1 /* Operating system specific code for generic dynamic loader functions. Linux.
2 Copyright (C) 2000-2021 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19 #include <dl-sysdep.h>
20 #include <endian.h>
21 #include <fcntl.h>
22 #include <stdint.h>
23 #include <not-cancel.h>
24
25 #ifndef MIN
26 # define MIN(a,b) (((a)<(b))?(a):(b))
27 #endif
28
29 #define DL_SYSDEP_OSCHECK(FATAL) \
30 do { \
31 /* Test whether the kernel is new enough. This test is only performed \
32 if the library is not compiled to run on all kernels. */ \
33 \
34 int version = _dl_discover_osversion (); \
35 if (__glibc_likely (version >= 0)) \
36 { \
37 if (__builtin_expect (GLRO(dl_osversion) == 0, 1) \
38 || GLRO(dl_osversion) > version) \
39 GLRO(dl_osversion) = version; \
40 \
41 /* Now we can test with the required version. */ \
42 if (__LINUX_KERNEL_VERSION > 0 && version < __LINUX_KERNEL_VERSION) \
43 /* Not sufficent. */ \
44 FATAL ("FATAL: kernel too old\n"); \
45 } \
46 else if (__LINUX_KERNEL_VERSION > 0) \
47 FATAL ("FATAL: cannot determine kernel version\n"); \
48 } while (0)
49
50 static inline uintptr_t __attribute__ ((always_inline))
_dl_setup_stack_chk_guard(void * dl_random)51 _dl_setup_stack_chk_guard (void *dl_random)
52 {
53 union
54 {
55 uintptr_t num;
56 unsigned char bytes[sizeof (uintptr_t)];
57 } ret;
58
59 /* We need in the moment only 8 bytes on 32-bit platforms and 16
60 bytes on 64-bit platforms. Therefore we can use the data
61 directly and not use the kernel-provided data to seed a PRNG. */
62 memcpy (ret.bytes, dl_random, sizeof (ret));
63 #if BYTE_ORDER == LITTLE_ENDIAN
64 ret.num &= ~(uintptr_t) 0xff;
65 #elif BYTE_ORDER == BIG_ENDIAN
66 ret.num &= ~((uintptr_t) 0xff << (8 * (sizeof (ret) - 1)));
67 #else
68 # error "BYTE_ORDER unknown"
69 #endif
70 return ret.num;
71 }
72
73 static inline uintptr_t __attribute__ ((always_inline))
_dl_setup_pointer_guard(void * dl_random,uintptr_t stack_chk_guard)74 _dl_setup_pointer_guard (void *dl_random, uintptr_t stack_chk_guard)
75 {
76 uintptr_t ret;
77 memcpy (&ret, (char *) dl_random + sizeof (ret), sizeof (ret));
78 return ret;
79 }
80