1/* Dynamic linker system dependencies for Linux.
2 Copyright (C) 1995-2016 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 <http://www.gnu.org/licenses/>. */
18
19/* Linux needs some special initialization, but otherwise uses
20 the generic dynamic linker system interface code. */
21
22#include <string.h>
23#include <fcntl.h>
24#include <unistd.h>
25#include <sys/param.h>
26#include <sys/utsname.h>
27#include <ldsodefs.h>
28
29#ifdef SHARED
30# define DL_SYSDEP_INIT frob_brk ()
31
32static inline void
33frob_brk (void)
34{
35 __brk (0); /* Initialize the break. */
36}
37
38# include <elf/dl-sysdep.c>
39#endif
40
41
42int
43attribute_hidden
44_dl_discover_osversion (void)
45{
46#if defined NEED_DL_SYSINFO_DSO && defined SHARED
47 if (GLRO(dl_sysinfo_map) != NULL)
48 {
49 /* If the kernel-supplied DSO contains a note indicating the kernel's
50 version, we don't need to call uname or parse any strings. */
51
52 static const struct
53 {
54 ElfW(Nhdr) hdr;
55 char vendor[8];
56 } expected_note = { { sizeof "Linux", sizeof (ElfW(Word)), 0 }, "Linux" };
57 const ElfW(Phdr) *const phdr = GLRO(dl_sysinfo_map)->l_phdr;
58 const ElfW(Word) phnum = GLRO(dl_sysinfo_map)->l_phnum;
59 for (uint_fast16_t i = 0; i < phnum; ++i)
60 if (phdr[i].p_type == PT_NOTE)
61 {
62 const ElfW(Addr) start = (phdr[i].p_vaddr
63 + GLRO(dl_sysinfo_map)->l_addr);
64 const ElfW(Nhdr) *note = (const void *) start;
65 while ((ElfW(Addr)) (note + 1) - start < phdr[i].p_memsz)
66 {
67 if (!memcmp (note, &expected_note, sizeof expected_note))
68 return *(const ElfW(Word) *) ((const void *) note
69 + sizeof expected_note);
70#define ROUND(len) (((len) + sizeof note->n_type - 1) & -sizeof note->n_type)
71 note = ((const void *) (note + 1)
72 + ROUND (note->n_namesz) + ROUND (note->n_descsz));
73#undef ROUND
74 }
75 }
76 }
77#endif
78
79 char bufmem[64];
80 char *buf = bufmem;
81 unsigned int version;
82 int parts;
83 char *cp;
84 struct utsname uts;
85
86 /* Try the uname system call. */
87 if (__uname (&uts))
88 {
89 /* This was not successful. Now try reading the /proc filesystem. */
90 int fd = __open ("/proc/sys/kernel/osrelease", O_RDONLY);
91 if (fd < 0)
92 return -1;
93 ssize_t reslen = __read (fd, bufmem, sizeof (bufmem));
94 __close (fd);
95 if (reslen <= 0)
96 /* This also didn't work. We give up since we cannot
97 make sure the library can actually work. */
98 return -1;
99 buf[MIN (reslen, (ssize_t) sizeof (bufmem) - 1)] = '\0';
100 }
101 else
102 buf = uts.release;
103
104 /* Now convert it into a number. The string consists of at most
105 three parts. */
106 version = 0;
107 parts = 0;
108 cp = buf;
109 while ((*cp >= '0') && (*cp <= '9'))
110 {
111 unsigned int here = *cp++ - '0';
112
113 while ((*cp >= '0') && (*cp <= '9'))
114 {
115 here *= 10;
116 here += *cp++ - '0';
117 }
118
119 ++parts;
120 version <<= 8;
121 version |= here;
122
123 if (*cp++ != '.' || parts == 3)
124 /* Another part following? */
125 break;
126 }
127
128 if (parts < 3)
129 version <<= 8 * (3 - parts);
130
131 return version;
132}
133