1 /* Dynamic linker system dependencies for Linux.
2 Copyright (C) 1995-2023 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 <_itoa.h>
20 #include <assert.h>
21 #include <dl-auxv.h>
22 #include <dl-osinfo.h>
23 #include <dl-parse_auxv.h>
24 #include <dl-procinfo.h>
25 #include <dl-tunables.h>
26 #include <elf.h>
27 #include <errno.h>
28 #include <fcntl.h>
29 #include <ldsodefs.h>
30 #include <libc-internal.h>
31 #include <libintl.h>
32 #include <not-cancel.h>
33 #include <stdlib.h>
34 #include <string.h>
35 #include <string.h>
36 #include <sys/mman.h>
37 #include <sys/param.h>
38 #include <sys/stat.h>
39 #include <sys/types.h>
40 #include <sys/utsname.h>
41 #include <tls.h>
42 #include <unistd.h>
43
44 #include <dl-machine.h>
45 #include <dl-hwcap-check.h>
46
47 #ifdef SHARED
48 extern char **_environ attribute_hidden;
49 extern char _end[] attribute_hidden;
50
51 /* Protect SUID program against misuse of file descriptors. */
52 extern void __libc_check_standard_fds (void);
53
54 int __libc_enable_secure attribute_relro = 0;
55 rtld_hidden_data_def (__libc_enable_secure)
56 /* This variable contains the lowest stack address ever used. */
57 void *__libc_stack_end attribute_relro = NULL;
58 rtld_hidden_data_def(__libc_stack_end)
59 void *_dl_random attribute_relro = NULL;
60
61 #ifndef DL_STACK_END
62 # define DL_STACK_END(cookie) ((void *) (cookie))
63 #endif
64
65 /* Arguments passed to dl_main. */
66 struct dl_main_arguments
67 {
68 const ElfW(Phdr) *phdr;
69 ElfW(Word) phnum;
70 ElfW(Addr) user_entry;
71 };
72
73 /* Separate function, so that dl_main can be called without the large
74 array on the stack. */
75 static void
76 _dl_sysdep_parse_arguments (void **start_argptr,
77 struct dl_main_arguments *args)
78 {
79 _dl_argc = (intptr_t) *start_argptr;
80 _dl_argv = (char **) (start_argptr + 1); /* Necessary aliasing violation. */
81 _environ = _dl_argv + _dl_argc + 1;
82 for (char **tmp = _environ; ; ++tmp)
83 if (*tmp == NULL)
84 {
85 /* Another necessary aliasing violation. */
86 GLRO(dl_auxv) = (ElfW(auxv_t) *) (tmp + 1);
87 break;
88 }
89
90 dl_parse_auxv_t auxv_values = { 0, };
91 _dl_parse_auxv (GLRO(dl_auxv), auxv_values);
92
93 args->phdr = (const ElfW(Phdr) *) auxv_values[AT_PHDR];
94 args->phnum = auxv_values[AT_PHNUM];
95 args->user_entry = auxv_values[AT_ENTRY];
96 }
97
98 ElfW(Addr)
99 _dl_sysdep_start (void **start_argptr,
100 void (*dl_main) (const ElfW(Phdr) *phdr, ElfW(Word) phnum,
101 ElfW(Addr) *user_entry, ElfW(auxv_t) *auxv))
102 {
103 __libc_stack_end = DL_STACK_END (start_argptr);
104
105 struct dl_main_arguments dl_main_args;
106 _dl_sysdep_parse_arguments (start_argptr, &dl_main_args);
107
108 dl_hwcap_check ();
109
110 __tunables_init (_environ);
111
112 /* Initialize DSO sorting algorithm after tunables. */
113 _dl_sort_maps_init ();
114
115 __brk (0); /* Initialize the break. */
116
117 #ifdef DL_PLATFORM_INIT
118 DL_PLATFORM_INIT;
119 #endif
120
121 /* Determine the length of the platform name. */
122 if (GLRO(dl_platform) != NULL)
123 GLRO(dl_platformlen) = strlen (GLRO(dl_platform));
124
125 if (__sbrk (0) == _end)
126 /* The dynamic linker was run as a program, and so the initial break
127 starts just after our bss, at &_end. The malloc in dl-minimal.c
128 will consume the rest of this page, so tell the kernel to move the
129 break up that far. When the user program examines its break, it
130 will see this new value and not clobber our data. */
131 __sbrk (GLRO(dl_pagesize)
132 - (((uintptr_t) _end) & (GLRO(dl_pagesize) - 1)));
133
134 /* If this is a SUID program we make sure that FDs 0, 1, and 2 are
135 allocated. If necessary we are doing it ourself. If it is not
136 possible we stop the program. */
137 if (__builtin_expect (__libc_enable_secure, 0))
138 __libc_check_standard_fds ();
139
140 (*dl_main) (dl_main_args.phdr, dl_main_args.phnum,
141 &dl_main_args.user_entry, GLRO(dl_auxv));
