(__i386)
76
# define TRY_EMPTY_VM_SPACE     0x60000000
77
#elif defined(__powerpc__)
78
# define TRY_EMPTY_VM_SPACE     0x60000000
79
#elif defined(__s390x__)
80
# define TRY_EMPTY_VM_SPACE     0x8000000000
81
#elif defined(__s390__)
82
# define TRY_EMPTY_VM_SPACE     0x60000000
83
#elif defined(__sparc__) && defined(__LP64__)
84
# define TRY_EMPTY_VM_SPACE     0x8000000000
85
#elif defined(__sparc__)
86
# define TRY_EMPTY_VM_SPACE     0x60000000
87
#else
88
# define TRY_EMPTY_VM_SPACE     0
89
#endif
90
 
91
/* Determine a location where we might be able to reliably allocate SIZE
92
   bytes.  FD is the PCH file, though we should return with the file
93
   unmapped.  */
94
 
95
static void *
96
linux_gt_pch_get_address (size_t size, int fd)
97
{
98
  size_t buffer_size = 32 * 1024 * 1024;
99
  void *addr, *buffer;
100
  FILE *f;
101
  bool randomize_on;
102
 
103
  addr = mmap ((void *)TRY_EMPTY_VM_SPACE, size, PROT_READ | PROT_WRITE,
104
               MAP_PRIVATE, fd, 0);
105
 
106
  /* If we failed the map, that means there's *no* free space.  */
107
  if (addr == (void *) MAP_FAILED)
108
    return NULL;
109
  /* Unmap the area before returning.  */
110
  munmap (addr, size);
111
 
112
  /* If we got the exact area we requested, then that's great.  */
113
  if (TRY_EMPTY_VM_SPACE && addr == (void *) TRY_EMPTY_VM_SPACE)
114
    return addr;
115
 
116
  /* If we didn't, then we need to look to see if virtual address
117
     randomization is on.  That is recorded in
118
     kernel.randomize_va_space.  An older implementation used
119
     kernel.exec-shield-randomize.  */
120
  f = fopen ("/proc/sys/kernel/randomize_va_space", "r");
121
  if (f == NULL)
122
    f = fopen ("/proc/sys/kernel/exec-shield-randomize", "r");
123
  randomize_on = false;
124
  if (f != NULL)
125
    {
126
      char buf[100];
127
      size_t c;
128
 
129
      c = fread (buf, 1, sizeof buf - 1, f);
130
      if (c > 0)
131
        {
132
          buf[c] = '\0';
133
          randomize_on = (atoi (buf) > 0);
134
        }
135
      fclose (f);
136
    }
137
 
138
  /* If it isn't, then accept the address that mmap selected as fine.  */
139
  if (!randomize_on)
140
    return addr;
141
 
142
  /* Otherwise, we need to try again with buffer space.  */
143
  buffer = mmap (0, buffer_size, PROT_NONE, MAP_PRIVATE | MAP_ANON, -1, 0);
144
  addr = mmap (0, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
145
  if (buffer != (void *) MAP_FAILED)
146
    munmap (buffer, buffer_size);
147
  if (addr == (void *) MAP_FAILED)
148
    return NULL;
149
  munmap (addr, size);
150
 
151
  return addr;
152
}
153
 
154
/* Map SIZE bytes of FD+OFFSET at BASE.  Return 1 if we succeeded at
155
   mapping the data at BASE, -1 if we couldn't.
156
 
157
   It's not possibly to reliably mmap a file using MAP_PRIVATE to
158
   a specific START address on either hpux or linux.  First we see
159
   if mmap with MAP_PRIVATE works.  If it does, we are off to the
160
   races.  If it doesn't, we try an anonymous private mmap since the
161
   kernel is more likely to honor the BASE address in anonymous maps.
162
   We then copy the data to the anonymous private map.  This assumes
163
   of course that we don't need to change the data in the PCH file
164
   after it is created.
165
 
166
   This approach obviously causes a performance penalty but there is
167
   little else we can do given the current PCH implementation.  */
168
 
169
static int
170
linux_gt_pch_use_address (void *base, size_t size, int fd, size_t offset)
171
{
172
  void *addr;
173
 
174
  /* We're called with size == 0 if we're not planning to load a PCH
175
     file at all.  This allows the hook to free any static space that
176
     we might have allocated at link time.  */
177
  if (size == 0)
178
    return -1;
179
 
180
  /* Try to map the file with MAP_PRIVATE.  */
181
  addr = mmap (base, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, offset);
182
 
183
  if (addr == base)
184
    return 1;
185
 
186
  if (addr != (void *) MAP_FAILED)
187
    munmap (addr, size);
188
 
189
  /* Try to make an anonymous private mmap at the desired location.  */
190
  addr = mmap (base, size, PROT_READ | PROT_WRITE,
191
               MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
192
 
193
  if (addr != base)
194
    {
195
      if (addr != (void *) MAP_FAILED)
196
        munmap (addr, size);
197
      return -1;
198
    }
199
 
200
  if (lseek (fd, offset, SEEK_SET) == (off_t)-1)
201
    return -1;
202
 
203
  while (size)
204
    {
205
      ssize_t nbytes;
206
 
207
      nbytes = read (fd, base, MIN (size, SSIZE_MAX));
208
      if (nbytes <= 0)
209
        return -1;
210
      base = (char *) base + nbytes;
211
      size -= nbytes;
212
    }
213
 
214
  return 1;
215
}
216
 
217
 
218
const struct host_hooks host_hooks = HOST_HOOKS_INITIALIZER;

powered by: WebSVN 2.1.0

© copyright 1999-2024 OpenCores.org, equivalent to Oliscience, all rights reserved. OpenCores®, registered trademark.