1 /* Dynamic linker system dependencies for Linux.
2 Copyright (C) 1995-2021 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 /* 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 #include <not-cancel.h>
29
30 #ifdef SHARED
31 # define DL_SYSDEP_INIT frob_brk ()
32
33 static inline void
frob_brk(void)34 frob_brk (void)
35 {
36 __brk (0); /* Initialize the break. */
37 }
38
39 # include <elf/dl-sysdep.c>
40 #endif
41
42
43 int
44 attribute_hidden
_dl_discover_osversion(void)45 _dl_discover_osversion (void)
46 {
47 #if defined NEED_DL_SYSINFO_DSO && defined SHARED
48 if (GLRO(dl_sysinfo_map) != NULL)
49 {
50 /* If the kernel-supplied DSO contains a note indicating the kernel's
51 version, we don't need to call uname or parse any strings. */
52
53 static const struct
54 {
55 ElfW(Nhdr) hdr;
56 char vendor[8];
57 } expected_note = { { sizeof "Linux", sizeof (ElfW(Word)), 0 }, "Linux" };
58 const ElfW(Phdr) *const phdr = GLRO(dl_sysinfo_map)->l_phdr;
59 const ElfW(Word) phnum = GLRO(dl_sysinfo_map)->l_phnum;
60 for (uint_fast16_t i = 0; i < phnum; ++i)
61 if (phdr[i].p_type == PT_NOTE)
62 {
63 const ElfW(Addr) start = (phdr[i].p_vaddr
64 + GLRO(dl_sysinfo_map)->l_addr);
65 const ElfW(Nhdr) *note = (const void *) start;
66 while ((ElfW(Addr)) (note + 1) - start < phdr[i].p_memsz)
67 {
68 if (!memcmp (note, &expected_note, sizeof expected_note))
69 return *(const ElfW(Word) *) ((const void *) note
70 + sizeof expected_note);
71 #define ROUND(len) (((len) + sizeof note->n_type - 1) & -sizeof note->n_type)
72 note = ((const void *) (note + 1)
73 + ROUND (note->n_namesz) + ROUND (note->n_descsz));
74 #undef ROUND
75 }
76 }
77 }
78 #endif
79
80 char bufmem[64];
81 char *buf = bufmem;
82 unsigned int version;
83 int parts;
84 char *cp;
85 struct utsname uts;
86
87 /* Try the uname system call. */
88 if (__uname (&uts))
89 {
90 /* This was not successful. Now try reading the /proc filesystem. */
91 int fd = __open64_nocancel ("/proc/sys/kernel/osrelease", O_RDONLY);
92 if (fd < 0)
93 return -1;
94 ssize_t reslen = __read_nocancel (fd, bufmem, sizeof (bufmem));
95 __close_nocancel (fd);
96 if (reslen <= 0)
97 /* This also didn't work. We give up since we cannot
98 make sure the library can actually work. */
99 return -1;
100 buf[MIN (reslen, (ssize_t) sizeof (bufmem) - 1)] = '\0';
101 }
102 else
103 buf = uts.release;
104
105 /* Now convert it into a number. The string consists of at most
106 three parts. */
107 version = 0;
108 parts = 0;
109 cp = buf;
110 while ((*cp >= '0') && (*cp <= '9'))
111 {
112 unsigned int here = *cp++ - '0';
113
114 while ((*cp >= '0') && (*cp <= '9'))
115 {
116 here *= 10;
117 here += *cp++ - '0';
118 }
119
120 ++parts;
121 version <<= 8;
122 version |= here;
123
124 if (*cp++ != '.' || parts == 3)
125 /* Another part following? */
126 break;
127 }
128
129 if (parts < 3)
130 version <<= 8 * (3 - parts);
131
132 return version;
133 }
134