142 return dl_main_args.user_entry;
143 }
144
145 void
146 _dl_sysdep_start_cleanup (void)
147 {
148 }
149
150 void
151 _dl_show_auxv (void)
152 {
153 char buf[64];
154 ElfW(auxv_t) *av;
155
156 /* Terminate string. */
157 buf[63] = '\0';
158
159 /* The following code assumes that the AT_* values are encoded
160 starting from 0 with AT_NULL, 1 for AT_IGNORE, and all other values
161 close by (otherwise the array will be too large). In case we have
162 to support a platform where these requirements are not fulfilled
163 some alternative implementation has to be used. */
164 for (av = GLRO(dl_auxv); av->a_type != AT_NULL; ++av)
165 {
166 static const struct
167 {
168 const char label[22];
169 enum { unknown = 0, dec, hex, str, ignore } form : 8;
170 } auxvars[] =
171 {
172 [AT_EXECFD - 2] = { "EXECFD: ", dec },
173 [AT_EXECFN - 2] = { "EXECFN: ", str },
174 [AT_PHDR - 2] = { "PHDR: 0x", hex },
175 [AT_PHENT - 2] = { "PHENT: ", dec },
176 [AT_PHNUM - 2] = { "PHNUM: ", dec },
177 [AT_PAGESZ - 2] = { "PAGESZ: ", dec },
178 [AT_BASE - 2] = { "BASE: 0x", hex },
179 [AT_FLAGS - 2] = { "FLAGS: 0x", hex },
180 [AT_ENTRY - 2] = { "ENTRY: 0x", hex },
181 [AT_NOTELF - 2] = { "NOTELF: ", hex },
182 [AT_UID - 2] = { "UID: ", dec },
183 [AT_EUID - 2] = { "EUID: ", dec },
184 [AT_GID - 2] = { "GID: ", dec },
185 [AT_EGID - 2] = { "EGID: ", dec },
186 [AT_PLATFORM - 2] = { "PLATFORM: ", str },
187 [AT_HWCAP - 2] = { "HWCAP: ", hex },
188 [AT_CLKTCK - 2] = { "CLKTCK: ", dec },
189 [AT_FPUCW - 2] = { "FPUCW: ", hex },
190 [AT_DCACHEBSIZE - 2] = { "DCACHEBSIZE: 0x", hex },
191 [AT_ICACHEBSIZE - 2] = { "ICACHEBSIZE: 0x", hex },
192 [AT_UCACHEBSIZE - 2] = { "UCACHEBSIZE: 0x", hex },
193 [AT_IGNOREPPC - 2] = { "IGNOREPPC", ignore },
194 [AT_SECURE - 2] = { "SECURE: ", dec },
195 [AT_BASE_PLATFORM - 2] = { "BASE_PLATFORM: ", str },
196 [AT_SYSINFO - 2] = { "SYSINFO: 0x", hex },
197 [AT_SYSINFO_EHDR - 2] = { "SYSINFO_EHDR: 0x", hex },
198 [AT_RANDOM - 2] = { "RANDOM: 0x", hex },
199 [AT_HWCAP2 - 2] = { "HWCAP2: 0x", hex },
200 [AT_MINSIGSTKSZ - 2] = { "MINSIGSTKSZ: ", dec },
201 [AT_L1I_CACHESIZE - 2] = { "L1I_CACHESIZE: ", dec },
202 [AT_L1I_CACHEGEOMETRY - 2] = { "L1I_CACHEGEOMETRY: 0x", hex },
203 [AT_L1D_CACHESIZE - 2] = { "L1D_CACHESIZE: ", dec },
204 [AT_L1D_CACHEGEOMETRY - 2] = { "L1D_CACHEGEOMETRY: 0x", hex },
205 [AT_L2_CACHESIZE - 2] = { "L2_CACHESIZE: ", dec },
206 [AT_L2_CACHEGEOMETRY - 2] = { "L2_CACHEGEOMETRY: 0x", hex },
207 [AT_L3_CACHESIZE - 2] = { "L3_CACHESIZE: ", dec },
208 [AT_L3_CACHEGEOMETRY - 2] = { "L3_CACHEGEOMETRY: 0x", hex },
209 };
210 unsigned int idx = (unsigned int) (av->a_type - 2);
211
212 if ((unsigned int) av->a_type < 2u
213 || (idx < sizeof (auxvars) / sizeof (auxvars[0])
214 && auxvars[idx].form == ignore))
215 continue;
216
217 assert (AT_NULL == 0);
218 assert (AT_IGNORE == 1);
219
220 /* Some entries are handled in a special way per platform. */
221 if (_dl_procinfo (av->a_type, av->a_un.a_val) == 0)
222 continue;
223
224 if (idx < sizeof (auxvars) / sizeof (auxvars[0])
225 && auxvars[idx].form != unknown)
226 {
227 const char *val = (char *) av->a_un.a_val;
228
229 if (__builtin_expect (auxvars[idx].form, dec) == dec)
230 val = _itoa ((unsigned long int) av->a_un.a_val,
231 buf + sizeof buf - 1, 10, 0);
232 else if (__builtin_expect (auxvars[idx].form, hex) == hex)
233 val = _itoa ((unsigned long int) av->a_un.a_val,
234 buf + sizeof buf - 1, 16, 0);
235
236 _dl_printf ("AT_%s%s\n", auxvars[idx].label, val);
237
238 continue;
239 }
240
241 /* Unknown value: print a generic line. */
242 char buf2[17];
243 buf2[sizeof (buf2) - 1] = '\0';
244 const char *val2 = _itoa ((unsigned long int) av->a_un.a_val,
245 buf2 + sizeof buf2 - 1, 16, 0);
246 const char *val = _itoa ((unsigned long int) av->a_type,
247 buf + sizeof buf - 1, 16, 0);
248 _dl_printf ("AT_??? (0x%s): 0x%s\n", val, val2);
249 }
250 }
251
252 #endif /* SHARED */